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Title: Plague

Author: Thomas Wright Jackson

Contributor: Otto Schöbl

Release date: October 12, 2013 [eBook #43942]

Language: English

Credits: Produced by Chris Curnow, Sandra Eder and the Online
        Distributed Proofreading Team at http://www.pgdp.net (This
        file was produced from images generously made available
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  Transcriber's note:

  Text in italics is marked with _ underscore, text in small caps
  changed to ALL CAPS. Illustrations were moved to paragraph breaks.
  The index is sorted by page numbers within the alphabetical groups.
  This has been retained. Footnotes were moved to the end of the
  corresponding paragraph. In the Latin1 file, oe/Oe was used for the
  unicode oe-ligature. A list of corrections made can be found at the
  end of the book.




  PLAGUE




  PLAGUE

  ITS CAUSE AND THE MANNER OF ITS
  EXTENSION--ITS MENACE--ITS CONTROL AND
  SUPPRESSION--ITS DIAGNOSIS AND TREATMENT

  BY
  THOMAS WRIGHT JACKSON, M.D.

  MEMBER AMERICAN RED CROSS SANITARY COMMISSION TO SERBIA, 1915; LATELY
  CAPTAIN AND ASSISTANT SURGEON, U. S. VOLUNTEERS; LATELY LECTURER ON
  TROPICAL DISEASES, JEFFERSON MEDICAL COLLEGE; MEMBER OF MANILA
  MEDICAL SOCIETY AND PHILIPPINE ISLANDS MEDICAL ASSOCIATION;
  AUTHOR OF A TEXT BOOK ON TROPICAL MEDICINE; DIRECTOR,
  DEPARTMENT OF SANITATION AND EPIDEMIOLOGY
  FOR H. K. MULFORD COMPANY

  WITH BACTERIOLOGIC OBSERVATIONS

  BY
  DR. OTTO SCHÖBL

  BUREAU OF SCIENCE, MANILA

  _ILLUSTRATED_

  PRESS OF
  J. B. LIPPINCOTT COMPANY




  COPYRIGHT, 1916
  BY THOMAS WRIGHT JACKSON, M.D.





  THIS BOOK IS DEDICATED BY THE AUTHOR TO

    DR. ALDO CASTELLANI

  REGIUS PROFESSOR OF TROPICAL DISEASES, UNIVERSITY OF NAPLES.
  EMINENT IN MEDICAL RESEARCH, MY FRIEND, COLLEAGUE AND COMRADE
  DURING STRENUOUS DAYS IN SERBIA.





  CONTENTS


                                                                   PAGE

 INTRODUCTION                                                        11

  CHAPTER I

 ITS HISTORY AND ITS EXTENSION                                       19

  History of Plague--The Widespread Dissemination of Plague in
  Recent Years--The Appearance of Plague in Porto Rico, New
  Orleans and Manila.

  CHAPTER II

 THE CAUSE AND THE MENACE OF PLAGUE                                  28

  Causation of the Disease and its Mode of Conveyance--Types of
  Plague--Chronic Plague and Immunity in Rats--Flea Conveyance of
  Plague Bacilli--The Stability of Virulence of Plague
  Bacilli--Summary of Facts Concerning the Cause and Manner of
  Extension of Plague.

  CHAPTER III

 ITS CONTROL AND SUPPRESSION                                         40

  Plague Prevention by Extermination of Rats--General Uselessness
  of the Rat and Its Enormous Destructiveness, with Details of
  Trapping and Other Extermination Methods--The Manila Epidemic,
  1912-1914--The First Cases--Unusual Character of Plague Cases at
  Quarantine--Clinical Description of Two Cases at
  Quarantine--Inauguration of the Manila Epidemic--Directed to
  Take Charge of Plague Suppression in Manila--Plague Fighting
  Organization--Method of Rat Proofing and Rat
  Destruction--Correspondence Between Dr. Jackson and Dr. Heiser,
  Director of Public Health--Observations on Fleas and Their
  Habits--Conditions of Habitations in Manila Favoring Rat
  Multiplication and Spread of Plague--Comparative Statistics on
  Methods of Catching Rats--The Natural Enemies of the
  Flea--Zoölogic Classification of Rats--A Collection of Notes
  Concerning Rat Runs, Rat Nests, Multiple House Infections and
  Other Data--Sample of Detailed Orders Issued Regarding Rat
  Extermination--Method of Procedure of Collecting and Forwarding
  Rats Suspected of Plague Infection to Laboratory--Memoranda in
  Plague Cases--Letter of Warning and Appeal for
  Coöperation--Bacteriologic Observations made During the Manila
  Plague Epidemic, by Dr. Otto Schöbl--Notes Concerning the
  Bubonic Plague in Hong Kong, by Dr. David Roberg.

  CHAPTER IV

 ITS DIAGNOSIS AND TREATMENT                                        165

  Biologic Diagnosis--Necessity for Trained
  Bacteriologist--Bacteriologic Procedure--Non-Biologic
  Diagnosis--Symptomatology--Pathologic Considerations--Treatment,
  Conditions and Prognosis--Serum Treatment--Symptomatic
  Treatment--Statistical Studies in Mortality--Dosage and
  Technique of Serum Administration--Prophylactic Serum and
  Anaphylaxis--Plague Vaccines.




  ILLUSTRATIONS


                                                                   PAGE

 RAT-PROOF STRUCTURE                                                 48
 CLEANING AND RAT-PROOFING IN BASEMENT                               69
 BAMBOO HOUSE SUPPORTS NOT SEALED WITH CEMENT                        86
 MATERIALS MUST BE MOVED ABOUT IN THE SEARCH FOR RATS                93
 A RAT-INFESTED PLAGUE INTERIOR                                      95
 PROGRESSIVE POST-MORTEM CHANGES IN RAT CADAVERS                    105
 PLAGUE HOUSE                                                       116
 BAMBOO HOUSE SUPPORTS SEALED WITH CEMENT                           119
 VIEW OF HOUSE WHERE INFECTED RATS WERE FOUND                       120
 ANIMAL HOUSE                                                       144




  PLAGUE

  ITS CAUSE AND THE MANNER OF ITS EXTENSION--ITS MENACE--ITS
  CONTROL AND SUPPRESSION--ITS DIAGNOSIS AND TREATMENT




  INTRODUCTION


The question of the need for new books upon medical topics must ever
remain undecided, by general agreement, in the medical profession.

There is no such thing in medical literature as an insistent demand
from the profession for new volumes upon old topics.

Authors need not hope, therefore, to create the impression that they
are meeting long-felt though unexpressed wants of medical readers in
launching new books.

On the other hand, the creator of a new volume upon an old subject
should seek justification for literary paternity in the progressive
changes in the status of our knowledge of disease, its causes,
prevention, and cure. Such changes are admittedly going on with a
certain degree of constancy and at such a rate of frequency that new
presentations of old themes, are both justified and desirable from time
to time.

With this idea in mind and with the desire to present, in useful and
practical form, a work which shall contain at least some unhackneyed
material and which shall represent modern studies and a record of
actual control work done in this justly-dreaded disease, the following
pages are submitted to the medical profession and to sanitarians
generally.

With a profound respect for the laboratory worker and his work and with
a profound conviction that to him belongs the greater measure of credit
for real accomplishment in connection with plague up to the present
time, I desire to insist that the true utility of knowledge gained
within laboratory walls lies in its intelligent application in the
outer world and that ofttimes this application must be made by men who
are themselves without extended laboratory training. An appreciation of
principles--with an intelligent ability to accept, to appropriate, to
apply and, most of all, to refrain from entering without due
preparation the domain of the laboratory worker--is an indispensable
requisite in the equipment of the practical sanitarian, upon whom must
fall the responsibilities of success or failure in combating the
disease we are now to consider.

During the past fourteen years it has been my privilege to observe two
epidemics of plague in the Philippine Islands. Some of these
observations were made in the capacity of a military medical officer,
but my later observations, upon which this report and study are chiefly
based, were made from the view-point of a civil health officer. At
different times I have been called upon to deal with the disease both
as sanitary officer and clinician, and from October, 1912, to July,
1914, I had charge of all plague suppressive measures in Manila. In
1914 I was also in charge, as acting chief, of the San Lazaro Hospitals
Division of the Bureau of Health, Manila, where all cases of plague are
brought, either for treatment or autopsy.

As some of the material which I have collected for text-book articles
during the past eight years bears directly upon the present discussion
and presentation, I have ventured to quote from it, sometimes without
rephrasing, such parts as are accurate at the present time. I am also
quoting freely from the records and from the experiences of my
predecessors and colleagues in the work in Manila.

It should be understood that the pathology of the disease has been
practically omitted from consideration as out of place in an
epidemiologic investigation and report. The pathologic side of the work
during the Manila epidemic of 1912-1914 was covered in a masterly
manner by Dr. B. C. Crowell and his associates at the Medical School of
the University of the Philippines, and I have no doubt that the record
of the work done and studies made will appear in appropriate form in
due time and will hereafter be referred to as among the most valuable
pathologic studies ever made during a plague epidemic, on account of
their accuracy and completeness.

I have included, as of great value and directly related to the
epidemiologic phase of this study, reports of some of the bacteriologic
work done in connection with this epidemic at the Bureau of Science,
Manila, by Dr. Otto Schöbl. I am sure that the value of his studies as
reported in part here, with his permission, will be apparent to every
careful reader. I am greatly indebted to him for his permission to make
use of this portion of his studies. Having been in daily touch with Dr.
Schöbl during the year and a half of the continuance of this epidemic,
I can appreciate to the fullest extent the painstaking and accurate
character of his work and findings, of which the part here presented is
by no means the greatest.

I am quite aware of the fact that there are those who view with some
question the practicability of controlling plague by the measures
applied in Manila, as recited here; but American plague workers are
likely to meet this unbelief by pointing to the accomplished fact, in
San Francisco, in Honolulu, in Porto Rico, as well as in Manila; and
before long, as we confidently expect, in New Orleans.

These exponents of the school which contends that plague epidemics are
little affected by rat-excluding, rat-destroying and rat-proofing
efforts, believe that the waning and disappearance of epidemic plague
in a given place depend in chief part upon the exhaustion of
susceptible material among the rodent population. However appealing
this argument may be, it is impossible for its exponents to duplicate
American results with equal results in the cities of China, India, Java
and elsewhere, where governmental control and adequate financial
ability to carry out campaigns have been lacking, from one cause or
another. Wherever our methods have been followed, at home and in the
insular possessions of the United States, we have terminated human
epidemics of plague and have apparently put an end to rat plague in
comparatively short campaigns. So long as this discrepancy in results
continues we shall favor the American plan. When we review the work
and results of Blue and his fellows of the United States Health Service
and the officers of the Bureau of Health of the Philippine Islands, we
find little reason for us to favor a change to the expectant plan of
waiting for an epidemic to run its course.

While speaking of the Philippine Islands, the admirable work of Strong
in Manila, covering years of study of the immunity problem, and his
dangerous and highly valuable work as a member of the Commission which
studied the Manchurian epidemic of pneumonic plague in 1911, must be
mentioned.

Some years ago I called attention to the fact that few, if any,
American cities were prepared to meet an outbreak of plague with an
adequate supply of antipest serum and that the preparation of
antiplague serum was a neglected or overlooked branch of serum
manufacture in the United States. Since that time, in the midst of a
plague epidemic in Manila, where, for a time, the supply of locally
prepared (Bureau of Science) serum threatened to become exhausted, I
looked into the possibilities of getting a supply elsewhere and found
that, to do so, in anything like a reasonable length of time, was
impossible. Fortunately the threatened serum famine did not occur, the
local supply in Manila proving adequate, although for a few weeks we
were obliged to make use of a stock of Japanese serum which had been on
hand for several years. Since the warning of some years ago, at which
time the plague danger was an anticipated one, bubonic plague has
actually appeared in the United States (New Orleans), the cases being
sufficiently numerous to cause grave concern and to call forth the
utmost repressive efforts of the authorities. The possibility of plague
appearance in the coast cities of the United States, at any time,
cannot be disregarded and provision for the treatment of human cases,
as well as repressive (antirat) measures, is imperative. Antiplague
serum is not producible upon a few hours' notice, nor is it
manufactured in the United States. In view of present war conditions
the difficulty of securing serum from overseas sources is greatly
increased, so that we are well-nigh compelled to depend upon
home-produced serum. In view of the uselessness of drug treatment it is
plainly the duty of national, state and municipal authorities to keep
on hand a reasonable supply of antipest serum to meet any outbreak.
Manufacturers of biological products realize that the preparations for
producing, storing and marketing antiplague serum are expensive and
that the maintenance of immunized animals and the employment of expert
serologists call for expenditures which are unlikely to be recovered
from any demand for serum and that, moreover, the government is doing
and will do all that lies within its power to make the serum
unnecessary, by excluding plague. These are not encouraging conditions
to lead American serum producers to add antiplague serum to the list of
their products. If, under these adverse conditions, any producer of
biologic products shall undertake to produce and maintain an adequate
supply of antiplague serum, he will merit credit for a truly
philanthropic service and will deserve the support of governments,
national, state and municipal, as well as that of the medical
profession.




  CHAPTER I

  ITS HISTORY AND ITS EXTENSION


In plague there exists the most intimate relationship between cause and
prevention. We will therefore set forth here, as briefly and concisely
as their importance will permit, the principal facts related to the
causation of the disease. Without an understanding of this relationship
there can be no rational preventive treatment.

These facts constitute one of the interesting stories of modern
medicine: the story of the arrangement and interpretation of certain
apparently unrelated facts, some of them long known to men, in the
clear light of modern method; the story of the application of analysis,
synthesis, logic and experiment, all leading to the creation of an
understanding which permits us to battle successfully with _pestis
bubonica_, one of the most ancient of human plagues.

HISTORY.--This disease has an historic interest, most engaging and
fascinating, which one finds it difficult to pass over with mere
mention.

I venture to recall, therefore, that plague almost certainly dates
back to the pre-Christian era, the earlier record naturally being
lacking in sufficient accuracy of description to enable us to identify
the recorded epidemics, definitely and positively, with true bubonic
plague.

An epidemic of the second century B.C., as described, seems to have
been one of true plague, while the pandemic which began in Egypt in the
sixth century A.D., thence extending to Constantinople, Europe and the
British Isles, was certainly the disease known in modern times as the
plague. This pandemic, beginning as the plague of Justinian, was
probably followed by the continuous presence of the disease in Europe,
marked by many local outbreaks and periods of quiescence and extending
down through the centuries to the period of the Crusades. In the
eleventh and twelfth centuries the returning Crusaders spread the
plague widely through Europe, which country it ravished from the
eleventh to the fourteenth centuries, reaching its climax of intensity
in the "Black Death" of Europe of the Middle Ages. The disease
thereafter continued to devastate Europe, the great population centres,
Paris and London, suffering especially from its visitations and its
more or less constant presence. The Great Plague of London, the last
important epidemic of the disease in that metropolis, began in 1664 and
lasted five years. With less than half a million of inhabitants it is
estimated that London gave one of every six or seven of her citizens to
the Black Death during the first year of the epidemic. Then followed a
remarkable disappearance of the disease from Western Europe. The
eighteenth century was marked by few epidemic appearances of plague.

At the end of the first half of the nineteenth century it had
practically disappeared from Egypt and from European and Asiatic
Turkey, formerly its favorite haunts. In interior Asia it has probably
existed for centuries, the non-emigrating character of the people
limiting and confining its devastations.

To these centres and to the commercial invasion of China, we must
probably trace the beginning of the present pandemic of plague, which
exists to-day, a menace to the civilized and uncivilized world. In the
days of the Crusades a religious invasion of the infected centres
caused the disease to spread throughout Christendom, while in the
present day a commercial invasion has caused it to spread completely
around the world.

That this is a truth and not a fanciful statement is shown by the
appearance of plague in the following countries since 1894, when it
spread from interior China. In every case it has followed those
sanitary lines of least resistance, the paths of commerce.

EXTENSION.--To the eastward, from China, it spread to Japan, the
Philippines, Australia, the Hawaiian Islands, Alaska, California,
Mexico, Peru and the western coast of South America. To the westward,
it invaded India, Mauritius, Egypt, Suez ports, Eastern, Central and
South Africa, Mediterranean ports, Great Britain (Scotland), the West
Indies and Brazil. In the last twenty years plague has caused millions
of deaths, and, during a single week in April, 1907, it destroyed more
than 75,000 lives in India, a number about equal to the deaths of a
year in London during the Great Plague of 1665. In contrast with India
the rest of the world has suffered little during the present
world-epidemic, but this loss, while relatively small, is enormous when
translated into lives and dollars. The figures for India are simply
huge.

MORTALITY.--The official lists of _deaths_ in India for the last twenty
years include some in which the number of _reported_ deaths per year
exceeded one million, and it has been estimated that the actual number
of persons dead from the plague during this period approximates
8,000,000.

It is gratifying to note a marked decrease in the total mortality in
the reports of the last few years, but so long as the annual death
list, year after year, was measured by hundreds of thousands, rather
than thousands, the situation could not be considered as anything but
grave.

WIDESPREAD DISSEMINATION IN RECENT YEARS.--Without going into
statistics deeply we may consider also the list of countries, states
and islands from which plague cases have been reported officially
during the last few years.

My purpose is to invite attention to the continued existence of various
plague foci, any one of which might serve to extend the infection
further, were governmental quarantine and public health supervision
relaxed.

During August, September, October, November and December, 1909, plague
cases occurred in India, Mauritius, China, Japan, Egypt, Turkey,
Russia, British East Africa, the Azores, Venezuela, Ecuador, Peru,
Chili, California (two cases), and the Hawaiian Islands.

During the first half of 1910 no very marked variation in the
distribution of plague occurred, cases being reported from practically
all of the foreign countries just named.

A year later the situation, so far as the distribution of plague cases
is concerned, was not greatly changed, as may be seen from the
following tabulation, which I have abstracted from the _British Medical
Journal_ of September 16, 1911.

_India._--Deaths from plague in India during the first six months,
604,634. Most prevalent (1) United Provinces, 281,317; (2) Punjab,
171,084; (3) Bengal, 58,515; (4) Bombay Presidency, 28,109. Deaths in
July, not included above, 8990.

_Hong Kong._--April 24 to August 21, 255 cases, 194 deaths.

_China._--Since January 1, 1911, plague was reported in varying
intensity in (provinces and towns) Manchuria, Peking, Tien-tsin, Chefo,
Shantung, Shanghai, Amoy, Foochow, Swatow, Canton, Pakhoi and Laichow.

_Indo-China._--At Saigon, in March and April, 1911, many cases
reported. April 17 to May 7, 56 cases; 17 deaths. May 22 to May 28, 37
cases; 12 deaths.

_Siam._--In Bangkok plague was more severe during 1911 than in any
previous year. March 15 to April 15, 33 cases and 29 deaths.

_Java and Sumatra._--In Java, May 25 to June 3, 105 cases and 62 deaths
(one province). In Sumatra plague was present, no statistics.

_Straits Settlements._--A few cases, mostly imported, reported in 1911.

_Japan._--A few cases at Kobe in 1911. In Formosa, from April 2 to
April 15, 31 cases; 24 deaths.

_Egypt._--Plague reported from Port Said, Suakin (on board ship), Cairo
and Alexandria; also from 11 provinces. The province of Kena had a
severe outbreak, May 5 to May 31, 51 cases and 49 deaths.

_Persia._--Several cases reported from ports on the Persian Gulf.

_Turkey in Asia._--A few cases at Muscat, Basra and at Port of Jeddah.

_British East Africa._--Kismayu and Port Florence reported a few cases
in April, 1911.

_Mauritius._--January 1 to April 11, 110 cases and 70 deaths.

_Portuguese East Africa._--Plague was reported present at Nahoria in
May, 1911.

_Russia._--In the Kirgis Steppe in the Astrakan Government in January,
50 cases; 30 deaths.

_South America._--Plague prevailed during 1911 in Peru, Ecuador,
Brazil, Chile and Venezuela. No severe outbreak except in Peru, where
from February to May many cases occurred and died. At Libertad, in
March, were reported 60 cases and 23 deaths.

APPEARANCE OF PLAGUE IN PORTO RICO, NEW ORLEANS AND MANILA.--The
developments of 1912, which most concern us, were the appearance of
human plague and the discovery of plague-infected rats in Porto Rico,
Cuba, and the Philippines, and the discovery of infected rats in New
Orleans. Thus the Atlantic cities of the United States were for the
first time seriously threatened, and the menace of the pestilence at
home loomed up on our horizon with sufficient prominence to excite
public concern. Our protectors and guardians of the United States
Public Health Service, to whose watchfulness we must credit our
prolonged escape from the plague, are carrying out all the protective
measures at their command with the utmost activity.

At the present time we find Porto Rico freed from the disease. New
Orleans has undergone and is still undergoing treatment which may be
expected, most confidently, to clear it of both human and animal
plague.

Of Manila and the work there, much will be found in the following
pages, but as both rat plague and human plague have been absent for
more than a year we may fairly look upon the epidemic as ended. After
so long an interval as this any reappearance of plague may fairly be
viewed as a new epidemic, although it is not humanly possible to say
that rat plague has entirely and permanently disappeared from the city
of Manila, as yet.




  CHAPTER II

  THE CAUSE AND THE MENACE OF PLAGUE


The foregoing facts are quite sufficient to make us realize both the
possibility and the danger of a world-epidemic; a danger which has
existed for some years and which recently has been especially menacing
to the United States.

CAUSATION OF THE DISEASE.--Plague is an acute infectious epizoötic
disease, caused solely by _Bacillus pestis_, a bacterial organism. The
disease is common to man and to a number of the lower animals and
fowls.

Prominent among the animals susceptible to the disease is the rat, and
from this animal, through the intermediation of the flea, by far the
most cases of human plague arise. In California the ground squirrel
(_Citellus beecheyi_), a rodent closely related to the marmots of Asia,
plays a similar rôle. Of the Asian marmots, the tarbagan, a large
rodent, also commonly suffers from subacute chronic plague, which is
transmissible to man as an acute disease by the fleas which the animal
harbors.

ITS CONVEYANCE.--Although conveyance of plague through rats by contact
alone--that is to say without the medium of the flea--is denied by
modern experimenters, it is perhaps wiser and safer to consider the
disease infectious, inoculable and contagious in the common medical
meaning of these terms. While it is usually conveyed to man by the
flea, it may be acquired by the inhalation of plague bacilli and,
according to some authorities, by ingesting or swallowing the bacilli.

When infection takes place through the digestive tract, or in other
words, by the ingestion of bacilli, either the flesh of plague-infected
animals or fowls, or food superficially contaminated with plague
bacilli by rats, cockroaches or other carriers, serves as the medium.

Speaking practically, the possibility of infection through ingestion is
nearly negligible. Indeed, the conclusion of Simpson in regard to this
possibility has been disputed and denied. However, the recent
occurrence of plague in a cat in Manila, in my own experience, observed
with me and carefully worked out by Dr. Otto Schöbl, points strongly to
the possibility of ingestion plague, the cat in this case apparently
having acquired plague from eating rats dead from plague.

A full account of this case appears in the bacteriologic observations
of Dr. Schöbl and in my recital of the history of the Manila epidemic.

TYPES OF PLAGUE.--Plague in man may be of several types and these are
designated by names descriptive of the symptoms or of the regions of
the body most affected. Thus we have bubonic, septicæmic and pneumonic
types. As both mild and virulent cases occur, we also use terms
descriptive of the severity and course of the cases. Thus we describe
certain cases as ambulant, abortive, larval and fulminant. In the rat
the evidences of plague are less striking in life than they are at the
post-mortem table. Indeed plague-stricken rats, either naturally or
artificially (experimentally) infected, often show very slight
evidences of disease before death. Chronic plague in rats and a
relative immunity to inoculation in certain wild rats are fairly well
recognized phenomena.

FLEA CONVEYANCE OF PLAGUE BACILLI.--Both male and female fleas convey
plague, but the exact method of carrying the plague bacilli from
diseased rats to man, while fairly well determined, is of such recent
decision as to leave room for further experimentation. At present it is
believed that the flea deposits plague bacilli, at the time of biting,
upon the skin, by ejecting the contents of its rectum and by
regurgitation of its stomach contents. At least the flea is known to
perform these acts at the time of biting, and the rubbing or scratching
of the flea bite with the hand may easily introduce the bacilli into
the skin at this spot.[1]

  [1] Acknowledgment is hereby made to the Contributors to "The Rat and
  Its Relation to Public Health" by various authors, prepared by
  direction of the Surgeon-General, P. H. and M. H. S., for numerous
  facts utilized in the preparation of this article. The particular
  contributors whose valuable chapters have been drawn upon for
  information are D. E. Lantz, C. W. McCoy, D. H. Currie, Carrol Fox,
  Rupert Blue, W. C. Rucker, R. H. Creel, M. J. Rosenau, V. C. Heiser,
  W. C. Hobdy, and J. W. Kerr.

The possibility that the flea introduces the plague bacilli upon his
mandibles, or the skin-piercing armament with which he is provided, is
also to be considered. However, the following facts support the first
proposition. It has been experimentally shown that the average capacity
of a flea's stomach is about one-half of a cubic millimetre and that
thousands of plague bacilli may be ingested by the flea during the
biting of a plague-diseased rat; that the plague bacilli multiply
enormously and for many days in the flea's stomach and that the bacilli
are found only in the insect's digestive tract; that plague bacilli are
regurgitated from the stomach and are voided from the rectum with the
digested blood.

It has also been proved that almost all varieties of rat fleas, under
favorable circumstances, will bite man and that the most common human
flea (_Pulex irritans_) is frequently found upon rats, the flea,
generally speaking, being much less particular in his choice of hosts
and in his permanence of residence than most insects and ectoparasites
in general.

Of the rat fleas, _Pulex pallidus_ (_Loemopsylla cheopis_) is common
under various names in India, the Philippines, Australia, Italy, Brazil
and in tropical countries generally. It bites both rat and man.
_Ceratophyllus fasciatus_, the common rat flea of Great Britain and the
United States, also bites both rat and man. In North America and
elsewhere certain other fleas of the genus _Ceratophyllus_ have been
found upon ground squirrels, cats, rats, sparrows and in chicken yards.

Dog fleas and cat fleas (genus _Ctenocephalus_) also infest rats, and
fleas of other genera are found upon mice, rats and ground squirrels
rather indiscriminately.

The significance of these facts in connection with prevention of
plague is apparent and it is plain that our warfare against fleas must
be made upon _all_ fleas and not upon a single variety. In this
connection the possibilities of the conveyance of plague bacilli by
other suctorial parasites and by insects which are not parasites, must
be borne in mind.

Thus the bed-bug, the louse, the tick and the mosquito must be
suspected as possible intermediaries and the fly and the cockroach as
possible food contaminators. Indeed, laboratory experiments have
already incriminated bed-bugs, flies and lice as potential vectors of
plague bacilli.

Experiment and observation have demonstrated, however, that above all
other parasites and insects, the flea is most likely to convey the
plague germ from rat to man, by reason of his frequent excursions from
rat-host to human-host, his taste for blood from either host, his
enormous activity and his ability to jump. After a searching inquiry
into the plague question the Indian Plague Commission came to the
conclusion that contagion plays a very minor part in the spread of the
disease, less than three per cent of human cases being so acquired.

This commission also decided that infection is conveyed from rat to
rat and from rat to man solely through the agency of fleas. While these
conclusions are probably true--and therefore of the utmost importance
from the standpoint of practical prevention--I should question whether
the other possibilities, however remote, are entirely negligible.

Seasonal conditions may affect the course of an epidemic in various
ways. (a) By effect upon flea prevalence, cold weather greatly
lessening the number of insects. (b) By effect upon rats, cold weather
and rains either driving them from overground to underground, or vice
versa, or from their principal avenues of travel in cities (the
sewers), into houses and buildings. (c) By effect upon the plague germ,
_Bacillus pestis_. The resistance of this organism is very variable,
sunlight and drying being its greatest enemies, while darkness and
dampness are its chief allies. So far as temperature is concerned, the
plague bacillus is not likely to be seriously affected by natural
temperatures, as it is not destroyed by heat below 150 degrees
Fahrenheit, nor by cold measured by zero Fahrenheit, which means that
it survives freezing, generally speaking.

It is probable that the periods of greatest seasonal prevalence of
plague will be found to correspond generally with increased prevalence
of rat fleas. During the periods when rat fleas are absent or least
prevalent, the disease is perpetuated in the form of chronic (subacute)
rat plague in a small number of the rodents. The India Plague
Commission made and verified this observation.

Cholera epidemics often abate spontaneously and this is believed to be
due in part to attenuations of virulence and changes in the cholera
organism which may be demonstrated in the laboratory. We can hardly
hope for such spontaneous abatements in plague epidemics, as it has
been found difficult to attenuate or to intensify cultures of plague
bacilli permanently in laboratory experiments with animals. If it is
true that plague epidemics are often marked by a preponderance of mild
cases in the early days and a gradual subsidence of intensity of the
cases as the epidemics wane, we probably will have to look to the
susceptibility of our patients for our explanation of this phenomenon,
rather than to variations in the virulence of the plague bacilli. If
plague bacilli continue to be distributed to susceptible people the
disease should continue with a general stability of virulence.

STABILITY OF VIRULENCE OF _B. Pestis_.--According to Strong, stability
of virulence is a marked characteristic of _B. pestis_, it having been
shown by him that it is difficult to increase the virulence of a very
virulent strain or to intensify an attenuated one in laboratory
animals, working with monkeys, rats and guinea-pigs.[2] If his
observations are correct (and they seem to correspond with the findings
of other observers), the oft-recorded occurrence of a preponderance of
mild cases of plague in the early days of an epidemic and the gradual
subsidence in intensity of the disease as the epidemic approaches its
close will have to be explained upon other grounds than those of
variability of virulence by attenuation of virulent strains alone.
While he admits that _B. pestis_ may become attenuated under certain
conditions many times during the course of an epidemic, it may also
regain its virulence, he contends, under other conditions.

  [2] "Studies in Plague Immunity," R. P. Strong, Philippines Journal
  of Science, June 1907, No. 3. Frequent reference has been made to
  these studies in the preparation of this article, for which
  acknowledgment is hereby made.

With these facts concerning the cause and the manner of extension of
plague and its menace before us, we are in position to approach the
problem of prevention intelligently, and in the case of plague
prevention is preëminently preferable to cure, as well as decidedly
more practicable.

I think we may be permitted here to sum up the problem of plague
prevention thus: Without fleas, without rats, or without human plague
cases, there can be no extension of plague, practically speaking.

Therefore the destruction of both rats and fleas, the isolation of
human plague cases, and the exclusion from them of all suctorial
parasites and insects, will provide practical security for mankind
generally.

A word concerning pneumonic plague may be permissible. This form of
plague occasionally occurs in epidemics of great fatality, as, for
example, the epidemic in Manchuria, North China, a few years ago.

The mystery of this outbreak was largely dispelled by the work of the
Americans, Strong, Teague and Barber, of the Bureau of Science of
Manila.

The occurrence of secondary pneumonia in bubonic or septicæmic plague
is rather common and it is likely that such secondary plague pneumonias
are the starting points of epidemics of pneumonic plague, _i.e._, of
cases of primary plague pneumonia, the point of infection being in the
respiratory organs and the infection being acquired through the
inspiration of plague bacilli.

The principal prerequisites seem to be an extremely moist atmosphere
under confined conditions and a low temperature; conditions most
unfavorable to evaporation and ventilation. Under these conditions the
pneumonic patient sprays plague bacilli into the air while coughing and
droplet infection follows.

It is therefore apparent that epidemic pneumonic plague is controllable
by sanitary and hygienic measures and, furthermore, that in the absence
of original cases of bubonic and septicæmic plague, with secondary
plague pneumonias which give rise to primary plague pneumonia in the
manner explained, respiratory plague in epidemic form will not occur.

There is no evidence pointing to the conveyance of respiratory plague
by insects or other carriers.




  CHAPTER III

  ITS CONTROL AND SUPPRESSION


PLAGUE PREVENTION.--At present the most promising and the most
rationally based phase of plague control is that of prevention. The
reason for this is plainly apparent. If the facts in the case are as
stated and if the conclusions of the Plague Commissioners and students
of epidemiology the world over are correct, to eradicate plague we need
only to control its carriers.

To exterminate the rat (and perhaps the marmot and ground squirrel), to
prevent the transportation of rats or of infected rat fleas in ships,
trains, clothing, merchandise and upon the bodies of men and animals
from the numerous foci or plague centres of the world to non-infected
localities, is a beautiful plan indeed.

Restricted to single communities, even where the intelligence,
patriotism, effort and wealth of the whole people are enlisted, the
undertaking is formidable, with obstacles to its execution, and
discouragement must often be expected. Extended in its application to
the whole plague-infected world it becomes an undertaking seemingly
impossible of accomplishment.

Yet we are encouraged to face the situation by a glance at what has
been accomplished. The United States, perhaps, presents the highest
examples of achievement in the cases of San Francisco and Manila. The
work in San Francisco is too recent and has been too well published to
require detailed review here. A successful campaign against rats in
1907 practically terminated an epidemic of considerable proportions
well within a year. Behind this movement, however, were the powerful
machinery of the Federal Government, money in generous amount and a
considerably aroused public, resentful of the mismanagement of the 1903
epidemic, whereby, through pure fear of financial loss to commercial
interests and by a disgraceful suppression of the truth, California was
made, permanently perhaps, one of the world's plague centres.

It has been estimated that the rat population of the world is equal to
the human population, and this estimate does not appear to be
unreasonable when one considers as indices the destruction of the
rodents in cities by the hundreds of thousands, upon single farms by
the thousand, and the wonderful procreative powers of the rat.

ECONOMIC IMPORTANCE OF RAT DESTRUCTION.--It is certain that the
economic importance of rat destruction upon grounds other than those
purely sanitary must be impressed upon the public wherever a rat
campaign is to be carried on.

The absolute inutility of the rat, its enormous destructiveness to
crops, to merchandise in warehouses and in transit, to poultry, eggs,
fruits and vegetables, to buildings and furniture, and its incendiary
habits causing annual fire losses of considerable magnitude, must be
emphasized in season and out of season. Such items as the value of the
grain consumed by a single rat per year, as estimated by the experts of
the Agricultural Department, are convincing arguments in the case. At a
daily consumption of two ounces, the ration for a full-grown rat, this
grain value varies from sixty cents per year, for wheat, to two dollars
per year, for oatmeal, for each rat subsisted. Similar data in great
variety, relating to direct and indirect losses, are available for the
purpose of making impressive the economic need for rat destruction.

Accumulated experience from various countries and cities shows plainly
that there is no single method of rat destruction to be depended upon
to the exclusion of all others and it also shows that without
governmental direction and supervision, backed by ample authority and
the ability and willingness to expend considerable money, neither
single nor combined methods will be successful. Moreover in the
countries where special effort is most needed there is often distrust
on the part of the natives, religious prejudice against the destruction
of animal life and frequently open opposition to the authorities in
their efforts to destroy rats. The same superstitions and religious
beliefs which prevent the killing of venomous snakes in India, at the
annual cost of thousands of human lives, operate against most measures
of rat destruction proposed by the Government.

EXTERMINATION METHODS.--The plans and weapons of warfare against rats
include the use of poisons; traps; starvation; rat-proof construction
of buildings, wharves, bakeries, stables, granaries, etc.; the
introduction of diseases among the rat population by bacterial viruses
and the conservation of the natural enemies of the rat, such as the
cat, the dog, the ferret, the mongoose, and certain wild animals and
birds of the woods and fields.

Among the most widely used and most effective poisons is arsenous acid
boiled with rice, or mixed with cheese or cornmeal in the form of a
paste, or placed upon sweets and fruits.

Crude phosphorus is chiefly used in similar pastes. When mixed with
glucose its inflammable properties are said to be lost. Its
inflammability is, of course, a serious obstacle to its general use.

Strychnine, owing to its bitter taste, is of little value in poisoning
rats, and when used is best combined with glucose and one per cent. of
cyanide of potassium. Soaked wheat, bread or similar food is then
treated with this mixture and placed where rats may eat it. It is said
to be eaten readily by ground squirrels with fatal effect. It is,
however, expensive and apt to be taken by domestic fowls. Most rat
poisons have the disadvantage of being dangerous to human life and must
be used with caution wherever children and ignorant native persons are
about.

TRAPPING.--Trapping has been found to be a very effective means of rat
destruction in cities. (See later pages for relative efficiency of
traps.) Rat traps are of several varieties and are constructed upon
various principles. It is sometimes desirable to catch the rats alive
and uninjured, and for this purpose barrel traps, wire cage traps and
similar devices are placed in the rat highways. These highways are
readily discovered in the cities. Considerable care must be taken to
overcome the natural caution of the rat, and this includes judgment in
the use of attractive bait, the concealing and smoking of traps after
handling and perhaps the use of some scent, such as the oil of anise,
of which rats seem to be fond. As a general rule bait should differ
from the food naturally supplied by the locality. For example, about
granaries and stables fresh animal food should be used for bait, while
about slaughter houses, meat-markets, fish-markets and similar places,
where animal offal is abundant, the rat should be tempted with
vegetable bait.

Where the circumstances will permit, and this is apt to be so for
ground-squirrel destruction, the burrows may be filled with some
asphyxiating or poisonous gas. In this manner whole families of
rodents, and their fleas as well, are destroyed.

The system is not often applicable in houses, but aboard ships it is
found most effective, the holds of ships being flooded with sulphur
dioxide, developed by burning sulphur in a special furnace provided
with a pumping and piping system for delivering the gas at distant
parts of the ship. In empty ships' holds and elsewhere the simple
burning of sulphur in open vessels effects the same results, provided
sufficient sulphur and a sufficient number of vessels be used and
further provided that the generation and confining of gas be
sufficiently prolonged. In San Francisco harbor, where for more than a
year nine vessels were disinfected per day, this method was adopted as
more effective, speedy and economical than any other system. It has the
disadvantage, in the case of laden ships, of affording some danger of
fire.

Carbon bisulphide has been extensively used in California in the
burrows of ground squirrels. Its fumes, being heavier than air,
penetrate the burrows and promptly poison or asphyxiate all living
animals and fleas. Absorbent material of some kind is saturated with
the liquid and placed in the entrance of the burrow, which is then
quickly sealed to confine the gas.

It will be seen that, in common with other methods of rat destruction,
fumigation has a limited application and a number of serious
objections. It is particularly useful aboard ships.

The method should never be employed by unskilled persons or those
unacquainted with the dangers to human life from noxious or
asphyxiating gases.

STARVING RATS.--The subjects of the starvation of rats and rat-proof
construction may be considered together.

Just as the pig in the Philippine Islands and elsewhere in the Orient
must give place as a scavenger of human excreta to modern and decent
methods of waste disposal, so must the rat, a garbage scavenger the
world over, give place to systematic garbage collection and removal,
with temporary storage of garbage in covered metal cans (rat proof).

Incidentally it may be mentioned that the effect of such measures upon
the prevalence of flies and the transmission of disease by these
insects will be very great and very beneficial to the public health.

Food must be kept from rats and rats must be kept from the food.
Perhaps the greatest resorts of rats are the places where cattle are
fed, where grain is stored and where animals are killed. Slaughter
houses, markets, grocery stores, restaurants, bakeries, wharves and
warehouses must be regulated by ordinances duly enforced. Much can be
done with screens of heavy iron wire with a mesh of less than one inch.

When concrete and metal have displaced wood and plaster as construction
materials; when plank sidewalks and refuse piles are no more and when
the catch basins of sewers have been made rat-proof the subsistence
problem for the rat will be greatly increased in difficulty, and
starvation should then begin to lessen the rat population, at least in
the cities.

RAT-PROOFING.--Municipal authorities should take up the matter of
rat-proof construction for new buildings and the rat-proofing of old
ones by approved alterations. In Manila, Hong Kong and elsewhere these
methods are receiving attention and encouraging reports are recorded,
more particularly with regard to the disappearance of plague in
districts so treated than in the disappearance of rats. This is most
important, for if the rat and his fleas are excluded from houses and
therefore from intimate association with man (an apparently feasible
matter through the rat-proof construction of buildings), protection
against human plague is in great measure accomplished.

[Illustration: RAT PROOF STRUCTURE WITH SOLID CEMENT BASE, SOLID
CONCRETE POSTS, AND UNBOARDED CEILING]

In Manila the disappearance and continued absence of human plague in
previously infected localities goes hand in hand with the introduction
of systematic rat-proofing in sections where cases of human plague
occur.

These measures were first instituted in 1906 and plague disappeared
from Manila in the same year and did not reappear until 1912.

From 1900 to 1905, $15,000 was paid in rat bounties and $325,000 was
paid for salaries, wages and expenses in rat catching, with little
appreciable effect upon the number of rats and without causing the
plague to entirely disappear. It must be admitted, however, that
practical control of the disease was attained during this period.

Rat-proofing of dwelling houses is less expensive than perpetual
wholesale rat destruction and is a perfectly effective measure against
human plague. In the suppression of the San Francisco epidemic in 1907
rat-proofing was also extensively resorted to.

The expense of rat-proofing has been generally considered as
prohibitive, but if the work be confined at first to the vicinity of
infected centres and if it be carried on subsequent to rat-destruction
in corresponding areas the expense need not always be prohibitive--at
least in American governed cities. The Manila plan of plotting the city
into "plague-infected" areas corresponding with the capture of
plague-diseased rats and systematically working within geographic
boundaries in which rat plague exists or is likely to spread, as
determined by rat captures and examinations of the rats for signs of
plague, has proved to be a good plan.

To prevent the transportation of rats in ships, trains and merchandise
is an undertaking of difficulty as well as of importance. In the case
of vessels it involves an understanding of the manner by which rats
gain ingress to the ship and the ways of preventing them from entering.
Few facts are better known, perhaps, than the fact that all ships
harbor rats, but, except to the initiated, the extent to which some
ships are infested is by no means understood. I have made voyages upon
steamships, which upon alternate trips carried forage for animals in
the holds, when the conditions were, to say the least, uncomfortable.
To have one's state-room taken possession of by rats, his clothing
carried away, or to awake with a rat in his berth are unpleasant, but
not uncommon, experiences. I personally know of a woman, prostrated
with sea-sickness, who was obliged to remain in her berth and see four
large rats disport themselves about her room, and in another case, on
the same ship, a rat jumped from the washstand into the berth of a
sleeping woman, running across her exposed face and arm.

In travelling upon small dirty steamers in the Orient I have often
slept on deck, quite as much to avoid the rats and vermin in the
state-rooms as for better ventilation. In a certain ship in which I
travelled some of the ship's officers amused themselves by shooting
rats with an air-rifle in the lower decks, quietly hiding themselves in
dimly-lighted places and shooting the rats as they crossed the lighter
spaces.

In many ships the rat population far exceeds the human population. In
San Francisco 310 rats were destroyed by a single fumigation on a
vessel of only 260 tons burden. In Bombay 1300 rats were destroyed at
one time upon a single ship and in London 1700 were secured at one
fumigation.

The ease with which rats adapt themselves to new environment is shown
by the fact that they live, when permitted to do so, in cold storage
and refrigerating rooms where they grow heavy coats of fur for
protection against the cold.

They gain ingress to ships in three principal ways: (1) By coming
overside upon gang-planks, wharf stringers, etc. (2) By passing along
the lines by which the ship is made fast to the dock, through hawse
holes, the rat being an expert rope walker. (3) By coming aboard in the
cargo.

By the latter method rats are often brought aboard by whole families,
their fleas included. Many styles of packages such as barrels, bales,
crated goods, grain in sacks and matting in rolls present the rat with
abundant opportunity to take passage and it is probably thus, as
stowaways, that rats go to sea in the largest number. Plainly, then,
the placing of rat-funnels upon all lines from ship to wharf, the use
of special fenders, the raising of gang-planks and even anchorage in
the stream will not prevent rats from getting aboard ships unless cargo
disinfection be practised before loading the vessel. The ship itself
should be fumigated every three months if possible.

Rats are doubtless carried in considerable numbers upon railway cars,
both freight and passenger.

While riding in a street car in Manila in 1908 I saw a rat run along
the window ledge, to the mingled fright and amusement of the
passengers.

The same principles which apply in the case of ships apply to cars and
trains as well. Grain cars in particular should receive especial
attention.

RAT DESTRUCTION BY THE SPREAD OF RAT DISEASES.--The proposal to destroy
rats by wholesale, by spreading epizoötic diseases among them, through
feeding them bacterial virus, has received much attention in the last
ten years. In 1900 Danysz isolated a bacillus from field mice suffering
an epidemic disease communicable to rats, and great hopes were
entertained that by means of this method decided reductions in the rat
population would result. Indeed the results in Cape Town, South Africa,
in 1901, and in Odessa, Russia, in 1902, seemed to justify the hope to
some extent and certain observers still believe the method to be
effective. Experience with the Danysz and other organisms has shown,
however, that introduced epidemic diseases do not destroy rats in
sufficient number to do much good and that nearly all the viruses
experimented with are more or less unreliable.

Most of the organisms are apparently related to the colon, typhoid or
hog-cholera groups. The mouse-typhoid bacillus (_B. typhi murium_) was
originally isolated by Loeffler in 1899. The paratyphoid bacillus and
Gärtner's _B. enteritidis_ correspond closely with the Danysz organism
and can scarcely be separated culturally. In rodents they produce
enteritis, sometimes hemorrhagic in character, and they are by no means
to be regarded as harmless for man, as originally supposed. In Japan,
in particular, serious and fatal cases of diarrhoeal disease have
followed the accidental eating by man of food treated by these
bacterial poisons.

On account of the natural resistance of rats to diseases of bacterial
causation (plague being the most notable exception to this rule), and
the clinical fact that no sufficient death rate among rodents is
produced by feeding them upon bacterial viruses, as well as on account
of the dangers to man just mentioned, this method of rat destruction is
not in favor at present.

Poisoning rats and ground squirrels by chemical poisons seems to be a
preferable method, at least equally effective and without most of the
disadvantages of uncertainty and danger which attach to the bacterial
viruses.

RAT DESTRUCTION BY DOMESTIC ANIMALS.--Concerning the utility of such
domestic animals as are natural enemies of the rat, in the warfare
against the offending rodents, there is considerable difference of
opinion, based upon varying experiences. I leave out of consideration
all but the cat and dog.

It will be found that wherever cats and dogs are well housed (indoors)
and well fed they are apt to be fat, lazy and inefficient. House cats
of this class will catch mice but will often leave rats alone, but
half-wild cats, obliged to forage for their own subsistence, are often
excellent rat-catchers. Small, active dogs, particularly of the terrier
breeds, will often keep houses practically free from rats and upon
farms they are especially valuable, particularly if the construction of
buildings is such as to permit them to get beneath the floors. The
employment of these animals will necessarily be confined to individuals
for the freeing of individual premises from rats.

A fact to be borne in mind is one already cited, viz.: that cats and
dogs sometimes harbor the same fleas as the rat. Infected rat-fleas
often leave dead rats for other animals and, all things considered,
there are many other objections to the intimate house dog and house cat
which find comfortable resting places impartially upon the beds of
adults or the cribs of babies and children.

Furthermore, my personal observations have been such as to cause
me to place small reliance in the value of the ordinary dogs and
cats found about habitations wherein the construction is favorable
to rat-harboring.

SUMMARY OF PREVENTION FOR THE COMMUNITY.--Before passing to the
consideration of other matters I would sum up the measures of
preventive treatment for the community. There must be (1) Active
warfare against rats and other plague-affected rodents and their fleas;
(2) Modified quarantine--detention or disinfection applied to persons,
goods and animals; (3) Disinfection of cargoes shipped from infected
ports; (4) Isolation of the sick and proper disposal of the dead; (5)
International notification between governments of the occurrence of
plague within their respective territories; (6) Lastly,--but we might
say first in importance,--the early recognition of the presence of
plague and the _rapid diagnosis_ in individual cases, both of which are
dependent upon laboratory workers.

All of these measures must be fostered, directed and aided in every
possible way by competent authority (national if possible), whose
officers must be men of great moral courage and of unselfish purpose.
Behind all of this must be generous financial support.

I can best emphasize the importance of the observance of the principles
I have laid down by introducing personal experiences in the conduct of
the antiplague campaign in Manila during 1912, 1913 and 1914.

I therefore present here the following account of the epidemic, the
campaign of suppression and the various lessons learned.

It should not be difficult for the reader to make applications of the
principles already set forth and to confirm by the reported facts the
assertion that methods based upon these principles are effective.

If repetitions of any of the foregoing principles occur it is hoped
that, when taken in connection with concrete applications cited, they
will not appear as redundant.

THE MANILA EPIDEMIC OF 1912 TO 1914.--The chronologic facts concerning
the development and extension of plague in Manila in 1912, 1913 and
1914 are as follows:

The disease made its reappearance in Manila, after an absence of six
years for the human disease and five years for rodent plague, two
verified human cases having been recorded in June, 1912.

Preceding the appearance of the first Manila cases there occurred upon
incoming ships a number of cases of plague during the Spring of 1912,
detected at quarantine. Although there is no conclusive evidence which
connects these imported cases, originating in Hong Kong, China, with
the epidemic which broke out in Manila a few months later, the fact of
their occurrence and recognition is interesting enough for us to
consider before taking up the study of the Manila epidemic. Concerning
these imported cases Dr. Victor G. Heiser, then Director of Health for
the Philippines, wrote as follows in the _Philippine Journal of
Science_, in February, 1914.

    UNUSUAL CHARACTER OF PLAGUE AT QUARANTINE.--It is perhaps
    worthy of note that, prior to the appearance of plague in
    Manila a number of cases of the disease were found on incoming
    steamers. For instance, on April 6, 1912, a death was reported
    on the steamship _Zafiro_, which had arrived the day previous
    from Hongkong and had been in the harbor for twenty-four hours
    at the time of the death. At the medical inspection of the
    vessel, which was made the day previous, no illness was
    detected. An investigation showed that the victim had been on
    deck on the night of April 5, 1912, in apparently good health.
    The next morning, at 6 o'clock, he was found dead in his
    bunk. The necropsy and subsequent biological findings
    reported by Dr. R. P. Strong of the Bureau of Science showed
    that death was due to pneumonic plague.

    On April 7, 1912, the steamer _Loongsang_ arrived in Manila
    from Hongkong, and the captain reported that a death had
    occurred the day previous in a Chinese member of the crew.
    Upon investigation of this case, the captain stated that the
    man was apparently in good health, but that while hauling on
    a rope he fell over in an apparent faint and was placed in a
    chair and in the course of a few hours expired. The necropsy
    and animal inoculations showed that he had died of plague and
    probably of the pneumonic variety.

    Beginning April 7, 1912, the temperature of all members of
    the crew and of the passengers that arrived in vessels from
    foreign ports was taken with a view to detecting any possible
    cases of plague.

    On the arrival of the steamship _Taisang_ from Amoy at the
    Mariveles Quarantine Station at about 6.30 A.M. on April 30,
    1912, the entire personnel was carefully examined and found
    free from sickness of a suspicious nature and from elevations
    of temperature. Seventy-three persons were detained to serve
    a quarantine detention of seven days. On the evening of April
    30, a Chinese passenger, aged fifty-one years, was found to
    have a temperature of 39° C. with a pulse of 100. He was
    placed in the hospital, but protested vehemently that he was
    not sick. He was carefully watched from the first; there was
    a slight cough; physical examination of the chest revealed a
    few râles; smears made of the sputum and stained for plague
    bacilli were negative. On the fifth day, the fever still
    persisted, but the patient stated that he did not feel ill
    and demanded to be released from the hospital. On this day,
    the expectoration was blood-stained, but no suspicious
    organisms could be found in the smears nor could any physical
    signs of pneumonia be detected. Furthermore, there were no
    palpable glands. On the morning of the seventh day, the
    temperature and pulse dropped and the general condition was
    distinctly worse. The patient now admitted that he felt ill.
    Several hours later, he flinched when pressure was made in
    the right axilla. Lymphatic enlargement was now made out, and
    by the evening of the seventh day the bubo in the axilla had
    increased markedly in size, the swelling approximating 3 by 7
    centimetres. Glands now became palpable in other portions of
    the body, particularly in the cervical region, and a few
    hours later there were inguinal and femoral buboes. The
    patient became rapidly worse, and died at 7 o'clock on the
    morning of the eighth day of his illness. At the necropsy,
    the glands of the right axilla and those of the right side of
    the neck were found enlarged; the other lymphatic glands were
    also enlarged, but to a lesser degree. There was
    consolidation of the lower lobe of the right lung, and the
    spleen was about twice its normal size. In brief, the
    necropsy findings of a typical case of septicæmic plague were
    present. Smears from the spleen and the right axillary gland
    showed immense numbers of bipolar-staining organisms.
    Cultures made from fresh pieces of tissues and later
    inoculated into animals gave positive results for plague.

BEGINNING OF THE MANILA EPIDEMIC.--Proceeding with the Manila epidemic
inaugurated with the two cases referred to as recorded in June, 1912,
we find that the total number of cases recorded from the time of the
outbreak in 1912 until the last case in 1914 was 90. (This includes
none of the imported cases from China which developed en route to
Manila from Chinese ports.)

Of these 90 human cases, 76 were fatal and autopsies were performed in
all instances. Fourteen persons recovered. The number of cases of
animal plague up to July, 1914, was 53. This refers only to
laboratory-proven cases of rat plague. As a matter of fact, hundreds of
dead rats, almost certainly plague rats, were found in the course of
rat-proofing operations.

Although the period covered by this epidemic approximates two years, it
must not be supposed that the progress and extension of the epidemic
was an uninterrupted or unobstructed one.

On the contrary, such extension as occurred was made in spite of the
most active suppressive effort, and it is believed that this effort
brought about a creditable result, as indicated by the accompanying
record.

When one considers the favorable conditions for the natural spread of
plague, both in Manila and throughout the Philippine Islands, and
realizes the interposed difficulties and obstructions, natural and
unnatural, geographic, human and domestic, which confront us at every
turn of the path to correction, removal and reformation, our success in
checking the spread of plague appears as a real achievement, especially
when contrasted with the results of effort during the same period in a
British city of similar size but a few days' sail from Manila, where
the cases were numbered by thousands and where the infection still
persists.

FIRST MANILA CASES.--The first case of plague (June 12, 1912) occurred
in a resident of Tondo, 920 Calle Antonio Rivera, and in the light of
subsequent developments it may perhaps be grouped with the October
cases traced to the Manila Railway Company's freight station and yard,
as 920 Calle Antonio Rivera is but a stone's throw from the Manila
Railway property. The connection, however, is not clear, and, on the
other hand, it is not wholly inconceivable that the rat epidemic and
human plague cases at the railway station in October may have been
secondary to this June case. Such speculation is fruitless, however, so
far as establishing facts is concerned.

The second case of human plague occurred 13 days later, June 25, in a
resident of a district somewhat removed from the first case, but in
the same general section of the city.

Then came a lull of more than a month, until August 4, during which
time no case of plague occurred; or at least none was reported.

August brought forth five cases on the fourth, eighth, fifteenth, and
twenty-first days of the month, in residents of the Quiapo and Binondo
districts.

These cases were unrelated to the preceding ones so far as could be
ascertained.

Another lull of a month, until September 24, now occurred without a
reported case of human plague. During this time, however, the first
cases of rat plague were discovered, one on August 30 and two on
September 6, all of them in the Quiapo district.

From this time (September 24) on, however, human cases occurred at
intervals of a few days until Christmas Day, 1912, the longest
plague-free period being one week; the number of cases by calendar
months being distributed as follows: September, 3 cases; October, 22
cases; November, 12 cases; and December, 6 cases.

GEOGRAPHIC GROUPING.--Not until October 21 was there any apparent
geographic grouping of cases indicating a well localized infected
centre. Upon this date there began the outbreak of plague among the
employees of the Manila Railway Company, laborers at the freight
station and yard of the company. This freight station and yard is
located between Calle Azcarraga, Calle Dagupan and Calle Antonio
Rivera. The outbreak totalled 17 human cases, all fatal, and extended
into November. Indeed, the last case traced to this focus occurred on
December 7, 1912.

During the present epidemic of plague in Manila this focus was the only
one to which a larger number of cases than five could be traced, and in
all the other instances where multiple cases were traced to an infected
centre, the foci were all single buildings.

The locations giving rise to multiple infections and the number of
cases of plague developing at each address, with months of incidence,
are as follows: Calle San Fernando (804-814), November, 1912, 4 cases;
Calle Teodoro Alonzo (518), November and December, 1912, 2 cases; Calle
Cabildo (Intramuros), November and December, 1912, 2 cases; Calle
Comercio (1028), February, 1913, 2 cases; Calle Sande (1364), April,
1913, 5 cases; Calle Juan Luna (1226), May, 1913, 2 cases.

Returning to the Manila Railway outbreak, it is necessary to state
that a well-defined epidemic among rats preceded this outbreak,
resulting in the death of a large number of rodents (undoubtedly from
rat plague). This epidemic was not reported by the railroad company
until the outbreak of human plague had begun. It was then too late to
identify plague in the dead and mummified rats found under floors,
platforms and elsewhere, but the fact that large numbers of rats had
recently died here was established by the unanimous testimony of the
employees at the freight station and the finding of rat cadavers.

As stated, the human outbreak here occurred upon October 21, and
fifteen cases developed within 3 days.

This indicates an extensive desertion of fleas from plague rat cadavers
and an attack upon human beings, after a fasting period, on the part of
the fleas, of several days. The human outbreak at the station and the
death of a large number of rats at the same place, just previous,
correspond to a nicety and establish to a moral certainty the
connection necessary to explain the epidemic.

After the railway epidemic of human plague, cases continued to occur
through November and December, without apparent relation to each other,
except in the following instances, which have already been mentioned:

Four cases under one roof on Calle San Fernando (November 12, 13, 16
and 22); 2 cases in one house on Calle Teodoro Alonzo (November 26 and
December 2); and 2 cases in the same house on Calle Cabildo
(Intramuros), November 23 and December 11.

These multiple cases will be referred to elsewhere.

The other cases during October, November and December were apparently
sporadic and unrelated, either to the other human cases or to the few
scattering cases of rat plague discovered from time to time. Without
doubt, however, all were actually related to preceding cases of rat
plague, _i.e._, to undiscovered rat cadavers, dead from plague and
deserted by infected fleas.

In the following plague houses (see list of cases) dead rats were
actually found, although the advanced degree of desiccation and
mummification defeated the biologic determination of the cause of
death: 518 Calle Teodoro Alonzo; 973 Calle Azcarraga; 282 Estero de
Binondo.

In other plague houses the recent finding of dead rats was alleged by
the occupants, but rather too indefinitely to record positively.

A study of the maps and lists showing the localities in which cases of
rat plague had been found up to this time (December 26, 1912), in
connection with the location of plague houses, was much less suggestive
than a similar study of the lists and maps covering the cases of 1913.

However, the existence of concurrent rat plague and human plague, in
corresponding sections of Manila, had been well established already by
bacteriologic studies of captured rats, made at the Bureau of Science.

Of nearly equal weight was the observation concerning the two
epidemics, rat and human, at the Railway Station, which I have already
described.

The year 1912 closed, then, with a recorded total of 50 human cases and
7 verified cases of rat plague.

January, 1913, saw but a single case of human plague. This occurred on
January 24, just a month from the last previous case, that of Christmas
Day. During this month no case of rat plague was reported.

In February, 3 human cases occurred and in March, 4 cases were
recorded.

Early in March, 1913, cases of rat plague began to occur in the Tondo
district in a section lying between Manila Bay and the Estero de la
Reina and extending northward from Calle Moriones. This was a new
district for rat plague and as the cases increased in number we were
able to foresee and predict the appearance of human plague in the same
district, which in point of congestion of population, poverty of its
residents and in the matter of dilapidation of its light material
houses and shacks, is about the worst locality in Manila.

From March 22 to September 20, 1913, all the cases of human plague, 11
in number, occurred in the midst of this district. During the same
period 25 cases of rat plague were reported from the same section, and
a glance at a map of this part of Tondo instantly shows the
relationship existing here between rat plague and human plague.

This relationship is additionally emphasized by referring to the
memoranda concerning certain overcrowded houses, in the midst of the
rat plague district, where multiple human cases occurred. (See
memoranda in re 1226 Calle Juan Luna and 1364 Calle Sande.)

[Illustration: CLEANING AND RAT PROOFING IN BASEMENT OF 1226 CALLE JUAN
LUNA IN WHICH TWO CASES OF PLAGUE OCCURRED. RAT CADAVERS FOUND UNDER
BROKEN FLOORS (MANILA PLAGUE CAMPAIGN)]

The human cases in April were 5 in number, all originating in the same
house, and the May cases numbered 4, two of which occurred in the same
house.

It may be explained, in passing, that two cases of human plague,
discovered in Malolos, 25 miles from Manila, on March 23 and March 26,
respectively, were definitely traced to the same house in Manila,
number 12 Calle Aguila, Tondo, both patients having lived in the
basement of this house until within 48 hours of the development of the
disease. These persons were unrelated and were two of a large number of
people who lived in a tenement at this address. Both patients were
detected, while still alive, in Malolos, where they were living in
different and widely separated houses. One of the patients died in
Malolos but the other one was brought to Manila by train and died at
San Lazaro Hospital. Fortunately no infection was transferred to
Malolos by these two persons. In this connection it is interesting to
note that no other cases have been reported from outside of Manila,
except the small outbreak in Iloilo in the southern islands, where the
antiplague work was successfully directed by Dr. Carroll Fox.
Concerning this outbreak, Dr. Heiser, then Director of Health for the
Philippines, writes as follows (_Philippine Journal of Science_,
February, 1914):

    PLAGUE IN ILOILO.--In Iloilo, a case suspicious of plague was
    reported on July 5, 1912, and this diagnosis was subsequently
    confirmed by the laboratory. It occurred in the person of a
    Chinaman who was reported to have come from Bais, Oriental
    Negros, but later investigation showed that he had been a
    resident of Iloilo at least since February, 1912. The next
    case was reported August 18, and the last case, September 17,
    1912. There was a total of 9 cases. All of the cases were
    confined to two houses. During July, August, September, and
    October, 1146 rats were caught in the vicinity of the houses
    in which the human cases had occurred, along the water front,
    and in the places which were regarded as suspicious, but in
    not a single instance was an infected rat found.

DIRECTED TO TAKE CHARGE OF PLAGUE SUPPRESSIVE MEASURES.--Upon my
arrival in Manila from the United States, on October 23, 1912, I
received orders from the Director of Health to take charge of all
plague suppressive measures in Manila and I remained in charge of this
work continuously until July 11, 1914.

PLAGUE FIGHTING ORGANIZATION.--The plague fighting organization was
composed of three American Sanitary Inspectors and from ten to fifteen
native Assistant Sanitary Inspectors of the Bureau of Health, rat
catchers and laborers of the Bureau and laborers of the City of Manila
supplied by the Department of Sanitation and Transportation. The
combined force varied in numerical strength from 100 to 150 men and was
usually divided into three parties, distributed in various parts of the
city according to the local indications and needs from time to time.

After the invasion of Tondo by rat plague we made special effort to
rat-proof the light material houses of that section, in the course of
our cleaning operations, by the closure of the open ends of bamboo
timbers with cement and with tin cans, in the manner shown in
photographs herewith. In addition to this, special attention was given
to the repair of broken cement work, and hundreds of Bureau of Health
orders, verbal and written, were issued to owners, at my request, in
the rat plague districts.

The number of houses in which bamboo timbers were closed by cement or
tin exceeded a thousand.

In addition to these means, the very important matter of depopulating
the insanitary basements of the light material houses in squares where
plague has occurred was given attention, with the result that hundreds
of families were moved from these insanitary and dangerous ground-floor
rooms to quarters well above ground and measurably removed from the
rats, which roam over the ground from house to house, foraging for food
under kitchens and in ground-floor storerooms, tiendas and eating
places. The fish packing factories afford them abundant food and a
number of cases of plague have occurred adjacent to these fish-drying
establishments.

RAT-PROOFING AND RAT DESTRUCTION.--While it is frankly admitted that
rats may not be completely exterminated by poisoning and trapping, the
statement, so frequently repeated of late, that destructive measures
really increase their number, is unwarranted and unsustained by facts,
at least in Manila. It seems to be the common practice for disbelievers
in trapping and poisoning to array the methods of rat-proofing and rat
destruction as alternative policies, whereas everyone practically
familiar with the work in such cities as Manila--or even in the United
States--knows that there is often no choice permitted. Rat-proofing is
highly desirable, permanent in its results, and in every respect the
"method of election." On the other hand, it is entirely inapplicable at
certain times and in certain localities where poverty, lack of interest
of property owners, and ofttimes lack of interest and of money on the
part of municipalities, absolutely preclude its immediate application.
It is therefore unfortunate that the statement, that rat poisoning and
trapping are ineffective, either in controlling plague or in reducing
the numbers of rats, is circulated. It may be shown easily, by the
daily records, that within a few weeks after extensive rat poisoning
and trapping (with the breaking up of nests) is pursued in a given
locality, the rat catch drops in the most decided manner.

Individual premises may be practically cleared of rats by continued
intelligent rat catching and poisoning, and while the normal rat
birth-rate may keep pace with the normal rat death-rate it will not
keep pace with the normal death-rate plus the poisoning and trapping
death-rate in any given locality, provided that the poisoning and
trapping, with the destruction of nests, be intelligently and
continuously carried out.

Rat-proofing and rat destruction, then, should not be contrasted as
alternative procedures or policies. Both are valuable and each has a
proper place. In communities non-infected with plague and unexposed to
infection it will probably be found that rat-proofing, carried out in
connection with the repairs of old buildings and the erection of new
ones, will meet the requirements. On the other hand, in cities exposed
to plague infection or already infected, rat destruction is bound to be
necessary for years to come.

In emergency, the removal of people from intimate relationship with
rats (so far as is possible), as practised recently in Tondo district,
Manila, will often have to take the place of rat-proofing; and rat
destruction and expulsion will be found, in the last analysis, to be
the methods upon which success or failure in fighting plague during
epidemic time will depend.

In this connection I quote correspondence which passed between the
Director of Health and myself in 1913.

    Upon March 22, 1913, I directed the following letter to the
    Director of Health:

    SIR: I have the honor to state that Estaban Masibac, aged
    twenty-two, laborer, who died at 140 Perla of bubonic plague,
    slept upon the ground floor of this house upon a bamboo bed.
    All these basement dwellers in this district now infected
    with rat plague are in considerable danger.

    The roving rats which wander over these ground surfaces from
    house to house come into pretty close contact with these
    basement dwellers, and it would appear that they visit the
    upper stories of the houses rather infrequently, unless food
    is stored there. Upon the ground they forage upon the food
    dropped there by the residents of the houses.

    I would like to have authority to order the vacation of these
    basement rooms which are almost invariably unfit for human
    habitations.

    I look upon this measure as an important one at this
    threatening time and believe it should be enforced in every
    square or block where plague rats have recently been found.
    If this authority is granted it will be used judiciously.

      Very respectfully,
      [Signed] T. W. JACKSON,
      _Medical Inspector in Charge of Plague Suppression_.

Upon March 24 I received the following letter of authorization:

    SIR: Confirming my verbal instructions of yesterday I have to
    request that, in accordance with the recommendation contained
    in your letter of March 22, that on account of the danger of
    the spread of plague in the district in which plague has
    appeared extensively, the basement dwellers in blocks, or
    squares, in which plague has been found, should be ordered to
    vacate.

      Very respectfully,
      [Signed] VICTOR G. HEISER,
      _Director of Health_.

Upon November 26, 1912, five dead rats were reported from the U. S.
Army Commissary Warehouses on the Pasig River near the Malecon. They
were found dead by workmen there and were thrown into the river by the
finders and thus, unfortunately, examination for plague was prevented.

Upon November 27, a cat, known to have caught and eaten rats recently
at the same place, was reported to be sick. I took the cat to the
Bureau of Science where she was observed until she died, three days
later.

At autopsy, typical bubonic plague (cervical) was disclosed, and
several guinea-pigs inoculated from the spleen and bubo died from the
same disease. A guinea-pig, inoculated from a swab introduced into the
cat's rectum, also died from plague (see report of Dr. Schöbl).

Four kittens, recently born of this plague cat, were observed for two
weeks but showed no sign of the disease.

Subsequently about 80 rats were caught at these warehouses and in the
vicinity, but none of them showed post-mortem signs of plague. The
Medical Department, U. S. Army, then took up the matter of rat catching
on all military reservations in Manila and in all buildings thereon,
but no more cases of animal plague were discovered.

FLEAS AND THEIR HABITS.--In "Observations Upon the Bionomics of Fleas
Bearing Upon the Epidemiology of Plague in Eastern Java," by N. H.
Swellengrebel, Ph.D., published by the government at Batavia, Dutch
India, in 1913, some interesting facts, developed by study and
experimentation, are presented. Some of these facts have a bearing on
the plague problem in the Philippines, for it should be borne in mind
that certain climatic similarities and racial similarities pertain
commonly to the Javanese and Filipinos and their respective countries.

While we are not prepared at present to make general application of the
Javanese findings to the Philippine Islands, for lack of parallel or
confirmatory studies in the Philippines, we may state some of the
conclusions of the Java workers with propriety, and we may also point
out similarities in the construction of certain Filipino and Javanese
habitations in their relation to rat harboring.

Swellengrebel, in Java, noted the number of fleas per rat, dealing with
_Xenopsylla cheopis_ (the commonest rat flea in Java) almost
exclusively. This flea, it will be remembered, is also the common rat
flea of India, the Philippines, Australia, Italy, Brazil and tropical
countries generally, being variously known as _Loemopsylla cheopis_,
_Pulex pallidus_, _P. brasiliensis_, _P. philippinensis_, and (in
Italy) _P. murinus_.

It would not be unreasonable, therefore, to expect to find at least
some of his observations applicable to the Philippine Islands.

Swellengrebel failed to find _Ctenocephalus canis_ (dog flea), _C.
felis_ (cat flea) and _Ceratophyllus fasciatas_ (the common rat flea of
the United States and Europe) upon Javanese rats. In attempting to
determine the normal flea census he found that field rats, and field
rats caught indoors, as well, generally carry fewer fleas than house
rats and that the number of fleas per house rat varies in different
districts from .02 per rat to 2.3 or 4 per rat and that this variation
is not invariably constant with the presence or absence of rat plague.
Concerning the question whether or not a high flea census may indicate
rat plague, Swellengrebel offers the reasonable opinion that there is
little doubt that plague in rats increases the number of fleas per rat
above normal and that, consequently, a sudden or marked increase in
the number of fleas per rat, without a known normal cause, indicates
increased rat mortality and probably rat plague.

As to the influence of temperature and humidity on the hatching of
larvæ, he concludes from experimentation that the duration of
development of the egg varies under various hygrometric conditions, the
general rule being, "the lower the humidity the longer the development
period."

As to the influences of temperature and humidity upon the transition of
larva to imago he finds that if humidity diminishes, a smaller number
of larvæ reach the adult stage; and also that a saturated humidity (in
artificial cultures), causing condensation of water in the substratum,
is very fatal to larvæ. He offers the thought that this, perhaps,
explains why only small numbers of fleas are found on field rats which
live in holes in rice fields which are necessarily damp, especially in
the rainy season.

His experiments to determine the duration of life of fasting fleas were
made with laboratory-bred fleas which had never fed on blood and with
fleas which had already sucked blood.

The duration of life was variable, but of those fleas already fed with
blood three-quarters (¾) perished within 10 days and the remainder
lived from ten to twenty days, only one-tenth, however, surviving for
13 days, if moist conditions were maintained. High temperature was
determined to be an unfavorable condition.

If from these findings one should attempt to predicate or predict the
extension of plague in house rats--based on flea prevalence--and this
with relation to climatic conditions, we should be led to the
conclusion that the rainy season, with its greater humidity, would be
quite the most favorable time of year for rat plague extension in
Manila and, upon the contrary, that the hot dry season through its
unfavorable influence upon flea breeding would be the least favorable
season for rat plague in Manila.

The hot months of 1913 did not bear out this reasoning, however, for
during these months rat plague was at its height.

That increased prevalence of human plague has not gone hand in hand
with increased prevalence of rat plague in Manila, may be explained, I
feel sure, by the activity of our efforts to destroy rats and to remove
the people from close relationship with them.

Another factor of possible explanation of the greatest prevalence of
human plague in Manila during the late rainy season of 1912 (October),
is the fact that rats are certainly driven above ground into houses and
therefore into closer relationship with man by heavy rainfall and the
consequent flooding of their subterranean homes.

It appears, therefore, that the seasonal explanation of greater plague
prevalence, rat or human, is susceptible of several interpretations and
I feel sure that in countries like the Philippines seasonal variations
in heat do not suffice to rid the rats of fleas during any months of
the year. If, then, conditions of rainfall serve to drive the rats
above ground and indoors during certain months, it would be reasonable
to expect more human plague from closer relationship of rat and
man,--provided that no special measures were carried out.

Such, however, is not invariably the rule, if statistical studies are
to be taken as evidence, and so we are reminded that generalizations
for countries of different climates and seasons are not wholly
reliable.

Rat breeding, as well as flea breeding, is influenced by climate, but
as the reproductive activity of the rat is most retarded by cold
weather--an unknown condition in the Philippines--and as the climate
of Manila is fairly equable so far as heat and cold are concerned, the
only factor which needs to be considered is that of rainfall. As
already mentioned, rainfall doubtless serves to drive rats above ground
and so, to a certain extent, away from their nests in burrows and
underground.

Their well-known adaptability to changing conditions, however, permits
them to house themselves comfortably above ground when driven out of
these burrows and holes.

JAVAN OBSERVATIONS.--The following conclusions were reached by Dr.
J. J. van Loghem in a report upon "Some Epidemiological Facts
Concerning the Plague in Java" (published by Civil Medical Service in
Netherlands India-Batavia, 1912):

    1. In plague-infected villages, as distinguished from
    plague-free villages, there exists a considerable mortality
    among house rats.

    2. Rats in plague houses and plague quarters have repeatedly
    died from plague. Fresh plague rats appear more often in the
    houses adjoining plague houses than in the houses themselves.

    3. The house rat exists even in the immediate vicinity of
    man.

    4. The ordinary parasite of the house rat is _Xenopsylla
    cheopis_, which experimentally is known to choose man as a
    host when starving.

    5. Fresh plague rats have repeatedly been found to harbor a
    great number of fleas.

    6. Virulent plague bacilli have been demonstrated in the
    stomachs of such fleas.

Concerning the prevention of plague by improving the native dwellings,
the same observer says: "Obviously an increase in the distance between
man and rat becomes an important factor as a means of preventing the
disease."

CONDITIONS OF MANILA HABITATIONS FAVORABLE TO RATS AND PLAGUE.--As
shown by our own experiences in Manila, this end, the separation of
rats and men, is not obtainable by destruction of rats by poison, traps
and rat catchers. Rats dying of plague in their nests furnish the
greatest danger to man. The plague problem, therefore, where rats are
already infected, from the stand-point of direct prophylaxis, is the
problem of dwellings. It was from this stand-point that we attacked the
problem in the Tondo (Manila) campaign in 1913.

MANILA VERIFICATION OF JAVAN OBSERVATIONS.--Having in mind the
experiences of the plague investigators in Java during the recent
epidemics there (1911-1912), we sought, from the time the Manila
outbreak occurred, to verify some of the findings of the Java
investigators, at least with special reference to the nesting of rats
in close proximity to human beings and the consequent exposure of these
persons to the infected fleas which desert the rats dying from plague
in these nests.

Not until rat plague invaded the special district of Tondo, in Manila,
in March, 1913, did the opportunity present itself. Theretofore the
Manila cases had generally appeared in houses of the so-called "hard
material districts," where house construction is entirely unlike that
with which the Java workers dealt. With the invasion of Tondo, however,
the Java and Manila conditions became similar. I quote the descriptions
of Javanese house construction from the report of Dr. J. J. Van Loghem,
"Some epidemiological facts concerning the plague in Java," Batavia,
1912.

THE JAVAN VILLAGE HOUSE.--In substance, he says that the Java village
house, as a general type, is a one-storied structure with its roof
sloping to the front and back, _i.e._, with its ridge parallel with the
front and back aspects of the building. It is not elevated above the
ground by supports or palisades and has no separate floor, the earth
serving as the floor.

The outer frame is of strong bamboo poles and the inner frame is also
constructed of bamboo. These bamboo timbers are perforated at various
points to permit of framing with other pieces of bamboo and for the
entrance of pegs, etc.

The roofs of these houses are often made of tiles, but at times the
familiar thatched roof is seen. In both cases the supports or rafters
are bamboo poles. The principal piece of furniture is the "bale bale,"
or bedstead, usually made of bamboo, except in the houses of the
well-to-do. Small storerooms are often located in the houses, and
stables are sometimes built against them. In many cases the family
provisions are kept in the house and the cattle are housed here as
well.

MANILA LIGHT MATERIAL HOUSES.--If, now, we turn our attention to the
average Tondo (Manila) light material house it will be apparent that
the description given for the Java village house fairly describes the
Tondo house, except that the Philippine house is commonly elevated 2
metres or more above the ground upon bamboo supports (see photographs).
The basement is usually enclosed in a manner similar to the principal
room of the Java house and the basement room may fairly be compared,
structurally and in the matter of its floor, with the one-story Java
house. In the Manila house, however, the floor of the upper room takes
the place of the roof of the Java house and like it is supported by
bamboo timbers.

Here, then, in our enclosed basement story, we have a practical replica
of the one-storied Java house.

Here, also, the principal piece of furniture is often a bamboo bed,
practically identical with the Java "bale bale," if we may judge from
photographs.

In the Java houses the favorite nesting places for rats were found to
be the interiors of horizontal bamboo pieces of the roof, house frame
and bedstead.

The rat usually gains entrance by gnawing through the natural
partitions between the bamboo sections near the outer end of the pole.
Our Manila photographs show both the natural open ends of such timbers
and the rat-gnawed perforations in the partitions.

In Java, rats also nest in the thatched roofs, as they occasionally do
in the Philippines.

NEST MATERIALS.--The materials utilized for nests by rats in Manila
and Java seem to be identical also. Straw, dry leaves and pieces of
cotton are mentioned in the Java reports. The same materials and
additional ones will be found mentioned in our reports upon nests.

[Illustration: BAMBOO HOUSE SUPPORTS NOT SEALED WITH CEMENT. NOTE HOLES
GNAWED IN BAMBOO ENDS. RATS FREQUENTLY MAKE NESTS IN THESE HOLLOW
BAMBOO RAFTERS.]

The presence of food was also noted in the bamboo nests in Java and we
often find articles of food in our Manila nests.

Dr. Korn, P. H. Service, and the writer (T. W. J.) investigated a good
many of these bamboo house-timbers and we not only found such evidences
of rats as food, rat fæces and nest materials, but in one case a rat
was actually driven out of a bamboo nest by introducing a long thin
strip of wood. The evidence of similar conditions then is complete.

We also duplicated the experiences of the Java workers in finding dead
rats inside of the bamboo house timbers in close proximity to patients
sick (or dead) with plague (see memoranda in the case of Esteban
Masabik, of 140 Calle Perla, March 22, 1913).

Very extensive rat destruction and cleaning operations, covering a
large portion of the city of Manila and including all sections where
cases of rat plague or human plague developed, were undertaken and
this work was carried on without interruption for about two (2) years.
City laborers to the number of 60 to 150 were used and the work was
supervised by Sanitary Inspectors Brantigan and Searcy, of the Bureau
of Health. During a part of the time a flying column of 50 men, under
Sanitary Inspector Hunniecutt, was detached from the main party and
employed at placing rat poison.

The total amount of accumulated dirt removed from houses and yards
approximated 5250 tons (for 17 months ending November 1, 1913).

Without doubt this general cleaning campaign and the removal of this
enormous accumulation of dirt and rubbish was of great value as an
antiplague measure.

The rat catch will always be found to depend upon several factors,
viz.: the number of persons employed; the number of traps and portions
of poison placed; the location of the operations and the length of time
a given locality is trapped, poisoned and cleaned. The variety of baits
and poisons will also affect the results.

In addition to these factors certain others are found to operate in
reducing the rat catch, as, for example, weather conditions and the
occurrence of Sundays, holidays and the days just preceding and
following holidays.

Upon rainy days and the days just mentioned the rat catch almost
invariably falls off.

From statistics collected by me in connection with this work, Dr. V. G.
Heiser, then Director of Health for the Philippine Islands, published
the following memorandum in 1914. As it is a correct transcript of my
records I introduce it here in its entirety.

    COMPARATIVE STATISTICS IN RAT-CATCHING METHODS.[3]--With a
    view to ascertaining which type of rat trap was most effective
    and also the average number of rats that are caught by a given
    number of poisoned baits that are set out, statistics were
    kept during the antirat campaign in Manila. The ratio
    maintained in catching rats with two types of traps is
    indicated in the following table, a perusal of which will show
    that for the three months ended June 30, 1913, there were
    120,565 spring or snap traps set and that for every 100 of
    this type of trap set there were caught 6.9 rats. During the
    same period there were 47,075 wire cage traps set; the total
    number of rats caught was 339; which gives 0.72 rat caught for
    each hundred traps set. For the quarter ended September 30,
    130,627 spring or snap traps were set and 9,753 rats were
    caught, which gives 7.47 for each 100 traps set. During this
    period 40,621 wire cage traps were set and 395 rats were
    caught, which gives 0.97 rat caught for each 100 wire cage
    traps set.

  [3] Reprint from the Public Health Reports, Vol. 29, No. 6, February
  6, 1914.

 ===================+==========================+=========================
                    |  Quarter ended June 30   | Quarter ended Sept. 30
                    +---------+---------+------+---------+---------+-----
     Kind of trap   |         | Number  |      |         | Number  |
      or poison     |  Number | of rats | Per  |  Number | of rats | Per
                    |   set   |caught or|cent. |   set   |caught or|cent.
                    |         |poisoned |      |         |poisoned |
 -------------------+---------+---------+------+---------+---------+-----
 Spring or snare    |         |         |      |         |         |
   traps            | 120,565 |   8,377 | 6.9  | 130,627 |   7,753 | 7.47
 Wire cage traps    |  47,075 |     339 |  .72 |  40,621 |     395 |  .97
 Poison bacon, rice,|         |         |      |         |         |
   or coconuts      | 166,237 |   1,216 |  .731| 177,309 |     216 |  .12
 -------------------+---------+---------+------+-----+---+---------+-----
                                                     | Quarter ended--
                                                     +---------+---------
                                                     | June 30 | Sept. 30
 ----------------------------------------------------+---------+---------
 Number of rats:                                     |         |
   Caught by dogs                                    |     160 |       5
   Killed with clubs and other weapons               |   2,889 |   3,818
   Found dead from other causes                      |     316 |     297
 ----------------------------------------------------+---------+---------

    No accurate record was kept of the number of each kind of rat
    bait set. Only the total of all was recorded. Bacon or coconut
    with strychnine and rice with arsenic were used. For instance,
    for the quarter ended June 30, 1913, there were 166,237 poison
    baits set in new territory and the rats found poisoned average
    for each 100 baits 0.72. During the next quarter there were
    177,309 baits set in territory that had been worked over, and
    only 216 rats, or 0.12 rat per 100 baits, were killed. From
    the foregoing it appears that the rat poison ranks lowest in
    efficiency but perhaps highest in economy. In view of the
    fact that the original cost of the cage trap is many times
    more than that of the spring trap, and the cost of maintenance
    is very high, it will be apparent that the spring trap is by
    far the more economical as well as more effective of the two.

Generally speaking, however, the number of rat catchers engaged and the
location of their operations has the largest influence upon the total
catch of rats. For the fiscal year July 1, 1912, to June 30, 1913,
inclusive, the total catch was 55,101 rats (Manila only); to December
1, 1913, 79,676.

The most natural explanation of the general correspondence between the
highest rat catch and the highest incidence of human plague would be
upon grounds of greater activity in rat catching effort at times of
greatest plague prevalence, but from the inauguration of general
systematic rat catching there was no cessation of effort, even during
the abatement of plague, and in consequence this explanation does not
apply strictly.

It is true, however, that whenever plague occurred in districts
theretofore free from the disease, rat catching was pushed vigorously
in the surrounding localities.

Making due allowance for all the factors mentioned I am impressed with
the probability, amounting almost to certainty, that the catch of more
than 79,676 rats definitely affected and checked the spread of plague
in Manila in 1913; and I am of the opinion that systematic and
wholesale rat catching, carried out in the most economical manner
possible, should be persisted in indefinitely, at least until plague
disappears, wherever the disease occurs.

Efforts to prevent the spread of plague to the provinces of Luzon, by
way of the railways, were successful and the present measures employed,
freight inspection, the fumigation of packages suspected or likely to
contain rats, and the similar treatment of freight cars showing signs
of rats, should be continued. In a few cases these measures have driven
rats out of both packages and cars and the animals have been killed by
the sanitarians on duty at the station.

The matter of water transportation was entirely within the control of
the authorities in charge of inter-island quarantine affairs.

Rat catching in Manila was systematically performed and all rats
captured were turned over to the Bureau of Science for examination for
plague.

[Illustration: MATERIALS MUST BE MOVED ABOUT IN THE SEARCH FOR RATS
(MANILA PLAGUE CAMPAIGN)]

When plague foci were discovered the localities were trapped and
poisoned both circumferentially and centrally, with a view to
preventing the diffusion of infected rats throughout the city.

RAT-PROOFING.--The theoretic desirability and superiority of "out
building" the rat, over all other methods of rat suppression, is
admitted. The apparent impracticability of actually rat-proofing Manila
at the present time and our inability to starve the animals out,
justify the other and less permanent measure, viz.: rat catching.
However, I heartily favor and urge the most complete and thorough-going
rat-proofing of buildings actually infected with human or animal
plague, in all cases. The building ordinances of Manila already provide
for rat-proof construction in all new buildings erected.

With a view to cutting off the food supply of the rat, more than 1100
orders upon householders, to provide covered garbage cans, were served
in the district of Tondo alone.

The open ends of bamboo timbers in more than 2300 houses were closed,
either by cement or tin cans, during 1913.

THEATRE DISINFECTION.--All the cinematographs and theatres in the city
were disinfected upon repeated occasions by spraying with petroleum
and cresols, with a view to destroying fleas and preventing plague
infection.

Attempts at deception and concealment of plague patients, upon the part
of members of their families, were numerous, but with the close
scrutiny of death certificates and dead bodies exercised at all health
stations it is believed that all cases were recognized.

One case of extremely careless diagnosis occurred. A death certificate
was furnished by a local native doctor who certified the cause of death
to be "uterine hemorrhage." Suspicion arising, an autopsy was ordered
and a pronounced case of bubonic plague was disclosed postmortem. No
evidence of uterine hemorrhage, except slight menstrual signs, was
found.

The destruction of infected fleas in plague houses is of course the
primary object of the disinfection by spraying, which is thoroughly
carried out in every house where a case of human plague or rat plague
appears. The method is a simple one and consists in spraying a mixture
of cresols (2 per cent.) and kerosene (98 per cent.) over all surfaces
of the house, floors, walls, underlying ground, furniture and the
spaces above ceilings, etc., using the mixture liberally and securing a
general surface distribution. There is no doubt of the toxicity of this
mixture to all fleas and bed-bugs which it reaches, and it is
undoubtedly an effective measure in rendering an infected house safe.
All of the instances of multiple house infections, where the cases
recurred after disinfection, in Manila, have been in houses where, for
one reason or another, the recommended structural rat-proofing has been
postponed or where it has not been done. Thus, on Calle San Fernando
the sequence of the four cases (their progress by days and in
consecutive houses) is explained by the travel of rats through
efficient rat runs present in the walls and ceilings, rather than by
the passage of fleas through partition walls, from uncommunicating
house to house.

[Illustration: A RAT INFESTED PLAGUE INTERIOR]

So also at Calle Cabildo, where the superstructure of the house was a
veritable sieve, there was a series of communicating double walls.

At the house on Calle T. Alonso a similar condition existed, but here
the two cases which occurred may have been synchronously infected, or
nearly so, previous to disinfection of the premises.

At Calle Comercio, where six days elapsed between two cases, the rooms
and building were piled full of merchandise, defeating immediate
disinfection, that is, efficient disinfection, until all the
merchandise was moved and the rooms were emptied.

At 1364 Calle Sande, Tondo, where 5 cases originated, the infections
were undoubtedly almost synchronous and no infection occurred after
disinfection of the house, while at 1226 Calle Juan Luna, Tondo, the
two cases were plainly infected at about the same time and this
previous to disinfecting the premises.

GUINEA-PIGS AS INDICATORS OF INFECTED HOUSES.--The following experiment
shows strikingly the necessity for disinfecting houses where human or
animal plague cases have occurred.

Upon December 17, 1912, Dr. O. Schöbl, of the Bureau of Science, and
myself, placed two healthy guinea-pigs, free from fleas, in a wire trap
cage in the house at No. 4 Calle Barraca, a few hours before the house
was disinfected, a patient with plague from this house having died
within the preceding twelve hours. The cage containing the guinea-pigs
was placed exactly where the patient had slept upon the floor, as
indicated by the other tenants of the house. Disinfection was delayed
for a few hours and the guinea-pigs were left in the house for one
day. Upon December 21 one of the guinea-pigs died from typical bubonic
plague--anatomically and bacteriologically positive--other inoculated
experimental animals also developing the disease.

Other guinea-pigs placed in plague houses on Calle Cabildo and Calle
San Fernando, after disinfection of the premises, failed to acquire
plague.

NATURAL ENEMIES OF THE FLEA.--It was observed during the studies in
Java that certain natural enemies of fleas exist and operate against
their laboratory cultivation and their natural reproduction.

Ants of several varieties, large and small red ants and small black
ones, were found to be very antagonistic to fleas, both in the larval
and adult states, destroying them actively.

Fleas in the laboratory were found to be affected with mites, with a
resultant high mortality among the insects. The same parasites were not
found upon wild fleas. On account of the prevalence of mites upon the
laboratory fleas certain experiments concerning the transmission of
plague were vitiated.

The activity of ants in attacking and disposing of rat cadavers found
in our antiplague work in Manila was frequently brought to my
attention. We invariably included an attack upon ants in treatment of
houses known to harbor, or suspected of harboring, plague rats. The
combination of kerosene and cresols, elsewhere referred to, was found
to be perfectly satisfactory in the destruction of ants; assuming, of
course, that the necessary procedure of exposing the ants, by the
moving of merchandise, boards or other protecting materials, was
performed, so that contact, by spraying the insecticide mixture, was
secured.

ACTIVITY OF FLEAS.--It was also observed during the Java studies that
the rat flea, while rather lazy, may and does cover distances of five
metres and that he sometimes covers eighteen centimetres at a single
leap.

In addition to this, of course, there must be considered the
possibility of his falling considerable distances.

ZOÖLOGIC CLASSIFICATION OF RATS.--The matter of accurately,
systematically and scientifically cataloguing and classifying rats is
one of great difficulty and is not to be undertaken by anyone but a
trained naturalist. However, some of the notes we have at our disposal,
gathered from many sources, may be set before the reader. It is
extremely difficult to find exact correspondence of statement in the
various classifications offered by writers upon plague and rats.

Dr. Lantz gives the following brief classification in his section of
the publication, "The Rat and Its Relation to Public Health."

    Order: _Rodentia._

    Family: _Muridæ._

    Genus: _Mus._

    Species are many, but only three or four are cosmopolitan.

    Cosmopolitan species: _Mus rattus_--black, brown, and roof
    (_Alexandrine_) rat; _Mus decumanus_--gray, barn, wharf,
    sewer, and Norway rat.

_Mus rattus_ has many varieties known throughout the world and these
are named according to color and habitat.

In addition to the names given in Lantz's classification, we constantly
see reference to the black house rat, the brownish-gray rat (_Mus
Alexandrinus_), the ordinary ship rat, the field rat, etc.; terms
descriptive of habitat and appearance being very loosely applied.
Little account is taken, by many, of the well-known variations in the
coloration of rats due to climate and season and of the well recognized
aptitude of the rat for living in-door or out-door according to
circumstances of food supply, weather, etc. The "sawah" rat of Dutch
India, implicated in the prevalence of plague there, was formerly
considered a variety of _Mus decumanus_, but is now described as a
field variety of _Mus rattus_. So too, varieties of _Mus decumanus_ are
frequently named according to alleged geographic origin, habitat, color
and habits, viz.: sewer rat, brown rat, Norway rat and migratory rat.

The inevitable confusion bound to arise from such loose classification
is obvious.

Another genus, _Gunomys_ (_Nesokia_), implicated in plague, is
represented in India by two species and by at least one (an
undetermined one) in Java, some confusion existing in the matter as
yet. Members of this genus are described as large, rough-coated rats
which live both as house rats and field rats. In India the Plague
Commission reported specimens of this genus as particularly susceptible
to plague.

In the Philippine Islands no specimens of _Gunomys_ have been observed,
but _M. rattus_ and _M. decumanus_ are both present and numerous and
both are subject to plague, as shown by the presence of the disease in
specimens examined.

In view of the unreliability of the points of difference in rats
usually given as identifying data, such as the number and location of
the mammæ, the variations in color and the peculiarities of the
footpads, the Javan observers depend upon the conformation of the
skulls for the determination of genera, the skull of _M. rattus_ being
oval and arched, that of _M. decumanus_ more closely approaching the
square and rectangular conformation, and that of _Gunomys_ being
broader, higher and longer than either.

In _M. rattus_ the prominent borders which separate the parietal from
the frontal surfaces of the skull are oval; in _M. decumanus_ they are
parallel or slightly divergent; in _Gunomys_ they are lyre-shaped.

[Illustration: _M. rattus_]

[Illustration: _M. decumanus_]

[Illustration: _Gunomys_]

To determine these differences the heads of the rats are cut off, the
tissues desiccated by antiformin, or by boiling and stripping.

From experiences in Porto Rico, Creel, of the U. S. Public Health
Service, concludes that _M. norvegicus_ (_decumanus_), while
essentially a burrowing animal and not addicted to climbing or
swimming, is nevertheless quite capable of doing either. He was found
to burrow in the hardest earth to a depth of two and one-half feet and
to pass through all kinds of wood, soft brick and lime mortar, probably
by gnawing.

The black rat and Alexandrine rat (_M. rattus_) in Porto Rico,
according to the same observer, do not burrow at all, but can climb and
jump in expert manner, and are the species found in the rural
districts, remote from houses. He found that all varieties of rats may
swim, from ships to the shore, distances of from one-fourth to one-half
mile, but that they lack the sense of direction and probably do not
land from ships naturally in this manner (_Public Health Reports_, No.
9, February 28, 1913).

The female _decumanus_ is a prolific breeder and brings forth larger
litters than the _Mus rattus_ female.

_Mus decumanus_ is generally conceded to be larger and more ferocious
than _Mus rattus_. For this reason he drives the smaller rats to the
upper floors, the _decumanus_ species generally living near the ground.
He is a burrower and is rarely found in the upper stories of
buildings. _Decumanus_ is known as a wharf rat, but is rarely trapped
on ships on the Pacific Coast, according to the observations of Surgeon
Simpson of the U. S. Public Health Service (_Public Health Reports_,
April 11, 1913). According to the same observer, _Mus rattus_ is the
commonest ship-borne rat. He also states that the black rat and the
roof rat (_Alexandrinus_), both varieties of _M. rattus_, differ
chiefly in color. They live in upper floors, between ceilings, in walls
and roofs and are remarkable climbers as well as being expert
rope-walkers and wire-walkers. On account of their natural wariness and
caution it is not always easy to induce them to enter or approach
traps.

The photographs introduced were taken under my direction in Manila in
1912, 1913 and 1914. Some of them show the character of the house
construction in Tondo District, Manila, where plague flourished in
1913. Others illustrate methods of rat-proofing bamboo timbers in
houses of light material. These end openings were either closed by
introducing cement or by placing tight-fitting tin cans over the ends
of the bamboo rafters.

There are many interesting memoranda, gathered and made in connection
with our antiplague work in Manila, especially concerning the location
and construction of rat nests found by our laborers; the materials used
and the fabrication of the nests. Memoranda giving details of rat
catching and rat-proofing are also presented and notes showing the
location of dead rats found in relation to dead human bodies of plague
victims.

Notes concerning cases of multiple house infection are also presented
as being of possible interest.

The Javan studies in 1911 and 1912 establish the fact that it is
possible to form a fair judgment as to the length of time a rat has
been dead, up to ten or twelve days, from the condition and appearance
of the rat cadaver, both as to decomposition and drying. A series of 50
rats was studied. It is to be understood that the conditions under
which these observations were made were tropical conditions. They would
be fairly comparable with summer conditions in America, but should not
be followed too closely at other seasons of the year. In my own
experience I have observed that ants are likely to attack the cadaver
early and to obscure the deductions by their destruction of the body.

[Illustration: PROGRESSIVE POST-MORTEM CHANGES IN RAT CADAVERS. THE
NUMBERS INDICATE THE NUMBER OF DAYS AFTER DEATH]

  Days after death                   Appearance

 First to third day      Distention of the abdomen, increasing.

 Second to third day     Loosening of hair by gentle pulling.

 Third to fourth day     Loosening of the epidermis by gentle
                         pulling.

 Third to fifth day      Perforation of abdominal wall with
                         collapse and disappearance of distention.
                         This perforation may result from bursting
                         of abdominal wall, or through anus, vulva
                         or thorax.

 Fourth to sixth day     Moist shrinking of the body. Swarming of
                         maggots. Spontaneous shedding of tufts of
                         hair.

 Fifth to eighth day     Drying of body.

 Eighth to twelfth day   Complete dryness and rigidity.

Photograph (after _Publications of the Civil Medical Service in
Netherlands, India_) shows the progressive postmortem changes in rat
cadavers, the numbers indicating the number of days after death.

A COLLECTION OF NOTES CONCERNING RAT RUNS, RAT NESTS, THEIR LOCATION
AND OTHER DATA.--Attention is invited to the following collection of
notes concerning rat runs, rat nests and their locations and other data
collected by the various working parties under the direction of
Sanitary Inspectors Brantigan, Renner and Kennard, of Manila.

Special attention has been given to the finding and destroying of rat
nests, and in this connection please note that during the month of May,
1913, one party of workmen (20 men) under Inspector Brantigan, killed
by hand 511 rats out of a total of 1319. This means that many nests
were broken up and that much breeding was interfered with. In June,
1913, two parties (40 men) killed 772 rats by hand out of a total of
3019.

This work occurred in Tondo District in connection with extensive
cleaning and moving operations.

At 1279 C. Sandejas[4] 7 rats were found in a nest at the foot of a
cluster of bamboo trees, between the trunks. Nest was made of leaves.

  [4] C. is abbreviation for Calle, the Spanish term for street.

At 728 C. Velasquez, Tondo, 12 rats were driven from a burrow
underneath a thick cement floor by formaldehyde gas delivered in the
burrow through a rubber hose. This burrow was in sand and the rats came
out about ten minutes after the flow of gas began. All were killed or
captured and two or three died from the effects of the gas.

On October 27, 1912, two of the rat terriers belonging to the Bureau
of Health caught 192 rats in one storeroom at the Manila Railway
Station, in 38 minutes. At various times they have killed from 10 to 25
rats at a single location, in connection with the cleaning and moving
work done by the laborers. The dogs caught about 600 rats in all.

On March 11, 1913, 27 rats were caught by laborers at 202 Calle Concha.
They were nesting in straw covers which had been removed from bottles.

On March 11, 1913, 13 rats were found beneath a pile of loose tiles at
203 C. Sardinas. The nest was made of fibres from coconut shells and
straw.

On March 13, 1913, 12 rats were found among stones scattered in a
shallow pile on the ground at C. Conservador (interior). Nest was made
of rice chaff and small pieces of cloth.

On March 15, 1913, 9 rats were caught at 1353 C. Anloague on the ground
floor beneath a pile of boards. Nest was made of coconut fibre and
shavings.

On March 16, 1913, 24 rats were caught at 934 (interior) Velasquez
beneath a wood pile. Nest was made of coconut-shell fibre and pieces of
cloth.

On March 17, 1913, 14 rats were caught under a pile of hay and straw
at 173 Velasquez. Nest was made from straw, chaff and hay.

The following articles of food were found in the above-mentioned nests:
chicken bones, rice, coconut, fish and bread.


MEISIC DISTRICT

At 822 Sacristia 6 dead rats found in holes.

At 540 T. Alonso a family of 8 rats was smoked out and all were killed.

At 514 same street 6 rats were smoked out and killed.

At 538, interior, same street, 4 rats were smoked out and killed.

At 546 same street 4 rats were smoked out and killed.

At 715 San Bernardo dead rat found in a hole. Nest made of banana
leaves and rags.

At 627, interior, Zacateros, 9 rats were smoked out and killed.

At 669 Benavides 6 rats were smoked out of four runs and were caught.

At 631 Zacateros 2 rats were smoked out and killed.

At 417, interior, Misericordia, 4 rats were secured in two holes under
a tile floor. Many rats were caught at this number (interior) in traps.

At 221 Espelita 7 rats were found in a nest made of palm leaves and
excelsior; location of run way and nest beneath tile floor.

At 124 Tetuan, in a nest of straw and lint, 5 rats were caught by hand,
alive.

At 415 T. Alonso one live rat and 3 dead ones were dug out from beneath
a tile floor.


SAMPOLOC DISTRICT

At 1001 Bilibid Viejo there were 5 rat runs, in a Chinese store. Eight
rats were secured in a nest under the cement floor. Nest made of straw
and paper.

At 928 San Sebastian there were 8 rat runs. In one of them there were
caught 8 rats. The nest was made of straw.

At the same address, later, 3 rats were caught in another run and 8
young rats, with eyes still unopened, were found in a nest of straw. A
supply of bread was on hand in this nest.

At 629 Tanduay 20 rats and nests of straw and paper were found.

At the same address upon another day another rat run was found and one
large rat and 16 small ones were taken from a nest made of rags, straw,
and fibres.


PACO DISTRICT

At 1115 San Andres in a Chinese tienda (food store), a long rat run and
a nest of rags, straw, and paper, and 30 small rats were found.

One nest in a bamboo tree 30 feet above ground was found. Rats had been
observed going up the tree and one was caught at the foot of the tree
in a trap.


SAMPOLOC DISTRICT

At 629 Tanduay 14 young rats and a nest of straw, paper and rags were
found in a stable.

Same address, later, one rat run and nest of straw and rags with one
large rat and 16 small ones were found.


TONDO DISTRICT

March 27, 1913, one rat was caught alive inside of a bamboo timber in
house at 51, interior, Pesqueria.

At 631 Azcarraga 4 young rats were found in a nest of paper, leaves,
and hay. Chicken bones, crab shells, and rice were present in the nest.

A young python was caught in a lumber yard in the Santa Cruz District
in June, 1913. In his stomach was found a half-grown rat. Another snake
was caught in a rat trap at the same address about the same time.

PLAN FOR HOUSEHOLD RAT DESTRUCTION.--The following plan for household
rat destruction was proposed by me to the Director of Health. It is
considered worthy of trial if rat plague appears in new districts.

    Proposal for periodic household rat poisoning in Manila.

    Proposed that, upon a certain day of each week, rat poison be
    issued free to all applicants (householders) in Manila who
    agree to place same about their premises, permitting the
    poison to remain in place for 48 hours.

    Instructions and poison placards to be issued with the
    poison. Issues to be made from Station Health Offices and
    records of issue to be kept.

    Collections of dead rats to be made at the end of 24 hours
    and 48 hours by Bureau of Health employees. Poison portions
    to be collected and turned in at the Station Health Offices
    at the end of 48 hours, that is, at the time of the last rat
    collection. Rats to be tagged and examined for plague in the
    usual manner.

    Due newspaper notice of the plan and of the gratuitous issue
    of poison to be given to the people and their coöperation
    requested.

    Plan to be tested for at least two months.


MULTIPLE HOUSE INFECTION

Memorandum concerning 1364 Calle Sande:

Within 72 hours (April 25-27) five fatal cases of plague, all in
Filipinos, occurred in Manila. The five deceased persons lived at 334
C. P. Rada (Meisic), 1419, interior, C. Dagupan, 1364 C. Sande (Tondo),
642 C. Ylala (Meisic), and 1492, interior, C. Dagupan (Tondo).

The following relationships were established by inquiry and
investigation and the circumstances point strongly to a common source
of infection and to a single geographic focus of plague infection in
connection with all of the cases, viz.: at 1364 C. Sande (Tondo).

    José Raymundo, boy, aged fifteen, lived at 334 C. P. Rada and
    worked daily until taken sick on Tuesday, April 22, at 1364
    Sande, in the shop of Simplicio Enriques, a silversmith, who
    lived part of the time at the same address.

    José Raymundo died of bubonic plague at San Lazaro Hospital
    on Friday, April 25, 1913.

    Norberta Mendoza, woman, aged fifty-six, lived at 1418,
    interior, C. Dagupan. She was the mother-in-law of Simplicio
    Enriques, the silversmith at 1364 Sande, and visited her
    son-in-law there frequently and within a few days of her last
    illness. She was taken sick April 22 and died at 1419,
    interior, C. Dagupan, on the morning of April 26. At autopsy
    at San Lazaro morgue, the same day, bubonic plague was found
    to be present and the cause of her death.

    Trinidad Galves, a young woman, aged sixteen, lived at 1364
    Sande and was taken sick there on April 25. She was removed
    to San Lazaro Hospital and died there April 26, extensive
    plague lesions being found at autopsy.

    Pablo Banzon, man, aged twenty-six, living at 646 C. Ylaya,
    was taken sick on Friday, April 25. He was removed to San
    Lazaro Hospital Saturday afternoon and died there Sunday
    evening, April 27. He was shown to have plague by
    bacteriologic examination made at the Bureau of Science. He
    worked at 1364 Sande as a silversmith, with José Raymundo and
    was employed by Simplicio Enriques.

    Simplicio Enriques, aged twenty-seven, a silversmith,
    conducting his business at 1364 C. Sande and employing José
    Raymundo and Pablo Banzon, was taken sick about April 23. He
    moved to two different houses in the interval between the
    onset of his sickness and his transfer to San Lazaro Hospital
    on April 27, first to 1419 C. Dagupan, interior, where he
    remained until the death of his mother at this house; then to
    1492 Dagupan, interior, from which place he was transferred
    to San Lazaro Hospital, where he died with bubonic plague a
    few days later. Diagnosis was confirmed at autopsy.

The two women were patients of Dr. Hernando of Calle Ylaya. He
recognized the case of the elder woman as a probable case of plague,
after death, and reported the matter to the Bureau of Health.

The house at 1364 C. Sande is of the type in which cases of rat plague
and human plague have recently been found. In our operations to put the
house in a safe condition we found one dead rat, mummified, in the
basement. Unfortunately, the workmen who swept it out did not note the
exact location at which it was found. The house is in the midst of the
district where rat plague has raged since early in March, 1913. The
basement contained unauthorized and illegal sleeping rooms until a few
days before this outbreak when they were removed in the course of our
antiplague operations. The building is constructed of bamboo with a
nipa thatch roof.

The front part of the basement was paved, but the pavement was
undermined and broken. Being convinced that dead plague rats were
present in the vicinity of this house and probably within it, I
directed that the cement floor under the silversmith shop and the
barber shop, located upon the ground floor at this address, be torn up.
Accordingly, this was done (April 28) and three dead rats and one live
one were found beneath the cement. As the bodies were mummified and
unfit for bacteriologic examination they were burned. The living rat
was examined at the Bureau of Science but was found to be healthy. The
cement floor was broken and permitted fleas from the dead rats to enter
the basement room of the house which was occupied by the silversmith
shop. The rats doubtless died from plague and the hungry fleas in due
time attacked the nearest persons at hand, the unfortunate occupants of
the silversmith shop and the two women who frequented the room also.

These facts account for the epidemic at 1364 Sande very completely.

The premises at 1364 Calle Sande were quarantined by the following
order:

      MANILA, April 27, 1913.

    The premises 1364 Sande are hereby declared in Quarantine for
    Bubonic Plague by order of the Director of Health.

    The inmates will be permitted to leave the building and find
    quarters elsewhere, provided they leave their addresses with
    the policeman in charge, so that they may be readily found.
    They must remain in the District of Tondo. If they remain in
    the house they will be obliged to stay in the upper story of
    the house and will have to arrange for meals to be sent in.

    The barber shop and "platero" shop are hereby ordered closed
    until further orders.

    By order of the Director of Health.

      [Signed] T. W. JACKSON,
      _Medical Inspector, in Charge of Plague Suppression_.

Memorandum reporting circumstance surrounding 2 cases of plague at
1226 C. Juan Luna (May 17, 1913):

    Valeriano Lausin, aged fourteen, Filipino male, Carmelo maker
    by trade but out of work at time he was taken sick, recently
    removed to this house from 917 C. Jaboneros where he had been
    employed. The patient fixes the date at about a week previous
    to his sickness, but the proprietors of 917 Jaboneros are
    positive in their statement that he left the place where he
    lived and worked, at least two weeks before. This boy
    recovered.

The circumstances and especially the occurrence of a second case at
1226 C. Juan Luna, indicate that infection was incurred here.

Moreover, this house is in the midst of a rat-plague infected district.

[Illustration: PLAGUE HOUSE, 1226 CALLE JUAN LUNA]

The house is of bamboo and nipa construction and contained illegal
basement rooms until a week ago. About 60 persons lived in this house
which was once licensed as a tenement but which is unsanitary in a
multitude of ways. Bamboo construction, overcrowding, dirty condition
and absence of proper drainage, water-closet, proper kitchens and paved
ground floors, together with bad ventilation, made it a dangerous
habitation and the added condition of plague infection made it
necessary to vacate and quarantine the building.

On May 15, at the daily inspection of contacts in the house 1226 C.
Juan Luna, Filomena Suñga, aged nineteen, and a relative of the owner
of the building, was found to be sick. Her only symptom was fever, but
she was transferred to San Lazaro upon suspicion and promptly developed
symptoms of plague. She died in a few days and the diagnosis of plague
was verified at autopsy. The following order was issued:

      STATION "C," TONDO, BUREAU OF HEALTH,
      MANILA, P. I., May 15, 1913.

    By order of the Director of Health, the house No. 1226 C.
    Juan Luna is declared infected and is quarantined this date,
    for Bubonic Plague. The house will be vacated and a policeman
    will register the names of all residents and the addresses to
    which they remove.

    The residents may remove their personal effects but will not
    be permitted to return while the quarantine is in effect.

      [Signed] T. W. JACKSON,
      _Medical Inspector, Station "C," Tondo_.

Memorandum: Human body (dead from plague) and dead rats found in the
same basement room. Upon March 21, 1913, a Filipino laborer living at
140 Calle Perla, Tondo, was found dead from bubonic plague.

Upon careful investigation and search of the premises the following
findings were disclosed:

One rat, large, mummified and dry and therefore dead for at least one
week, was found clinging to a bamboo wall just back of the cot upon
which the dead human body was found.

In a section of bamboo, in a timber constituting the ceiling of the
basement and also the upper part of the door frame, a rat, dead and
dried up, was found. This section was the end section of the timber
which was partly covered with nipa thatch, with which the sides of the
house were covered. The ends of a number of the outside rafters
(bamboo) were found to be gnawed through.

[Illustration: BAMBOO HOUSE SUPPORTS SEALED WITH CEMENT TO PREVENT
ENTRANCE OF RATS (MANILA PLAGUE CAMPAIGN)]

Similar conditions were found in adjoining houses and in one case a
live rat was driven out of a nest in the bamboo.

SAMPLE OF DETAILED ORDERS ISSUED.--Sample of detailed orders issued by
Medical Inspector in Charge of Plague Suppression. Similar orders were
issued whenever new districts were entered or new work undertaken.

    Memorandum Order. Effective March 25, 1913:

    Beginning to-day, 13 men under Assistant Inspector Parás,
    will commence cleaning operations at C. Ostra, extending
    from the Bay to C. Sande and will clean towards C. Moriones.
    They will be provided with a disinfecting pump and will
    disinfect the ground surfaces wherever disturbed, outdoors
    and indoors. Cleaning is to be done in the most thorough
    manner possible, searching meanwhile for rat nests and rat
    harbors; re-piling wood, tiles, stones and merchandise;
    moving all movable goods out of doors in their search for
    rats and rat-holes or nests. All goods are to be piled above
    ground at an elevation of at least one foot. All bamboo beds
    and bamboo rafters and parts of the house (in the basements)
    made of bamboo or of double walls are to be thoroughly
    investigated for rats. All foodstuff attractive for rats is
    to be placed in covered boxes or galvanized iron cans, tin
    cans or barrels, with tight-fitting covers. Special attention
    is to be paid to straw, hay, shavings, grain, rat-holes, and
    food.

    Two men will be detailed to cement up ends of bamboo and
    rat-holes, but will not do general repairing. They will carry
    materials for mixing cement as needed and will not be
    wasteful of materials.

    If this force proves to be insufficient in numbers,
    additional men may be detailed from the other working
    parties.

      [Signed] T. W. JACKSON,
      _Medical Inspector in Charge of Plague Suppression_.

Specimen order issued to Sanitary Inspector assisting in Plague
Suppression by Medical Inspector in charge.

    Sanitary Inspector, Bureau of Health:

    Please place the gang of workmen under your charge in the
    square bounded by Calles Velasquez, Moriones, Concha and
    Manila Bay which is infected with rat plague. Treat the
    houses and properties there in the same manner in which other
    plague-infected districts have been treated, viz.: by
    policing the houses and yards, vacating all basements of
    light-material houses in which human habitations are
    illegally present; removing (with the consent of the
    occupants) all unauthorized basement sleeping places, beds,
    platforms, etc., and other illegal structures, closing up the
    open ends of bamboo rafters or timbers of the house with tin
    or cement.

    Where the occupants resist this action sanitary orders should
    be issued in the usual manner and interference should be
    stopped until the order is served and complied with. There
    are a number of most insanitary and unsuitable shelters of
    bamboo, tin, etc., used for houses by a number of families in
    this square and it is desirable to tear down these huts if
    permission can be secured. If permission is refused orders
    should be issued on the usual form.

      [Signed] T. W. JACKSON,
      _In Charge of Plague Suppression_.

[Illustration: VIEW OF HOUSE AT 447 CALLE CONSERVADOR, TONDO, WHERE
INFECTED RATS WERE FOUND (MANILA PLAGUE CAMPAIGN)]

Specimen order issued by the Medical Inspector in charge of Plague
Suppression.

      STATION "C," TONDO, May 21, 1913.

    Redistribution of rat catchers and laborers engaged in
    antiplague work. Effective May 2, 1913.

    Sanitary Inspector Kennard and 20 rat catchers will move into
    Tondo District and trap and poison rats in the district
    bounded on the west by Manila Bay and on the east by Estero
    Reina. The work will be begun at the extreme north water
    boundary of this district and will proceed toward the south.

    Sanitary Inspector Brantigan with a similar number of rat
    catchers (20) will work within the same east and west
    boundaries and will begin trapping and poisoning at Calle
    Moriones, proceeding north. The poisoning and trapping is to
    be done in the most thorough manner possible, as this is a
    dangerously infected district and rat-plague must be
    controlled and terminated here.

    The laborers, 60 men, divided into 4 parties of 15 men each
    under Assistant Sanitary Inspectors Jesús, De la Rosa,
    Laxamana and Parás, will continue the cleaning operations now
    under way on both sides of C. Juan Luna south of C. Moriones
    (plague localities in the same neighborhood), and thoroughly
    disinfect.

    One party of 15 men will work in the vicinity of C. Perla,
    vacate basements as habitations, search for dead rats in
    yards, houses, bamboos, under broken concrete, etc., and will
    close up openings in structural bamboo by means of tin and
    cement. Emphasis is placed upon the necessity for permanently
    vacating basements and men will be sent back over the ground
    daily to see that the persons moved out do not return.
    Reports are desired so that prosecutions for violations of
    the law may be instituted if necessary.

      [Signed] T. W. JACKSON,
      _Medical Inspector in Charge of Plague Suppression_.

Specimen order issued to Assistants.

    May 4, 1913. STATION "C," BUREAU OF HEALTH:

    Please place work parties in (interior) 1627-1629 Sande and
    525 C. Azcarraga, to clean, disinfect and thoroughly
    investigate these premises and the houses, stables and other
    buildings in the vicinity. Search for rats, living and dead,
    rat nests and rats in bamboos and wood piles, stone piles,
    stables, under planks and elsewhere. Cement the openings in
    bamboos in houses or close with tin. Make notes on needed
    structural work. Do the work as thoroughly as possible.

      [Signed] T. W. JACKSON,
      _Medical Inspector in Charge of Plague Suppression_.

METHOD OF PROCEDURE IN COLLECTING AND FORWARDING RATS SUSPECTED OF
PLAGUE INFECTION TO THE LABORATORY IN MANILA, P. I.--Rat
catching,--trapping and poisoning,--is conducted in accordance with
instructions contained in the Sanitary Inspector's Handbook (pp. 36,
37, 38) issued by the Bureau of Health.

Rats are collected in Manila and forwarded to the Bureau of Science for
autopsy and for biologic examination for the presence of plague bacilli
in the following manner:

The various groups of rat catchers are provided with receptacles (iron
pails) and a supply of a mixture of kerosene, cresol and water
(kerosene 10 parts, cresol 2 parts; water 88 parts).

In these vessels, filled with the pulicidal mixture, the rats are
immersed, with a minimum amount of handling, as soon as they are found
(whether in traps or dead from poison).

If captured alive they are killed and then promptly immersed. The
mixture must be well shaken or stirred when used, as it separates upon
standing. The immersion is, of course, for the purpose of destroying
any fleas which may be present upon the captured rat.

A paper tag showing the date and the exact location of the place of
capture, with the name or group number of the rat catcher, is next
affixed to a foot or to the tail of the rat and firmly tied upon the
same, where it remains until the rat cadaver is finally disposed of.
This tag is a card of strong Manila paper and the record upon it is
made with an ordinary lead-pencil, as both ink and indelible pencil
marks are apt to become illegible from wetting, whereas lead-pencil
marks are little affected thereby.

If desired, the disinfected tag in any given case of rat plague may be
returned to the Bureau of Health, for identification, where an accurate
record of every rat captured is kept.

After dipping and tagging, the rats are taken to a central point, again
dipped, and placed in large, tightly-covered, galvanized iron cans, in
which containers they are delivered to the laboratory by cart, once or
twice daily.

THE CASE OF MR. C.--The following are the facts concerning the case of
Mr. W. C., a prominent American resident of Manila who suffered and
died from plague in 1914.

Mr. C., an editor, was taken ill with plague on the night of September
18, sought medical advice and entered St. Paul's Hospital September 19,
and was transferred to San Lazaro Hospital, September 20, with an
established clinical and bacteriologic diagnosis of bubonic plague. He
survived till September 22.

Upon September 21, in the course of disinfecting the business office of
Mr. C., located in a district which had furnished a number of cases of
both rat and human plague, a dead rat, mummified, was found in the
right hand drawer of his desk and fleas were seen to hop from the
drawer upon opening it.

A flea killed by the disinfecting mixture at this desk was identified
at the Bureau of Science as a rat flea (_Xenopsylla cheopis_).

The rat cadaver was sent to the Bureau of Science and the following
facts were reported from there some days later:

The mummified rat and skeleton were pulverized in a sterile mortar and
an emulsion was made and injected into guinea-pigs. The animals died
from plague in a few days and plague bacilli were recovered from the
tissues, as well as from the rat cadaver, by culture.

A second rat cadaver, found at the same time in the same building,
during cleaning operations, was similarly treated with identical
results.

There could scarcely be a stronger chain of convincing evidence against
the rat and the flea, nor a more complete and convincing explanation of
Mr. C.'s death than that afforded by these established facts and
official documents. So far as I know there is no more striking case on
record in the modern history of plague.

LETTER OF WARNING AND APPEAL.--The following letter of warning and
appeal for coöperation was suggested and framed by me February 10,
1914, at the time that extensive rat plague was discovered in the heart
of the business district of Manila. I presented it to the Director of
Health with a strong recommendation for approval and publication and
after consideration he approved and authorized publication upon
February 10. No change was made in the wording of the proclamation,
but it was issued over the signature of the Director of Health to give
added force and authority to the appeal. The results were, as I had
hoped they might be, highly beneficial. The taking of the public into
the confidence of the health authorities brought about a coöperation,
without which our efforts in this difficult situation would have been
sadly handicapped. It is my belief that this method should often be
used by health authorities, particularly where an intelligent community
is threatened.

    TO WHOM IT MAY CONCERN:

    You are hereby informed that the district bounded by Calles
    Rosario, Juan Luna, Dasmariñas and Plaza Calderon (and
    possibly the neighborhood bordering upon this congested
    district) is a dangerous one for all persons living or
    conducting business therein, on account of the presence there
    of extensive rat plague. Six human cases (with five deaths)
    have recently developed there and many dead rats have been
    found. All human cases have been directly traced to rats dead
    from plague.

    The Bureau of Health is now doing everything within its power
    to make this district safe, but the attention of all
    citizens, property owners and tenants is called to the fact
    that they are required by law to keep their premises free
    from rats and to abolish all structural conditions of the
    buildings which favor the harboring of rats. This means
    rat-proofing, and owners are earnestly urged to perform this
    necessary work now, under the direction of the Bureau of
    Health.

    As a temporary expedient and safeguard all interiors, walls,
    floors and ceilings should be sprayed with kerosene daily, or
    at intervals of two days, to kill the fleas which carry
    plague from rats to human beings. All dark insanitary places
    used for living rooms should be vacated at once; all
    merchandise should be piled upon trusses at least a foot
    above the floor; all straw, shavings and other material
    attractive to rats for nesting, should be removed and burned
    and all food materials upon which rats may feed and live
    should be placed in covered boxes, bins or cans.

    All rat-holes should be permanently closed and all broken
    cement or masonry should be repaired.

    Observance of these instructions may save the lives of
    yourselves, your families and your tenants. It is your duty
    to do your part in this matter, a part which neither the
    Bureau of Health nor the Government can do for you.

    Through very great effort the Bureau of Health has controlled
    plague in Manila and the Philippine Islands during the last
    two years.

    Residents must now do their part, and owners of property must
    permanently make their buildings safe for tenants, both for
    business and residential purposes.

BACTERIOLOGIC OBSERVATIONS MADE BY DR. OTTO SCHÖBL.--The following
observations upon the bacteriologic aspect of the Manila epidemic which
we are considering were made by Dr. Otto Schöbl of the Biological
Laboratory of the Bureau of Science, Manila, and pertain to the cases
of the first year of the epidemic. They were printed in the December
number of the _Philippine Journal of Science_ in 1913, but as they
belong so definitely to the epidemic I am describing and as Dr. Schöbl
has expressed his willingness for me to quote them in full, I gladly
accept his permission. Dr. Schöbl advanced the possibilities of
blood-culture diagnosis to such a point of reliability that it became
practically possible for us to expect positive culture in nearly every
case of true plague and the whole matter of bacteriologic diagnosis was
perfected to a high degree of efficiency under his administration of
the laboratory work.

He relates his observations as follows:

    During the recent outbreak of plague in Manila, I had the
    opportunity to make certain observations which are of
    interest. These observations were made in the examination of:
    (1) Specimens taken from patients and from dead bodies at
    autopsies, (2) samples of blood-sucking insects collected in
    houses where plague patients had lived, (3) rodents caught by
    trap or poisoned in the parts of the city where plague cases
    occurred from time to time, and (4) domestic animals suspected
    of plague infection.

      I. BACTERIOLOGICAL EXAMINATION OF PLAGUE PATIENTS

    In order to secure as early diagnosis as possible, the
    following procedure of investigation was adopted:

    1. The bubo was aspirated by means of a sterile hypodermic
    syringe. The material thus obtained was placed in the water
    of condensation of an agar-slant culture tube.

    2. At least 7 centimetres of blood were withdrawn from the
    _cubital_ vein by means of another sterile syringe, and 5
    centimetres of it were placed in an Erlenmeyer's flask,
    containing 200 centimetres of neutral meat broth. The rest of
    the blood was emptied into a sterile tube, and used for
    agglutination tests.

    Cultures obtained by this method were examined
    microscopically, and the growths on various culture media
    were studied. Gram stain, Löffler's methylene blue, and
    hanging-drop method were used. Polar-staining and chain
    formation in liquid media and the characteristic type of
    colony on the surface of agar were looked for. Animal
    inoculation was performed in every case, and the culture
    isolated from each case was identified by agglutination test,
    rabbit's immune serum being used.

    The results of the bacteriological examination of a series of
    24 patients are tabulated in the two following tables. Table
    I includes the fatal cases and Table II those cases which
    recovered.

    The diagnosis of plague could be safely made from the
    microscopical examination of the liquid aspirated from the
    bubo in the majority of the cases. However, in certain
    instances the amount of the aspirated fluid being small and
    the bacilli very few, it was impossible to diagnose the case,
    especially when the cultures from the bubo were negative.
    Repeated examination of the patient was necessary under those
    conditions, but it happened in cases 22 and 23 that the
    patients died of plague before a second examination could be
    made. The smears and cultures from case 22 remained sterile,
    while the smears and cultures made from the swelling on the
    neck of patient 23 revealed the presence of pneumococci. Both
    patients died of plague, as was ascertained by examination of
    the organs after death.

  TABLE I.--EXAMINATION OF FATAL CASES OF PLAGUE

 ========================================================================
                                     |Date of Examination 1912
                                     |        +--------------------------
                                     |        |Duration of illness _Days_
                                     |        |   +----------------------
                                     |        |   |Hours before death
                                     |        |   |     +----------------
                                     |        |   |     |          Bubo
                                     |        |   |     |Smear
                                     |        |   |     |  Culture
                                     |        |   |     |    Animal
                                     |        |   |     |    inoculation
                                     |        |   |     |     +----------
                                     |        |   |     |     |   Blood
                                     |        |   |     |     |Culture
               |        |    |  Age  |        |   |     |     |  Aggluti-
      Patient  |  Race  |Sex |_Years_|        |   |     |     |  nation
 --------------+--------+----+-------+--------+---+-----+-----+----------
  1. Sing Nu   |Chinese |Male|  (?)  |July  11| 5 | 48  |+ + +|0 0
               |        |    |       |        |   |     |     |
  3. Aluncion  |        |    |       |        |   |     |     |
     Raymundo  |Filipino|Male|  15   |Sept. 29| 3 | ... |+ + +|0 0
               |        |    |       |        |   |     |     |
  4. Filo      |        |    |       |        |   |     |     |
     Almalas   |Filipino|Male|  39   |Oct.  10| 4 | 22  |+ + +|+ -
               |        |    |       |        |   |     |     |
  6. Polycarpio|        |    |       |        |   |     |     |
     Guzman    |Filipino|Male|  34   |Oct.  22| 2 | ... |+ + +|0 0
               |        |    |       |        |   |     |     |
  7. José      |        |    |       |        |   |     |     |
     Sarmiento |Filipino|Male|  37   |Oct.  22| 3 | ... |+ + +|0 0
               |        |    |       |        |   |     |     |
  8. Julian    |        |    |       |        |   |     |     |
     Gonzales  |Filipino|Male|  41   |Oct.  22| 3 | 23½ |0 0 0|+ -
               |        |    |       |        |   |     |     |
  9. Valeriano |        |    |       |        |   |     |     |
     Buencamino|Filipino|Male|  31   |Oct.  22| 3 | 10  |+ + +|+ -
               |        |    |       |        |   |     |     |
 10. Pedro     |        |    |       |        |   |     |     |
     Nicomedes |Filipino|Male|  30   |Oct.  22| 2 |  5¾ |+ + +|+ -
               |        |    |       |        |   |     |     |
 12. Regino    |        |    |       |        |   |     |     |
     Gulano    |Filipino|Male|  34   |{Oct. 22| 2 |106  |0 0 0|+ -
               |        |    |       |{Oct. 24| 4 | 82  |0 0 0|0 0
               |        |    |       |        |   |     |     |
 13. Martin    |        |    |       |        |   |     |     |
     Dimalanta |Filipino|Male|  35   |Oct.  23| 3 | 25½ |+ + +|+ -
               |        |    |       |        |   |     |     |
 14. Roberto   |        |    |       |        |   |     |     |
     Obiso     |Filipino|Male|   5   |Oct.  23| 1 | 53  |+ + +|+ -
               |        |    |       |        |   |     |     |
 15. Juan      |        |    |       |        |   |     |     |
     Barceta   |Filipino|Male|  23   |Oct.  24| 3 | 37  |+ + +|+ -
               |        |    |       |        |   |     |     |
 16. Yu Tum    |Chinese |Male|  14   |Oct.  24| 2 | ... |+ + +|0 0
               |        |    |       |        |   |     |     |
 17. Augustin  |        |    |       |        |   |     |     |
     Monterey  |Filipino|Male|  29   |Nov.   1| 1 | 27  |+ + +|+ -
               |        |    |       |        |   |     |     |
 18. Demetrio  |        |    |       |        |   |     |     |
     Pabraw    |Filipino|Male|  27   |Nov.  23| 4 | 15  |0 0 0|+ -
               |        |    |       |        |   |     |     |
 21. Ambrosio  |        |    |       |        |   |     |     |
     Sobremonte|Filipino|Male|  20   |Dec.   7| 6 |  1  |+ + +|+ -
               |        |    |       |        |   |     |     |
 22. Mateo     |        |    |       |        |   |     |     |
     Marcelo   |Filipino|Male|   8   |Aug. 20 |(?)| ... |- - -|0 0
               |        |    |       |        |   |     |     |
 23. Alejandro |        |    |       |        |   |     |     |
     Gita      |Filipino|Male| [A]17 |Nov. 24 | 3 | ... |- - -|0 0
 --------------+--------+----+-------+--------+---+-----+-----+----------

 ========================================================================
                                     |Date of Examination 1912
                                     |        +--------------------------
                                     |        |Duration of illness _Days_
                                     |        |   +----------------------
                                     |        |   |Hours before death
                                     |        |   |     +----------------
                                     |        |   |     |         Skin
                                     |        |   |     |Smear
                                     |        |   |     |  Culture
                                     |        |   |     |    Animal
                                     |        |   |     |    inoculation
                                     |        |   |     |     +----------
                                     |        |   |     |     |   Sputum
                                     |        |   |     |     |Smear
                                     |        |   |     |     |  Culture
                                     |        |   |     |     |    Animal
               |        |    |  Age  |        |   |     |     |    inocu-
     Patient   |  Race  |Sex |_Years_|        |   |     |     |    lation
 --------------+--------+----+-------+--------+---+-----+-----+----------
  1. Sing Nu   |Chinese |Male|  (?)  |July  11| 5 | 48  |+ + +|- - -
               |        |    |       |        |   |     |     |
  3. Aluncion  |        |    |       |        |   |     |     |
     Raymundo  |Filipino|Male|  15   |Sept. 29| 3 | ... |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
  4. Filo      |        |    |       |        |   |     |     |
     Almalas   |Filipino|Male|  39   |Oct.  10| 4 | 22  |+ + +|0 0 0
               |        |    |       |        |   |     |     |
  6. Polycarpio|        |    |       |        |   |     |     |
     Guzman    |Filipino|Male|  34   |Oct.  22| 2 | ... |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
  7. José      |        |    |       |        |   |     |     |
     Sarmiento |Filipino|Male|  37   |Oct.  22| 3 | ... |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
  8. Julian    |        |    |       |        |   |     |     |
     Gonzales  |Filipino|Male|  41   |Oct.  22| 3 | 23½ |0 0 0|+ + +
               |        |    |       |        |   |     |     |
  9. Valeriano |        |    |       |        |   |     |     |
     Buencamino|Filipino|Male|  31   |Oct.  22| 3 | 10  |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 10. Pedro     |        |    |       |        |   |     |     |
     Nicomedes |Filipino|Male|  30   |Oct.  22| 2 |  5¾ |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 12. Regino    |        |    |       |        |   |     |     |
     Gulano    |Filipino|Male|  34   |{Oct. 22| 2 |106  |0 0 0|0 0 0
               |        |    |       |{Oct. 24| 4 | 82  |0 0 0|+ + +
               |        |    |       |        |   |     |     |
 13. Martin    |        |    |       |        |   |     |     |
     Dimalanta |Filipino|Male|  35   |Oct.  23| 3 | 25½ |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 14. Roberto   |        |    |       |        |   |     |     |
     Obiso     |Filipino|Male|  25   |Oct.  23| 1 | 53  |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 15. Juan      |        |    |       |        |   |     |     |
     Barceta   |Filipino|Male|  23   |Oct.  24| 3 | 37  |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 16. Yu Tum    |Chinese |Male|  14   |Oct.  24| 2 | ... |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 17. Augustin  |        |    |       |        |   |     |     |
     Monterey  |Filipino|Male|  29   |Nov.   1| 1 | 27  |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 18. Demetrio  |        |    |       |        |   |     |     |
     Pabraw    |Filipino|Male|  27   |Nov.  23| 4 | 15  |+ + +|0 0 0
               |        |    |       |        |   |     |     |
 21. Ambrosio  |        |    |       |        |   |     |     |
     Sobremonte|Filipino|Male|  20   |Dec.   7| 6 |  1  |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 22. Mateo     |        |    |       |        |   |     |     |
     Marcelo   |Filipino|Male|   8   |Aug. 20 |(?)| ... |0 0 0|0 0 0
               |        |    |       |        |   |     |     |
 23. Alejandro |        |    |       |        |   |     |     |
     Gita      |Filipino|Male| [A]17 |Nov. 24 | 3 | ... |0 0 0|0 0 0
 --------------+--------+----+-------+--------+---+-----+-----+----------

  [A] Months.

  TABLE II.--EXAMINATION OF PLAGUE PATIENTS WHO RECOVERED

 =========================================================================
                                         |Date of examination 1912
                                         |        +-----------------------
                                         |        |Duration of disease
                                         |        |      +----------------
                                         |        |      |    Bubo
                                         |        |      |Smear
                                         |        |      |  Culture
                                         |        |      |    Animal
                                         |        |      |    inoculation
                                         |        |      |     +----------
                                         |        |      |     |   Blood
                                         |        |      |     |Culture
                 |        |      |  Age  |        |      |     |  Aggluti-
      Patient    |  Race  |  Sex |_Years_|        |      |     |  nation
 ----------------+--------+------+-------+--------+------+-----+----------
                 |        |      |       |  1912  |_Days_|     |
                 |        |      |       |{Sept.29|   2  |- - -|0 0
                 |        |      |       |{Oct.  2|   5  |+ + +|0 0
  2. Dionisio    |Filipino|Male  |  18   |{Oct.  3|   6  |0 0 0|- +1:16
     Capate      |        |      |       |{Oct.  7|  10  |- - -|0 0
                 |        |      |       |{Oct. 15|  18  |- - -|- +1:64
                 |        |      |       |        |      |     |
  5. Alejandra   |European|Female|   6   |Oct.  20|   7  |+ + +|0 0
     Fisher      |        |      |       |        |      |     |
                 |        |      |       |{Oct. 22|   2  |+ + +|+ -
                 |        |      |       |{Oct. 24|   4  |+ + +|0 0
 11. Gabriel     |Filipino|Male  |  21   |{Oct. 26|   6  |0 0 0|- +1:16
     Sevilla     |        |      |       |{Nov.  8|  18  |- - -|0 0
                 |        |      |       |{Nov. 15|  25  |- - -|- +1:64
                 |        |      |       |        |      |     |
                 |        |      |       |{Nov. 26|   3  |+ + +|+ -
                 |        |      |       |{Dec.  6|  13  |0 0 0|- +1:32
 19. Esteban     |Filipino|Male  |  15   |{Dec. 16|  23  |- - -|- +1:60
     Roa         |        |      |       |{ 1913  |      |     |
                 |        |      |       |{Jan. 11|  48  |- - -|- +1:120
                 |        |      |       |        |      |     |
                 |        |      |       |{Dec.  2| (?)  |+ + +|0 0
 20. Sia Su      |Chinese |Male  |  35   |{Dec.  5|  --  |0 0 0|+ -
                 |        |      |       |{Dec. 16|  --  |- - -|- +1:80
                 |        |      |       |        |      |     |
 24. Purificacion|Filipino|Female|  19   |{Dec. 11|   3  |+ + +|0 0
     del Val     |        |      |       |{Feb. 11|  33  |- - -|0 0
 ----------------+--------+------+-------+--------------------------------
    NOTE.--The bubo in Nos. 2, 5, and 24 never opened
    spontaneously. The pus was aspirated at the time of the
    second, eventually third, examination. Nos. 11 and 19 opened
    spontaneously. A fistula formed along the canal which was
    caused by the puncture, and healed up in several weeks. Hard
    inguinal buboes of secondary order persisted in patient 19 at
    the time of second examination. No plague bacilli were found
    either in the bubo of the first or second order. Patient 20
    had a considerable amount of pus in the inguinal primary bubo,
    but it was not opened until after the last examination.

    Two of the patients, cases 8 and 12, had numerous plague
    bacilli in the sputum at the time when the expectoration
    showed the presence of blood (twenty-three and one-half and
    eighty-two hours, respectively, before death). In 3 cases I
    was able to prove the presence of _Bacillus pestis_ in the
    skin lesions, _intra vitam_, fifteen, twenty-two, and
    forty-eight hours, respectively, before death. In case 18
    there was no doubt that the skin lesions, which covered the
    whole body and the face, were of secondary nature, as the
    patient died shortly afterward. It was undoubtedly a case
    similar to those reported by Gotschlich and Zabolotny.[5] In
    the other two patients there was only 1 maculopapulous
    efflorescence on the foot in case 1 (with a corresponding
    femoral bubo) and 2 lesions of the same type on the arm and
    forearm in case 4 (with a corresponding axillary bubo). It is
    possible that these lesions were the original port of entry of
    infection. Numerous plague bacilli were found in the skin
    lesions of these cases, both microscopically and in culture.

      [5] Kolle und Wassermann: Handbuch der pathogenen
      Mikroorganismen. Gustav Fischer, Jena (1903), =2=, 521.

    The plague patients tabulated in Table II recovered. They
    were all treated with antiplague serum. While cases 5, 11, 19,
    and 24 appeared clinically to be rather severe, cases 2 and
    20 were mild.

    It can be seen from the table that the plague bacilli may not
    be detected in the enlarged gland at first (case 2) and that
    their presence may be revealed only after repeated
    examination of the bubo. It is also evident from the results
    of repeated examinations that the plague bacilli disappear
    from the infected gland in a comparatively short time, as a
    rule at the time when pus starts to form. Contrary to the
    findings in patients who died, distinct phagocytosis was
    noticed in the smears made from the aspirated liquid in those
    patients who recovered and who had been treated with serum
    soon after the onset of the disease. It is undoubtedly this
    process that clears the gland of the infectious agents.

    The general opinion in regard to the presence of _Bacillus
    pestis_ in the circulating blood seems to have been, as
    Thompson remarks, that "the bacillus is rarely to be found in
    the peripheral blood stream before the agonal stage."[6]

      [6] Journ. Hyg., Cambridge (1906), =6=, 558.

    The Austrian Commission, using few drops of blood, found
    positive blood culture in 40 per cent; Calvert in Manila in
    100 per cent when examined twenty-four hours before death;
    Choksy, Berestneff, and Mayr in 45 per cent; and Greig in 60
    per cent. The Indian Commission examined 28 patients, and
    obtained positive blood cultures in 16 out of 23 fatal cases.
    Not a single positive blood culture was obtained from the
    patients who survived. The time of blood examination in
    positive cases was three and one-half to seventy-five and
    one-half hours before death. The amount of blood used was 1
    cubic centimetre. Only 6 out of the 30 samples, which gave
    positive blood culture, were found positive by microscopical
    examination of blood smears. The following conclusions are
    based on these observations in regard to the septicæmic stage
    of bubonic plague: (1) "A severe septicæmia may be present
    at a comparatively early stage of the disease and for a
    considerable number of hours before death, and (2) the
    septicæmia may be of an irregular and fluctuating type."[7]

      [7] _Ibid._ (1907), =7=, 395.

    From the tables it will be seen that out of 15 patients
    examined by me, 14 gave positive blood culture; and of these
    3 recovered. One blood culture revealed the presence of
    streptococcus in addition to _Bacillus pestis_. The results
    of the examinations tabulated in Tables I and II show, in
    agreement with the findings of the Indian Commission, the
    occasional early occurrence of plague bacilli in the blood
    stream, as the time of examination in the positive cases
    varied from one hour to one hundred six hours before death.
    In consideration of the ephemeral character of the septicæmic
    stage of plague, as evidenced by repeated blood cultures in
    the three patients who recovered, one can hardly avoid the
    impression that there is a certain degree of septicæmia in
    every case of plague. The possibility of detecting the
    bacillus in the circulating blood increases in proportion
    with the quantity of blood used for culture. The best chance
    to recover plague bacilli from the circulating blood seems to
    be in the stage of high fever and general prostration.

    The phenomenon of agglutination of plague bacilli by the
    serum of patients was first observed by Wissokowitsch and
    Zabolotny in 1897[8] and later confirmed by the German Plague
    Commission. Vagedes, Klein, and others[8] pointed out the
    defects of the reaction as a diagnostic means. Aside from
    the technical difficulties, the reaction was found
    inconstant, and its occurrence was not noticed until the
    second week of the disease and even then only in low
    dilutions of the serum.

      [8] Referred to in Kolle und Wassermann: Handbuch der
      pathogenen Mikroorganismen (1903), =2=, 524.

    Although the recent work of Strong[9] and of Strong and
    Teague[10] has reduced the technical difficulties, the fact
    remains that positive agglutination of plague bacilli by the
    patient's serum cannot be obtained in the first week of the
    disease, and, therefore, the isolation of plague bacilli from
    the body of the patient is still the only quick and safe
    method of plague diagnosis.

      [9] The Philippine Journal of Science, Sec. B. (1907), =2=,
      155.

      [10] _Ibid._ (1912), =7=, 194-201.

    Having utilized the technic devised by Teague, I have had no
    difficulty in performing the agglutination test in plague.
    The emulsion of plague bacilli, to be used for the test, was
    prepared by suspending young cultures of virulent plague
    bacilli, grown at 30° C., in salt solution and filtering the
    suspension through filter paper. No antiseptic was added nor
    heat applied. Serial dilutions of unheated patient's serum
    were mixed with equal amounts of bacterial suspension in
    small test tubes. Incubation at 35° C. followed. Controls,
    consisting of serial dilutions of normal human serum as well
    as bacterial suspensions without serum, excluded any possible
    error which might have been caused by spontaneous
    sedimentation of the bacterial suspension; while a parallel
    test with highly agglutinant serum facilitated the reading of
    positive results.

    Altogether, 22 tests were performed on 15 patients, 11 of
    whom were fatal cases and 4 of whom recovered. In the
    negative reactions, the duration of the disease at the time
    of examination ranges from two to six days. The non-fatal
    cases showed slight agglutination from the sixth day on. From
    that day, the agglutination titer of the serum was found to
    rise, and the agglutinins persisted in the blood of
    convalescents up to the seventh week of the disease.[11]

      [11] It is hoped that it will be possible to examine some of
      the survivors for agglutination from time to time.

    It must be borne in mind that the patients, who showed
    positive agglutination, had been vigorously treated with
    antiplague serum. Nevertheless, in consideration of the low
    titer of the curative serum (dilution 1:32, agglutination
    positive; dilution 1:64, agglutination negative), the rise of
    the agglutinant power of the patient's serum in dilutions
    higher than 1:16 cannot be explained as wholly due to passive
    immunity, but rather to active immunity arrived at on the
    principle of simultaneous immunization.

    From the preceding observations the following conclusions are
    drawn:

    1. The importance of blood cultures as a diagnostic means is
    evident from the fact that positive blood culture was
    obtained in practically every case that was examined in the
    febrile stage of the disease, even when buboes or signs of
    pulmonary involvement had not been detected clinically.

    2. It is also evident that _Bacillus pestis_ may be found in
    the circulating blood of the patients even in cases which
    subsequently recover.

    3. The period of time during which _Bacillus pestis_
    circulates in the blood is evidently short and irregular.

    4. Mixed infection may be encountered in plague septicæmia
    (_Streptococcus_, _Pneumococcus_).

    5. The agglutination test is of no value for the diagnosis of
    plague, as it was found positive only in convalescents.

    6. Phagocytosis of plague bacilli in the bubo was noticed
    only in patients who recovered after being vigorously treated
    with curative serum.

    7. The presence of numerous plague bacilli in comparatively
    insignificant skin lesions during the life of the patient
    points to the possibility of direct transmission, while the
    fact that a patient without any apparent bubo, who is not so
    sick as to be detained from his daily occupation, may
    expectorate large numbers of plague bacilli, are facts of
    great importance with regard to the communication of the
    disease. It is obvious that the last-mentioned condition
    might, and very likely does, give rise to an epidemic of
    pneumonic plague if the atmospheric and sanitary conditions
    are favorable.

  TABLE III.--INSECTS FOUND TO CONTAIN BACILLUS PESTIS

 ======================================================================
                |               |                           |Experi-
                |               |                           |mental
     Author     |    Insect     |    Source of infection    |trans-
                |               |                           |mission
 ---------------+---------------+---------------------------+----------
 Yersin         |Flies          |Laboratory infection       |
 Nuttal         |Flies          |Experimental infection     |
 Nuttal         |Bedbugs        |Experimental infection     |Negative
                |               |                           |  by bite.
 Nuttal         |Flea           |Experimental infection     |Negative.
 Hankin         |Ant's fæces    |Fed on plague material     |
 Hankin         |Bedbugs        |Plague hospital            |
 Ogata          |Flea           |Plague rats                |
 Simond         |Flea           |Plague rats, experimental  |Positive.
 Tindswell, 1900|Flea           |Plague rats                |Negative.
 Tindswell, 1903|Flea           |Plague rats                |Negative.
 Kolle          |Flea           |Experimental infection     |Negative.
 Gauthier and   |Flea           |Experimental infection     |Positive.
   Raybaud      |               |                           |
 Liston         |Flea           |Epidemic among pigs;       |
                |               |  harbored fleas;          |
                |               |  dead rats found          |Positive.
 Zirolia        |Flea           |Retained _Bacillus pestis_,|
                |               |  7-8 days                 |
 British        |Flea           |Repeated experiments       |Positive.
   Commission   |               |                           |
 Verbijtski     |Flea and bedbug|Experimental infection     |Positive.
 La Bonadière   |Fly            |                           |
   and          |               |                           |
   Xanthopulides|               |                           |
 Herzog         |_Pediculus     |Dead body of plague case   |
                |  capitis_     |                           |
 ---------------+---------------+---------------------------+----------


      II. OBSERVATIONS ON THE TRANSMISSION OF PLAGUE BY
      BLOOD-SUCKING INSECTS

    Judging from the data which have been collected from the
    literature[12] on the transmission of plague (Table III),
    Simond seems to have been the first to call attention to
    the important part which blood-sucking insects, particularly
    fleas, play in the transmission of plague. Although many
    investigators have been successful in demonstrating the
    presence of _Bacillus pestis_ in the digestive system of
    blood-sucking insects, it was not until the experiments of
    Gauthier and Raybaud that the actual transmission of plague
    infection by fleas was convincingly proved. Ever since the
    exhaustive and conclusive experiments, which were carried out
    both under natural and artificial conditions by the British
    Plague Commission, and the work of Verbijtski, which antedates
    the British Commission, were presented, there has been no
    doubt that the transmission of plague by blood-sucking
    insects, particularly by the fleas, is one, although not the
    only, mode of spreading this disease. It is obvious, as Herzog
    correctly remarks, that the factors which are responsible for
    the spreading of plague must be considered individually in
    each epidemic and in various parts of the world as well. There
    is no doubt that the importance of any insect in the
    transmission of plague depends on its habits as well as on
    those of the host, be it either animal or man.

      [12] Centralbl. f. Backt., 1 Abt. (1897), =22=, 87, 437.
      Report of Indian Plague Commission (1898-99). Zeitschr. f.
      Hyg. u. Infectionskrankh. (1901), =36=, 89. Kolle und
      Wassermann: Handbuch der pathogenen Mikroorganismen (1903),
      =2=, 538. Zeitschr. f. Hyg. u. Infectionskrankh. (1905), =51=,
      268. Journ. Hyg., Cambridge (1907-10), plague numbers. _Ibid._
      (1908), =8=, 162, 260.

    During the recent outbreak of plague in Manila, several
    samples of bed-bugs from the beds of the plague patients and
    dog fleas from a plague-infected house were collected and
    examined, but with negative result.

    In spite of the fact that it adds nothing new to the question
    of whether or not plague can be transmitted by fleas, since
    the question has been conclusively answered by the work of
    the Indian Commission, nevertheless the following
    observations of a small outbreak of plague among animals, the
    spreading of which was due solely to fleas, are of interest.

    One wild rat was inoculated with strain Iloilo 3 of
    _Bacillus pestis_. The skin adjoining the root of the right
    ear was scarified, and a loopful of the culture was smeared
    on the scarified skin. The rat was found dead three days
    after the inoculation.

    The cage containing the dead rat was immersed in kreolin
    solution. At autopsy the cervical glands were found slightly
    swollen, somewhat reddened, but no hæmorrhagic oedema of the
    surrounding tissue was noticeable. There was slight necrosis
    at the place of inoculation, showing superficial, purulent
    discharge. Clear effusion in both pleural cavities and one
    hemorrhage in the pleura were found. The lungs were
    hyperæmic, but otherwise normal. The spleen was of somewhat
    darker color, but otherwise normal in size and appearance.
    The liver showed a slight degree of parenchymatous
    degeneration, the congestion making prominent the structure
    of the organ. The typical, although not constant, changes of
    the organ, which are characteristic of natural plague
    infection in rats, were absent. The kidneys were without
    macroscopic change. The lymph glands, with exception of the
    cervical nodes, were normal.

    Examination of the rat's fur revealed ectoparasites on the
    neck, under the chin, and back of the ears; these at the time
    of the examination apparently were dead. About 6 common rat
    fleas were found and identified as _Loemopsylla cheopis_
    Rothsch. The parasites were immersed in sterile salt solution
    for three hours. When removed in a dry test tube, they began
    to move about sluggishly. The intestinal tract of these fleas
    contained blood.

    Five of the fleas were crushed by means of sterile forceps,
    and inserted in a pocket under the shaved skin of a
    guinea-pig. The animal died of plague within three days,
    showing considerable hemorrhagic oedema around the place of
    inoculation, typical bilateral inguinal buboes, and
    characteristic changes in the spleen. Smears and cultures
    made from the bubo and spleen were positive for _Bacillus
    pestis_.

    Another wild rat, which was in a separate cage in the same
    room where rat 1 had been kept, died twenty-four hours after
    rat 1. The two cages were at least 10 centimetres apart. Rat
    2 harbored fleas of the same species as were found on rat 1.

    Numerous severe bites were detected back of the ears and on
    the neck of the dead animal. The post-mortem findings were
    identical with those described in rat 1; that is, cervical
    buboes, pleural effusion, and slightly enlarged spleen.

    It is well to remark that both rats had been kept in the same
    room for about six months. Fleas had never been noticed on
    our guinea-pigs. During the time the rats had been kept in
    the plague house no irregular results were noticed in
    plague-inoculated animals. At the time the first rat was
    inoculated no other plague-infected animals were in the
    plague house, and since that time another building has been
    used for plague-infected animals.

    Two days after the death of rat 2 three guinea-pigs, which
    were kept in separate cages in the same room, were found dead
    of plague (smears and cultures were both positive). Several
    fleas (_Loemopsylla cheopis_) were found on the necks of these
    animals. They were collected and inoculated in the same way
    as the fleas from the first rat. The experimental animal,
    which was inoculated with the fleas, was killed and found to
    be infected with plague. The findings were local reaction,
    inguinal buboes, and typical spleen. Smears and cultures were
    positive for _Bacillus pestis_.

    Although numerous healthy guinea-pigs were examined in the
    same plague house, no fleas could be found at that time, only
    the 2 rats and the first 3 guinea-pigs are positively known
    to have harbored fleas, the latter after the death of the
    rats and not before.

    The gross lesions in these naturally infected guinea-pigs
    were somewhat unlike those found in guinea-pigs infected
    either by vaccination or by intraperitoneal or subcutaneous
    inoculation. All except one showed primary buboes on the neck
    with more or less extensive hemorrhagic oedema extending in
    some cases over the thorax. There was little pleural effusion
    present; the spleen always showed typical changes of necrotic
    foci varying in size and number. In one instance similar foci
    were found also in the liver, large enough to be visible
    macroscopically. This was in a case where like changes were
    found in the lungs.

    Only one of the guinea-pigs showed an exception, in that the
    primary buboes were located in the inguinal region, with
    pelvic and axillary glands secondarily involved. These are
    the findings usually met within guinea-pigs artificially
    infected with plague by the vaccination method, if the lower
    part of the abdomen be chosen for inoculation. The reason for
    such a deviation from the findings in the rest of the
    guinea-pigs may lie in the fact that this animal was almost
    completely deprived of hair by a skin disease.

    It is of importance to mention the skin lesions which were
    found on the necks of the guinea-pigs, particularly under the
    chin. Besides small red spots which appeared to be fresh flea
    bites, small, elevated, and fairly deep infiltrations partly
    covered with moist scab were found in the skin under the
    chin. Other animals showed changes usually found in the
    scarified skin of guinea-pigs after artificial inoculation
    with plague material. The base of each cutaneous
    efflorescence was hemorrhagic and oedematous.

    A histological study of the tissues of these guinea-pigs
    known to be naturally infected by plague fleas showed the
    following changes:

    THE CERVICAL BUBO.--The enlarged lymphatic gland was
    surrounded with a thickened capsule. Necrosis existed in the
    subcapsular part of the gland, where it formed an almost
    continuous circular zone, leaving the central part less
    changed. Smaller irregular necrotic foci were scattered
    throughout the section. Polymorphonuclears in various stages
    of disintegration were found throughout the section.

    _The Lungs._--Very few blood extravasations were present in
    the alveoli; otherwise normal.

    _The Spleen._--The capsule was thin. There were subcapsular
    hemorrhages. The Malpighian bodies were somewhat enlarged,
    but of normal structure. Throughout the parenchyma irregular
    multiple necrotic foci were found, leaving but little of
    spleen tissue intact. Numerous polymorphonuclears which were
    present showed varying degrees of karyorrhexis.

    _The Kidneys._--The outline of the cells was indefinite; a
    few miliary hemorrhages existed in the cortical part of the
    organ.

    _The Liver._--There was excessive congestion, fatty
    degeneration, and pigmentation of the cells. The capsule was
    slightly thickened.

    _The Skin._--The epithelium was missing in one place in the
    section, and cellular infiltration extended from that place
    into the subepithelial layer of the surrounding skin. The
    same kind of infiltration reached deep into the skin, stripes
    of cellular infiltration penetrating into the tissue along
    the muscle fibres. There was no direct connection between the
    cellular infiltration and the follicles of the hair.

    It may be well to describe in detail the time of death from
    plague among these and the other animals in this outbreak, as
    well as the time when the plague house was disinfected.

    The first animal (rat 1) having been inoculated on August 27,
    in the afternoon, died of plague within three days (August
    30). The second animal (rat 2) died twenty-four hours later.
    Guinea-pigs 3, 4, and 5 (see plan) were found dead on the
    morning of September 2; that is, two days after the death of
    rat 2 and three days after the death of rat 1.

    The same day that the three guinea-pigs were found dead of
    plague, rooms I, III, IV, and VI were thoroughly disinfected.
    The floor, the ceiling, and the walls were sprayed with
    kerosene and lysol solution. The remaining animals in room VI
    were destroyed, and the cages disinfected. No animals were
    kept in rooms I, III, and IV at that time.

    Three days after the death of animal 5, guinea-pigs 6 and 7
    were found dead of plague, while the next day guinea-pigs 8
    and 9 died. No death occurred on September 7, but the next
    two days each recorded two plague guinea-pigs (10, 11, 12,
    and 13). On September 11, the last guinea-pig died of plague
    in this outbreak. The whole building was then thoroughly
    disinfected. No plague-inoculated animals were kept in the
    rooms after the first sign of the epidemic. After September
    11, no more cases of spontaneous plague infection were
    observed.

[Illustration: ANIMAL HOUSE]

    It will be noticed that the epidemic lasted eleven days
    after the first animal died and fourteen days after animal 1
    was inoculated. Altogether, 14 animals out of at least 200
    animals exposed died of plague.

    No death occurred among rabbits, although these animals were
    distributed among the guinea-pigs. In fact, 2 rabbits were
    surrounded by plague guinea-pigs 8, 9, and 10, but did not
    contract plague.

    From the epidemiological standpoint it is interesting to know
    the dimensions and location of the cages in which the animals
    were kept.

    Aside from the 2 rats which were confined in ordinary traps
    that stood on a table 80 centimetres high, the rest of the
    animals were kept in regular metal animal cages. The
    dimensions of the cages are: Fifty centimetres long, 36
    centimetres broad, and 30 centimetres high. The cage stands
    on four legs each 10 centimetres long; the centre of the
    bottom of the cage holds a drain opening 8 centimetres above
    the floor.

    The majority of the cages in room II were located on the
    floor; some on the second shelf of a wooden rack. This
    last-mentioned arrangement, judging from the construction of
    the wooden frame, allowed a continuous passageway for the
    fleas to the second shelf of the racks. On the other hand,
    the deaths among the guinea-pigs in room V were restricted to
    the cages standing on the floor, the majority of cages in
    that room being placed on tables 80 centimetres high.

    Only a theoretical explanation can be given of the short
    duration and sudden cessation of the outbreak. One can assume
    with great probability that the first partial disinfection
    drove the fleas away from the primary source of infection,
    and that they traveled as far as possible. They finally
    settled in those guinea-pig cages which had not been molested
    by the first disinfection. Having no new supply of plague
    blood (all of the plague-infected guinea-pigs having been
    removed, most of them before death), the fleas soon cleared
    themselves of plague bacilli. The peculiar feature of the
    outbreak, namely, the failure to find fleas on the animals in
    rooms II and V, finds its explanation in the observation of
    the Indian Commission who found that the fleas "died or
    disappeared very rapidly."

    The following conclusions can be drawn from these
    observations:

    1. The common rat flea (_Loemopsylla cheopis_) prefers the rat
    to the guinea-pig.

    2. In the absence of rats it will attack guinea-pigs rather
    than rabbits.

    3. The fleas which have sucked blood from rats or guinea-pigs
    afflicted with plague septicæmia were found to harbor
    virulent plague bacilli inside of their bodies.

    4. The transmission of plague infection by direct or indirect
    contact being excluded in our case, the fact that fleas of
    the same species and harboring plague bacilli were found on
    the rat and on the guinea-pigs, the presence of flea bites on
    the rats and on the guinea-pigs with positive findings of
    skin lesions on that part of the body where the fleas and
    flea bites were located, together with the anatomical picture
    of the findings in the guinea-pigs, lead to but one
    explanation; namely, that the plague infection was
    transmitted by fleas.


      III. OBSERVATIONS ON ANIMALS SUSPECTED OF PLAGUE

    Out of the several tens of thousands of rodents examined
    during the antirat campaign, we have found only two plague
    rats which showed the typical picture of natural plague
    infection in rat; that is, cervical buboes with surrounding
    oedema, subcutaneous injection, pleural effusion, enlarged
    spleen, and such changes of the liver as are characteristic
    of natural plague infection in rats. Microscopically, large
    numbers of plague bacilli were found in these cases, and pure
    cultures of _Bacillus pestis_ were recovered from the spleen.
    Histological examination of internal organs, particularly
    that of the liver, confirmed the bacteriological findings.
    The remainder of the plague rats exhibited only two of the
    signs of plague infection, namely, bubo and oedema of the
    surrounding tissue, and eventually hemorrhages.

    Besides plague infection, a great number of rats showed
    purulent conditions from causes other than plague. Abscesses
    of the lungs were frequently met with, and cervical or
    axillary buboes are not uncommon in Manila rats. Various
    pyogenic bacteria were found in the pus of such abscesses. Of
    the less common was _Bacillus pyocyaneus_ and the
    pneumobacillus of Friedländer. Chronic plague was excluded in
    these cases since the animal inoculation failed to produce
    plague infection.

    More than half of the rats examined harbored parasites in
    their organs. _Echinococcus taeniæformis_ was found in the
    liver of practically every gray rat, while a small _Ascaris_
    and _Tænia diminuta_ were not uncommon in the intestines. Two
    rats were found to have sarcosporidiosis, 2.6 per cent.
    showed rat leprosy, and 7.4 per cent. trypanosomiasis. One
    tumor of the mammary gland and one tumor in the axillary
    region were encountered, while one tumor of the large
    curvature of the stomach proved to be a chronic inflammatory
    tumor due to parasites. One peritoneal tumor in a rat (_Mus
    decumanus_) gave the impression of a malignant tumor on
    account of the miliary dissemination of the peritoneum. It
    was found to consist of muscle and spindle-cell sarcomatous
    tissue. Ectoparasites were very seldom noticed, on account of
    the method of collecting the rats. When present, they were
    mites and fleas.

    In the naturally infected plague rats the rigidity of the
    fresh cadaver was pronounced. The primary bubo was in every
    case cervical. Cervical glands were enlarged and hemorrhagic
    with slight oedema of the surrounding tissue. The subcutaneous
    injection extended over the neck and chest. The inguinal
    glands were small and pigmented. The lungs were collapsed,
    and showed hemorrhagic foci. The spleen was slightly
    enlarged, firm, and dark red. The liver was rather large,
    firm, pale red, with shade of yellow, which was caused by
    minute yellowish foci thickly scattered throughout the tissue
    and visible through the capsule. The kidneys were hyperæmic.
    The intestines were without change. The serous membranes were
    pale with no hemorrhages.

    Histological examination of the tissue of naturally infected
    plague rats showed the following changes:

    _Liver._--The structure of the organ was well marked; the
    veins dilated, trabeculæ slightly compressed, nuclei well
    stained, and few of the liver cells showed vacuoles. Small
    foci, most numerous under Glisson's capsule, were scattered
    throughout the organ; they varied in size, but were not
    larger than a miliary tubercle. The small necrotic foci were
    found to consist of few necrotic liver cells. The centre of
    the larger foci was formed by degenerated and necrotic liver
    tissue, surrounded by round-cell infiltration.
    Polymorphonuclears were also found in the zone of cellular
    infiltration. There was a slight degree of hemorrhage in
    each focus. Epithelioid cells and large vesicular cells with
    several nuclei were to be found. The foci, mentioned above,
    were sharply demarcated from the surrounding liver tissue,
    which appeared to be intact.

    _Spleen._--The structure was well preserved, the capsule
    thin. The Malpighian bodies were normal as to the elements of
    which they consist. Cells with pycnotic nuclei were scattered
    throughout the organ, and vesicular cells with small, deeply
    stained, excentrically located nuclei were present.
    Polymorphonuclears were found in the tissue in considerable
    numbers. No localized necrotic foci could be found in
    sections through the spleen.

    _Cervical Glands._--The blood-vessels were considerably
    distended. A few hemorrhages and polymorphonuclears were
    present. Oedema of the capsules and surrounding tissue
    existed. Part of the gland was necrotic.

    _Lungs._--The blood-vessels were distended. The alveoli
    contained homogeneous masses and blood. There were numerous
    subpleural hemorrhages. The bronchi were collapsed, and
    contained mucus.

    _Kidneys._--The cortical part showed subdued structure; the
    epithelial cells had an indefinite outline and occasionally
    showed vacuolization. The medullar part was better preserved.
    There were miliary subcapsular hemorrhages. A few small foci
    were scattered throughout both medullar and cortical parts.
    They consisted of round-cell infiltration.


      NATURAL PLAGUE INFECTION IN A CAT

    The experiments of the German Plague Commission proved that
    cats showed considerable resistance to plague infection as
    cutaneous and subcutaneous inoculations failed to infect
    them. According to the Austrian Commission, cats develop
    submaxillary buboes if fed on plague material. They are said
    by Albrecht and Gohn[13] sometimes to recover. Out of four
    cats fed on plague material two died of plague, one showing
    submaxillary, the other mesenterial buboes. Virulent plague
    bacilli were found in the discharge from the nose and also in
    the fæces of cats which apparently did not become infected
    after having been fed on plague material.

      [13] Über die Beulenpest in Bombay im Jahre 1897 (1897), II
      B, II C.

    One case of spontaneous plague infection of a cat was
    recorded by Thompson[14] in Sydney.

      [14] Report of an outbreak in Sydney, 1900. Referred to in
      Kolle and Wassermann (1903), =2=, 510.

    W. Hunter,[15] in Hongkong made observations on cats
    suffering from plague infection. The author also undertook a
    few experiments, and arrived at the following conclusions:

    1. Cats suffer from plague.

    2. The disease may be acute or chronic.

    3. The type of the disease is septicæmic.

    4. The animals may occasionally play a part in the
    dissemination of plague.

    5. In plague-infected areas cats probably become infected
    through rats, which they devour as food.

    6. In plague-infected districts possible plague infection in
    cats is of great importance from a domestic point of view.

      [15] Lancet (1905), =I=, 1064.

    On November 27, 1912, a sick cat was brought to the
    laboratory for examination. It was reported that the animal
    was found in a warehouse in which dead rats had been found
    some time previously. The rats were not examined. In the
    morning of the 30th, the cat was found dead in the cage where
    it had been kept under observation. The following are the
    post-mortem findings:

    The animal was a fairly well-nourished female.[16] The
    subcutaneous tissue, pericardium, mediastinum, and
    mesenterium contained considerable amounts of fat.

      [16] The cat was the mother of 4 kittens which were about 3
      weeks old at the time the cat was delivered for examination.
      They were kept under observation for several weeks, but
      showed no signs of plague infection.

    The subcutaneous tissue of the neck showed oedema and small
    hemorrhages. The submaxillary tissues were swollen on both
    sides. When the fasciæ and superficial muscles of the neck
    were removed, enlarged glands were found on both sides. These
    were closely attached to the submaxillary salivary glands.
    The surrounding tissue was oedematous, but no hemorrhages were
    noticed in the vicinity of the enlarged glands. Upon section
    the glands were found to be necrotic, and upon pressure a
    thin purulent liquid escaped. There were no hemorrhages
    within the glands. Several enlarged lymph-nodes, smaller in
    size, could be followed down the neck on the left side. The
    lymph-nodes in the axillæ as well as in the groins and
    peribronchial nodes were normal. The mesenteric glands were
    slightly enlarged and reddened.

    The lungs were slightly collapsed. A clear, sanguineous,
    slightly coagulated effusion was observed in both pleural
    cavities. The tissue of the lungs showed considerable oedema
    and hypostasis. The bronchi and pharynx showed no changes,
    the mucous membrane being pale and thin.

    The heart was normal.

    The spleen was enlarged, of light red color, with follicles
    slightly prominent.

    The stomach contents was blackish in color; there were no
    hemorrhages or ulcers in the mucosa.

    The liver was somewhat enlarged. The organ showed prominent
    structure, the centres of the acini being red, the periphery
    lighter in color.

    The kidneys were slightly enlarged and pale. The capsule
    peeled off easily, the venæ stellatæ were prominent, the
    surface smooth; there were no hemorrhages. The cortex was
    increased in breadth and was of the same color as the
    surface; the pyramids were darker in color. The organ was of
    fragile consistence.

    Suprarenals were normal, as were also intestine and bladder.

    The histological findings were as follows:

    _Bubo._--The capsule of the gland was oedematous. The whole
    gland as seen in cross section had undergone necrosis, except
    a few foci which still showed cellular structure.

    _Lungs._--The alveoli were filled with homogeneous masses,
    containing but few degenerated epithelial cells and
    leucocytes. The blood-vessels were dilated, particularly in
    the subpleural part of the organ. In some places capillary
    mycotic emboli with subsequent hemorrhage were encountered.
    The large blood-vessels and bronchi were normal.

    _Salivary Glands._--Those glands attached to the primary bubo
    showed the normal structure of a combined mucous and serous
    gland.

    _Liver._--There was considerable congestion. The centres of
    the acini showed parenchymatous and fatty degeneration. The
    cells on the periphery of the acini exhibited typical fatty
    infiltration. The large blood-vessels and small ducts were
    without change.

    _Kidney._--The cells of the kidney showed various degrees of
    degeneration, ranging from parenchymatous to fatty
    infiltration. There were a few capillary hemorrhages and
    hyaline casts present.

    _Suprarenals._--These showed slight degeneration.

    _Spleen._--This organ showed congestion, a few hemorrhages,
    and bacterial emboli; otherwise normal.

    The bacteriological examination of the material from this cat
    gave the following results:

    1. _Smears:_

      _a._ From the buboes showed degenerated leucocytes, many
      lymphocytes, and numerous bacteria, some of which resembled
      _Bacillus pestis_ in their polar staining.

      _b._ From the spleen showed numerous plague-like,
      polar-stained bacilli. Round involution forms were present.

    2. _Cultures:_

      _a._ From the buboes were badly contaminated with _Bacillus
      coli_ and _Bacillus pyocyaneus_ colonies.

      _b._ From the spleen: A few scattered colonies of _Bacillus
      pyocyaneus_ developed on the surface of the agar. Between the
      large colonies a scanty growth of dewy appearance was
      noticed. Smears made from this growth revealed plague-like
      bacilli of the cultural type, showing a few club-shaped
      involution forms. Subcultures were made in order to secure
      pure culture. They showed a pure growth of _Bacillus pestis_
      as indicated by the morphology of bacilli and shape of the
      colonies. Agglutination with plague-immune serum was
      positive.

    3. _Inoculation experiments (vaccination method):_

      _a._ One guinea-pig was inoculated with the material from the
      left bubo, another one with material from the right bubo.
      They died of plague on the third and fifth days,
      respectively.

      _b._ One guinea-pig was inoculated with the material from the
      spleen. It died of plague on the third day.

      _c._ One guinea-pig was inoculated with material from the
      nostrils obtained by swab. The animal survived, showing no
      indication of plague.

      _d._ One guinea-pig was inoculated with material from the
      rectum obtained by swab. It died of plague on the fifth day.

    Although plague infection among cats is apparently a rare
    occurrence, the fact that cats may contract the disease in
    spite of the high degree of resistance to plague infection
    has to be considered from the hygienic standpoint.

    To appreciate the important rôle which cats may play in the
    spreading of the disease one need only consider the close
    contact of these animals with rats on one side and human
    beings on the other. It is also a well-established fact that
    not only plague-infected cats, but also those which have
    devoured plague-infected material and remained apparently
    normal, may excrete plague bacilli which have retained their
    full virulence.

NOTES ON PLAGUE IN HONG KONG BY DR. ROBERG.--During the Hong Kong
epidemic of plague which preceded and was coincident with that of
Manila, I visited that city twice (December, 1913, and July, 1914), but
I did not closely investigate the methods adopted and carried out by
the authorities there, for the reason that the Manila plan was so much
more productive of results, as shown by the apparent inability of the
Hong Kong officials to gain control of the disease. However, I received
from Dr. David Roberg, of the Oregon State Board of Health, a copy of a
report made by him to the Secretary of his State Board of Health,
following an investigation of the Hong Kong epidemic and the methods
there followed. I have Dr. Roberg's permission to use his report and it
is herewith presented. It is dated Manila, April 16, 1914, and is as
follows:

    I have the following notes to present on the epidemic of
    bubonic plague in Hongkong.

    On April 5th when I arrived in Hongkong the epidemic was
    rapidly approaching its height. With its onset in January
    there were 47 cases, in February 42, and in March 223. During
    the week previous to April 5th, there were 91 cases; during
    the six days I was in Hongkong they averaged 15 a day.

    Judging from previous epidemics the present one will be
    exceptionally severe. The season for the occurrence of human
    plague is from the months of February to July. The onset is
    gradual; in May it reaches its maximum and then declines. In
    the epidemic of 1912, for the city of Victoria the monthly
    rate showed the following, January 9, February 22, March 61,
    April 265, May 513, June 346, July 105, August 11, and
    September 1. Comparing these rates with those of the present
    year it will be seen that the number for March far exceeds
    that of two years previous.

    Illustrating the season for human plague, with its onset,
    maximum and decline, are the monthly rates for the city of
    Kowloon during 1912, when the following cases occurred:
    February 2, March 12, April 52, May 246, June 152, July 39,
    August 8, and September 3.

    The season for human cases is determined by the condition of
    the rats. At the close of the season in July the rats die off
    from plague in great numbers as it is then the hottest time
    of the year. During the months from September to February the
    rats increase in number and in susceptibility to the extent
    of being sufficient to again infect human beings. Moreover
    every other year shows a marked severity in the epidemics of
    human bubonic plague. This is explained by the fact that it
    requires two years' time for the rat population to become of
    sufficient greatness and susceptibility to cause a severe
    human outbreak. This is shown by the yearly number of cases
    since the year 1911. During the years 1911, 1912 and 1913
    respectively, there were 253, 1847, and 408 cases. During the
    present year the monthly rate is exceeding that of the heavy
    year of 1912.

    The severe epidemic in 1912 was a result of the influx of
    50,000 Chinese refugees into Hongkong during the revolution
    in 1911. The number of rats in the native district depends
    upon the available food supply, and as a result of this human
    overcrowding the amount of waste food so increased in the
    houses, yards and streets, that the over accumulation of
    garbage could not be kept pace with. This influx also brought
    in great numbers of susceptible rats.

    The number of rats killed off during the epidemic in 1912
    were so great that in 1913 they had not recovered
    sufficiently to cause a severe outbreak during that year, and
    as a result of the lightness of epidemic in 1913, they are so
    increased in number and susceptibility now that they are
    causing a very severe epidemic in human beings.

    Of rats in Hongkong they have the _Mus decumanus_ or drain
    rat and the _Mus rattus_ or house rat. It is noteworthy that
    the drain rat is found plague-infected throughout the year,
    while the house rat is found infected only during the period
    in which the human epidemics occur, namely from February to
    July. The number of infected rats a year run parallel to the
    number of monthly cases.

    The bulk of human infection is due to the spread of house
    rats. Man also becomes infected by the drain rat when the
    drains are flooded by rain storms and the rats are driven
    into the houses.

    What has made plague permanent in Hongkong is the
    overcrowding of the native districts. Besides there is a
    floating population entering and leaving the native quarters,
    numbering about 4000 a day. The native houses have been built
    with double floors and walls which harbor the rats. Where the
    construction is of wood it is possible to remove the rat
    spaces. It has been found since the introduction of plague
    into Hongkong in 1894, that those districts containing the
    greatest number of soft brick houses with hollow walls, have
    shown the greatest incidence of plague. This can not be
    remedied as it would involve the destruction of buildings on
    too large a scale.


      THE WORK OF THE SANITARY BOARD

    The area under the control of the Board comprises the Island
    of Hongkong containing 32 square miles, with a sea frontage
    of 13 miles in length. Included also is the old city of
    Kowloon which is situated one mile and a third across the
    harbor and contains two and three-fourths square miles. The
    city of Victoria on the northern shore of the Island of
    Hongkong has a sea frontage of 5 miles, contains about ten
    thousand domestic buildings, of which about one thousand are
    non-Chinese.

    The population of Hongkong is difficult to estimate, as the
    floating population is so great. In the 1912 census there
    were 446,614 Chinese and 21,163 non-Chinese.

    The city of Victoria is divided into 10 Urban Health
    Districts and old Kowloon into 2. There is an inspector in
    charge of each. These districts are built over an area
    averaging from 31 to 140 acres. The houses in these districts
    average one thousand and the population from 8000 to 33,000.
    There are four inspectors in charge of the scavenging work,
    one for the disinfection stations in Victoria and old
    Kowloon, one for the cemeteries and two for general duty.

    The measures employed by the Sanitary Board are summarized as
    follows:

    1. The exclusion of rats from all dwellings by means of
    concreted ground surfaces, the protection of all drain
    openings and ventilating openings by iron gratings, and the
    prohibition of ceilings and of hollow walls in new buildings
    and in those existing buildings from which they have been
    removed by order.

    2. The collection and bacteriological examination of all dead
    rats. Facilities for the collection of rats in the quarters
    are provided in the shape of small covered bins attached to
    lamp posts, telephone posts, electric light poles, etc. These
    bins contain a carbolic acid disinfectant, and the
    inhabitants are invited to at once put into them all rats
    found or killed by them. There are 650 of these bins
    distributed throughout the city and its suburbs, and each of
    them is visited twice daily by rat collectors who take all
    rats found by them to the City Bacteriologist. Each rat is at
    once labelled with the number of the bin from which it is
    taken, and if subsequently found to be plague infected, a
    special survey is immediately made of the block of houses in
    that vicinity. All rat-holes and rat runs are filled up with
    broken glass and cement, defective gratings and drains dealt
    with, and rat poison distributed free to the occupants. If
    several plague-infected rats are found in one locality, a
    special house-to-house survey and cleansing of that district
    is made.

    3. The destruction of rats by poison, traps and birdlime
    boards; special efforts in this direction being made just
    before the onset of the regular plague season which is in the
    months of from March to July.

    4. The encouraging of the community to keep cats.

    5. The systematic cleaning and washing out of all native
    dwellings at least once in three months with a flea killing
    mixture made by emulsifying kerosene in water.

    6. An efficient daily scavenging of all streets and lanes
    and the daily removal of refuse from the houses, coupled
    with the provision of covered metal dust-bins, to reduce as
    far as possible the amount of food available for rats.

    7. The disinfection of plague-infected premises by stripping
    them and washing them out thoroughly with a kerosene
    emulsion. The bedding, clothing, carpets, rugs, etc., are
    conveyed in a huge covered basket to the disinfecting plant
    and sterilized with superheated steam. No objection is made
    to the treatment of plague cases in native hospitals, and no
    restrictions are imposed in regard to the burial of those
    dead with plague except the provision of a substantial
    coffin.

    8. Every effort is made by means of lectures, addresses and
    explanations to induce the native population to participate
    in the above preventive measures.

Upon my last visit to Hong Kong, in July last, plague was abating. _The
South China Morning Post_ of July 15, 1914, contained the following
statement:

    Plague is gradually disappearing from Hongkong. Last week's
    return shows that there were 26 cases, of which 19 were fatal.
    All were Chinese. The total number of cases for the current
    year to date is 2093, with 1939 deaths resulting.

I regret that circumstances do not permit me to relate in detail the
work done and the observations made during the closing six months of
the Manila epidemic.

Up to the day of my departure from the Philippines, in July, 1914, I
remained in charge of plague suppression, but the added duties of
administration at San Lazaro Hospital and the coincident occurrence of
a cholera epidemic prevented me from keeping a detailed record in such
form as to permit reproduction here. It will therefore suffice to say
that the first six months of 1914 witnessed the passing of the most
threatening situation that has confronted the city of Manila in years.
The record of plague rats found does not convey an accurate idea of the
prevalence of rat plague by any means, for the simple reason that, when
found, the rat cadavers were in such condition as to forbid
bacteriologic examination; and inasmuch as the bacteriologic test of
plague had been used exclusively in determining rat plague up to this
time, it seemed desirable to adhere to the original method.

In February we found in one of the districts, in which we undertook
systematic work in consequence of a few cases of human plague, a very
large number of dead rats, in and adjacent to houses which furnished
human plague cases. In one building alone more than 150 rat cadavers
were found during our cleaning and rat-proofing operations. It is this
district concerning which the letter to the public (already quoted) was
written.

The methods followed in treating this new and dangerous focus of
infection did not differ from those practised during the previous year,
except in the matter of intensity. Forces of the cleaning and
rat-catching gangs were increased and the utmost thoroughness of
treatment was insisted upon. The results fully justified our policy and
demonstrated again how feasible it is to fight plague successfully if
adequate authority be given.

During the last year of the epidemic in Manila it became the rule for
us to expect our plague workers to locate and find the identical rat
cadaver from which the infected fleas bore the disease to the human
victim, provided the spot upon the floor where the patient's sleeping
mat had been placed was known. In the better class of houses the rat
(sometimes more than one) was found dead beneath the floor, behind some
post casing, or in other space caused by double construction. Time and
again I have directed the removal of some panel of woodwork, some post
casing, or a board of the floor with the full expectation (seldom
unrealized) of finding a dead rat or a rat nest. These experiences were
positively uncanny at times. In the houses of the poorer class, usually
of bamboo and thatch construction, the finding of the rat was less easy
and more uncertain, although the nest was repeatedly found, and as
related elsewhere the dead rat itself might be found in a hollow bamboo
timber, or in the thatch construction of the wall. In a house on Calle
Echague, from which a Filipino and his wife were removed, dead, within
a few hours of each other, several dead rats were found in the floor
(the only piece of double construction in the whole house) within four
feet from the spot where the sleeping mats were placed. A rat hole led
to the nest and through this hole the fleas from the dead rats found
their way to the human victims sleeping on the floor above the encased
nest.

These instances could be multiplied many times, but there is no longer
any special reason to do so, as the rat and the rat-flea are so
completely incriminated as to render these repetitions quite
unnecessary, however interesting they may be to the plague worker. The
danger of pursuing these investigations, to the persons so engaged,
must not be lost sight of, and exposure of such nests and rat cadavers
should invariably be preceded by thorough spraying of the place, and
particularly of the spot where tearing out of double construction is to
be done. I know of no more dangerous employment than this, both for
laborer and bystander.




  CHAPTER IV

  ITS DIAGNOSIS AND TREATMENT


It was not my original intention to include the subjects of diagnosis
and treatment in this presentation, except in so far as I have already
referred to them in the relation of my Manila experiences in the
preceding pages. I have decided, however, to add a chapter upon
Diagnosis and Treatment, for the sake of completeness. No attempt will
be made to present these subjects in the orthodox way.

Rather, my remarks will be confined to such matter as I believe to be
thoroughly practical and relevant.

In my opinion, the day has arrived when we may properly exclude from
such handbooks as this one (intended for practical guidance), all such
methods of diagnosis and treatment as have failed to meet the test of
actual experience through a reasonable length of time. Twice in recent
years,[17] I have described the diagnosis and treatment of plague,
attempting in each case to present a reasonably full account of the
methods employed and advocated by authorities, for theoretic reasons
and from the recorded personal experiences of medical men throughout
the world. There comes a time, however, when wheat and chaff must be
separated and when methods which have failed, in application, to
justify preformed expectations must be relegated to the department of
historical medicine.

  [17] Tropical Medicine (1907) and Hare's Modern Treatment (1911),
  vol. 1.

Judging from recent medical text books it is evident that medical
writers are generally accepting this view as the proper one. At any
rate, my experiences and those of my medical friends during the Manila
epidemic of 1912-1914, have led me to discard as impracticable,
unproven, disproven or unpromising, certain plans of treatment formerly
deemed worthy of trial. I do not refer to these methods individually
but will content myself, instead, with reciting briefly the methods
which I believe, from personal experience and the collected experience
of others, to be worthy of continuance and of further trial.

DIAGNOSIS.--The rapid diagnosis of plague is always of the utmost
importance, both from the view-point of prognosis and treatment, in the
individual case, and from the community view-point of the recognition
of the presence of a dangerous communicable disease, with the resultant
obligation falling upon the health authorities.

THE BIOLOGIC DIAGNOSIS.--Let us understand, first and finally, that but
one diagnosis is absolutely and irrefutably dependable, viz.: the
biologic diagnosis. Herein I would include not only the recovery of the
pest bacillus from the patient, but the recovery and identification of
the organism from inoculated animals, infected from blood, tissues,
secretions or cultivated plague bacilli derived from the human patient
or cadaver.

This entire process involves a lapse of time of several days, and,
while it is indispensable in the earliest cases of an epidemic, and
highly desirable for the proper study of all cases of plague, it is
impracticable and unnecessary, in communities where plague is known to
exist, to carry out more than the first steps of the biologic
diagnosis, viz.: the recovery of _B. pestis_ (morphologic
identification) from the patient.

NECESSITY FOR TRAINED BACTERIOLOGIST.--It is evident that the services
of a trained bacteriologist are indispensable in the accurate diagnosis
of plague, unless (as rarely is the case) the observer himself is both
clinician and bacteriologist. Even in this case it is far better for
two persons, clinician and bacteriologist, to work together. I will not
discuss the technic of the procedures of biologic diagnosis, which is
described by Dr. Schöbl in the preceding pages. Except under
circumstances of necessity, the clinician should always turn this work
over to the bacteriologist.

Serum reactions, when present, occur too late to be of service in
practical diagnosis.

The necessary procedures of the biologic diagnosis include
blood-culture, smear examination (microscopic) of aspirated material
from the oedematous tissues surrounding gland masses and from glands
themselves; examination of sputum smears and of thick-blood smears.

All should be practised but, according to our Manila experiences, smear
examinations of aspirated material and blood cultures are the most
reliable methods, in the hands of a competent bacteriologist. Attention
is invited to the reports of Dr. Otto Schöbl, already quoted.

BACTERIOLOGIC PROCEDURE.--Dr. Schöbl was able to secure positive blood
cultures, within 24 hours, from all of a long series of cases of
plague, both bubonic and septicæmic. As much blood as it was possible
to secure was aspirated from superficial veins and introduced into the
culture media at the bedside, ten c.c. being secured whenever it was
possible.

The smear preparations for staining and culture inoculations upon
slants were also made at the bedside from aspirated matter obtained
from oedematous periglandular tissues or from gland puncture, an
aspirating syringe being used. The drop or two of fluid which can be
expelled from the hollow needle is usually sufficient for smears and
tube inoculations.

NON-BIOLOGIC DIAGNOSIS.--I do not contend that other diagnostic means
than biologic ones should not be used in plague.

On the contrary, it will inevitably happen at times that resort must be
had to methods of diagnosis which are purely clinical. When this is the
case, treatment, along lines to be detailed presently, should be
instituted upon the establishment of a presumptive diagnosis. This
presumptive diagnosis may be reached after due consideration of
physical signs and symptoms. A carefully taken history of the onset
and course of the disease will be valuable but unfortunately such
histories can rarely be secured. It is far safer to mistakenly
pronounce a case "plague" and to institute appropriate treatment, than
it is to hesitate in the absence of a perfect clinical picture and to
permit the golden moment for treatment to pass.

It must be remembered that septicæmic, bubonic and pneumonic plague are
all manifestations of systemic infection with _B. pestis_; that they
are all expressions of the same disease; that they call for the same
treatment and that when the distinctive signs of bubo or pneumonia
appear the disease is dangerously advanced.

It should also be realized that every case is, almost from its onset, a
septicæmic case, either mildly or overwhelmingly so. Accordingly the
treatment should invariably be the treatment of septicæmic plague.

The attitude of the diagnostician should be one of suspicion and he
should have the courage to carry out antiplague treatment, practically
upon suspicion. In this way only can the mortality of plague be greatly
reduced. It is true of plague, just as it is true of cholera, that many
of the fatal cases develop and become hopeless before the disease is
suspected or diagnosticated. It is also true that many fatal cases of
plague, in times of epidemic, completely escape recognition during
life, the diagnosis being made in the autopsy room.

Therefore, I lay great stress upon the necessity for an attitude of
suspicion on the part of practitioners, wherever even a single case of
plague (human or rodent) is known to have occurred.

When it becomes necessary to establish a presumptive diagnosis, _i.e._,
without resort to the microscope, the following symptoms and physical
signs will be found to be most significant.

SYMPTOMATOLOGY.--Acuteness of onset; rapidity of fever development;
rapidity of the development of mental dulness or cloudiness, impairment
of speech, delirium, stupor or restlessness; early and extreme
prostration (perhaps more pronounced than in any other acute disease);
extreme tenderness over involved gland masses, in the bubonic type of
plague; cough, with considerable frothy sputum, soon becoming
blood-discolored, in the pneumonic type of plague; and early cardiac
asthenia in all clinical types of plague, septicæmic, pneumonic and
bubonic.

The following diseases may be confounded with plague, if symptoms
alone are considered: typhus (_exanthematicus_), influenza pneumonia,
broncho-pneumonia, severe malaria, septicæmia, acute toxic typhoid,
venereal bubo, mumps and tonsillitis.

I call attention again to the fact that mild cases of plague,
septicæmic and bubonic, occur at times, clinical pictures in such cases
being incomplete.

The statement that the prognosis in all cases of septicæmic plague is
hopeless is not confirmed by my experience.

It should also be remembered that primary pneumonic plague and
secondary pneumonia developing in the course of systemic plague are
quite different in their significance and mortality, primary pneumonic
plague being well nigh invariably fatal.

PATHOLOGIC CONSIDERATIONS.--Only the student of plague pathology, who
has seen a large number of complete autopsies, can understand how
universal is the involvement of organs, glands and tissues in systemic
plague and how widespread is the distribution of _B. pestis_ throughout
the body, and he will best understand how treatment, to be in the
least effective, must be given in the very earliest hours of the
disease.

Plague is an exquisitely septicæmic disease and this fact must never be
lost sight of by the therapeutist, who must realize that from the
earliest moment of infection all plague is septicæmic plague.

TREATMENT, CONDITIONS AND PROGNOSIS.--Passing to the subject of
treatment let us, first of all, admit that even under the most
favorable and approved conditions of treatment the mortality is
extremely high. On account of the delay which usually occurs in the
recognition of plague,--a delay which in the natural order of things is
and must be the rule rather than the exception, because of the rapidity
of onset of the disease and the fact that it occurs much more
frequently in the lower social classes than elsewhere,--no brilliant
results are to be expected from any plan of treatment.

The matter of plague treatment is far from being in the same
satisfactory state as the matter of preventive control. I do feel,
however, that biologic treatment from the earliest possible moment,
with serum, is of the greatest promise, however discouraging the
general prognosis may be in plague.

SERUM TREATMENT.--Recent writers agree that there is no treatment with
curative value except that with antipest serum. To this belief I
subscribe assent, as I find it entirely in accord with my experience
and that of my colleagues in Manila during 1912-1914.

Holding this view, I can see no reason for repeating here the details
of purely symptomatic treatment. Symptomatic treatment has for its
object the securing of comfort and of relief from suffering for the
patient and is highly proper in its place, remembering always that it
is not curative and that if employed alone it is worse than inadequate.

SYMPTOMATIC TREATMENT.--Opiates (morphine by needle) for pain, delirium
and excitement; application of ice bags and cold or tepid sponge
bathing for high temperature; stimulants for heart weakness, are all
indicated and are required in nearly every case of plague.

As a rule surgery is not called for nor appropriate, except in cases
which develop secondary surgical conditions, which conditions we need
not consider at this time.

STATISTICAL STUDIES IN MORTALITY.--The statistical study of plague
mortality from the point of view of treatment is misleading and
unsatisfactory for reasons already given in our discussion of
treatment, viz.: failure to secure early recognition and early serum
treatment, and the greater incidence of plague in the lower social
classes.

Few statistical compilations divide the cases studied into moribund and
non-moribund, and indeed such division, being a matter of judgment,
largely involves the personal equation of the observer.

The ease with which statistics may be moulded to support theories, or
to break them down, all with perfect honesty of purpose, is proverbial.

To me, the spectacle of a single case of plague, apparently ill unto
death, recovering under the administration of antiplague serum, is more
impressive than the contemplation of statistics; and I have seen more
than one such case respond to serum treatment and recover.

So far as it goes, however, the study of statistics supports the view
that treatment with antiplague serum is effective.

I have not at hand the records of the last 20 or more cases, but of
the first 68 cases of plague in the recent Manila epidemic, 32 were
either found dead or died upon the same day that they were found.

If we exclude these cases from consideration there remain 36 cases. All
of these patients received serum treatment and ten of them recovered.

It is at once apparent that this percentage of recoveries (27 per cent.
plus) is far more favorable than the actual percentage of recovery in
the series in which cases found dead and moribund are considered, the
recovery percentage here being a little more than 14 per cent. It is
also quite fair, it seems to me, to make this separation of cases, or
even a more liberal one, if we are to consider the effects of serum
treatment statistically.

DOSAGE AND TECHNIQUE OF SERUM ADMINISTRATION.--The amount of antiplague
serum to be given will vary somewhat with the age and weight of the
patient and with the apparent severity of the case.

In general terms it may be said that adults should be given from 300
c.c. to 500 c.c. of serum by injection, 100 c.c. being given every four
hours. The injection may be either intramuscular or intravenous.

In view of the improvements in technic of intravenous administrations
and its comparative simplicity, and especially in view of the
uncertainties and delays of absorption from the tissues, the
intravenous route should be given the preference. The serum may be
delivered intravenously from a large glass syringe, the introduction
being very slowly made, or through a gravity apparatus, as in the
administration of salvarsan. The serum should not be diluted.

The use of antiplague serum for protective (immunizing) purposes is
also recommended--especially when exposure to infection has
occurred--in the same way in which diphtheria antitoxin is used. Its
protective properties are conceded to be somewhat superior to those of
plague vaccines as the protection conferred is immediate, whereas
plague vaccines do not protect until sometime after their
administration. The dose is from 30 c.c. to 50 c.c.

PROPHYLACTIC SERUM AND ANAPHYLAXIS.--On one occasion in Manila in 1913,
when some 30 persons were given prophylactic doses of serum,
intramuscularly, following a particularly dangerous exposure to fleas
from rats dead from plague, there occurred a number of cases of "serum
sickness" (anaphylaxis). These persons suffered from severe urticarial,
arthralgic and nervous symptoms, lasting for several days and a few
were obliged to enter a hospital. In one case the symptoms did not
entirely abate for a week. It has been stated that newly-prepared serum
is particularly apt to produce serum sickness when used for immunizing
purposes. This form of protection is brief (1 to 2 weeks) and is best
suited for use where there has been special exposure.

PLAGUE VACCINES.--Haffkine originally proposed prophylactic
immunization, using killed broth cultures of _B. pestis_ (carbolized to
½ per cent.), giving two injections at intervals of 10 days.
Statistically it seems to be shown that this prophylactic immunization
with dead bacteria reduces the incidence and mortality one-fourth or
one-half (approximately). Experimentally, also, it appears that
antibodies (agglutinins) are produced by the vaccine (and modifications
thereof). Instead of broth cultures, normal salt solution suspensions
of killed pest bacilli are usually used in vaccines at present.

Castellani[18] has prepared a combined cholera and plague vaccine for
use in countries where both diseases coincidentally prevail. It is a
mixed vaccine, so prepared that 1 c.c. of the emulsion contains 1000
millions of plague bacilli and 2000 millions of cholera vibrios. The
cultures are grown on agar, killed by phenol and suspended in normal
salt solution.

  [18] A. Castellani: Journal of Ceylon Branch of British Medical
  Association, June, 1914.

He finds (1) that inoculation of the vaccine in the lower animals
induces a production of protective substances for the plague bacillus
and the cholera vibrio; (2) that the inoculation of human beings is
harmless (producing less reaction than the Haffkine inoculation); (3)
that a small amount of agglutinins, both for plague and cholera, appear
in the blood of most inoculated persons (similar to amounts produced by
Haffkine's vaccine), a rough index only of the amount of immunity
produced.




  INDEX


 Anaphylaxis, 177
 Appearance of plague in Porto Rico, 26
   New Orleans, 26
   Manila, 26
 Appeal for public coöperation, 126, 127
 Australia, plague in, 22
 Alaska, plague in, 22
 Africa, South, plague in, 22
 Africa, Central, plague in, 22
 Africa, East, plague in, 22
 Africa, British East, plague in, 25
 Africa, Portuguese East, plague in, 26
 Asian marmot, 28
 Australia, rat fleas of, 32
 Activity of fleas, 33
 Attenuation of virulence of cholera organism, 35
   Bacillus pestis, 35
 Adaptability of rat to temperature and environment, 51
 Anti-plague campaign in Manila, 1912-1914, 57
 Amoy, importation of plague from, 59
 Anti-rat measures in R. R. cars, 92
 Activity of fleas, 98
 Austrian Plague Commission, 133
 Agglutination of plague bacilli, 134-135
 Animals suspected of plague, observations on, 146-149
 Abatement of plague in Hong Kong in 1914, 160
 Anti-plague work, dangers of, 163, 164

 Bacteriologic observations, 127
 Bacillus pestis, in air, 38
   in ants, 138
   in bedbugs, 33, 138
   conveyance by fleas, 28, 30, 31
   cultivation of, 133, 138
   cultural characteristics of, 133, 138
   in circulating blood, 133, 136
   in cats, 150
   effect of temperature upon, 34
   in flies, 33, 138
   in fleas, 138
   in lice, 33, 138
   effect of seasonal conditions on, 34
   in cockroaches, 33
   in sputum, 132
   stability of virulence of, 35, 36
   in skin, 132
 Blue, Dr. Rupert, 31
 Brazil, plague in, 22
 Black Death of Europe, 20
 British East Africa, plague in, 25
 Bite of flea, 31
 Brazil, rat fleas of, 32
 Bedbug, conveyance of B. pestis by, 33
 Barber, Dr. M., 38
 Bacterial viruses for rat destruction, 43
 Bacterial virus, Danysz, 53
 Bacillus, Danysz, 53
   use of, in Odessa, 53
   use of, in Cape Town, 53
 B. typhi murium, 53
 Bacillus, mouse-typhoid, of Loeffler, 53
 B. enteritidis, Gärtner's, 54
 Bacterial rat poisons, use of, in Japan, 54
 Beginning of Manila epidemic, 60
 Binondo, Manila, plague in, 63
 Bamboo timbers, closing ends of, 71
 Basements, insanitary, 72
 Birth-rate of rats, 73
 Bionomics of fleas, 77
 Batavia, Dutch India (Java), 77
 Bureau of Science, Manila, 92
 Barn rat, 99
 Burrowing ability of rats, 102
 Breaking up rat nests, Manila, 106
 Bacteriologic examination of plague patients, 128
 Blood-sucking insects, transmission of plague by, 137
 Bacillus pestis, insects found to contain (Table III), 138, 139
 Biologic diagnosis of plague, 167
   procedure, diagnosis, 168

 Cause of plague, 28
 Conveyance of plague, 28
 Control of plague, 40
 Crowell, Dr. B. C., 14
 China, plague in, 21, 22, 24
 California, plague in, 22
 Central Africa, plague in, 22
 California ground squirrel, 28
 Contact, plague through, 29
 Contagious plague, 29
 Contagion, India Plague Commission on, 33
 Cockroaches in plague conveyance, 29, 33
 Cats, plague in, 29, 76, 149
 Chronic plague in rats, 35
 Chronic rat plague, India Plague Commission on, 35
 Currie, Dr. D. H., 31
 Creel, Dr. R. H., U. S. P. H. Service, 31, 101
 Castellani, Dr. Aldo (dedication), 179
 Ceratophyllus fasciatus, 32
 Cat fleas, 32
 Ctenocephalus, 32
 Citellus beecheyi, 28
 Cholera epidemics, spontaneous abatement of, 35
   organism, attenuation of virulence of, 35
 California, a plague centre, 41
 Cost of rat proofing, 49
 Chemical poisoning of rats and ground squirrels, 54
 Community, summary of prevention for, 56
 Close of year 1912 in Manila, 67
 Closing ends of bamboo timbers, 71
 Cat plague case in Manila, 76, 149 fleas, 78
 Correspondence of Philippine and Japan conditions, 83
 Comparative statistics in rat catching methods, 89
 Cresols, 94
 Coloration of rats, 99
 Conformation of skulls in rats, 101
 Climbing ability of rats, 102
 Collection and forwarding of rats (Manila), 122, 123
 Case of Mr. C. (Manila), 124, 125
 Concealing plague cases, 94
 Conclusions concerning blood culture in plague diagnosis, 136
   from observations of plague outbreak among experimental animals
     (Manila), 146
 Cat, natural plague infection in, 149-154
 Conditions, treatment and prognosis, 173
 Combined vaccines, 179

 Diagnosis of plague, 165
 Definition of plague, 28
 Digestive tract, infection through, 29
 Dog fleas, 32
 Droplet infection, 38
 Destruction of rats by diseases, 53
 Danysz bacterial virus, 53
   bacillus, 53
     use of, in Odessa, 53
     use of, in Cape Town, 53
 Destruction of rats by domestic animals, 54
 Disinfection of ship cargoes, 56
 Dead, proper disposal of, 56
 Dispersion of fleas from rat cadavers, Manila, 65
 Death-rate of rats, 73
 Dutch India, Batavia (Java), 77
 Duration of life of fasting fleas, 79
 Dead rats in bamboo house timbers, 87
 Disinfection, theatre, Manila, 93
 Deception and concealment of plague cases, 94
 Differential points in rats, unreliability of, 101
 Driving out rats with formaldehyde gas (Manila), 106
 Dangers of anti-plague work, 163, 164
 Diagnosis, rapid, of plague, importance of, 166
   biologic, of plague, 167
   non-biologic, 169, 170
 Dosage and technique of serum administration, 176, 177

 Extension of plague, 19, 22
 Egypt, plague in, 20, 23, 25
 East Africa, plague in, 22
 Epidemics, effect of seasonal conditions on, 34
   wane of, 35
 Epidemic pneumonic plague, 38
 Economic importance of rat destruction, 42
 Estimations of loss by U. S. Agricultural Department, 42
 Effect of superstitions and religious beliefs in India, 43
   of rat poisoning and trapping, 73
 Epidemiologic facts concerning plague in Java, 82
 Examination of fatal cases of plague (Table I), 130
   of cases of plague who recovered (Table II), 131
 Experimental animals, plague in, 139-145

 Flea conveyance of B. pestis, 30
 Flies, conveyance of B. pestis by, 33
 Fowls, plague conveyance by, 29
 Flea's stomach, capacity of, 31
   bite and plague conveyance, 31
 Flea prevalence, effect of seasonal conditions on, 34
 Fox, Dr. Carrol, 31, 70
 Fleas, dog, 32
   cat, 32
   mice, 32
   ground squirrel, 32
   activity of, 33, 98
 Fumigation of ships, 46
 Flea carriers, objection to domestic cats and dogs as, 55
 Favorable conditions for spread of plague in Manila, 61
 First Manila cases in 1912, 62
 Fleas and their habits, 77
   bionomics of, 77
   rat, of Philippines, 78
     of Australia, 78
     of Italy, 78
   cat, 78
   per rat, variations in number of (Java), 78
 Flea larvæ, effect of temperature and humidity on, 79
   imago, effect of temperature and humidity on, 79
 Fasting fleas, duration of life of, 79
 Flea prevalence, prediction of plague extension from, 80
   natural enemies of, 97
   activity of, 33, 98
 Field rat, 99
 Family Muridæ, 99
 Ferocity of Mus decumanus, 102
 Feasibility of fighting plague successfully, 162
   of Manila policy of plague control, 162

 Great plague of London, 21
 Great Britain, plague in, 22
 Ground squirrel, California, 28
 Great Britain, rat fleas of, 32
 Ground squirrel, fleas of, 32
 Gärtner's B. enteritidis, 54
 Geographic grouping of plague cases in Manila, 63
 Ground-floor sleeping quarters, 72
 General cleaning campaign, Manila, 88
 Garbage cans, sanitary orders, Manila, 93
 Guinea-pigs as indicators of infected houses, 96
 Genus Mus, 99
 Gray rat, 99
 Gunomys (Nesokia), 100
 Gnawing ability of rats, 102
 German Plague Commission, 149

 History of plague, 19
 Hawaii, plague in, 22
 Hong Kong, plague in, 24, 58, 154
 Heiser, Dr. V. C., 31, 58, 70, 75, 89
 Hobdy, Dr. W. C., 31
 House cats as rat catchers, 55
 Half wild cats as rat catchers, 55
 Human plague in Tondo district, Manila, 68
 Houses in Tondo, light material, 71
 House disinfection by spraying, 94
 Household rat destruction, plan for, 111
 Hong Kong, notes on plague in, by Dr. Roberg, 153, 154, 155, 156, 157,
     158, 159, 160
   the work of the Sanitary Board, 158
   abatement of plague in 1914, 160
 Haffkine vaccine, 178, 179

 Introduction, 11
 India, plague in, 24
 Indo-China, plague in, 24
 Infection through digestive tract, 29
 Ingestion, plague, 29
 India, rat fleas of, 32
 Italy, rat fleas of, 32
 India Plague Commission on contagion, 33
   on chronic rat plague, 35
 Immunity, plague, 36
 India, effect of superstitions and religious belief in, 43
 Isolation of sick, 56
 Importation of plague from Amoy, 59
 Iloilo, P. I., plague in, 70
 Insanitary basements, 72
 Interpretation of the rat catch and plague incidence, 91
 Infected houses, guinea-pigs as indicators of, 96
 India Plague Commission, 100
 Insects found to contain Bacillus pestis (Table III), 138, 139
 Importance of rapid diagnosis of plague, 166

 Japanese anti-plague serum, 18
 Japan, plague in, 22, 25
 Java, plague in, 25
 Japan, bacterial rat poisons, use of, in, 54
 Jackson, Dr. T. W., correspondence, 75
 Java, Batavia, Dutch India, 77
   Xenopsylla cheopis in, 77
   variations in number of fleas per rat, 78
   epidemiologic facts concerning plague in, 82
 Javan village house, 84
   "bale bale," rats in, 86
 Java, sawah rat of, 100
 Jumping ability of rats, 102
 Java, studies of rat cadavers in, 104

 Kerr, Dr. J. W., 31
 Korn, Dr. W., U. S. P. H. Service, 87
 Kerosene as an insecticide, 94

 London, great plague of, 21
 Lantz, Dr. D. E., 31
   classification of rats, 99
 Loemopsylla cheopis, 32
 Louse, conveyance of B. pestis by, 33
 Loeffler, mouse-typhoid bacillus of, 53
 Laboratory-proven plague rats and others in Manila, 61
 Light material houses in Tondo, 71
   Manila, 85
 Letter of warning and appeal, 125, 126
 Location of rat cadavers in relation to human plague cases, Manila,
  162, 163

 Mortality, 22, 23, 174, 175
 Menace of plague, 28
 Manila, plague in, 26
 Manufacture of anti-plague serum, 18
 Middle Ages, plague in, 20
 Mexico, plague in, 22
 Mauritius, plague in, 22, 25
 Mediterranean ports, plague in, 22
 Marmot, Asian, 28
 Mice, fleas of, 32
 Manchuria, pneumonic plague in, 37
 Methods of entry of rats into ships and cars, 52
 Mouse-typhoid bacillus of Loeffler, 53
 Murium, B. typhi, 53
 Manila, Anti-plague Campaign in 1912-1914 in, 57
   epidemic, 1912-1914, 57
   plague at quarantine in, 58
   importation of plague from Hong Kong in 1912, 58
 Mariveles Quarantine Station, 59
 Manila epidemic, beginning of, 60
 Mortality and numbers of Manila plague cases, 61
 Manila cases in 1912, first, 62
   geographic grouping of plague cases in, 63
   R. R. station focus, 64
   dispersion of fleas from rat cadavers, 65
   close of year 1912 in, 67
 Malolos, P. I., plague in, 69
 Manila, taking charge of plague suppression measures in, 70
   plague fighting organization in, 71
   rat plague in U. S. Army Commissary warehouse, 76
   habitations and plague, 83
   light material house, 85
   general cleaning campaign, 88
   theatre, disinfection in, 93
 Mus rattus, 99
   alexandrinus, 99
 Mus decumanus, 99
   ferocity of, 102
 Manila, breaking up of rat nests, 106
   driving out rats by formaldehyde gas, 106
   rat killing with dogs, 107
   rat nests in trees, 110
   snakes in rat traps, 111
   rat swallowed by snake, 111
 Multiple house infection (Manila), 112-117
 Manila, collection and forwarding of rats, 122, 123
 Mr. C., case of Manila, 124, 125
 Manila, bacteriologic observation, 127
   outbreak of plague among experimental animals, 139-145
   conclusions from observation of plague outbreak among experimental
     animals, 146
   San Lazaro Hospital, 13, 69, 161
   location of rat cadavers in relation to human plague cases, 162, 163
 Mortality, statistical studies in, 22, 174, 175, 176
 McCoy, Dr. C. W., 31

 New Orleans, plague in, 26
 Natural enemies of the rat, 43
 National aid, necessity of, 56
 Numbers and mortality of Manila plague cases, 61
 Nest materials, 86
 Natural enemies of the flea, 97
 Norway rat, 99
 Notes on rat runs, 105
   nests, 105
   food, 105
 Natural plague infection in a cat, 149-154
 Notes on plague in Hong Kong by Dr. Roberg, 153-160
 Non-biologic diagnosis, 169, 170

 Objection to domestic cats and dogs as flea carriers, 55
 Order Rodentia, 99
 Outbreak of plague among experimental animals (Manila), 139-145
 Observations of animals suspected of plague, 146-149

 Plague conveyance, 28
   in 1910, 24
   conveyance by suction of insects, 33
 Porto Rico, plague appears in, 26
 Public coöperation in plague control, 126, 127
 Practicability of plague control, 15
 Philippines, plague in, 22
 Peru, plague in, 22
 Persia, plague in, 25
 Portuguese East Africa, plague in, 26
 Public Health Service, U. S., 26, 37
 Pulex irritans, 32
   pallidus, 32
 Plague pneumonia, secondary, 39
 Pneumonic plague epidemic, 38
 Prevention problem, summary of, 37
 Pneumonic plague, 37
   in Manchuria, 37
 Plague immunity, 36
   treatment and diagnosis of, 165
   control, 40
   prevention, 40
   suppression, 40
   campaign in San Francisco, 41
 Poisons used for rat destruction, 43, 44
 Poisonous gases, rat destruction by, 45
 Prevention for community, summary of, 56
 Proper disposal of dead, 56
 _Philippine Journal of Science_, 58, 70, 128
 Plague at quarantine in Manila, 58
   from Hong Kong, Manila, importation of, in 1912, 58
   from Amoy, importation of, 59
   cases, numbers and mortality of Manila, 61
   rats, laboratory-proven, and others in Manila, 61
   in Quiapo, Manila, 63
   in Binondo, Manila, 63
   cases in Manila, geographic grouping of, 63
   in Malolos, P. I., 69
   in Iloilo, P. I., 70
 Plague suppressive measures, Manila, taking charge of, 70
   fighting organization in Manila, 71
 Population, removal of, in emergency, 74
 Plague, cat, case of, Manila, 29, 76, 150
   rat, in U. S. Army Commissary warehouse, Manila, 76
 Prediction of plague extension from flea prevalence, 80
 Plague prevalence, seasonal explanation of, 81
   in Java, epidemiologic facts concerning, 82
   Manila habitations and, 83
   Tondo (Manila) habitations and, 83
   cases, deception and concealment of, 94
   commission, India, 100
 Postmortem changes, in rats (Table), 105
   in rats (illustration), 105
   time of death of rats as indicated by, 104
 Plan for household rat destruction, 111
 Plague patients, bacteriologic examination of, 128
   examination of fatal cases of (Table I), 130
   of cases who recovered from (Table II), 131
   commission, Austrian, 133
   bacilli from circulating blood, recovering, 134
 Plague bacilli, agglutination of, 134, 135
   diagnosis, conclusions concerning blood culture in, 136
   by blood sucking insects, transmission of, 137
   among experimental animals, outbreak of (Manila), 139-145
   outbreak among experimental animals, conclusions from observations
     of (Manila), 146
   observations on animals suspected of, 146-149
   commission, German, 149
   in Hong Kong, notes on, by Dr. Roberg, 153-160
   in Hong Kong in 1914, abatement of, 160
   feasibility of fighting successfully, 162
   control, feasibility of Manila policy of, 162
   cases (human), location of rat cadavers in relation to
     (Manila), 162, 163
   importance of rapid diagnosis of, 166
   biologic diagnosis of, 167
   a septicæmic disease in all cases, 170
   symptomatology of, 171
 Pathologic considerations, 172
 Prognosis, treatment, conditions and, 173
 Plague, serum treatment of, 174
   symptomatic treatment, 174
 Prophylactic serum and anaphylaxis, 177
 Plague vaccines, 178, 179

 Quarantine, modified, 56
   station, Mariveles, 59
 Quiapo, Manila, plague in, 63

 Rat fleas of Italy, 32
   of Brazil, 32
   of Great Britain, 32
   of United States, 32
 Rats, chronic plague in, 35
   subacute plague in, 35
 Requisites of the practical sanitarian, 12
 Russia, plague in, 26
 Rats, wild, plague in, 29
   effect of seasonal conditions on, 34
 Rucker, Dr. W. C., 31
 Rosenau, Dr. M, J., 31
 Rat fleas, varieties of, 32
   of India, 32
   of Australia, 32
 Rat population of the world, 41
   destruction, economic importance of, 42
   extermination methods, 43
   natural enemies of, 43
   destruction, bacterial viruses for, 43
   poisons used for, 43, 44
   trapping, 44
   traps, varieties, 45
   destruction by poisonous gases, 45
 Rats, starving, 47
 Rat proofing, 48
     cost of, 49, 93
   infestation of ships, 50
   adaptability of, 51
 Rat's, methods of entry of, 52
 Rat destruction by rat diseases, 53
 Resistance of rat to diseases of bacterial causation, 54
 Rats and ground squirrels, chemical poisoning of, 54
 Rat destruction by domestic animals, 54
   catchers, house cats as, 55
     half wild cats as, 55
     terrier dogs as, 55
     on farms, terrier dogs as, 55
 Rapid diagnosis, importance of, 56
 Rat cadavers, dispersion of fleas in Manila from, 65
   plague in Tondo district, Manila, 68
   proofing and rat destruction, 72
     inapplicable at times, 73
   poisoning, trapping, effects of, 73
 Rats, birth-rate of, 73
   death-rate of, 73
 Removal of population in emergency, 74
 Rat plague in U. S. Army Commissary warehouse, Manila, 76
   fleas of Philippines, 78
     of Australia, 78
 Rat fleas of Italy, 78
   breeding as influenced by climate, 81
   in Javan "bale bale," 86
   in thatched roofs, 86
   dead, in bamboo house timbers, 87
 Rat catch, variations in, 88
 Rat catching methods, comparative statistics in, 89
 Rat catch and plague incidence, interpretation of, 91
 Rats, zoölogic classification of, 98
 Rat, ship, 99
   field, 99
 Rats, coloration of, 99
 Rat, Norway, 99
   gray, 99
   barn, 99
   sewer, 99
 Rats, unreliability of differential points in, 101
   conformation of skulls in, 101
   gnawing ability of, 102
   burrowing ability of, 102
   climbing ability of, 102
   jumping ability of, 102
   swimming ability of, 102
 Rat litters, size of, 102
 Rats as wire walkers, 103
   as rope walkers, 103
 Rat cadavers in Java, studies of, 104
   time of death as indicated by postmortem changes of, 104
 Rats, postmortem changes in (Table), 105
   (illustration), 105
 Rat runs, notes on, 105
   nests, notes on, 105
   food, notes on, 105
   nests (Manila), breaking up, 106
 Rats driven out with formaldehyde gas (Manila), 106
 Rat killing with dogs (Manila), 107
 Rat's nests in trees (Manila), 110
 Rat traps, snakes in (Manila), 111
   swallowed by snake (Manila), 111
 Rats, collection and forwarding of (Manila), 122, 123
 Recovering plague bacilli from circulating blood, 134
 Roberg, Dr. David, 154

 Stability of virulence of B. pestis, 36
 Spread of plague in recent years, 23
 Suppression of plague, 40
 San Lazaro Hospital, Manila, 13, 69, 161
 Schöbl, Dr. Otto, 14, 29, 30, 76, 96, 127
 Strong, Dr. R. P., 16, 36, 38, 59, 135
 Sixth century, plague in, 20
 South America, plague in, 22, 26
 Siam, plague in, 25
 Suez, plague in, 22
 South Africa, plague in, 22
 Scotland, plague in, 22
 Sumatra, plague in, 25
 Straits Settlements, plague in, 25
 Simpson, Dr. W. J.
 Suctorial parasites in plague conveyance, 33
 Seasonal conditions, effect on epidemics of, 34
   on rats of, 34
   on Bacillus pestis of, 34
   on flea prevalence of, 34
 Subacute plague in rats, 35
 Spontaneous abatement of cholera, 35
 Secondary plague pneumonia, 39
 Summary of prevention problem, 37
 San Francisco, plague campaign in, 41
 Ships, fumigation of, 46
 Starving rats, 47
 Ships, rat infestation of, 50
 Summary of prevention for community, 56
 Ship cargoes, disinfection of, 56
 Sick, isolation of, 56
 Steamer, Loongsang, 59
   Taisang, 59
 Spread of plague in Manila, favorable conditions for, 61
 Sleeping quarters, ground floor, 72
 Swellengrebel, Ph.D., N. H., 77
 Seasonal explanations of plague prevalence, 81
 Sanitary orders, Manila (garbage cans), 93
 Ship rat, 99
 Sewer rat, 99
 Sawah rat of Java, 100
 Swimming ability of rats, 102
 Size of rat litters, 102
 Simpson, surgeon, U. S. P. H. Service, 103
 Studies of rat cadavers in Java, 104
 Snakes in rat traps (Manila), 111
 Snake, rat swallowed by (Manila), 111
 Specimen, sanitary orders, 116-121
 Sanitary Board (Hong Kong), the work of, 158
 Symptomatology of plague, 171
 Serum treatment of plague, 174
 Symptomatic treatment of plague, 174
 Statistical studies in mortality, 174-176
 Serum administration, dosage and technique of, 176, 177

 Types of plague, 30
 Treatment of plague, 165
 Turkey in Asia, plague in, 25
 Tarbagan, 28
 Teague, Dr. O., 38
 Terrier dogs as rat catchers, 55
 Terrier dogs as rat catchers on farms, 55
 Tondo district, Manila, rat plague in, 68
   human plague in, 68
 Taking charge of plague suppressive measures, Manila, 70
 Tondo, light material houses in, 71
 Tondo, Manila, habitations and plague, 83
 Theatre disinfection, Manila, 93
 Time of death of rat as indicated by postmortem changes, 104
 Transmission of plague by blood-sucking insects, 137
 Trained bacteriologist, necessity for, 167
 Treatment, conditions, and prognosis, 173
   serum, of plague, 174
   symptomatic, of plague, 174
 Technique and dosage of serum administration, 176, 177

 United States Public Health Service, 26
   rat fleas of, 32

 Varieties of rat fleas, 32
   of rat traps, 45
 Variations in number of fleas per rat (Java), 78
 Van Loghem, Dr. J. J., 82, 84
 Variations in the rat catch, 88
 Vaccines, plague, 178, 179
 Vaccine, Haffkine, 178, 179
 Vaccines, combined, 179

 Widespread dissemination in recent years, 23
 West Indies, plague in, 29
 Wane of epidemics, 15, 35
 Work of Sanitary Board (Hong Kong), 158

 Xenopsylla cheopis in Java, 77

 Zoölogic classification of rats, 98




  Transcriber's note:

  The following corrections have been made:

  Title page: Period added after J in "J B. Lippincott Company"

  Dedication: Period added after "DAYS IN SERBIA"

  Table of Contents: "Epidemic, By Dr. Otto Schöbl" By changed to by

  p. 21: "christendom" changed to Christendom

  p. 32: Removed italic type from the word genus in "genus
  Ctenocephalus"

  p. 62: "secondary to this July case" July changed to June

  p. 78: "known as Loemopsylla cheopsis" Loemopsylla changed to
  Loemopsylla

  p. 132: "While cases 5, 2, 19, and 24 appeared" 2 changed to 11

  p. 139: "fleas from a plagueinfected house" plagueinfected changed to
  plague-infected

  p. 142: "usually met with in" with in changed to within

  p. 147: "Echinococcus teniæformis was found in the liver" teniæformis
  changed to taeniæformis

  Index: "Swellengreble" changed to Swellengrebel

  Footnote 5: "Jena (1903) 2" added comma after closing bracket

  Everything else retained as printed, including inconsistencies in
  hyphenation. The index entry for Simpson, Dr. W. J. is missing its
  page reference.







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