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+*** START OF THE PROJECT GUTENBERG EBOOK 76630 ***
+
+
+
+
+
+ TREASURY DEPARTMENT
+
+ Public Health and Marine-Hospital Service of the United States
+
+
+
+
+ THE RAT AND ITS RELATION TO THE PUBLIC HEALTH
+
+ BY VARIOUS AUTHORS
+
+ PREPARED BY DIRECTION OF THE SURGEON-GENERAL
+
+[Illustration: [Logo]]
+
+ WASHINGTON
+ GOVERNMENT PRINTING OFFICE
+ 1910
+
+
+
+
+ TABLE OF CONTENTS.
+
+
+ Page.
+
+ _Introduction_ (Walter Wyman) 9
+
+ _Natural History of the Rat_ (David E. Lantz) 15
+
+ Classification of rats 15
+
+ Distribution of the genus _Mus_ in America 17
+
+ History of the brown rat 19
+
+ General description of the species in America and key to the
+ species 20
+
+ Habits of rats 22
+
+ Breeding habits 22
+
+ Abundance 23
+
+ Migrations and invasions 24
+
+ Food 26
+
+ Feeding habits 26
+
+ Ferocity 27
+
+ _Plague Infection in Rats_ (George W. McCoy) 29
+
+ Mode of examination 30
+
+ Gross lesions of natural rat plague, acute 32
+
+ Subcutaneous injection 32
+
+ The bubo 33
+
+ The granular liver 34
+
+ The spleen 35
+
+ Pleural effusion 35
+
+ Gross lesions of natural rat plague, chronic 36
+
+ Rat plague without gross lesions 37
+
+ Microscopical examinations 37
+
+ Bacteriological diagnosis of rat plague 38
+
+ Pest-like bacteria found in rats 41
+
+ Artificial infection of rats with plague 41
+
+ Modes of infection 42
+
+ Local reaction 43
+
+ The bubo 44
+
+ The liver and spleen 44
+
+ Chronic plague due to artificial inoculation 44
+
+ The histology of rat plague 45
+
+ Natural rat plague 46
+
+ Immunity of rats to plague 46
+
+ References 48
+
+ _Rat Leprosy_ (Walter R. Brinckerhoff) 49
+
+ Introduction 49
+
+ Review of literature 49
+
+ Description of disease 50
+
+ Etiology 52
+
+ Summary 52
+
+ Bibliography 53
+
+ _Bacterial Diseases of the Rat other than Plague_ (Donald H.
+ Currie) 55
+
+ Danysz bacillus or bacillus typhi Murium of Loeffler 55
+
+ Pneumonia 55
+
+ Staphylococcus abscesses 56
+
+ Bacillus pseudo-tuberculosis rodentium (Pfeiffer) 57
+
+ Toyama’s bacillus 57
+
+ Infections of mice 57
+
+ _Organic Diseases of the Rat, Including Tumors_ (George W. McCoy) 59
+
+ Usefulness of wild rats for laboratory purposes 59
+
+ Circulatory apparatus 60
+
+ Pulmonary apparatus 60
+
+ Digestive tract 61
+
+ Cirrhosis of the liver 61
+
+ Fatty degeneration of the liver 61
+
+ Hernia 61
+
+ Genito-urinary tract 62
+
+ Nephritis 62
+
+ Abscess of the kidney 62
+
+ Atrophy of the kidney 63
+
+ Vesical calculi 63
+
+ Tumors 64
+
+ Metastases 67
+
+ Histological structure 67
+
+ Lipomata 67
+
+ Fibromata 67
+
+ Sarcomata 67
+
+ Adenomata and Carcinomata 67
+
+ _Ectoparasites of the Rat_ (Nathan Banks) 69
+
+ Fleas—Siphonaptera 69
+
+ Lice—Anoplura 77
+
+ Mites—Acarina 80
+
+ _Internal Parasites of Rats and Mice in Their Relation to
+ Diseases of Man_ (Ch. Wardell Stiles and Charles G. Crane) 87
+
+ Summary 87
+
+ Introduction 87
+
+ Protozoa 88
+
+ Cestoda 95
+
+ Nematoda 101
+
+ Acanthocephala 108
+
+ _Compendium of Animal Parasites Reported for Rats and Mice—(Genus
+ Mus)_ (Ch. Wardell Stiles and Albert Hassall) 111
+
+ _The Flea and Its Relation to Plague_ (Carroll Fox) 123
+
+ Theories as to the transmission of plague 123
+
+ Insects that have been suspected in the transmission of plague 124
+
+ Experiments proving that fleas can transmit plague 125
+
+ The bacillus in the flea 126
+
+ How the flea clears itself of bacilli 127
+
+ Regional distribution of fleas on rats 127
+
+ Anatomy of the mouth parts of the Ceratophyllus Fasciatus 128
+
+ Outside the head 128
+
+ Inside the head 129
+
+ The act of biting 131
+
+ How the flea infects its host 132
+
+ Enumeration of fleas that have been found on rats 133
+
+ Results of identification of fleas in California 135
+
+ Synopsis of fleas commonly found on rats 136
+
+ Ceratophyllus Fasciatus, Bosc 136
+
+ Lœmopsylla Cheopis, Rothschild 138
+
+ Ctenopsyllus Musculi, Dugés 140
+
+ Pulex Irritans, Linnæus 142
+
+ Ctenocephalus Canis, Curtis 143
+
+ References 144
+
+ _Rodents in Relation to the Transmission of Bubonic Plague_
+ (Rupert Blue) 145
+
+ Epidemiological observations in San Francisco 147
+
+ Theories as to the cause of seasonal prevalence 149
+
+ The occurrence of plague in the marmot of Asia and ground
+ squirrel of California 150
+
+ Plague infection in ground squirrels 150
+
+ The natural habitat of plague 151
+
+ References 152
+
+ _Rodent Extermination_ (Wm. Colby Rucker) 153
+
+ Trapping 154
+
+ Poisoning 156
+
+ Natural enemies 159
+
+ Cutting off of the rat’s food supply 160
+
+ Building the rat out of existence 161
+
+ _Natural Enemies of the Rat_ (David E. Lantz) 163
+
+ Animals that destroy rats 163
+
+ Hawks 163
+
+ Owls 164
+
+ Wild mammals 166
+
+ Skunks 166
+
+ Weasels 166
+
+ Minks 167
+
+ Domestic animals 167
+
+ Dogs 167
+
+ Cats 167
+
+ Ferrets 168
+
+ Other animals 168
+
+ Mongoose 168
+
+ Alligators 168
+
+ Snakes 169
+
+ Bounties on predatory animals 169
+
+ _Rat-Proofing as an Antiplague Measure_ (Richard H. Creel) 171
+
+ Rat-proofing of primary importance 173
+
+ Rat-proofing is expensive 174
+
+ Methods of rat-proofing 175
+
+ Rat-proofing ordinances should be specific 177
+
+ Choice of architecture and building materials 178
+
+ _Inefficiency of Bacterial Viruses in the Extermination of Rats_
+ (Milton J. Rosenau) 179
+
+ Introduction 179
+
+ Experiments upon rat virus in the Hygienic Laboratory 183
+
+ Experiments with microorganisms for destroying rats by the U.
+ S. Biological Survey 186
+
+ Experiments during the San Francisco plague outbreak 188
+
+ Opinions of others 190
+
+ Pathogenicity for man 193
+
+ References to the literature 201
+
+ Résumé 204
+
+ _Plague Eradication in Cities by Sectional Extermination of Rats
+ and General Rat-Proofing_ (Victor G. Heiser) 205
+
+ _The Rat in Relation to Shipping_ (Wm. C. Hobdy) 207
+
+ Adaptability of the rat to his surroundings 208
+
+ Damage to cargo 209
+
+ Fumigation 211
+
+ Summary 213
+
+ _The Rat as an Economic Factor_ (David E. Lantz) 215
+
+ Introduction 215
+
+ Utility of the rat 215
+
+ Destructiveness of the rat 216
+
+ Grains 216
+
+ Merchandise in stores and warehouses 218
+
+ Merchandise in transit 219
+
+ Poultry and eggs 219
+
+ Game and wild birds 220
+
+ Fruit and vegetables 221
+
+ Flowers and bulbs 221
+
+ Fires 222
+
+ Buildings and furniture 222
+
+ Miscellaneous 223
+
+ Amount of losses caused by rats 224
+
+ Indirect losses 225
+
+ _The Rat in Relation to International Sanitation_ (John W. Kerr) 227
+
+ International sanitary regulations 228
+
+ Inquiry into the crusade against rats throughout the world 230
+
+ Rat extermination in United States ports 231
+
+ Rat extermination in Chinese cities 232
+
+ Rat extermination in Madras, Bombay, and Calcutta, India 234
+
+ Rat extermination in Yokohama and Nagasaki, Japan 235
+
+ Rat extermination in East Africa 237
+
+ Rat extermination in Cape Town, South Africa 238
+
+ Rat extermination in Alexandria and Cairo, Egypt 238
+
+ Extermination of rats at the port of Constantinople 238
+
+ Rat extermination in Russian ports 239
+
+ Destruction of rats in Trieste, Austria 240
+
+ Destruction of rats in Genoa, Italy 240
+
+ Destruction of rats in Barcelona, Spain 241
+
+ Rat destruction in French ports 241
+
+ Ministerial decree relating thereto 242
+
+ Destruction of rats in German ports 243
+
+ Measures against rats in Rotterdam, Holland 245
+
+ Destruction of rats at Antwerp, Belgium 245
+
+ Destruction of rats in Denmark 245
+
+ Danish law of March 22, 1907 245
+
+ Collection and destruction 247
+
+ Destruction of rats in Swedish ports 248
+
+ Destruction of rats in English ports 249
+
+ Measures against rats in Australian ports 250
+
+ Measures against rats in South American ports 252
+
+ Measures against rats in West Indian ports 252
+
+ Destruction of rats in Panama 253
+
+ Measures against rats in Vancouver, B. C. 253
+
+ Necessity of concerted action of nations 254
+
+
+
+
+ LIST OF ILLUSTRATIONS.
+
+
+ Page.
+
+ Fig. 1a. Upper molars of the brown rat (_Mus_): tubercles in 16
+ three rows
+
+ Fig. 1b. Upper molars of the rice rat (_Oryzomys_): tubercles in 16
+ two rows
+
+ Fig. 2a. Right hind foot of brown rat, showing long sixth foot 17
+ pad
+
+ Fig. 2b. Right hind foot of house mouse, showing round sixth 17
+ foot pad
+
+ Fig. 3a. Ears of brown rat and black rat, showing relative size 21
+ fig. 3b.
+
+ Fig. 4. Necropsy appearance of normal rat 48
+
+ Fig. 5. Necropsy appearance of plague-infected rat 48
+
+ Fig. 6. Flea, showing the various parts 70
+
+ Fig. 7. Louse—_Polyplax spinulosus_ 78
+
+ Fig. 8. Mite—_Lælaps echidninus_ 81
+
+ Figs. 9 Internal parasites of rats and mice 90–109
+ to 58.
+
+ Fig. 59. Isolated plague-infected center, Manila, P. I. 206
+
+ Fig. 60. Scheme for testing rat-plague infection, Manila, P. I. 206
+
+ Plate I. Mouth parts of _Ceratophyllus fasciatus_ 130
+
+ II. _Ceratophyllus fasciatus_ 136
+
+ III. _Lœmopsylla cheopis_, Rothschild 138
+
+ IV. _Ctenopsyllus musculi_, Duges 140
+
+ V. _Pulex irritans_, Linnæus 142
+
+ VI. _Ctenocephalus canis_, Curtis 144
+
+
+
+
+ THE RAT AND ITS RELATION TO THE PUBLIC HEALTH.
+
+ By WALTER WYMAN,
+
+ _Surgeon-General of the Public Health and Marine-Hospital Service_.
+
+
+
+
+ INTRODUCTION.
+
+
+The science of bacteriology has elucidated many facts with respect to
+the causation of disease, and with this advance in knowledge, old
+theories regarding the miasmatic and humoral origin of human ills have
+been abandoned.
+
+Epidemiological studies have likewise determined the methods of
+transmission of many of the infectious and contagious diseases, thus
+eliminating erroneous conceptions that they are attributable to some
+mysterious condition of the atmosphere or soil, or to a visitation of
+the wrath of the Almighty.
+
+Both these sciences have contributed to our knowledge of the
+relationship of living things, particularly with respect to their
+influence upon each other in relation to health and disease. It is now
+known, for instance, that mosquitoes are the pests of man, not only
+because of their bites, but because they at times transmit malaria,
+dengue, filariasis, and yellow fever. So, too, it is known that rodents
+are the enemies of man, not only because of the toll exacted from him,
+but because they are the principal agents in the propagation and spread
+of bubonic plague.
+
+Ancient writings abound in allusions to pestilences and their connection
+with epizootics among rats and mice.
+
+In the Book of Samuel there is reference to a pestilence having relation
+to mice, and that it might be stayed the Philistines made offerings of
+golden images of the mice that marred the land.
+
+During the centuries that have intervened rats have migrated to
+practically every quarter of the earth, causing untold losses on account
+of their depredations. They have also, in all probability, been the
+primary agents of transmission in the pandemics of plague which have
+visited the earth. The fact that plague is due to a specific
+microorganism, and that its presence in man is also associated with
+epizootics in rats, has led to a more careful study of this animal,
+particularly in relation to his habits, the diseases from which he
+suffers, and the methods necessary to his control. Prior to the
+beginning of the present pandemic of plague which had its origin in
+China, interest in the rat was almost wholly an economic and financial
+one. Since that time evidence has been rapidly accumulating which proves
+that this animal and his parasites are responsible for the transmission
+of plague and that plague itself is essentially a disease of the rat.
+
+A knowledge of this animal on the part of the sanitarian therefore
+becomes essential. During the enforcement of antiplague measures in
+California, Hawaii, the Philippine Islands and elsewhere, observations
+of great value have been made and their practical application has
+resulted in better directed efforts for the elimination of the disease.
+
+In studies of plague and leprosy with the view to their diagnosis and
+control, it is not enough now to isolate the microorganisms responsible
+for these diseases, but the sanitarian must be able to recognize the
+pathological conditions present in animals affected, and to do so he
+must have practical knowledge of this subject in order that he may
+differentiate between the various diseases from which these animals
+suffer.
+
+Opportunity for observation and study of the diseases of rats and the
+methods necessary to their eradication has been afforded to the officers
+of the Public Health and Marine-Hospital Service who are constantly
+stationed on the outposts in the warfare against exotic diseases. The
+results of these observations have been utilized by officers of the
+service, and some of them have been published for the benefit of others.
+
+The rat has received much attention of late in other parts of the world.
+In Denmark, for instance, a legalized warfare against rodents has been
+begun, principally on account of their influence in the transmission of
+trichinosis. In England there exists The Incorporated Society for the
+Destruction of Vermin, and in other places rat destruction is being
+agitated both from economic and public health standpoints.
+
+In view of the great importance of the rat in relation to the public
+health, it has been thought advisable to collect and publish all
+pertinent information on the subject, in order that public health
+officials who should be on the lookout for the appearance of plague
+among rodents might have available a reliable treatise on the subject.
+
+Studies of rodents from a biologic and economic standpoint come within
+the province of other departments of the public service, and the
+cooperation of the Biological Survey and Bureau of Entomology of the
+Department of Agriculture was therefore requested and received.
+
+The subjects dealt with in this publication have been prepared by those
+having wide experience.
+
+In the chapter on natural history by Mr. David E. Lantz there is given a
+classification of rats as well as the distribution of the genus _Mus_ in
+America. An interesting and important fact is mentioned that the
+Biological Survey has no records of the presence of the brown rat in
+Nevada, Utah, Wyoming, Idaho, and the greater part of Montana. Mr. Lantz
+also describes the different species in America, and refers to their
+habits as to breeding, feeding, migrations, invasions, and ferocity. The
+facts presented by him emphasize the great difficulty of ridding cities
+of these pests.
+
+Passed Assistant Surgeon McCoy discusses plague infections in rats and
+describes the methods of examination. He also describes the gross
+lesions found in plague rats, gives the bacteriologic diagnosis of rat
+plague and the cultural characteristics of the plague bacillus on
+various media. He gives the methods of artificial infection of rats with
+plague, and reviews the recent work of Ledingham in relation to the
+histology of rat plague. Finally, he presents results of his own
+investigations to show that the wild rat is not especially susceptible
+to plague infection, and that a certain percentage of such animals enjoy
+a natural immunity to plague.
+
+Doctor Brinckerhoff discusses rat leprosy; states that it is very
+similar to human leprosy, and that it is caused by a bacillus which
+closely resembles the bacillus of Hansen. He describes the pathological
+changes found, and expresses the hope that the disease will receive
+further earnest study, in order that additional information may throw
+light on the problems presented by leprosy in man.
+
+Passed Assistant Surgeon Currie briefly outlines the bacterial diseases
+of the rat, other than plague and leprosy. He mentions the great utility
+that would follow the discovery of a rat destroying bacterium, but
+states that it appears now more than probable that few such natural
+diseases of rats exist.
+
+In a chapter on organic diseases of the rat, Doctor McCoy summarizes the
+results of his observations made during examinations of these animals in
+the Federal laboratory of the service at San Francisco. These
+observations are of interest, and will assist those engaged in such work
+to further classify the pathological changes noted as well as
+differentiate them from plague.
+
+The ectoparasites of the rat are classified and described by Mr. Nathan
+Banks, and he has presented in condensed form information of much
+practical value upon the subject.
+
+Dr. Ch. Wardell Stiles discusses the internal parasites of rats and mice
+in relation to the diseases of man. He regards the rat as a permanent
+reservoir for trichinosis, and states that this disease will probably
+never be eradicated from man until rats and mice are practically
+eradicated, and a national campaign directed against trichinosis must
+take the rat into consideration.
+
+A compendium of animal parasites reported for rats and mice is presented
+in a chapter by Ch. Wardell Stiles and Albert Hassall. While, as the
+authors state, no list of this kind can ever lay claim to being
+complete, it represents the present knowledge of the subject.
+
+In a discussion of the flea and its relation to plague, Passed Assistant
+Surgeon Fox summarizes the theories as to the transmission of this
+disease. He also mentions the insects that have been suspected of
+transmitting plague and presents accumulated evidence that fleas
+actually convey the infection. He then gives the anatomy of the mouth
+parts of the _Ceratophyllus Fasciatus_, the common rat flea of North
+America. He also enumerates the fleas that have been found on rats, and
+gives the results of identifications of 19,768 fleas in San Francisco
+and Oakland, Cal. The plates accompanying this article, and their
+description should be of great value to those engaged in antiplague
+measures.
+
+Surgeon Blue briefly discusses the subject of rodents in relation to the
+transmission of bubonic plague. He discusses the theories as to the
+cause of seasonal prevalence of this disease and presents a table
+showing the number of rats examined during the different months of the
+year, the number found infected, the average temperature and rainfall
+for those months and the character of the days, as to the number clear,
+partly cloudy, or cloudy. He refers to plague infection in ground
+squirrels in California and warns against the possibility that this
+animal may become responsible for the establishment of a permanent focus
+of plague on the Pacific coast of the United States, as the marmots are
+so concerned with regard to India.
+
+The all-important subject of rodent extermination is considered in
+detail, various phases of the subject being dealt with by different
+authors.
+
+Passed Assistant Surgeon Rucker discusses the destruction of these
+animals by trapping, poisoning, cutting off of food supply, and
+destroying of existing nests and at the same time preventing the making
+of new ones. He describes the methods of use of the various mineral
+poisons, but finally states that rodents must be builded out of
+existence; in other words, habitations must be rendered rat proof.
+
+Mr. Lantz, in discussing the natural enemies of the rat, mentions the
+animals that destroy these pests. He concludes that on account of this
+function bounties for the destruction of small animals that prey on
+rodents can not be justified and that they should in the future be
+protected in every way possible.
+
+Passed Assistant Surgeon Creel discusses rat proofing as an antiplague
+measure, and gives in detail the principles of construction necessary.
+He concludes that rat proofing is the most valuable antiplague measure,
+and that it should precede auxiliary measures such as trapping and
+placing of poisons.
+
+Surgeon Rosenau discusses the bacterial viruses in relation to rat
+destruction. As a result of his investigations in the hygienic
+laboratory and the reports of investigations and practical use
+elsewhere, he concludes that the bacterial viruses have signally failed
+to accomplish the mission for which they were intended, and that they
+are not entirely harmless to man, as has been stated.
+
+Passed Assistant Surgeon Heiser briefly outlines the measures
+recommended for the eradication of plague in cities by means of
+sectional extermination of rats and general rat proofing. He gives
+results following this method of procedure in Manila, and presents
+charts showing how to deal with infected city districts.
+
+Passed Assistant Surgeon Hobdy, in a chapter on the rat in relation to
+shipping, refers to the voyage-making tendencies of the rodent, its
+destructiveness aboard ship, and its power of adapting itself to unusual
+conditions and surroundings. In one small lumber vessel fumigated by
+Doctor Hobdy at the Angel Island quarantine station there were collected
+525 dead rats. Mention is also made of another vessel on which were
+collected 1,700 rats after fumigation. He discusses the methods by which
+it gains access to vessels, and outlines the practices that should be
+observed to keep it off. He also describes in some detail the measures
+to be adopted for its destruction after it has gotten aboard ship, and
+mentions the different methods of fumigation.
+
+Mr. Lantz, in a third paper, discusses the rat as an economic factor,
+and states in his paper that they do not serve any useful purpose. On
+the other hand, they cause enormous loss through damage to grain,
+merchandise, poultry and eggs, game and wild birds, fruit and
+vegetables, and flowers and bulbs. They also cause damage by setting
+fire to buildings and destroying furniture. He refers to various
+estimates made of the losses in the United States from rats, and they
+vary from $35,000,000 to $50,000,000 a year; but at the same time he
+states that, with present information, any attempt to state the amount
+of loss from rats would be largely guesswork.
+
+Assistant Surgeon-General Kerr refers to the rat as a factor in
+international sanitation, and briefly outlines the provisions contained
+in international sanitary agreements for their eradication. He reviews
+the efforts being made at the more important seaports to exterminate
+rats, as well as the methods being employed to that end. The information
+presented is, in part, compiled from consular reports received through
+the Department of State. There are given, so far as obtainable, copies
+of laws and ordinances enacted for the destruction of rats and the
+different methods practiced in ports where plague has prevailed, and the
+facts presented indicate that a more or less widespread crusade against
+rats is being carried on. He expresses the belief that it is too much to
+expect that the rat population can ever be exterminated from any city,
+but that it is not too much to expect that ocean carriers can be freed
+from rodents and kept so, which action would confine plague within
+continental boundaries.
+
+Epidemiological studies made of plague since the adoption of the
+International Sanitary Convention of Paris and the International
+Sanitary Convention of Washington have proven that the rat and its
+parasite, the flea, are the agents of transmission of the disease. In
+other words, where rats go plague will go. I believe, therefore, that in
+order to stop the further progress of plague, radical measures should be
+adopted, and in a communication of February 26, 1909, addressed to the
+Secretary of State, I suggested the advisability of submitting the
+question of a systematic destruction of rodents aboard ship to an
+international sanitary conference, with the view to the adoption of an
+international sanitary regulation on the subject. The adoption of such a
+regulation would undoubtedly lessen quarantine restrictions, prevent the
+destruction of cargo by rodents, and obviate the danger of the further
+spread of plague.
+
+Until ships are freed from rats, each country must take all necessary
+precautions, consistent with international agreements, to destroy rats;
+and the sanitary authorities of infected localities must, at great
+expense, determine the extent of infection among rodents, with the view
+to its elimination. This problem when it presents itself in a community
+is of great magnitude, and those responsible for its solution should be
+familiar with all its phases.
+
+It is with the view to supplying the necessary information in one
+treatise that this publication is issued. In its preparation the bureau
+has had the cooperation of the Department of Agriculture and
+acknowledgements are due, and here made to, the officers of that
+department for their hearty cooperation in contributing some of the
+chapters which follow.
+
+
+
+
+ NATURAL HISTORY OF THE RAT.
+
+ By DAVID E. LANTZ.
+
+ _Assistant, U. S. Biological Survey, Department of Agriculture_.
+
+
+ INTRODUCTION.
+
+The extermination of rats has become one of the serious problems of
+modern times. That such noxious animals should have flourished so long
+is not creditable to our civilization. While no kind of rat can be
+regarded as harmless, the various species differ greatly in harmfulness.
+In comparison with the cosmopolitan species that have reached our shores
+from the Old World, our native rats do little damage. It is important,
+therefore, to be able to recognize the introduced forms, to understand
+their habits, and to concentrate efforts for their extirpation.
+
+
+ CLASSIFICATION OF RATS.
+
+Rats and mice belong to the _Rodentia_, an order which comprises more
+than a third of all living species of mammals. Also, it exceeds any
+other mammalian order in the number of its individuals.
+
+Rodents are mainly herbivorous mammals, mostly of small size, having a
+furry, sometimes a spiny, integument, clawed digits, and usually
+plantigrade feet. The most important distinguishing character of the
+order is its dentition. This is marked by the absence of canine teeth
+and the presence of strongly developed incisors growing from permanent
+pulps. The incisors are never more than two in the lower jaw and usually
+but two in the upper. They are elongated, curved, chisel-like in shape,
+and continue to grow throughout the life of the animal. Only the front
+of these teeth is covered with enamel, a provision which keeps them
+sharp by the more rapid wearing away of the softer dentine in the body
+of the tooth, as the upper and lower pairs meet in gnawing. Between the
+incisors and the cheek, or molar, teeth of rodents there is a wide,
+vacant space, marking the entire absence of canines.
+
+The most extensive family of rodents is the _Muridæ_, a name which
+applies to rats and mice in the widest sense of those terms. It is
+difficult to characterize the family, since its members differ widely.
+However, most of them are rat-like in form and light and active in
+movements. None of the family have premolars; and, except in a single
+genus (_Hydromys_), the number of molars is three. Oldfield Thomas, the
+eminent English zoologist, includes in this family no less than 77
+genera, or almost half the total of 159 which he ascribes to the whole
+order _Rodentia_.[A] He further subdivides the _Muridæ_ into a dozen
+subfamilies, of which the _Murinæ_ and the _Sigmodontinæ_ are the most
+extensive. The name _Cricetinæ_ is now generally used instead of
+_Sigmodontinæ_, though not always with the same limitations.
+
+Footnote A:
+
+ Proc. Zool. Soc., pp. 1012–1028, 1896.
+
+The _Murinæ_ comprise only Old World rats and mice, while the
+_Cricetinæ_ are, in the main, American forms. In the _Murinæ_ the cusps,
+or tubercles, of the unworn upper molars are arranged triserially, or in
+three longitudinal rows; in the _Cricetinæ_ they are arranged
+biserially, one row on the outer and one on the inner margin (fig. 1).
+The wearing away of these cusps leaves characteristic curved lines of
+hard enamel surrounding areas of dentine. When the cusps are in pairs
+the worn pattern looks somewhat like the Greek letter sigma (Σ), whence
+the name sigmodont, often applied to native American rats and mice.
+
+[Illustration:
+
+ Fig. 1a. Fig. 1b.
+
+ FIG. 1a.—Upper molars of the brown rat (_Mus_): tubercles in three
+ rows.
+
+ FIG. 1b.—Upper molars of the rice rat (_Oryzomys_): tubercles in two
+ rows.
+]
+
+The _Murinæ_ are the true rats and mice, typified by the genus _Mus_,
+which contains by far the largest number of species. Trouessart, in his
+Catalogus Mammalium, enumerates 260 species of _Mus_ described before
+1905. Since that date a number of new forms have been described.
+
+The genus _Mus_ is characterized by narrow, ungrooved incisors; three
+small, rooted molars; soft fur mixed with hairs, sometimes with spines;
+a rudimentary pollex having a short nail instead of a claw; a long tail
+bearing rings of overlapping scales and often naked or nearly so. The
+ears are rather large, the eyes bright and prominent, and the muzzle
+somewhat pointed. The members of the genus are natives of the Old World,
+throughout which, with the exception of Madagascar, they are quite
+generally distributed. Nearly seven-eighths of the whole number of
+species are commonly called rats.
+
+The distinction between rats and mice is arbitrary and based on size.
+Exclusive of the tail, rats may be said to vary in length from 4½ to 10
+inches or more, while mice measure from 2 to 4 inches. With few
+exceptions, rats have six well-defined footpads (plantar tubercles), the
+last on the hind foot being elongated in shape; the last hind-foot pad
+of mice is usually circular (fig. 2).
+
+Of the many species of _Mus_ only three or four have developed the
+ability to adapt themselves to such a variety of conditions as to become
+cosmopolitan. Four have found lodgment in America: The common house
+mouse (_Mus musculus_); the old English black rat (_Mus rattus_); the
+Egyptian, or roof, rat (_Mus alexandrinus_); and the brown rat (_Mus
+norvegicus_), known also as the gray rat, barn rat, wharf rat, sewer
+rat, and Norway rat. The black rat and the roof rat differ from each
+other chiefly in color. Indeed some zoologists regard them as races of
+the same species, and the trinomial _Mus rattus alexandrinus_ for the
+roof rat is now in use among zoologists.
+
+[Illustration:
+
+ FIG. 2a.—Right hind foot of brown rat, showing long sixth foot pad.
+
+ FIG. 2b.—Right hind foot of house mouse, showing round sixth foot pad.
+]
+
+
+ DISTRIBUTION OF THE GENUS MUS IN AMERICA.
+
+The common house mouse (_M. musculus_) found its way to America soon
+after the first settlement by Europeans. It now inhabits all settled
+parts of North and South America, as well as nearly the entire Old
+World; but in very cold regions it does not always survive the winters,
+and is therefore comparatively scarce or local. It almost always reaches
+a new settlement sooner than the rat.
+
+The black rat (_M. rattus_) has been known in Europe since the twelfth
+century. It was carried to South and Middle America about three and a
+half centuries ago (1554). The time of its arrival in the English
+colonies of North America is not known with certainty, but it was well
+established in the settled parts by the beginning of the eighteenth
+century. Soon after the arrival of the brown rat, the black species
+began to decrease in numbers, and has become extinct in most localities.
+At present it is not uncommon in some parts of the South, and still
+occurs in scattered colonies in Canada and some of the States east of
+the Mississippi, and also on some of the coastal islands. It is
+occasional in many of our seaports, being apparently brought from the
+Far East in merchandise. Except in a few ports like San Francisco, where
+new arrivals are probably rather frequent, these introduced individuals
+are often destroyed before they multiply. The history of the black rat
+in Europe and its disappearance before the brown rat is an exact
+parallel to its history here, and the animal is now comparatively rare
+north of the Alps, except in the Channel Islands.
+
+The Biological Survey has specimens of the black rat from Massachusetts,
+New Hampshire, Georgia, Florida, Alabama, California, and Washington,
+and also from Mexico, Honduras, Nicaragua, and Hawaii. There are
+authentic records of its recent occurrence in Newfoundland, Quebec, Nova
+Scotia, New York, North Carolina, Tennessee, West Virginia, and
+Mississippi. In parts of South and Middle America it is abundant.
+
+The roof or Alexandrian rat (_M. alexandrinus_) is similar to the black
+rat in form and general habits, though not in color. Little is known of
+its history, but it is thought to be a native of Egypt, where it is
+still abundant. It has established itself in many parts of the world,
+mainly in warm climates, and is common near the coast in the southern
+parts of the United States.
+
+The Biological Survey has specimens of the roof rat from North Carolina,
+Georgia, Florida, Alabama, Mississippi, Texas, Arizona, and California.
+In the last-named State it is abundant in the Sacramento Valley. It is
+known also from Dismal Swamp, Virginia, and from Cuba, the Bermudas,
+Trinidad, San Domingo, Costa Rica, Nicaragua, Mexico, and Hawaii. Also,
+it inhabits many parts of South America, where in places it is the
+dominant species.
+
+The most destructive of the rat family is the brown rat (_M.
+norvegicus_). In most parts of the United States it is the common rat
+about houses and barns in the country and about markets, wharves, and
+warehouses in cities. It is larger and more robust than either the black
+or the roof rat, and differs from both in habits. It is more of a
+burrower, and lives in excavations which it makes under buildings and in
+loose soil along hedges and river banks. This habit, combined with its
+greater strength and ferocity has enabled it to supplant the other
+species in temperate latitudes; but in the warmer parts of America and
+the Old World it has not been able to drive out the others. The house
+mouse everywhere holds its own against the brown rat by its ability to
+escape into retreats too small for the rat to follow.
+
+The brown rat inhabits most of the thickly populated parts of America.
+North of Panama it occurs generally except in the arid interior, from
+the Isthmus to the Yukon Valley and southern Greenland. In the Great
+Basin it is practically unknown, and in New Mexico and Arizona it is
+confined chiefly to towns along the railroads. The Biological Survey is
+without records of its presence in Nevada, Utah, Wyoming, Idaho, and the
+greater part of Montana. The reason for its absence in that region is
+not understood, but its ability to withstand extreme cold is proved by
+the fact that it flourished in latitude 78° 37′ north on board Doctor
+Kane’s ship _Advance_, in the Second Grinnell Expedition, during the two
+winters when that vessel was icebound. It has also adapted itself to the
+continuous low temperatures of cold-storage warehouses, in which it
+appears to breed freely.
+
+
+ HISTORY OF THE BROWN RAT.
+
+We know little of the history of this species. Greek and Roman writers
+make no mention of rats of any kind, but possibly knew the animals and
+included them in their frequent references to mice. Pallas, in 1778,
+described the brown rat under the name _Mus decumanus_, and this was
+generally used until it was found that Erxleben had called it _M.
+norvegicus_ in 1777. Previously, the common name Norway rat had often
+been used for this species.
+
+The brown rat is generally supposed to be of Asiatic origin. Various
+modern writers have asserted that it came originally from Persia or
+India; but W. T. Blanford states that the species is at present unknown
+in Persia, and that in India the black rat is the generally distributed
+species, while the brown rat occurs only along the coast and the
+navigable rivers.[B] This implies that the latter species is a
+comparatively recent immigrant into India.
+
+Footnote B:
+
+ Fauna of British India. Mammals, p. 409, 1891.
+
+As regards the arrival of the brown rat in Europe, two facts are known.
+The species reached England from some eastern port about 1728 or 1729,
+and according to Pallas, a little earlier, 1727, crossed the Russian
+frontier from Asia and soon spread over the greater part of that
+country.[C] This statement, taken in connection with that of Blanford,
+makes it highly probable that before this migration the Asiatic home of
+the species was north, rather than south, of the high mountains of
+northern India. This view, which has been adopted by several
+naturalists, is further strengthened by the fact that the animal
+flourishes better in temperate than in tropical climates.
+
+Footnote C:
+
+ Zoographica, Rosso-Asiatica, vol. 1. p. 165, 1831.
+
+Possibly earlier and unrecorded westward migrations of the brown rat
+took place. A few years ago Professor Waile, the archeologist, while
+making excavations at Cherchell on the coast of Algeria, dug up the
+skull of a rat, which he stated was contemporary with the Roman
+occupation of the country under the Cæsars. The skull had but one molar,
+much worn, but the cranial bones were intact, and French zoologists
+pronounced the remains as undoubtedly those of the “surmulot,” or brown
+rat.[D] This shows that we have little more than conjectures for the
+early history of this species.
+
+Footnote D:
+
+ Comptes Rendus des Séances de L’Académie des Sciences, Paris, vol.
+ 116, p. 1031, 1893.
+
+The brown rat is said to have first appeared in Paris in 1750. It was
+brought to the United States, probably from England, about the beginning
+of the Revolution, 1775. According to Audubon, it was unknown on the
+Pacific coast of the United States in 1851; but Dr. J. S. Newberry
+thought it must have arrived at San Diego, Monterey, and San Francisco
+at a much earlier date.[E] Doctor Cooper recorded its arrival at Fort
+Steilacoom, Washington, as occurring about 1855.
+
+Footnote E:
+
+ Pac. R. R. Reports, Vol. 6, Zoological Report, pt. 2, p. 60, 1857.
+
+
+ GENERAL DESCRIPTION.
+
+The brown rat differs considerably from the black rat and the roof rat.
+It is larger, has a shorter head, a more obtuse muzzle, smaller ears,
+and a relatively shorter and stouter tail. The general color is
+grayish-brown above and whitish below. The over hairs of the upper parts
+have black tips. The tail is usually shorter than the head and body
+combined. The average measurements of adult specimens of the brown rat
+in the Biological Survey collections are as follows: Total length, 415
+millimeters (16.3 inches); tail, 192 millimeters (7.1 inches); hind
+foot, 43 millimeters (1.7 inches). This species sometimes attains a
+total length of 19 to 20 inches, and has been known to weigh 24 to 28
+ounces and even more. The average weight of an adult brown rat is
+considerably less than a pound.
+
+The black rat is less robust than the brown rat. It has a longer head, a
+sharper muzzle, and larger and broader ears (fig. 3). The tail is longer
+than the head and body combined. The fur is of a sooty, or plumbeous
+black, color, paler on the underparts. It is much softer and denser than
+that of the brown rat, and the mixture of very dark and lighter over
+hairs gives it a peculiar shining appearance. The average measurements
+of 20 apparently adult specimens in the collection of the Biological
+Survey are as follows: Total length, 379 millimeters (14.9 inches);
+tail, 207.4 millimeters (8.1 inches); hind foot, 35.8 millimeters (1.4
+inches).
+
+The roof rat in general resembles the black rat, except as to color and
+texture of fur. Above it does not greatly differ in color from the brown
+rat, but its underparts are usually more yellowish. The fur is commonly
+shorter and harsher in texture than that of the black rat, but this
+difference might not always be apparent in specimens of the two forms
+from the same latitude. The average measurements of 50 adult specimens
+of the roof rat in the collections of the Biological Survey are as
+follows: Total length, 393.3 millimeters (15.5 inches); tail, 212.8
+millimeters (8.4 inches); hind foot, 36.2 millimeters (1.4 inches).
+
+[Illustration:
+
+ FIG. 3A, FIG. 3B.—Ears of brown rat and black rat, showing relative
+ size.
+]
+
+Both albinism and melanism are frequent among rats, and pied forms also
+are common. It has been claimed that all the white rats (albinos) of the
+bird stores are _Mus rattus_, but albinism is by no means confined to
+this species. Doctor Hatai found that all the colonies of white rats
+maintained at the neurological laboratories of Chicago University and
+the Wistar Institute of Anatomy, Philadelphia, were of the _M.
+norvegicus_ species.[F] The same is true of all the albino rats in the
+collections of the National Museum and the Biological Survey. These
+collections contain also several spotted rats (gray and white) and
+sooty-black specimens indistinguishable in color from _M. rattus_, all
+being undoubtedly of the _M. norvegicus_ species.
+
+Footnote F:
+
+ Biological Bulletin, vol. 12, pp. 266–273, March, 1907.
+
+
+ KEY TO THE SPECIES OF MUS IN AMERICA.
+
+ Size small. Total length of adult less than 200
+ millimeters _Mus musculus_
+
+ Size large. Total length of adult exceeding 300
+ millimeters.
+
+ Ears moderate, when laid forward barely or not
+ reaching eye; tail shorter than (rarely equal
+ to) the length of head and body, darker above
+ than below; color of body normally gray-brown
+ above, white below; hind foot 38–46 millimeters _Mus norvegicus_
+
+ Ears larger, when laid forward reaching at least
+ to middle of eye; tail longer than head and
+ body, dusky all around; hind foot 33–37
+ millimeters.
+
+ Color grayish-brown above, white or yellowish _M. rattus
+ white below. alexandrinus_
+
+ Color blue-black above, slaty below _M. rattus_
+
+
+ HABITS OF RATS.
+
+
+ BREEDING HABITS.
+
+Both climate and food supply affect the rate of multiplication of most
+rodents. The rat probably increases more rapidly in a temperate and
+equable climate than in one of great variability. Extremes of heat and
+cold retard multiplication, decreasing both the number of litters in a
+year and the number of young at a time. In northern latitudes,
+apparently, more or less interruption of breeding occurs in the winter
+months.
+
+Where the country is well settled the food supply of rats is not likely
+to be deficient; and when the animals have access to stores of grain,
+the young mature very quickly and probably reproduce earlier than when
+grain is absent.
+
+The brown rat is more prolific than either the roof rat or the black
+rat. The female brown rat has usually 12 mammæ—3 pairs of pectoral and 3
+pairs of inguinal—although these numbers are not constant, one or more
+teats frequently being undeveloped. The black rat and the roof rat have
+only 10 mammæ—2 pairs of pectoral and 3 pairs of inguinal—with but
+little tendency to vary. Records of actual observations on the number of
+young confirm the deductions that might be drawn from the above facts.
+At Bombay, India, during the recent investigations made by the India
+Plague Commission, 12,000 rats were trapped and examined. The average
+number of embryos found in pregnant brown rats was 8.1; the highest
+number, 14. The average for the black rat was 5.2; the largest number,
+9.[G]
+
+Footnote G:
+
+ Etiology and Epidemiology of Plague, p. 9, Calcutta, 1908.
+
+In temperate latitudes the average number of young produced by the brown
+rat is undoubtedly greater. Instances of very large litters observed in
+England are recorded in The Field (London). In two instances 22 and 23
+young, respectively, were found in a single nest, though no evidence is
+offered that these were the progeny of a single female; but in two other
+cases 17 and 19 embryos were found in gravid females. A dealer in
+feedstuffs in Washington, D. C., relates that he found 19 young rats in
+a single nest in his store. Within the past few months the writer has
+examined four pregnant brown rats taken in traps. The numbers of embryos
+they contained were 10, 11, 11, and 13, respectively. While we have not
+enough data for definite conclusions, we may safely state that the
+average litter for this latitude is not less than 10.
+
+Frank T. Buckland, in Curiosities of Natural History, relates that a
+white rat which he kept in captivity gave birth to 11 young when only
+eight weeks old. As gestation in rats occupies three weeks, this animal
+must have bred when only five weeks old.
+
+The number of times rats breed in a year is not definitely known, and
+probably varies considerably with local conditions. Kolazy makes the
+almost incredible statement that two female white rats, kept by him in
+confinement and well fed, within thirteen months gave birth to 26
+litters of young, numbering 180 in all. One of them produced young
+regularly at intervals of 25 days.[H]
+
+Footnote H:
+
+ Verh. Zool. Bot. Gesel. Wien., pp. 731–734, 1871.
+
+The writer recently kept two young female brown rats with a male in a
+large open cage for several months. One of the females gave birth to
+young on April 15; the other on April 17. The number in these litters
+was not observed, as some were devoured soon after birth, and all within
+three days, presumably by the male rat. On May 23 both females gave
+birth to young, 24 in number, all in one nest.
+
+The known facts concerning the breeding of the brown rat may be briefly
+summarized as follows: The animals breed from three to five times a
+year, each time bringing forth from 6 to 19 young. After a gestation
+period of twenty-one days, the females give birth to their young in
+nests built in underground burrows or under floors, stacks, lumber,
+woodpiles, or other shelter. The young are blind and naked when born,
+but grow rapidly, and young females are capable of breeding when less
+than three months old.
+
+Early spring and summer are the periods of greatest reproductive
+activity among rats. Young, however, are to be found every month of the
+year.
+
+The above statements apply in the main also to the black and the roof
+rat, but the number of young in a litter is somewhat smaller. The newly
+born young of the black rat have not the bright pink color of those of
+the brown and the roof rat, but are bluish, especially on the upper
+parts. Black-and-white spotted rats are at first bluish-and-red spotted,
+the red areas representing the white of the adults.
+
+
+ ABUNDANCE OF RATS.
+
+From the foregoing account of the breeding habits of rats, the great
+difficulty of ridding cities or large areas of the animals may be
+readily understood. Ordinarily, they breed more rapidly than they are
+destroyed. Although few are seen in daytime, at night they fairly swarm
+along river fronts and wharves, as well as in sewers, stables,
+warehouses, markets, and other places where food is abundant. Their real
+numbers may sometimes be discovered when any such harbor is demolished.
+
+An ordinary farm sometimes supports an astounding number of rats. In
+1901, an estate of 2,000 acres near Chichester, England, was badly
+infested with the pests. They were systematically destroyed by traps,
+poisons, and ferrets, under the supervision of the proprietor. In this
+way 31,981 were killed, while it was estimated that tenants at the
+thrashing had destroyed fully 5,000 more. Even then the property was by
+no means free from rats.[I]
+
+Footnote I:
+
+ The Field (London), vol. 100, p. 545, 1902.
+
+During a plague of rats on the island of Jamaica in 1833, the number of
+rats killed on a single plantation in a year was 38,000. The injury to
+sugar cane on the island caused by the animals was at that time
+estimated at half a million dollars a year.[J]
+
+Footnote J:
+
+ New England Farmer, vol. 12, p. 315, 1834.
+
+The report of the Indian Famine Commission presented to the English
+Parliament in 1881 affords one of the best illustrations of the number
+of rats that may infest a country. An extraordinary number of the
+animals at that time inhabited the southern Deccan and Mahratta
+districts of India. The autumn crop of 1878 and the spring crop of 1879
+were both below the average, and a large portion of each was destroyed
+by rats. The resulting scarcity of food led to the payment of rewards
+for the destruction of the pests, and over 12,000,000 were killed.[K]
+
+Footnote K:
+
+ British Medical Journal, Sept. 16, 1905, p. 623.
+
+
+ MIGRATIONS AND INVASIONS.
+
+Migrations of rats have often been recorded. The brown rat is known in
+Europe quite generally as the migratory rat. The Germans call it the
+Wanderratte. Pallas narrates that in the autumn of 1727 this species
+arrived from the east at Astrakhan, southeastern Russia, in such great
+numbers and so suddenly that nothing could be done to oppose them. They
+crossed the Volga in immense troops. The cause of this general migration
+was attributed to an earthquake; but since similar movements of the same
+species often occur without earthquakes, it is probable that only the
+food supply of the animals was involved in the migration which first
+brought the brown rat to Europe.
+
+A seasonal movement of rats from houses and barns to the open fields
+takes place in spring when green and succulent plant food is ready for
+them. The return movement takes place in the autumn. This seasonal
+migration is noticeable even in large cities.
+
+But more general movements of rats frequently occur. In 1903 a multitude
+of migrating rats spread over several counties in western Illinois. They
+were noticed especially in Rock Island and Mercer counties. For several
+years previous no abnormal numbers of the animals were seen, and their
+coming was remarkably sudden. An eyewitness to the occurrence informed
+me that as he was returning to his home one moonlit night he heard a
+general rustling in a nearby field, and soon a great army of rats
+crossed the road in front of him, all moving in one direction. The host
+stretched away as far as they could be seen in the dim light. These
+animals invaded the farms and villages of the surrounding country and
+caused heavy losses during the winter and summer of 1904. A local
+newspaper stated that between March 20 and April 20, 1904, Mr. F. W.
+Montgomery, of Preemption, Mercer County, killed 3,435 rats on his farm.
+He caught most of them in traps.[L]
+
+Footnote L:
+
+ Moline (Ill.) Evening Mail, Apr. 25, 1904.
+
+In 1877 a similar migration of rats into parts of Saline and Lafayette
+counties, Mo., took place.[M] Also, one came under my own observation in
+the Kansas River valley in 1904. This valley, for the most part, was
+flooded by the great freshet of June, 1903, and for about ten days was
+covered with several feet of water. Probably most of the rats in the
+valley at the time perished in the flood. Yet in the fall of 1903 much
+of the district was visited by hordes of rats, which remained during the
+winter and had so increased by the following spring that serious losses
+to grain and poultry resulted.
+
+Footnote M:
+
+ Forest and Stream, vol. 8, p. 380, July 12, 1877.
+
+No doubt most of the so-called migrations of rodents, were all the facts
+known, could be accounted for as instances of abnormal reproduction or
+of failure of food supply in one place, compelling change of habitat. In
+England a general movement of rats inland from the coast occurs every
+October. This is known to be closely connected with the closing of the
+herring season. During the fishing the rodents swarm to the coast,
+attracted by the offal left in cleaning the herring; and when this food
+fails, the animals troop back to the farms and villages.
+
+In South America plagues of rats are often periodical, occurring in
+Parana, Brazil, at intervals of about thirty years and in Chile at
+intervals of from fifteen to twenty-five years. It has been discovered
+that these plagues in the cultivated lands follow the ripening and decay
+of the dominant species of bamboo in each country. The ripening of the
+seed furnishes for two or more years a favorite food for rats in the
+forests, where the animals multiply greatly. When this food fails, they
+are forced to the cultivated lands for subsistence. In 1878 almost the
+whole crops of corn, rice, and mandioca in the State of Parana were
+destroyed by rats, causing a serious famine.[N]
+
+Footnote N:
+
+ Nature, vol. 20, p. 65, 1879.
+
+An invasion of rats (_Mus rattus_) in the Bermuda Islands occurred about
+the year 1615. Within two years they had increased so alarmingly that
+none of the islands was free from them. The rodents “devoured everything
+that came in their way—fruits, plants, and even trees”—so that for a
+year or two the people were nearly destitute of food. A law was passed
+requiring every man in the islands to keep 12 traps set. In spite of all
+efforts the animals continued to increase, until finally they
+disappeared so suddenly that they must have been victims of a
+pestilence.[O]
+
+Footnote O:
+
+ Popular Science Monthly, vol. 12, p. 376, January, 1878.
+
+
+ FOOD OF RATS.
+
+Instead of being strictly herbivorous, as might be inferred from their
+dentition, rats are practically omnivorous.
+
+The bill of fare of the rat includes grains and seeds of every kind,
+flour, meal, and all food products made from them; fruits and garden
+vegetables; mushrooms; bark of growing trees; bulbs, roots, stems,
+leaves, and flowers of herbaceous plants; eggs, chicks, ducklings,
+squabs, and young rabbits; milk, butter, and cheese; fresh meat and
+carrion; mice, rats, fish, frogs, mollusks, and crustaceans. This great
+variety of food explains the ease with which rats maintain themselves in
+almost any environment.
+
+
+ FEEDING HABITS.
+
+Rats resemble squirrels in the manner of holding food while eating. As
+soon as they have separated a small portion of food from a larger mass,
+they sit up, arching the back and holding the morsel in the paws and
+turning it as a squirrel does. After eating, they brush the mouth and
+fore parts, including the whiskers (vibrissæ), with the paws until all
+are clean. Rats drink much water, a habit often taken advantage of in
+placing traps or poisons for them.
+
+Rats generally feed after sunset, but in places where they are not often
+disturbed they come out and feed in broad day and even in the sunshine.
+
+The roof rat and the black rat are more expert climbers than the brown
+rat, which is larger and clumsier. In buildings, the brown rat keeps
+mainly to the cellar and lower parts, where it commonly lives in
+burrows. From these retreats it makes nightly excursions to the upper
+parts of the house in search of food. The roof rat and the black rat
+live in the walls or in the space between ceilings and roofs. They nest
+in any of these places.
+
+Rats readily climb trees to obtain fruit. In the Tropics the roof rat
+and the black rat habitually nest in trees and spend much of their time
+in these arboreal retreats, while the brown rat makes only occasional
+excursions into the branches in search of food.
+
+In the open, rats seem to have defective vision by daylight. They move
+slowly and uncertainly. On the contrary, at the side of a room and in
+contact with the wall they run with great celerity. This fact suggests
+that the vibrissæ serve as feelers and that the sense of touch in them
+is extremely delicate. The animals always prefer narrow spaces as
+highways—another circumstance which may be made use of in placing traps.
+
+
+ FEROCITY OF RATS.
+
+The ferocity of rats has been grossly exaggerated. The stories of their
+attacks upon human beings, sleeping infants especially, have but slight
+foundation. If attacked, nearly all rats defend themselves with the
+teeth; and no doubt a horde of rats, if hungry, would be formidable.
+Ordinarily the probability of being bitten by rats is remote, and the
+bite is not poisonous.
+
+The ferocity of rats is mainly exercised against members of their own
+order. The brown rat is undoubtedly the most formidable of the genus in
+America, and possibly in the world; yet when captured it adapts itself
+readily to confinement, and in a few days will take food and water
+whenever offered. The enmity of this species toward other rats and mice
+is well known. It is supposed to have destroyed the black rat over the
+greater part of Europe and America, although it is possible that disease
+carried by the brown rat was a factor in the disappearance of the other
+species. That the black and the roof rat in tropical countries have not
+been displaced by the brown rat is probably owing largely to their more
+arboreal habits. It is not uncommon in the Far East to find two species
+of rats living side by side in the same locality. An example is _M.
+imperator_ and _M. rex_ living on one of the Solomon Islands. The first
+is a burrowing species; the other arboreal. In 1877 two native species
+of rats, _M. macleari_ and _M. nativitatis_, were found living together
+in amity on Christmas Island, in the Indian Ocean.[P] About ten years
+ago the brown rat was accidentally introduced, and it is now thought
+that both the native species are extinct.
+
+Footnote P:
+
+ Proc. Zool. Soc. 1888, pp. 517, 534.
+
+When pressed by hunger rats become cannibals and destroy their weaker
+fellows. However, when ordinary food is abundant, cannibalism among rats
+is rare.
+
+
+
+
+ PLAGUE INFECTION IN RATS.
+
+ By GEORGE W. MCCOY,
+
+ _Passed Assistant Surgeon United States Public Health and
+ Marine-Hospital Service._
+
+
+The rat is a known or a suspected factor in the transmission of several
+diseases, yet at present, and perhaps for many years to come, the most
+immediate and pressing question that concerns us is its relation to the
+origin and spread of plague among human beings. For this reason a
+discussion of the reaction of these animals to natural and to artificial
+infection with _B. pestis_ becomes of prime importance.
+
+Not only are rats believed to be more or less directly responsible for
+cases of human plague in a community, but in addition, they are believed
+to be the most frequent medium through which plague is carried from one
+locality to another, for these animals are good travelers, can live on a
+very meager ration, and can do without water for a long time if food is
+available. We have found that on a diet of dry grain alone a rat may
+live for over a month.
+
+In this connection it may not be amiss to call attention to the
+importance of the rat as an agent in conveying plague infection to other
+rodents and especially to ground squirrels. There is every reason for
+believing that the infection among the squirrels in California was
+derived originally from rats. Wherry[16] states that more rats than
+ground squirrels have been trapped in the squirrel burrows in the
+vicinity of Berkeley, Cal. This shows how easy it might be for rats to
+infect squirrels and vice versa.
+
+The clinical manifestations of plague in rats are of little importance.
+It is generally said that the plague-infected rat staggers about with a
+drunken gait, loses fear of its natural enemies, and is readily
+captured. Our experience with artificially infected rats indicates that
+the animals show no marked manifestations of illness until shortly
+before death when they become quiet, crouch in the corner of the cage,
+and try to hide.
+
+It is rather surprising to observe that comparatively few plague rats
+are found dead. In the San Francisco campaign, while no accurate figures
+are obtainable, certainly not more than 20 per cent of the infected
+rodents were found dead, the remainder being trapped. This is probably
+due to the fact that the disease is one of several days’ duration, from
+two to six most frequently, and during this period there are more
+chances of catching the sick rodent in a trap than there are of finding
+the body after death, unless the immediate surroundings are known to
+harbor infected animals and an especially careful search is made for
+cadavers in the places, often difficult of access, where rats have their
+burrows and nests.
+
+As plague is a disease that gives rise to such characteristic gross
+pathological lesions in man and in laboratory animals, it is but
+reasonable to expect that equally distinctive lesions would be found in
+the rat, and this we find to be the case.
+
+Skschivan[1], Kister and Schumacher[2], and other writers have observed
+and recorded the gross lesions of plague in rats. It remained, however,
+for the Indian Plague Commission[3], which had the opportunity of
+examining an enormous number of plague rats in Bombay and elsewhere in
+India, to crystallize our knowledge of this subject and to point out its
+field of usefulness.
+
+As to the comparative value of microscopical and macroscopical methods
+of diagnosis, the Indian Plague Commission[3] states that: “The results
+of tests carried out for the purpose of comparison make it manifest that
+the naked eye is markedly superior to the microscopical method as an aid
+in diagnosis, and as the result of our experience we are prepared to
+make a diagnosis of plague on the strength of the macroscopical
+appearances alone, even though the other results of cutaneous
+inoculation and culture are negative and the animal shows signs of
+putrefaction.”
+
+Our experience with rat plague, though limited, leads us to the same
+conclusion as that arrived at by the Indian Commission in regard to the
+value of the gross lesions of plague in making the diagnosis. To one who
+is acquainted with them, these lesions are as characteristic as those of
+any infectious disease in man. It is quite true that occasionally
+atypical cases are encountered where the majority of the gross lesions
+are wanting, and in such cases it becomes necessary to resort to the
+inoculation of animals or to cultural investigations in order to make a
+diagnosis. Such cases are, however, if anything, rarer than are atypical
+post-mortem findings in pneumonia or in typhoid fever in man.
+
+
+ MODE OF EXAMINATION.
+
+A brief description of the actual manner of examining rats for plague
+infection will be given here.
+
+The rats are immersed in any convenient solution for the purpose of
+killing fleas and other ectoparasites that might be capable of carrying
+infection from a plague-infected rat.
+
+The following plan of handling rats has been found satisfactory in the
+federal laboratory at San Francisco. The rats are nailed to a shingle by
+an attendant. Another attendant reads off the address on the tag
+attached to the rat, puts a check number on the shingle, and records the
+address from which the rat was taken and the check number on the card
+shown on page 48. This card is arranged so as to give the data as to the
+address from which the rat came, its size, sex, and species. After being
+checked the rats are dissected and finally, after examination by the
+medical officer, they are removed from the shingle; any plague-infected
+rats are burned as soon as the necessary investigation has been made.
+The dissection is made by reflecting the skin from the whole front of
+the body and neck so as to expose the cervical, axillary, and inguinal
+regions. The thoracic and abdominal cavities are then opened with
+scissors.
+
+In the inspection, careful search for buboes must be made in the regions
+of the various peripheral lymph glands. The abdominal and thoracic
+organs must be subjected to a careful scrutiny. It is needless to say
+that this work should be done in a rat-proof, well-lighted building that
+is provided with water, gas, and sewer connections. The utmost care
+should be taken to avoid any undue risk of infection. The wearing of
+rubber gloves is not necessary. Everyone who has to handle infected
+animals must be sufficiently alive to the danger of infection.
+
+In the extensive work conducted by the Indian Plague Commission[3],
+attendants were protected with Haffkine’s prophylactic. This is
+undoubtedly a wise precaution and should be taken if possible.
+
+For a worktable on which to dissect the rats we use in San Francisco a
+table which slopes gently from the sides and ends toward the center,
+where a drain pipe is attached which leads to a vessel containing a
+disinfectant. The table is covered with sheet lead.
+
+The layman of average intelligence readily learns to recognize the gross
+lesions of rat plague and it is wise to train the laboratory attendants
+to do this. Every rat should, however, be subjected to a careful
+scrutiny by the physician responsible for the work. The great majority
+of rats may be put aside after a cursory examination as entirely beyond
+suspicion of infection. Probably 8 or 10 per cent of them will require a
+very careful examination for the gross lesions of plague. A card which
+we have found very useful for keeping records of suspected and infected
+animals is shown on page 34. Probably all of the species of the genus
+_Mus_ are susceptible to plague infection. I shall, however, confine
+myself to a consideration of plague in the rats found the world over
+(_M. norvegicus_, _M. rattus_, _M. alexandrinus_).
+
+In Bombay[18] it has been found that the epizootic among _Mus
+norvegicus_ appears first and is probably responsible for the diffusion
+of plague among _Mus rattus_. It precedes the infection among _Mus
+rattus_ by about ten days, and the opinion is expressed by the Indian
+Plague Commission that the usual course of the infection is from the
+_Mus norvegicus_ to the _Mus rattus_, and as the latter rodent is a
+house dweller in India it is the most frequent source of human
+infection.
+
+In San Francisco the _Mus rattus_ population is comparatively small,
+contributing perhaps 2 per cent of the total rat population of the city;
+but in the section of the city where the large warehouses are found,
+especially those where oriental goods are stored, about 15 per cent of
+the rats taken are _Mus rattus_. So far as concerns plague infection
+about 5 per cent of the rat cases were in _Mus rattus_. It may be of
+interest to note that the last infection found among rats in San
+Francisco was among the _Mus rattus_ in a large warehouse near the water
+front. Two plague-infected rats were found in this building, one October
+21, 1908, and the other October 23, 1908. A large number of mummified
+carcasses, all _Mus rattus_, were found in the building, and it seems
+not unlikely that a somewhat extensive epizootic had occurred among
+them. No previous case of rat plague had been found in the city for
+eighty-five days, though about 25,000 rats had been examined during that
+period, and none have been found in the six months since, although over
+30,000 rats have been examined. Our records show that of 84 infected
+rats, 79 were _Mus norvegicus_, and the remainder were _Mus rattus_.
+Some of the latter may have been _Mus alexandrinus_, as the two species
+(_Mus rattus_ and _Mus alexandrinus_) were not clearly differentiated in
+the earlier examinations.
+
+
+ THE GROSS LESIONS OF NATURAL RAT PLAGUE—ACUTE PLAGUE.
+
+
+ SUBCUTANEOUS INJECTION.
+
+This is the sign which usually first attracts attention. White[4], in
+discussing plague in rats, states that “the most noticeable post-mortem
+appearance of the plague rat is the engorgement of the subcutaneous
+blood vessels, together with a diffuse pink color of the subcutaneous
+muscles, which have a peculiar dry, waxy translucency.” It has been our
+experience frequently to have an attendant who is dissecting rats remark
+that he had found an infected rat after the first incision was made in
+reflecting the skin. The injection is dark red, and upon close
+inspection one sees that the small vessels are uniformly distended with
+blood. It is usually distributed over the whole surface of the body, but
+on two occasions we have seen it confined to the side of the body on
+which the primary bubo was found. A bright pink injection is a rather
+common finding among rats in San Francisco. It is not likely to be
+mistaken for the injection of plague infection. Subcutaneous œdema,
+confined to the vicinity of the bubo, is occasionally encountered.
+
+In our experience in San Francisco an injection identical in appearance
+with that found in plague infection was found only twice, and in each
+case there was associated with it a small discharging subcutaneous
+abscess. There were no other lesions in either case and the pus from
+these abscesses failed to produce plague in guinea pigs.
+
+In a series of 61 consecutive plague rats in San Francisco, injection
+was present fifty-two times, it was confined to the region of the bubo
+twice, it was unilateral twice, and was general in distribution
+forty-eight times. It was slight thirteen times, moderate fifteen times,
+marked sixteen times, intense eight times.
+
+
+ THE BUBO.
+
+This is the most reliable single sign of plague infection, and when
+present in typical form is enough on which to base a diagnosis which
+rarely proves erroneous.
+
+The gland involved is usually surrounded by a more marked injection than
+is present elsewhere, and an infiltration which at times is hemorrhagic.
+This surrounding hemorrhage which was common in the plague rats
+described by the Indian Plague Commission was met with very rarely in
+San Francisco. The gland proper is usually caseous. The contents may be
+shelled out very readily, though prior to section the gland feels very
+firm. In the cases seen at the federal laboratory in San Francisco, the
+contents of the buboes were recorded as being hemorrhagic four times and
+as caseous twenty-nine times. Pest-like bacilli were noted as present in
+18 cases, in 6 of which the “coccoid” form predominated. They were
+recorded as absent five times.
+
+Indolent enlargement of the lymph glands is very commonly encountered in
+rats that are not infected with plague. Among old rats probably 15 per
+cent will show this. Such glands, however, are tough, elastic, and not
+surrounded by infiltration. They are not likely to be mistaken for the
+plague buboes. In the leprosy-like disease of rats, the glands may reach
+an enormous size.
+
+Observers differ as to the location of the primary bubo. Skschivan[1]
+states definitely the location of five primary buboes in plague rats
+seen in Odessa in 1901. Two were in the axilla, two in the inguinal
+region, and one in the neck. Kitasato[5] says: “To judge from the
+experience of the past it can be suggested that in examining rats
+particular attention should be paid to their submaxillary and cervical
+glands and to the spleen. These organs in most cases show the evidence
+of infection, if there be any.” From this it would appear that he
+regarded the neck glands as the most frequent seat of the bubo. It may
+be remarked here that his experience was derived from plague rats seen
+in Asia.
+
+We find a marked difference between the experience in San Francisco and
+that in Bombay. This is demonstrated in the following table, which shows
+the location in percentage of single buboes in each situation:
+
+ ───────────────────────────────────────┬───────┬───────┬───────┬───────
+ │ Neck.│Axilla.│ Groin.│Pelvis.
+ ───────────────────────────────────────┼───────┼───────┼───────┼───────
+ │ _Per│ _Per│ _Per│ _Per
+ │ cent._│ cent._│ cent._│ cent._
+ Indian Plague Commission, Bombay—2,923 │ 75│ 15│ 6│ 4
+ rats[3] │ │ │ │
+ Wherry, Walker, and Howell, San │ 12│ 12│ 75│
+ Francisco[6]—8 rats │ │ │ │
+ Federal laboratory, San Francisco—32 │ │ 22│ 72│ 6
+ rats │ │ │ │
+ ───────────────────────────────────────┴───────┴───────┴───────┴───────
+
+The American figures are too small to be of much significance, but one
+is struck with the fact that in Bombay three-fourths of the buboes are
+in the neck, while in San Francisco three-fourths of all found are in
+the inguinal region. We have records of only three multiple buboes found
+in rats in San Francisco, and in no case was either of the buboes in the
+neck; while in Bombay, to quote from the report[3], “Of the rats with
+multiple buboes 54.5 per cent had a bubo in the neck.” Striking as these
+figures are, we have collected further evidence that the inguinal region
+is the commonest location of the bubo in plague rats in this vicinity.
+
+Passed Asst. Surg. J. D. Long, Public Health and Marine-Hospital
+Service, who has had an extensive experience with rat plague in Oakland,
+Cal., tells me that the majority of the buboes were found in the groin,
+very few in the neck. Acting Assistant Surgeon Wherry, Public Health and
+Marine-Hospital Service, informs me that in a series of plague rats
+examined after the report made in association with Walker and Howell[6],
+the cervical bubo was very rarely encountered.
+
+Particular care was taken to look for cervical buboes, as it seemed
+rather inconsistent to find the other lesions so fully in accord with
+those found in India, yet to have the location of the bubo to differ so
+radically. We have not encountered a mesenteric bubo in our work in San
+Francisco. The Indian Plague Commission found none in over 5,000
+naturally infected plague rats. As mesenteric buboes are very commonly
+encountered in plague infection brought about by feeding, they conclude
+that the absence of these buboes in naturally infected rats is strong
+evidence that the infection does not enter by the alimentary canal.
+
+
+ THE GRANULAR LIVER.
+
+Two lesions of the liver are encountered in plague rats. The one most
+frequently observed is spoken of by the Indian Plague Commission as
+“fatty” change, though it is explained that this term refers to the
+naked eye appearance as, microscopically, the lesion is found to be due
+to a necrosis of the liver tissue. When this change is present the organ
+is found to be rather yellowish in color and is studded with an enormous
+number of yellowish white granules which are about the size of a pin
+head. This lesion, which was very common in the San Francisco cases, is
+very readily recognized.
+
+The other lesion is a marking of the organ with grayish white spots;
+“they are typically of the size of a pin’s point, and give the surface
+of the organ a stippled appearance as if dusted over with gray
+pepper”[3] (p. 331). This appearance, which is less frequently
+encountered than is the preceding one, is more difficult to recognize;
+indeed the most careful scrutiny is necessary to avoid overlooking it.
+
+Rats that have been fed with certain biological preparations used to
+destroy rodents (Danysz’s virus and similar preparations) often present
+lesions in the liver resembling those due to plague infection. The
+granules are, however, larger and more distinct. In these cases the
+spleen is enlarged and generally granular, but rarely dark and friable
+as in plague infection.
+
+
+ THE SPLEEN.
+
+The size of the spleen of healthy rats of the same weight varies so
+greatly that often one can not be sure as to what constitutes an
+enlargement of this organ.
+
+In plague rats this organ is markedly enlarged, firm, friable, rather
+dark in color, and occasionally presents small granules under the
+capsule. As Skschivan[1] pointed out, these granules are not encountered
+as often as are granules in the liver. At times the organ presents a
+very distinctly mottled appearance. This latter appearance is much more
+frequently seen in artificially inoculated rats than in those found
+infected in nature. We have seen the organ distinctly slate-colored on
+several occasions.
+
+
+ PLEURAL EFFUSION.
+
+The last sign of rat plague is one of great importance when associated
+with other suspicious lesions. The effusion is bilateral, and is serous
+in character, usually clear, though it is occasionally blood stained.
+Pleural effusion is rarely found in rats other than those that are
+plague infected. The following table shows in percentage the frequency
+of the various macroscopical lesions of acute natural rat plague, as
+observed in Bombay and in San Francisco:
+
+ ────────────────────────┬────────────┬──────┬────────┬───────┬─────────
+ │Subcutaneous│Bubo. │Granular│ Large │ Pleural
+ │ injection. │ │ liver. │ dark │effusion.
+ │ │ │ │spleen.│
+ ────────────────────────┼────────────┼──────┼────────┼───────┼─────────
+ │_Per cent._ │ _Per │ _Per │ _Per │ _Per
+ │ │cent._│ cent._ │cent._ │ cent._
+ Indian Plague │ 69 │ 85 │ 58 │ │ 72
+ Commission, │ │ │ │ │
+ Bombay—4,000 rats │ │ │ │ │
+ Wherry, Walker, and │ 59 │ 14 │ 14 │ 68 │ 71
+ Howell, San │ │ │ │ │
+ Francisco—88 rats │ │ │ │ │
+ Federal laboratory, San │ 85 │ 57 │ 87 │ 74 │ 59
+ Francisco—62 rats │ │ │ │ │
+ ────────────────────────┴────────────┴──────┴────────┴───────┴─────────
+
+It is recognized that the data from the San Francisco records is so much
+smaller than that from the Indian report that perhaps no just comparison
+is to be made. However, the figures are quite similar, except for the
+small percentage of buboes and of liver lesions in the work of Wherry,
+Walker, and Howell. The work of these observers was done in the early
+part of the epizootic in San Francisco while the other figures from that
+city are drawn from records later in the campaign.
+
+No single sign is pathognomonic, though only once have we been deceived
+by what was regarded as a typical plague bubo. This was in a rat that
+presented no other suspicious lesions and the inoculation test resulted
+negatively.
+
+It is a combination of two or more of the signs that is of moment. The
+subcutaneous injection with a typical liver or these signs associated
+with a typical spleen afford good grounds for a diagnosis. A rat showing
+a typical liver associated with a pleural effusion will usually prove to
+be plague infected, and if a large, dark, firm spleen is also found a
+diagnosis may be considered as practically established.
+
+As has been pointed out by several writers gross lesions of plague may
+be distinguished even in rats that are badly decomposed.
+
+
+ CHRONIC PLAGUE.
+
+No case of natural chronic plague has been encountered in San Francisco.
+Only one case was found among the many hundreds of plague rats examined
+by the Indian Plague Commission[3] (p. 457) in Bombay. However, this
+commission encountered a considerable number of cases among _Mus rattus_
+in the Punjab villages of Kasel and Dhand. The lesions were purulent, or
+caseous foci. They classify these cases as follows: Chronic plague of
+the visceral type, which is further subdivided into splenic nodules and
+abscesses, and mesenteric abscesses; chronic plague of the peripheral
+type in which abscesses are situated in the regions of the peripheral
+lymph glands.
+
+Plague bacilli were either absent or very scanty upon microscopical
+examination. They were, however, quite frequently recovered by cultural
+methods, and in the great majority of the cases the organisms were fully
+virulent. No evidence was forthcoming to show that this chronic rat
+plague had anything to do with the recurrence of acute plague among the
+rats.
+
+We have diligently sought for chronic plague among the rats in San
+Francisco, but, as we said above, without success, although a
+considerable number of lesions that correspond perfectly to the
+description of chronic plague have been submitted to the guinea-pig
+inoculation test, but invariably with a negative result. An account of
+the lesions of chronic plague as observed among inoculated rats is given
+in another part of this paper.
+
+Pound[7] believes that recovery from plague in rats is shown by the
+presence of pigmented lymphatic glands. Kister and Schumacher[2] mention
+pigment deposits in the inguinal region, but remarked that they are not
+characteristic of plague, a view which I believe is correct, as we have
+frequently seen them in San Francisco among the older rats, in which
+there was no reason to suspect previous plague infection, and they have
+been almost uniformly absent in the case of rats that have been
+experimentally infected with plague but have recovered.
+
+
+ RAT PLAGUE WITHOUT GROSS LESIONS.
+
+Plague infection may be present in a rat without bringing about any
+recognizable gross lesions. For example: Dunbar and Kister[8] mention a
+rat, which came from a ship on which plague rats had been found, that
+had no lesions, and cultures were negative; but a guinea pig cutaneously
+inoculated died of plague.
+
+Among a considerable number of inoculated rats we have very rarely,
+perhaps once or twice in a hundred cases, found nothing at the
+post-mortem examination that would suggest plague infection, yet
+cultures or inoculation of guinea pigs would demonstrate the presence of
+_B. pestis_. Such cases are very infrequent, but it should be kept in
+mind that they do occur. When a large number of rats are to be examined
+it would be impracticable to inoculate a guinea pig from each rat; and
+even if one did this the occasionally resistent guinea pig would
+introduce a larger error than exists by placing dependence upon the
+gross lesions for a diagnosis.
+
+
+ MICROSCOPICAL EXAMINATION.
+
+The exact weight to be given to the morphology of the organisms found in
+smears from the organs of a rat suspected of being plague infected is a
+matter of individual judgment. Smears from a bubo and from the spleen
+may show no organisms at all, or none even remotely resembling _B.
+pestis_, and yet by culture and inoculation methods we may be able to
+demonstrate that the animal is plague infected. Attention has been
+called to this point by several observers, and every worker in this
+field has the experience sooner or later.
+
+In other cases the smears will show such numbers of perfectly typical
+bipolar bacilli and “involution” (coccoid) forms as to leave scarcely
+any doubt as to the nature of the organism. But even here cases that are
+not plague are encountered that will deceive even the most experienced.
+We have been accustomed to put great dependence on the “coccoid” forms
+of the organism, but late in the San Francisco experience, smears from a
+splenic nodule that was not regarded as due to plague showed perfectly
+typical “involution” (“coccoid”) forms. Animal inoculations and cultures
+showed that the tissues contained no plague bacilli.
+
+In addition to these two classes of cases we have a third, where smears
+show a few typically shaped bacilli, or where a considerable number of
+typical-looking bacilli are found along with many other bacterial forms.
+There is no safe rule for reaching a conclusion in these cases, and one
+must resort to culture or to inoculation methods, or both. In any such
+case it is always a good plan to let the macroscopical findings have
+more weight than the microscopical.
+
+The bipolar appearance of _B. pestis_ is so largely dependent upon the
+technique of staining, fixing, length of time the stain is allowed to
+act, and the length of the washing, that it should never be given great
+weight. Here, as elsewhere in bacteriology, many errors are to be
+avoided by not depending too much upon the morphology of the organism
+under investigation.
+
+
+ BACTERIOLOGICAL DIAGNOSIS OF RAT PLAGUE.
+
+While the gross lesions of rat plague are often sufficiently
+characteristic to justify a positive diagnosis, and the gross lesions in
+conjunction with the microscopical examination will in other cases
+enable us to say definitely that a rat is plague infected, still a
+certain number of cases occur in which it is necessary to resort to
+other methods, and there are circumstances, such as the first case in a
+community, that make a complete bacteriological confirmation of a
+diagnosis necessary.
+
+This is not the proper place in which to discuss fully the bacteriology
+of plague. However, a brief outline of what is necessary to establish
+beyond question the existence of plague infection in an animal will be
+given.
+
+_B. pestis_ may often be isolated in culture from the tissues (bubo,
+liver, spleen, or heart’s blood) of an infected rat. Unless the tissues
+are badly contaminated with other organisms, plate or stroke culture
+will yield a growth of _B. pestis_ in pure culture, or isolated
+pest-like colonies may be transferred to other media.
+
+It is unwise, however, to trust to cultural methods alone. In the
+majority of doubtful cases it is advisable to inoculate guinea pigs or
+white rats. The lesions of plague in these animals are quite
+characteristic, and _B. pestis_ may readily be recovered from their
+tissues if cultures are made at once after death.
+
+A pure culture of the organism under suspicion is obtained from the
+naturally infected animal or from a laboratory animal inoculated from
+the one under suspicion. This culture is studied in regard to its
+morphology; first, on agar, where it grows as a short rod, or often in
+the shape of a coccus; second, in broth, where it often grows in
+streptococcus-like chains; third, on agar containing 3 per cent sodium
+chloride, where most extraordinary alterations in morphology occur,
+giving large balloon-shaped bodies, objects resembling gigantic cocci
+and enormous trypanosome-shaped forms, the so-called “involution” forms.
+These involution forms must not be confused with the so-called
+“involution” (coccoid) forms of the organism found in smears from animal
+tissues.
+
+We think it worth while to call special attention to the great
+diagnostic value of involution forms developed when _Bacillus pestis_ is
+grown on salt agar. No other organism that we have had the opportunity
+of working with gives forms that are at all likely to be mistaken for
+those of _Bacillus pestis_, except _B. mallei_, and of course the other
+points of difference would at once serve to distinguish the latter
+organism.
+
+_B. pestis_ is Gram negative, though this point is of no great value
+except to distinguish the “coccoid” forms from pus cocci.
+
+The appearance and character of the culture should be as follows:
+
+_Agar._—Smooth, glistening, round whitish colonies which are found to be
+sticky when touched with an inoculating needle.
+
+_Broth._—A scanty surface growth which falls, often in globular masses,
+when the tube is gently agitated; and a fine flocculent precipitate.
+
+_Litmus milk._—Generally rendered slightly acid.
+
+_Glucose broth._—Rendered slightly acid. Gas is not formed.
+
+_Lactose broth._—Unchanged in reaction. Gas is not formed.
+
+The other cultural reactions are of no material assistance in the
+identification of the organism. Indeed, in routine work the appearance
+of the growth on agar and in broth, together with the involution forms
+on salt agar, are sufficient for identifying the organism.
+
+The plague bacillus is a nonmotile organism, a point worth bearing in
+mind.
+
+A culture answering the above description when rubbed into the shaven
+skin of a guinea pig or a white rat should cause the death of either of
+these animals of plague within ten days, and an organism must be
+isolated from their tissues after death corresponding to the one
+inoculated.
+
+If one wishes to be doubly certain, one may inoculate a series of
+laboratory animals, giving to half of them a sufficient dose of antipest
+serum. The protected animals should recover, or markedly outlive the
+controls, which should die in the usual time.
+
+As to the virulence of cultures of the bacillus from cases of rat plague
+Klein[17] states “that _B. pestis_ bred in the rat is of decidedly less
+virulence than that bred in the human subject; moreover, the former is
+liable, outside the animal body, to a much greater extent to rapidly
+lose its virulence.” It is evident that in any given epidemic it will be
+very difficult to say just which strain, rat or human, one is dealing
+with.
+
+In the case of the strains of _B. pestis_ recovered from rats in San
+Francisco we have seen nothing to justify such an opinion as Klein
+expresses. The cultures are all highly virulent and retain their
+virulence under artificial cultivation.
+
+The value of inoculation by the cutaneous method to demonstrate the
+presence of plague infection in putrefying tissue is well known. We have
+had one example in which the value of inoculation by this method was
+proven in the case of a rat that was so badly decomposed as not to admit
+of any opinion being formed as to whether the animal was infected or
+not. A rat was brought from a warehouse where a typical plague rat had
+been taken a few days previously. The specimen was so badly decomposed
+that the abdominal organs could not be distinguished with any degree of
+certainty. Smears from tissue that was thought to represent spleen were
+negative so far as pest-like organisms were concerned. A guinea pig
+vaccinated from this splenic material died in seven days of typical
+plague, and a pure culture of _B. pestis_ was obtained from its organs.
+
+Kolle and Martini [9] compare the cutaneous method of inoculation to the
+use of an agar plate in separating plague bacilli from other organisms,
+and so regularly does _B. pestis_ penetrate the skin and infect the
+animal, and so rarely do other organisms do this, that it offers a
+certain and accurate method of “filtering out” _B. pestis_ from any
+badly decomposed tissue.
+
+The technique of the cutaneous method of inoculation, or “vaccination”
+as it is sometimes called, is very simple. An area about an inch square
+is shaven on an animal’s belly, taking care to abrade the epithelium
+slightly. The culture or suspected tissue is rubbed on this shaven area
+with a platinum loop or a dressing forceps. Guinea pigs when inoculated
+in this manner generally die before the seventh day; white rats die a
+day or two earlier.
+
+Kister [10] uses a drop of juice from an organ rich in bacilli for
+agglutination experiments with antipest serum. This would appear in many
+cases to be of very material assistance, and the objection that it is
+difficult to form a uniform emulsion of the bacteria would be avoided.
+The well-known tendency of _B. pestis_ to grow in clumps in culture is
+the main reason why agglutination reactions have not been more
+extensively used in plague work.
+
+Skschivan [1] makes use of Pfeiffer’s phenomenon in establishing the
+identity of a given organism as _B. pestis_.
+
+To assist in the early diagnosis of plague, Dunbar and Kister [8]
+practiced intraperitoneal inoculation of laboratory animals and used a
+parallel series of immunized animals. As is well known, intraperitoneal
+inoculation with plague cultures or infected material leads to the early
+death of the inoculated animal, and it is evident that the survival of
+the immunized animal would afford considerable evidence that the
+material used for inoculation contains _B. pestis_.
+
+
+ PEST-LIKE BACTERIA FOUND IN RATS.
+
+The somewhat general impression that there are a considerable number of
+organisms that are readily mistaken for _Bacillus pestis_ is not
+justified, provided one gives attention to cultural and inoculation
+investigations. It is quite true that there are a considerable number of
+organisms which in smears from tissues are scarcely to be distinguished
+_morphologically_ from _B. pestis_. The similarity, however, usually
+ends there. A few resemble plague somewhat closely in cultural
+reactions, and especially _B. pseudo-tuberculosis rodentium_ (Pfeiffer)
+should be mentioned here; but these differ in pathogenicity. For
+example, the above-named organism is not pathogenic for rats.
+
+Neumans[11] reviews the subject of pest-like organisms pathogenic for
+rats, and describes an organism belonging to this group which he
+isolated from the body of a rat. His work clearly shows that none of the
+organisms that have been described should cause any serious difficulty
+in the hands of a careful investigator.
+
+Kister and Schmidt[12] describe an organism closely resembling _B.
+pestis_ in many respects, and with which guinea pigs could be
+successfully infected by the cutaneous method. This organism, which was
+also pathogenic for rats and mice, belongs to the hemorrhagic septicæmic
+group. It differed from _B. pestis_ in that it gave no involution forms
+when grown upon salt agar and was much more rapidly fatal to laboratory
+animals.
+
+Augeszky[13] observed an epidemic among gray rats in his laboratory
+which was due to a pest-like organism belonging to the Friedlander
+group. The animals died after a couple of days of illness. At the
+post-mortem examination the spleen was found large, soft, and congested.
+There was a hyperæmia of the intestines, lungs, and liver. In the spleen
+were found many, and in the heart’s blood few, capsulated bacilli, some
+of which resembled _B. pestis_. The cultural reactions were in nowise
+similar to those of _B. pestis_. He found that inoculation of rats with
+a pure culture of this organism sometimes killed in as short a time as
+twenty-four hours, sometimes as late as two or three weeks, and in some
+cases the lesions were not very unlike those sometimes produced by _B.
+pestis_. However, this organism by its different cultural reactions, and
+the fact that the capsule is usually easily demonstrated, would probably
+never be a source of any confusion.
+
+
+ ARTIFICIAL INFECTION OF RATS WITH PLAGUE.
+
+For laboratory purposes in general it is customary to use tame white
+rats, and in plague work they are especially satisfactory, as they are
+easily handled, rarely harbor fleas, are very susceptible to the
+infection, and finally and most important, they frequently die a day or
+two earlier than guinea pigs. At times it may be necessary to use wild
+rats on account of a failure in the supply of white rats, or for the
+sake of economy. This may be done very satisfactorily, if one bears in
+mind the fact that a considerable number of wild rats are more or less
+immune to plague infection, especially when the infectious material is
+introduced by Kölle’s (cutaneous) method. Therefore, it is always
+advisable to use three or four wild rats where one white rat would be
+sufficient. They should be kept in a container of such design that there
+is no possibility of their escaping. The inoculation is best conducted
+with the animal under the influence of ether.
+
+
+ MODES OF INFECTION.
+
+Rats may be infected experimentally by the ingestion of contaminated
+material, and by the application of virulent plague bacilli to a mucous
+or a cutaneous surface, or by subcutaneous injection of the organism.
+
+Practically we may confine our study to inoculation by the cutaneous
+method, and to subcutaneous inoculation, when the material is injected
+in the ordinary manner. A useful modification of the latter method is to
+make a small pocket under the skin of the abdomen and thrust the
+suspected material into this pocket. This avoids the necessity of making
+an emulsion of infectious matter, such as the organs of an animal. The
+time that elapses between the inoculation of a rat with virulent culture
+of plague bacilli and its death varies somewhat with the size of the
+dose and with the mode of inoculation. The following table, compiled
+from work in San Francisco, shows the day of death of a few white rats
+and a considerable number of wild rats using the strain of _B. pestis_
+that was found in the recent epidemic here. Some were inoculated by the
+cutaneous and some by the subcutaneous method:
+
+ ───────────────────────────────────┬─────────────────┬─────────────────
+ Day of death. │ White rats. │ Wild rats.
+ ───────────────────────────────────┼─────────────────┼─────────────────
+ Second │ │ 3
+ Third │ 5│ 27
+ Fourth │ 7│ 41
+ Fifth │ 1│ 30
+ Sixth │ 1│ 9
+ Seventh │ │ 8
+ ───────────────────────────────────┼─────────────────┼─────────────────
+ Total │ 14│ 118
+ ───────────────────────────────────┴─────────────────┴─────────────────
+
+The wild rats were all _Mus norvegicus_.
+
+The _lesions_ found, when an artificially inoculated rat is examined
+after death, are in a general way similar to those found in naturally
+infected rats with certain differences to be mentioned later.
+
+In order to obtain accurate figures as to the frequency of the various
+lesions in inoculated rats, I have compiled the data from the records of
+the federal laboratory in San Francisco of a considerable number of wild
+rats that have been inoculated in the course of various investigations
+and have died of acute plague. The rats were practically all of the
+species _Mus norvegicus_.
+
+_Artificially inoculated (subcutaneously) plague rats._
+
+ ──────────────┬─────────┬────────────┬─────┬────────┬────────┬─────────
+ │ Local│Subcutaneous│Bubo.│Granular│Enlarged│ Pleural
+ │reaction.│ injection.│ │ liver.│ dark│effusion.
+ │ │ │ │ │ spleen.│
+ ──────────────┼─────────┼────────────┼─────┼────────┼────────┼─────────
+ Present │ 36│ 48│ 19│ 47│ 56│ 18
+ Very extensive│ 1│ [Q]2│ │ │ │ 8
+ Slight │ 2│ 6│ │ │ │ 8
+ ──────────────┼─────────┼────────────┼─────┼────────┼────────┼─────────
+ Total present │ 39│ 56│ 19│ 47│ 56│ 34
+ Absent │ 10│ 4│ 39│ 15│ 3│ 21
+ Not recorded │ 13│ 2│ 4│ │ 3│ 7
+ ──────────────┼─────────┼────────────┼─────┼────────┼────────┼─────────
+ Total │ 62│ 62│ 62│ 62│ 62│ 62
+ ──────────────┴─────────┴────────────┴─────┴────────┴────────┴─────────
+
+Footnote Q:
+
+ Intense.
+
+All of the lesions aside from the local reaction were present and well
+marked in six cases.
+
+_Artificially inoculated (cutaneously) plague rats._
+
+ ──────────────┬─────────┬────────────┬─────┬────────┬────────┬─────────
+ │ Local│Subcutaneous│Bubo.│Granular│Enlarged│ Pleural
+ │reaction.│ injection.│ │ liver.│ dark│effusion.
+ │ │ │ │ │ spleen.│
+ ──────────────┼─────────┼────────────┼─────┼────────┼────────┼─────────
+ Present │ 16│ 34│ 42│ 58│ 58│ 22
+ Very extensive│ 1│ [R]15│ │ │ │ 6
+ Slight │ 6│ 13│ │ │ │
+ ──────────────┼─────────┼────────────┼─────┼────────┼────────┼─────────
+ Total present │ 23│ 62│ 42│ 58│ 58│ 28
+ Absent │ 37│ 6│ 26│ 11│ 8│ 37
+ Not recorded │ 9│ 1│ 1│ │ 3│ 4
+ ──────────────┼─────────┼────────────┼─────┼────────┼────────┼─────────
+ Total │ 69│ 69│ 69│ 69│ 69│ 69
+ ──────────────┴─────────┴────────────┴─────┴────────┴────────┴─────────
+
+Footnote R:
+
+ Intense.
+
+All of the lesions aside from the local reaction were present and well
+marked in five cases.
+
+
+ LOCAL REACTION.
+
+The most striking difference between natural and artificial plague in
+rats is the presence of a reaction at the site of inoculation in the
+majority of cases where the organism is introduced subcutaneously, and
+in about a third of the cases where the infectious material is rubbed on
+the shaven skin (cutaneous inoculation). The local reaction may exist
+only as a yellowish-brown crust, overlying a granulating surface, and
+associated with a trifling thickening of the skin and subcutaneous
+tissue. It may appear as one or more firm papules 3 or 4 millimeters in
+diameter. The most frequent appearance is a brawny œdematous and
+blood-stained reaction which extends over an area perhaps an inch in
+diameter; at times purulent change may be well advanced. Very rarely one
+finds so extensive an œdema as to cause the lesion to somewhat resemble
+the widespread gelatinous reaction seen so commonly in the guinea pig.
+On one or two occasions we have seen an extensive slough at the site of
+inoculation.
+
+
+ BUBO.
+
+It is very exceptional that one finds in cases of induced plague the
+typical, firm, caseous bubo surrounded by an infiltrated area, as is so
+commonly seen in natural infection in rats. The glands are sometimes
+enlarged and injected without other changes. The commonest lesion,
+however, is a markedly enlarged gland which upon close inspection is
+seen to have a number of yellowish points just under the capsule. These
+points are especially well seen when a section is made through the
+gland. The gland may be squeezed out of the capsule and it breaks down
+readily enough when pressure is made upon it; but the uniform necrotic
+process that one sees so often in natural rat plague is absent.
+
+
+ LIVER.
+
+Granular lesions precisely like those found in natural infections are
+very common. If the rat has died on the sixth day or later, the ordinary
+lesions are apt to be replaced by necrotic foci that may be as much as 2
+millimeters in diameter.
+
+
+ SPLEEN.
+
+This organ is found mottled more frequently than in natural plague
+infection, and large granules are much more common.
+
+The subcutaneous injection is rarely so well marked as it is in natural
+infections.
+
+Pleural effusion of the same nature as that found in natural plague is
+common. Hemorrhagic foci are not rare in the lungs, and occasionally the
+organs are partly consolidated.
+
+
+ CHRONIC PLAGUE DUE TO ARTIFICIAL INOCULATION.
+
+Occasionally a rat that has been inoculated but has survived a week or
+longer, will show, when killed, only an abscess at the site of the
+injection. Stained smear preparations may show a large variety of
+bacterial forms. We have not been able to demonstrate the presence of
+_B. pestis_ in these lesions, yet there is no doubt but that the lesion
+is the result of the inoculation.
+
+A lesion more frequently found is a caseous or a purulent lymphatic
+gland. If the inoculated rat has been killed about ten days after the
+inoculation, in some cases one or more of the peripheral lymph glands
+will be found to be surrounded by an infiltration, and the gland itself
+will be purulent or less frequently caseous. Such lesions are
+occasionally met with in rats in which there is no suspicion of plague
+infection; but they are seen so frequently among rats that have survived
+artificial inoculation with _B. pestis_, there is no doubt but that in
+these cases they are the result of the inoculation. In several such
+cases pest-like organisms have been demonstrated in smears, and acute
+plague has been produced in guinea pigs by inoculation with the pus
+found in these lesions. Not infrequently in these cases the spleen will
+be found enlarged and looking very much like the organ in acute plague,
+but cultures from this organ in such cases have in my experience
+remained sterile.
+
+In other cases the only lesions will be found in the spleen. The organ
+is enlarged and contains a number of caseous nodules. These nodules vary
+in number from four or five to thirty or forty and in size from the head
+of a pin to a lesion 0.3 centimeter in diameter. In a number of such
+cases the nature of the lesion has been demonstrated by animal
+inoculation. For example, in a series of experiments carried out to
+determine the susceptibility of San Francisco rats to plague infection a
+large _Mus rattus_ died on the eleventh day after inoculation. The
+post-mortem examination showed nothing except an enlarged spleen which
+contained about a dozen caseous nodules, the largest of which was not
+over 2 millimeters in diameter. The nodules were very firm and the
+capsule smooth, so that they were held with difficulty with dressing
+forceps. Cultures from the liver and the spleen remained sterile, but a
+piece of the spleen was placed beneath the skin of a guinea pig. This
+animal died of acute plague, and a pure culture of _B. pestis_ was
+isolated from its liver. In some of these cases the liver will show
+large, distinct, whitish caseous foci. In another case a small _Mus
+norvegicus_ was killed on the twelfth day after a cutaneous inoculation
+from an artificially infected squirrel. No lesion was found except in
+the spleen which was not materially enlarged, but which presented two
+small whitish caseous granules on the surface, neither being over 1
+millimeter in diameter. A piece of the spleen containing one of these
+granules was put under the skin of the belly of a guinea pig. The guinea
+pig died on the fourth day with the usual lesions of acute plague.
+Occasionally in these cases of chronic plague punctate hemorrhages or
+even areas of consolidation are found in the lungs.
+
+
+ THE HISTOLOGY OF RAT PLAGUE.
+
+The most recent and satisfactory work on this subject is that of
+Ledingham [14], who has studied the lesions of both natural and induced
+plague in rats. The following is a very brief abstract of his work. The
+reader is referred to the original for a full study of the subject.
+
+
+ NATURAL RAT PLAGUE.
+
+Two groups of cases are distinguished, first, those in which a large
+number of _B. pestis_ are found in the liver and in the spleen. In the
+spleen this is accompanied by hemorrhages and congestion of the pulp
+sinuses and in the liver with congestion of the capillaries. These are
+early cases.
+
+In the second group, or the later cases, there are extensive reaction
+changes in the tissues. In the spleen this leads at times to distinct
+abscess formation, but more frequently to a walling off of the foci of
+necrosis. In the liver more or less focal necrosis is found; sometimes
+the areas of “necrosis” may be so extensive that little healthy liver
+tissue remains. Bacilli are usually to be demonstrated in these areas of
+necrosis. Giant cells of the Langhans type may be found in the
+neighborhood of these foci.
+
+The granular appearance of the liver is attributed to “hemorrhages and
+the focal necroses, together with the fatty changes in the liver cells.
+It must be understood, however, that a peculiar honeycomb-like vacuolar
+degeneration of the liver cell protoplasm was far more frequent than any
+actual, coarse, fatty infiltration. The granular appearance of the
+spleen is due partly to endothelial catarrh and partly to subcapsular
+changes.”
+
+In experimental rat plague Ledingham found the lesions to resemble those
+of the first group of cases referred to above. There is usually marked
+bacteraemia; focal necroses of the liver are scanty.
+
+In a chronic case, minute abscesses were found scattered through the
+spleen. In the center of the abscesses were found clumps of degenerated
+bacilli. The areas were walled off by epithelioid and spindle cells and
+numerous giant cells of the tubercular type.
+
+
+ IMMUNITY OF RATS.
+
+Contrary to the general impression the wild rat is not an animal
+especially susceptible to plague infection. The Indian Plague Commission
+[19] found that when rats are inoculated by the cutaneous method from
+the spleen of infected rats 59 per cent are immune to infection. A
+series of experiments conducted in the federal laboratory in San
+Francisco showed that when inoculated with highly virulent cultures of
+_B. pestis_ there is an immunity which is, however, more frequent among
+the large rats. When inoculated cutaneously with tissue containing large
+numbers of _B. pestis_ from plague infected human beings, rats, or
+squirrels, about 15 per cent of small rats and about 50 per cent of
+large ones were found to be immune. There is no good reason for
+believing that this immunity of San Francisco rats was due to a previous
+attack of the disease. Indeed, it was known beyond a doubt that some of
+the immune rats had never had an opportunity of becoming infected with
+plague in nature and thereby establishing an acquired immunity. We may
+mention here the fact that has been observed by many workers, and which
+we have amply confirmed, that rats are readily immunized by antiplague
+serum.
+
+The subject of the transfer of infection directly from rat to rat by
+cutaneous or subcutaneous inoculation through a series of the animals is
+one that is evidently intimately associated with the preceding subject,
+as it is quite evident that an immune rat or several of them might
+terminate a series without any actual diminution in the virulence of the
+organism transferred. It is quite plain that the success of such an
+experiment would depend largely upon the number of rats used in each
+transfer. The Indian Plague Commission [19] had no difficulty in
+carrying infection through twenty-six transfers, using from six to fifty
+rats in each transfer.
+
+Pound [7] in a series of eight experiments, was never able to convey the
+infection successfully beyond the sixth rat, using but one rat for each
+transfer. There was no apparent lessening of the virulence of the
+organism and each series appears to have been terminated abruptly by
+encountering an immune rat.
+
+Baxter-Tyrie [15] says:
+
+
+ It is probable that under certain natural circumstances a reduction in
+ the virulence of the organism is effected and a comparative immunity
+ is conferred on the rats. The infection of immigrant rats is, however,
+ severe, and their arrival is heralded by a heavy mortality. In the
+ same manner an infected rat imported into a fresh locality produces a
+ similar result. This attenuation of virulence is responsible for the
+ condition known as chronic rat plague.
+
+
+Several experiments conducted in San Francisco to determine this point
+have given results that I regard as showing merely the presence of a
+considerable percentage of immunity among the rats. It was observed that
+in each case certain of the rats died of acute plague even in the last
+transfer. It was very evident that had certain combinations of immune
+rats been encountered the experiment might have terminated at any point.
+On the other hand, by being especially fortunate in using nonimmune
+rats, the experiments might have given a much higher percentage of cases
+of acute plague. Unfortunately it was necessary to terminate these
+experiments in each instance before they could be regarded as completed.
+
+The reason for the natural subsidence of plague among rats in any
+community is a point about which much more evidence must be obtained
+before we can speak with any degree of certainty. It may be due to the
+lack of susceptible material, possibly to a loss of virulence of the
+organism; but it seems more probable that it is due to a change in the
+number or relations of the ectoparasites of the rat.
+
+Adequate measures of rat extermination, while they may never bring about
+the ideal condition of a community that is free from rats, are, as is
+shown by the recent experience in San Francisco, of the utmost value in
+shortening the epizootic.
+
+
+ REFERENCES.
+
+Endnote 1:
+
+ Skschivan (Centralblatt für Bacter., etc., 1903, Vol. XXXIII, No. 4,
+ p. 260).
+
+Endnote 2:
+
+ Kister & Schumacher (Zeit. für Hyg. u. inf. Krank., Vol. LI, 1905).
+
+Endnote 3:
+
+ Indian Plague Commission (Journal of Hygiene, 1907, Vol. VII, No. 3).
+
+Endnote 4:
+
+ White (Medical Record, vol. 67, No. 4, Jan. 28, 1905).
+
+Endnote 5:
+
+ Kitasato (Philippine Journal of Science, Vol. I, No. 5, 1906).
+
+Endnote 6:
+
+ Wherry, Walker & Howell (Journal Am. Med. Assn., April 11, 1908, Vol.
+ L, No. 15).
+
+Endnote 7:
+
+ Pound (1907, Report on Plague in Queensland, B. B. Ham, p. 134).
+
+Endnote 8:
+
+ Dunbar & Kister (1904, Centralblatt für Bact., etc., Vol. XXXVI, No.
+ 1, p. 127).
+
+Endnote 9:
+
+ Kolle & Martini (Deut. Med. Woch., Jan. 2, 1902, Vol. XXVIII).
+
+Endnote 10:
+
+ Kister (Centralblatt für Bact., etc., July 24, 1906, Vol. XLI, No. 7).
+
+Endnote 11:
+
+ Neumans (1903, Zeit. f. Hyg. u. inf. Krank., Vol. XLV, No. 3, p. 451).
+
+Endnote 12:
+
+ Kister & Schmidt (1904, Centralblatt für Bact., etc., Vol. XXXVI, No.
+ 3, p. 454).
+
+Endnote 13:
+
+ Aujeszky (1904, Centralblatt für Bact., etc., Vol. XXXVI, No. 5, p.
+ 603).
+
+Endnote 14:
+
+ Ledingham (Journal of Hygiene, 1907, Vol. VII, No. 3).
+
+Endnote 15:
+
+ Baxter-Tyrie (Journ. of Hygiene, Vol. V, 1905, p. 315).
+
+Endnote 16:
+
+ Wherry (The Journal of Infect. Diseases, Dec. 18, 1908, Vol. V, No.
+ 5).
+
+Endnote 17:
+
+ Klein (The Bacteriology and Etiology of Oriental Plague, MacMillan and
+ Co., London, 1906).
+
+Endnote 18:
+
+ Indian Plague Commission (Journal of Hygiene, 1907, Vol. VII, No. 6,
+ p. 761).
+
+Endnote 19:
+
+ Indian Plague Commission (Journal of Hygiene, 1906, Vol. VI, No. 4).
+
+
+ RAT RECORD CARD.
+
+ [Legend: O = Ordinary; W = White belly; R = Red; Go. = Gopher rat; S =
+ Small; M = Medium; L = Large; M. R. = Mus rattus; M. N. = Mus
+ norvegicus.]
+
+ ───┬────────┬───────────────┬─────┬────────┬────────────┬─────┬─────────
+ No.│ Date. │District No. 6.│Sex. │ Size. │ M. N. │M. R.│Pregnant.
+ ───┼────────┼───────────────┼──┬──┼──┬──┬──┼──┬──┬──┬───┼──┬──┼─────────
+ „ │ „ │ „ │M.│F.│S.│M.│L.│O.│W.│R.│Go.│O.│W.│ „
+ ───┼────────┼───────────────┼──┼──┼──┼──┼──┼──┼──┼──┼───┼──┼──┼─────────
+ 19 │Dec. 10,│ 401 Fillmore │1 │ │ │1 │ │ │ │1 │ │ │ │
+ │ 1908 │ street │ │ │ │ │ │ │ │ │ │ │ │
+ 20 │ do │ do │ │1 │ │ │1 │1 │ │ │ │ │ │ [S]7
+ ───┴────────┴───────────────┴──┴──┴──┴──┴──┴──┴──┴──┴───┴──┴──┴─────────
+
+Footnote S:
+
+ Number of fœtuses.
+
+
+ PLAGUE RAT CARD.
+
+ PLAGUE RAT NO. 50.
+
+ Date: June 20, 1908.
+ Species: _M. norvegicus_.
+ From District No. 6, sewer, Haight and Steiner Streets.
+ Condition: Badly injured by trap; thorax crushed.
+ Subcutaneous injection: General, marked.
+ Lymphatic glands, bubo or other lesions: Right inguinal bubo, caseous.
+ Liver: Typical whitish granules.
+ Spleen: Large, dark, firm.
+ Pleural effusion: Unable to say.
+ Purulent or caseous foci:
+ Diagnosis from gross lesions: Plague.
+ Diagnosis from smears: Plague (spleen and bubo).
+ Cultures: _B. pestis_ recovered from liver culture.
+ Inoculation, guinea pig No. 50 A, +6.25.08.
+ Vaccination, guinea pig No. 50 B, +6.26.08.
+ Date suspicious:
+ Date positive: June 20, 1908.
+ Date negative:
+
+[Illustration:
+
+ A HOEN & CO BALTIMORE.
+
+ NECROPSY APPEARANCE OF PLAGUE-INFECTED RAT
+]
+
+[Illustration:
+
+ A HOEN & CO BALTIMORE
+
+ NECROPSY APPEARANCE OF NORMAL RAT
+]
+
+
+
+
+ RAT LEPROSY.
+
+ By WALTER R. BRINCKERHOFF, S. B., M. D.,
+
+ _Assistant Director Leprosy Investigation Station, United States Public
+ Health and
+ Marine-Hospital Service, Honolulu, Hawaii_.
+
+
+ INTRODUCTION.
+
+The leprosy-like disease of the rat is of great interest to leprologists
+because of its close similarity to the disease leprosy in man. Its
+practical importance to those engaged in the study of the human disease
+is increased by the fact that it can be artificially propagated under
+laboratory conditions from animal to animal and, still more important,
+can be transferred from the species in which it occurs naturally (_Mus
+norvegicus_) to a more tractable laboratory animal (_Mus albus_). The
+brief description of the affection which follows is intended to assist
+in its recognition and to stimulate the interest of investigators in the
+disease, which presents problems replete with interest to the study of
+pathology or bacteriology and of great promise to those engaged in the
+investigation of human leprosy. It is earnestly hoped that the
+investigation of this disease will be undertaken in general medical
+research laboratories, as it is extremely probable that certain of the
+most difficult problems presented by leprosy in man can be studied in
+this disease of the rat, and if solved there the information gained can
+be directly applied to the solution of the analogous problems in the
+human disease.
+
+
+ REVIEW OF LITERATURE.
+
+The first publication on rat leprosy was made by Stefansky (1903), who
+observed the disease in Odessa during an antiplague campaign against
+rats.
+
+Rabinowitch (1903) found the disease among rats in Berlin and confirmed
+the work of Stefansky.
+
+Dean (1903) discovered the disease independently in London, and in a
+later publication (1905) reports success in transferring the disease by
+artificial inoculation.
+
+Tidswell (1906) reports a case of the disease in a rat caught in Sydney,
+New South Wales, Australia.
+
+The English Plague Commission observed the disease in India in 1907
+(Wherry).
+
+Wherry (1908) and McCoy (1908) report upon the finding of the disease in
+rats caught in San Francisco, Cal.
+
+Mezincescu (1908) has studied the disease and attempted to determine its
+relationship to known human lepra by complement fixation tests.
+
+
+ DESCRIPTION OF DISEASE.
+
+_Geographical occurrence._—It would be premature at present to make
+didactic statements as to the geographical distribution of the disease,
+for its discovery has usually depended upon antiplague measures, which
+are not world-wide in their scope. In spite of this it seems profitable
+to briefly review the known occurrence of the disease in relation to
+that of human leprosy. When such a comparison is made we note that the
+disease is present among the rats of Berlin, a city which is practically
+free from human lepra. On the other hand in Honolulu, which is an
+endemic focus of human leprosy, in the examination of 16,000 rats,
+during an antiplague campaign, no case of rat leprosy was encountered.
+In addition to the scrutiny of the rats examined for plague in Honolulu,
+an attempt was made to obtain leper rats by offering a reward for a rat,
+dead or alive, infected with the disease. This offer was given wide
+publicity in the Territory, but brought no results.
+
+_Occurrence of the disease._—The proportion of rats infected with the
+disease in different localities varies greatly, as will be seen in the
+following table:
+
+TABLE 1.—_Proportion of leper rats to the total rats examined._
+
+ ───────────────────────────┬───────────────────────────┬───────────────
+ Place. │ Observer. │ Proportion.
+ ───────────────────────────┼───────────────────────────┼───────────────
+ │ │ _Per cent._
+ Odessa │Stefansky [301] │ 4–5.000
+ Sydney │Tidswell [305] │ .001
+ San Francisco │Wherry [308] │ .210
+ Do │McCoy [310] │ .160
+ Honolulu │Currie[T] │ .000
+ ───────────────────────────┴───────────────────────────┴───────────────
+
+Footnote T:
+
+ Personal communication.
+
+Rats in the late stage of the disease are easily recognized by the
+presence of a patchy alopecia associated with cutaneous and subcutaneous
+nodules, which may or may not be the site of open ulcers. The diagnosis
+can be readily confirmed by a microscopic examination of a smear from an
+ulcer or a nodule, which will show the specific bacillus of the disease
+in enormous numbers.
+
+Stefansky[301] describes two clinical types of the disease, the one
+localized particularly in the lymph nodes, the other in the skin and
+muscles. The glandular type was the more common. Dean[304] thinks that
+no line of demarcation can be drawn between these clinical types.
+
+Dean[304] and Wherry[307] both mention that attention was attracted to
+the diseased animals by the fact that they were seen abroad during
+daylight in an obviously sick condition.
+
+The skin, in a well-developed case of the disease, presents a patchy
+alopecia coincident with thickening and nodule formation, which is
+situated in the subcutaneous tissue. The cut surface of the nodules or
+thickenings is light yellow in color, is clean, dry, and cheese-like. In
+the region of the nodules the skin is atrophic, and ulcers often form on
+the prominent parts of the affected area. The subcutaneous fat tissue is
+diminished in amount. Histologically the process is seen to be
+practically confined to the subcutaneous tissue and to consist
+essentially in the presence of cells rich in protoplasm, with vesicular
+nuclei, whose cell body is more or less completely filled with slender
+acid-fast bacilli. The subcutaneous fat is replaced by such a tissue.
+All investigators who have studied the disease agree in emphasizing the
+similarity of the histology of the lesion to that in leprosy in man.
+
+When the musculature is involved the muscle fibers atrophy and the
+fibers are infiltrated with the specific bacilli. The affected muscle is
+friable, and macroscopically grayish white in color.
+
+The peripheral lymph nodes are commonly involved, though McCoy[310]
+reports a case in which only the pelvic and mesenteric nodes were
+diseased, and in the Tidswell case[305] the peripheral nodes were not
+enlarged. The typically affected nodes are enlarged, sometimes measuring
+as much as 3 centimeters in the greatest extent, firm, and, on section,
+opaque pale yellow-white in color. In the experimental disease the
+writer has frequently found the characteristic bacilli of the disease in
+peripheral lymph nodes which were very slightly enlarged and presented
+no macroscopic lesion. Dean[304] has observed invasion of the
+submaxillary or salivary glands by extension from infected cervical
+lymph nodes. Wherry[308] notes that in his cases he did not find the
+submaxillary or cervical glands involved, which fact he contrasts with
+two early cases in which the skin and adjacent axillary or inguinal
+nodes were involved.
+
+Microscopically the lymph nodes show large numbers of cells in the
+sinuses similar to those in the skin lesions. Multinuclear giant cells
+are frequently observed which may measure as much as 70 to 80
+microns[304]. The protoplasm of the cells is loaded with the specific
+bacilli of the disease. The lymph follicles, trabeculæ, and capsule of
+the glands are also invaded by the bacilli.
+
+The internal organs are relatively slightly affected in the natural
+disease. Small foci have been found in the liver by Dean[304] and in the
+liver and spleen by McCoy[310]. Wherry[307] reports finding the bacilli
+in smears from both the liver and spleen. The writer has found
+microscopic lesions containing the characteristic bacilli in the liver
+in a case of the experimental disease.
+
+Lesions have been observed in the bone marrow by Dean[304], and the same
+author states that the nerves are invaded by the bacilli of the disease.
+McCoy[310] found the bacilli in the urinary bladder in one case.
+
+With a disease showing such a striking similarity to human leprosy,
+attention has naturally been directed to the bacteriological examination
+of the nasal mucus. Dean[304] and Wherry[307] have both found the
+characteristic bacilli in the nasal mucus, while McCoy[310] has failed
+to do so. The writer’s experience has been confined to the experimental
+disease, and in his animals the nasal examinations have been negative.
+
+
+ ETIOLOGY.
+
+The accepted etiological factor in the disease is an acid-fast bacillus
+3 to 5 microns in length and 0.5 micron wide. The bacilli resemble very
+closely the lepra bacillus of man, but seem to have somewhat greater
+power to hold carbol-fuchsin stain against mineral acids. The bacilli
+often have rounded ends and may be curved. The beaded appearance so
+often seen in lepra bacilli is common. The bacilli show the same
+tendency to form bundles that is such a marked characteristic of
+_Bacillus lepræ_. To one familiar with the microscopic appearance of
+smears from the discharges and lesions of human leprosy the picture
+presented by similar preparations from the disease of the rat is most
+striking.
+
+The organism does not grow on the usual culture media—Stefansky [301],
+Rabinowitch[302], Dean[304], Tidswell[305]—or on certain special
+media—Dean[304].
+
+The organism is not pathogenic for the guinea pigs—Dean[304],
+Tidswell[305]—rabbit, mouse, monkey—Dean[304]. The disease can be
+transmitted to black and white rats—Dean[304], Wherry.
+
+
+ SUMMARY.
+
+In the leprosy-like disease of rats we have an affection which closely
+resembles, both in its etiological factor and in its pathology, the
+disease leprosy in man. The fact that the disease is readily propagated
+in a laboratory animal permits of its investigation in any laboratory.
+It is earnestly hoped that the study of this disease will be taken up by
+bacteriologists and pathologists, as in this way valuable information
+may be gained which will be applicable to the problems presented by
+leprosy in man.
+
+
+
+
+ BIBLIOGRAPHY.
+
+
+Endnote 301:
+
+ Stefansky, W. K., ’03. Eine lepraähnliche Erkrankung bei Wanderratten.
+ Cent. f. Bact., Bd. 33, Orig. S. 481. Baum. Jahres., Bd. 19, S. 496.
+
+Endnote 302:
+
+ Rabinowitch, L., ’03. Ueber eine Hauterkrankung der Ratten. Cent. f.
+ Bact., Bd. 33, Orig. S. 577. Baum. Jahres., Bd. 19, S. 496.
+
+Endnote 303:
+
+ Dean, G., ’03. A Disease of Rats caused by an acid-fast Bacillus.
+ Cent. f. Bact., Orig. Bd. 34, S. 222. Baum. Jahres., Bd. 19, S. 494.
+
+Endnote 304:
+
+ Dean, G., ’05. Further Observations on a Leprosy-like Disease of the
+ Rat. Jour. Hyg., vol. 5, p. 99.
+
+Endnote 305:
+
+ Tidswell, F., ’06. Note of Leprosy-like Disease of Rats. Lepra, vol.
+ 6, p. 197.
+
+Endnote 306:
+
+ English Plague Commission. Jour. Hyg., vol. 7, p. 337. Cited by
+ Wherry.
+
+Endnote 307:
+
+ Wherry, W. B., ’08. The Leprosy-like Disease among Rats on the Pacific
+ Coast. Jour. Am. Med. Asso., vol. 50, No. 23. Cent. f. Bact., Ref. Bd.
+ 42, S. 664.
+
+Endnote 308:
+
+ Wherry, W. B., ’08. Notes on Rat Leprosy and on the Fate of Human and
+ Rat Lepra Bacilli in Flies. Public Health Reports, U. S. P. H. and M.
+ H. S., vol. 23, p. 1841. Jour. Infec. Dis., vol. 5, p. 507.
+
+Endnote 309:
+
+ Mezincescu, D., ’08. Maladie Lépreuse des Rats et ses Relations avec
+ la Lèpre Humaine. Compt. Rend. Soc. Biol., T. 64, p. 514. Cent. f.
+ Bact., Ref. Bd. 42, p. 664.
+
+Endnote 310:
+
+ McCoy, G. W., ’08. Rat Leprosy. Public Health Reports, U. S. P. H. and
+ M. H. S., vol. 23, p. 981. Jour. Am. Med. Asso., vol. 51, p. 690.
+
+The writer wishes to express his gratitude to Dr. George Dean for
+histological material from the natural and experimental disease, and to
+Doctors Wherry and McCoy for rats inoculated with the disease and normal
+animals for its propagation.
+
+
+
+
+ BACTERIAL DISEASES OF THE RAT, OTHER THAN PLAGUE AND RAT LEPROSY.
+
+ By DONALD H. CURRIE,
+
+ _Passed Assistant Surgeon, United States Public Health and
+ Marine-Hospital Service_.
+
+
+So far as is known, the several species of rats that are found about the
+habitations of man—_Mus norvegicus_, _Mus rattus_, _Mus alexandrinus_,
+and _Mus musculus_—are naturally subject to but few bacterial diseases
+as compared to some other animals. Interest in this matter has only
+recently been aroused, owing to the rôle played by the rat in the spread
+of bubonic plague. When we consider the immense number of rats that have
+been examined in connection with antiplague work by trained
+investigators in recent years, and that to many investigators the
+thought must have come that the discovery of some rat destroying
+bacterium would be of the greatest utility, it appears more than
+probable that few such natural diseases exist.
+
+Plague is the one natural bacterial disease that has demonstrated its
+power to destroy these rodents in numbers sufficiently large to attract
+general attention; scientific investigation has only been able to add a
+few other bacterial diseases, and these are probably for the most part
+rare ones, causing the death of a very small percentage of the total rat
+population.
+
+Of the “natural” diseases (i. e., spontaneous, in distinction to
+diseases that can only be produced artificially, under laboratory
+conditions) the following are the more important ones:
+
+Rat plague and rat leprosy, which are made the subject of special
+chapters in this publication, must be mentioned as the most important
+diseases observed among rat populations.
+
+
+ DANYSZ’S BACILLUS OR BACILLUS TYPHI MURIUM OF LOEFFLER.
+
+These are probably identical organisms, differing only in their degree
+of virulence, at least their pathogenicity alone distinguishes them in
+the laboratory. They are both members of the paracolon group. They
+produce a diffuse cloudiness in broth, ferment glucose but not lactose
+or saccharose, do not liquefy gelatin nor coagulate milk.
+
+_B. typhi murium_ (Loeffler) is fatal to mice (_Mus musculus_), but not
+to rats. M. Danysz isolated a bacillus during an epidemic of field mice
+which was indistinguishable from the above, except that its virulence
+was capable of being raised to a point where it would destroy a
+relatively large percentage of rats inoculated with it by feeding. We
+see from this that, strictly speaking, it is not a natural disease among
+rats, still there are cases where its virulence has for a time remained
+high enough to infect a considerable per cent of rats exposed to those
+that have sickened of it. Not only is this true in cage experiments, but
+probably it sometimes occurs in nature after the virus is once
+thoroughly introduced (an article by M. Danysz; also experience of this
+service in plague in San Francisco, 1903 to 1905), and may therefore be
+grouped under the list of “natural” infections. This bacillus is
+unfortunately of a very unstable nature, in so far as its virulence is
+concerned; some cultures appearing to be avirulent, while others cause
+an all but absolute mortality among the rodents eating it.
+
+The duration of the disease is variable and appears to depend somewhat
+on the size of the dose received, as well as virulence of the culture.
+We have seen death in thirty-six hours or less following ingestion. On
+the other hand, it may occur in two weeks. Usually it occurs in from six
+to twelve days. In a typical case when the animal has lived ten or
+twelve days it is much emaciated, its tissues are dry, and intestinal
+hemorrhages are sometimes met with. When the disease is much prolonged a
+pustular eruption may be present over the skin. The organism can often
+be isolated from the heart blood by plating, such isolation alone
+affording means of diagnosis. The only present interest this organism
+has is as a means of destroying the rat. It was believed to be harmless
+to man, but more recently cases of human illness have been reported that
+were believed to have been caused by infection with this bacillus.
+
+
+ PNEUMONIA.
+
+We have recently seen a case of lobar pneumonia in a rat in which a
+diplococcus was present in pure culture. Possibly connected with this is
+a condition of abscess of lung, which is not very uncommon. The cavity
+is filled with a creamy or cheesy matter composed of broken-down cells.
+Often these cavities break into the pleura. Several morphological types
+of organisms are found, but from their variation this laboratory has
+regarded them as secondary or accidental, especially as we have failed
+to demonstrate that this material was infectious.
+
+
+ STAPHLOCOCCUS ABSCESSES.
+
+These are rather common and may occur subcutaneously or in the
+superficial muscles of any part of the body.
+
+
+ BACILLUS PSEUDO-TUBERCULOSIS RODENTIUM (PFEIFFER).
+
+This organism that infects rats is of interest from its close
+resemblance to the plague bacillus. It is difficult to distinguish the
+two organisms by ordinary cultural or animal tests. The earlier writers
+claimed that _B. pseudo-tuberculosis rodentium_ could be differentiated
+by its power of coagulating milk, but more recently this difference has
+been found to be an inconstant one.
+
+
+ TOYAMA’S BACILLUS.
+
+Toyama has described an organism which he states is pathogenic for _Mus
+rattus_, field and house mice (_Mus musculus_), but not pathogenic for
+_Mus norvegicus_.
+
+It causes congestion of lungs, enlargement of lymph nodes, especially in
+the neck, and enlargement of the spleen. It was isolated from a natural
+epizootic among _Mus rattus_. It is a nonspore-bearing bacillus, without
+capsule, stains without showing bipolarity, and grows upon ordinary
+media.
+
+Among other bacteria that have been described as causing diseases in
+rats may be mentioned:
+
+_Von Schilling’s bacillus_, allied to Danysz’s organism.
+
+_Bacillus “Eris,”_ a member of the colon group.
+
+_Bacillus muris_, a member of the _B. diphtheria_ group.
+
+Of the bacteria that show virulence for rats under laboratory
+conditions, but, so far as is known, cause no spontaneous outbreaks, the
+following are the best-known examples:
+
+_Bacillus bovisepticus_ produces a fatal disease bacillus of swine
+erysipelas (especially for albino rats), and the bacillus of tetanus.
+
+Of the higher fungi (not strictly bacterial) we have:
+
+_Streptothrix maduræ_ produces local swellings when inoculated
+artificially.
+
+It has been stated that rats occasionally suffer from a disease similar
+or identical to the affliction in man known as favus (_Achorion
+Schönleinii_).
+
+
+ INFECTIONS OF MICE (MUS MUSCULUS).
+
+This species of _Mus_ is very susceptible to a large number of bacterial
+diseases when inoculated under laboratory conditions. The following are
+some of the best-known examples:
+
+_B. murisepticus_, _Staphlococcus pyogenes_, _Streptococci_,
+_Diplococcus pneumoniæ_, _B. pneumoniæ_ (Friedlander), Diplococcus of
+pleuro-pneumonia of horses, _B. Typhi murium_, _B. anthracis_, B. of
+malignant edema, _B. tetani_, _B. mallei_, _B. diphtheriæ vitulorum_,
+_B. bovisepticus_, _B. suisepticus_, the bacillus of Mereshkowsky, and
+many others. The last-named organism has been utilized to a limited
+extent for the destruction of mice about dwellings.
+
+
+
+
+ ORGANIC DISEASES OF THE RAT, INCLUDING TUMORS.
+
+ By GEORGE W. MCCOY,
+
+ _Passed Assistant Surgeon, United States Public Health and
+ Marine-Hospital Service_.
+
+
+The lesions described here are those that have been found in the routine
+examination of rats for plague infection in the federal laboratory at
+San Francisco during the past year, in which time approximately 120,000
+rats have been examined.
+
+As the subject had no special bearing upon the plague investigations,
+but little time was spent in examining and recording the nature of
+organic lesions that were observed. Notes, however, were made of many of
+the conditions which were encountered, and these notes have been used as
+the basis of this paper.
+
+It is well known that various lower animals are subject to some of the
+so-called organic diseases from which man suffers, and not a little
+experimental work has been done in endeavoring to establish in animals
+certain of the lesions commonly found in human pathology.
+
+_Usefulness of wild rats for laboratory purposes._
+
+We would call special attention to the fact that wild rats suffer
+spontaneously from cirrhosis of the liver, fatty degeneration of the
+liver, nephritis, and calculi of the urinary tract, and would,
+therefore, probably furnish excellent subjects for the experimental
+investigation of these diseases.
+
+The objection may be made that the very fact that these animals do
+suffer from these diseases spontaneously makes them unsuitable for
+experimental purposes, as one could not be certain that any lesions
+found were not spontaneously developed rather than that they were due to
+the conditions imposed in an experiment. In reply to this objection we
+would say that the most of these organic lesions occur so rarely in rats
+in nature that one could almost ignore them.
+
+The ease with which wild rats are obtained and the readiness with which
+they adapt themselves to the conditions of life in captivity are factors
+which should make them more extensively used for laboratory purposes
+than is the case at present. We have described (New York Medical
+Journal, Feb. 6, 1909) the methods that have been found useful in
+keeping and handling these rodents. Without going into details here we
+may say that if rats of approximately the same size are kept together in
+a cage there will be practically no mortality from fighting. Of course,
+there should be no overcrowding. Rats should be fed meat or cheese and
+plenty of green food such as carrots or cabbage. In our experience in
+San Francisco it has been found practicable to keep for a year one
+series of ten inoculated wild rats without any loss. Judging from my
+experience I have no hesitancy in saying that the natural mortality in
+the laboratory is higher among both guinea pigs and white rats than it
+is among wild rats.
+
+It is almost certain that some of the lesions described below are due to
+animal parasites, or to bacteria, but no such causative agent has been
+identified.
+
+
+ CIRCULATORY APPARATUS.
+
+We have seen no lesion of the circulatory system with the exception of a
+few cases of pericardial effusion. The most extreme example was one in
+which the pericardial sac was dilated to such an extent that it filled
+almost the entire cavity of the thorax. The fluid in the sac was blood
+stained and there were a number of recent adhesions between the visceral
+and the parietal surfaces of the pericardium.
+
+
+ PULMONARY APPARATUS.
+
+Pleural effusion, as is stated in another place, is an important sign of
+plague infection. A clear, watery effusion has been found in a few cases
+in rats that were not plague infected.
+
+One example has come under observation of a large _Mus norvegicus_ that
+had both pleural cavities almost entirely filled with a milky fluid. The
+lungs were compressed and congested. Microscopical examination for
+animal parasites and for bacteria was negative.
+
+A condition of consolidation of the lungs which closely resembles the
+stage of gray hepatization in lobar pneumonia in man is seen
+occasionally. The area may involve half of a lung. Upon microscopical
+examination one finds the air spaces and the small bronchi filled with
+leucocytes. There was no cavity formation in any of the cases that have
+come under observation.
+
+Two relatively common purulent conditions of the lungs are encountered.
+In the first of these, large and more or less distinctly loculated sacs
+are found, which are filled with yellow semifluid caseous matter; in the
+second, the lesion is of much the same nature, but the material in the
+sac has the consistency of tough, ropy mucus. Aside from the main focus
+of this sort, numerous smaller areas of the same nature are seen
+scattered through the otherwise normal parts of the lungs. The extent of
+some of these purulent processes is remarkable. We have seen cases in
+which the chest cavity was almost filled by the lesions described.
+
+
+ DIGESTIVE TRACT.
+
+
+ CIRRHOSIS OF THE LIVER.
+
+It was a matter of surprise to find well-marked cases of hepatic
+cirrhosis in rats, as this disease in man has been pretty generally
+regarded as very largely due to intemperance in the use of alcoholic
+beverages. Such an etiology hardly accounts for the condition in the
+rat. The lesion is by no means rare; well-marked cases are encountered
+probably as often as once in a thousand rats. We have never seen it in a
+young rat, probably because the condition develops slowly and the rat
+reaches adult life before the process is complete. The organ is usually
+somewhat yellowish, very firm, often, but not always, somewhat shrunken
+in size. The surface of the whole organ is covered with small, rounded
+elevations; a typical “hobnail-liver” in miniature.
+
+Microscopically we find various degrees of increase of connective
+tissue. In a well-marked case the capsule is much thickened, and heavy
+bands of connective tissue run through the organ in every direction.
+This increase of connective tissue is most marked in the vicinity of the
+portal vein and its companion vessels. The microscope will show that in
+some fields over half of the structure is made up of fibrous tissue. The
+liver cells that remain appear to be normal. The presence of animal
+parasites in the liver is frequently associated with a considerable
+hypertrophy of the connective tissue of the organ. In a majority of
+cases of hepatic cirrhosis, however, no parasites are to be found. One
+case has come under observation in which the surface of the liver was
+covered with a number of flattened, wart-like elevations. Upon section
+nothing was to be found to account for this except an enormous
+overgrowth of connective tissue.
+
+
+ FATTY DEGENERATION OF THE LIVER.
+
+A considerable number of cases of well-marked fatty degeneration of the
+liver have been seen. At times the fatty change is so extensive that the
+organ floats when placed in water. Microscopically the liver cells are
+found to be extensively infiltrated with fat granules.
+
+
+ HERNIÆ.
+
+A few ventral herniæ have been observed. In the majority of the cases
+the sac contained intestine only and this was easily reduced. On two
+occasions other viscera have been found in the sac; the spleen on one
+occasion and in another case along with several loops of intestine which
+were easily reduced there was found the upper extremity of the right
+division of the uterus which carried a cyst about 1 centimeter in
+diameter. The cyst was partly adherent to the sac of the hernia. The
+other division of the uterus was dilated and full of pus. The hernial
+sac is rarely situated in the median line. One inguinal hernia has been
+seen.
+
+
+ GENITO-URINARY TRACT.
+
+
+ NEPHRITIS.
+
+Nephritis is a rather common condition in rats. Among the large (old)
+ones it will be found probably once in every fifteen or twenty examined.
+It has been found to be especially frequent in rats that are suffering
+from the leprosy-like disease, as probably two-thirds of those having
+that interesting infection will show marked evidence of nephritis. The
+kidney is usually brownish or grayish, mottled, friable and often shows
+cysts upon the surface and in the substance of the organ. Some of these
+cysts may be as large as a pea, or indeed even much larger. The capsule
+strips very readily.
+
+Microscopically the lesions are found to be due partly to epithelial and
+partly to interstitial change. There is a marked increase of connective
+tissue rather irregularly distributed throughout the organ. The
+epithelial cells show various degrees of degeneration; the nuclei are
+stained very lightly, or not at all; granular change of the protoplasm
+is well marked. Some tubules are encountered in which the epithelial
+cells are entirely wanting.
+
+Cyst formation is a conspicuous feature in many of the cases. These
+cysts vary considerably in size, are often filled with granular débris,
+and are more or less completely lined with epithelial cells which are
+sometimes flattened. At times the epithelial lining is entirely wanting.
+The glomeruli, on the whole, appear to be better preserved than are the
+tubules. Occasionally areas are found in which there is a very marked
+round cell infiltration between the epithelial structure. One of the
+most marked cases of nephritis we have observed was in a large female
+_Mus alexandrinus_, in which both kidneys were almost entirely replaced
+by cystic formation, the largest cyst being perhaps 3 centimeters in
+diameter by 4 centimeters in length, and full of a clear, watery fluid.
+So extensive was the cystic formation that only a few remnants of kidney
+tissue remained. Microscopical examination showed a marked increase in
+the capsular and interstitial connective tissue, a shrinking of the
+glomeruli, which were surrounded by well-marked fibrous capsules, and
+extensive cyst formations. The lining of some of these cysts was made up
+of epithelial cells. Others were quite bare. This rat had, in addition,
+a large, rough calculus in the urinary bladder.
+
+
+ ABSCESS OF THE KIDNEY.
+
+A female _Mus norvegicus_ had on one side of the neck a large cavity
+full of caseous matter. In each kidney there were five or six
+circumscribed collections of pus, the largest of which was about the
+size of a pea. Microscopical sections through these abscesses showed
+that they were walled off from the kidney structure proper by beginning
+connective tissue formation. The abscess cavity was filled with
+polynuclear leucocytes, some of them very markedly disintegrated. The
+epithelial structure of the kidney proper showed some parenchymatous
+degeneration.
+
+
+ ATROPHY OF A KIDNEY.
+
+On one occasion we have seen a kidney represented by a very small
+flattened mass of tissue, the nature of which was not quite clear until
+microscopical examination showed a few fairly well-defined glomeruli and
+a few cell groupings suggestive of tubules. Whether the condition was
+congenital or acquired is not known. The other kidney appeared to be
+normal in every respect. There was no evidence of compensatory
+hypertrophy.
+
+
+ VESICAL CALCULI.
+
+The bladder of rats very frequently contains very irregularly shaped,
+rough, somewhat branching concretions. These concretions are rather soft
+and tough and are dirty white in color.
+
+In addition to these concretions we have seen several cases of
+well-marked vesical calculi. In one case 21 smooth round stones which
+completely filled the bladder were found. The total weight of the stones
+was 3.8 grams. In another case 6 calculi were found, the total weight of
+which was 7.8; the largest one weighing 5 grams. In a third case 8
+smooth, round stones weighing 1.7 grams were found, the largest of which
+weighed 0.6 gram. The last two cases were female rats; the sex of the
+first was not recorded.
+
+In each of these cases the bladder showed to the naked eye very marked
+evidence of inflammation. The mucous membrane was reddened, villous, and
+covered with tenacious mucus. In one case in which microscopical
+examination was made the mucous membrane was found to be covered with
+pus cells, the surface layers of which were undergoing degeneration.
+
+Diseases of the genital tract in the human race analogous to those
+mentioned below are so generally regarded as due for the most part to
+infections from impure sexual relations that it was a distinct surprise
+to find such lesions in rodents.
+
+In the male abscesses are occasionally met with in connection with the
+seminal vesicles. We have seen them varying in size from a pea to a sac
+whose contents would have measured 3 or 4 cubic centimeters. In the
+female purulent collections in the horns of the bifid uterus are
+encountered, but they are rare. We have seen cases that were
+anatomically exactly like the purulent lesions so commonly found in the
+fallopian tubes of women. In one case one horn of the uterus was closed
+at both ends and distended by a thin, watery pus into a large
+sausage-shaped mass about the size of an index finger. The opposite horn
+of the uterus contained six fœtuses. A very curious case was one in
+which four fœtuses, each one a little less than an inch in length, were
+found lying in the midst of a large, yellowish, puttylike mass that
+distended one horn of the uterus into a balloon-shaped mass about 3
+centimeters in diameter. The fœtuses were partly dried, and had
+evidently been dead for a long time.
+
+
+ TUMORS.
+
+Tumors among rats and mice are not infrequent when these animals are
+kept in captivity, and the tumors of mice especially have been made the
+subject of very extensive experiments for the purpose of determining the
+mode of transmission, the question of immunity, and other subjects that
+might throw light upon malignant growths in the human family. White or
+tame rats have been much less used than mice. However, it is interesting
+to note that the earliest observations on the successful transplantation
+of a malignant growth from one animal to another was that of Hanau[101],
+who reported a carcinoma of the external genitals of a white rat and he
+succeeded in transplanting this tumor into other white rats.
+
+I shall not make any attempt to review the enormous literature on tumors
+in tame rats and mice, but shall merely mention some of the more
+important points that have been learned in an experimental way in regard
+to this subject. The histological nature of the tumors found in white
+rats was of particular interest, as we wished to compare them with the
+tumors that have come under observation among the wild rats in San
+Francisco.
+
+In addition to Hanau’s case of carcinoma cited above the following
+tumors of white rats are mentioned. Herzog[102] observed a cystic
+sarcoma of the neck of a white rat. Loeb[103] mentions three tumors of
+white rats; an adenoma in the mammary gland, an adenocarcinoma of the
+pancreas, and a carcinoma of the thyroid. Flexner and Jobling[104]
+report a mixed cell sarcoma of the seminal vesicles of a white rat. This
+tumor upon transplantation showed a marked tendency to produce
+metastases. Gaylord and Clowes[105] report cases of fibrocarcinoma of
+white rats arising apparently from infected cages, and they present
+evidence that in certain breeding establishments carcinoma is endemic
+among the white mice. Spontaneous tumors are much more frequently met
+with in mice than in rats, and a number of epidemics of malignant
+growths have been observed among mice in captivity.
+
+Tyzzer[106] found in a mouse a primary adenocarcinoma of the lung and an
+adenoma of the kidney. Loeb[107] found that upon the transplantation of
+a pure gland-like tumor (carcinoma) which originated in the submaxillary
+gland of a Japanese mouse both carcinoma and spindle cell sarcoma were
+developed, and this observation, that transplanted tumors may give rise
+to a different histological growth from that which was transplanted, has
+been made by others. Tyzzer[108] reports 20 spontaneous tumors in mice.
+Of these tumors 12 were papillary cyst-adenomas of the lung and were
+mostly very minute, some of them microscopic; 2 were cyst-adenomas of
+the kidney; 2 lymphosarcoma, 1 of the groin and 1 of the mediastinum,
+and 4 were adenocarcinoma. These 20 spontaneous tumors occurred in 16
+mice, 4 of them having tumors of 2 different types. Ehrlich and
+Apolant[109] record the occurrence in a white mouse of a mixed tumor
+(carcinoma sarcomatodes). Saul[110] mentions spontaneous papillary
+adenocarcinoma and teleangiectatic carcinoma both in the mammary glands
+of mice.
+
+Saul showed that by planting the common liver worm of the rat
+(_Cysticercus fasciolaris_) subcutaneously in a mouse he was able to
+develop a tumor which partook of the nature of a malignant
+(carcinomatous) growth. It will be seen by an examination of the data
+presented below relating to spontaneous tumors in wild rats that a
+considerable number of them have been associated with the presence of
+the parasite Saul used in his experiments. He also states[111] that
+Borrel found worms or their remnants in malignant tumors of mice.
+
+When metastases occur in mouse tumors the most usual seat of the
+secondary growths is in the lungs, thus Tyzzer[112] observed metastases
+in 4 cases out of 73 mice inoculated with the Jensen tumor. He
+demonstrated that the metastases took place by the blood vessels, not by
+the lymphatic channels, although the tumors were of a carcinomatous
+nature.
+
+Simon[113], who reviews the subject of mouse tumors with special
+reference to the subject of immunity, remarks that mouse carcinomata,
+although found most frequently in old females, when transplanted grows
+equally well in males, and better in young than in old animals. It has
+been found by some observers that a rat or a mouse unsuccessfully
+inoculated with a strain is thereafter immune, to even the most virulent
+strain.
+
+Haaland[114] and other writers have found a marked variation in the
+susceptibility of different races of mice to mouse carcinoma.
+
+Ehrlich[115] and his co-workers Apolant and Haaland have recorded many
+experiments in transplantation of tumors of mice. They have demonstrated
+that moderate heating of a mouse tumor lengthens the incubation period,
+diminishes the number of successful transplantations, and brings about
+certain changes in the histology of the tumors reproduced.
+
+Gay[116] found a difference in the susceptibility of white rats from
+different sources. In his work with carcinoma in rats he found
+metastases regularly in the lungs and rarely in the lymph nodes. He was
+able to raise the virulence of the tumor by transplantation of the lung
+metastases. This increase of virulence was shown by increase in the
+rapidity in growth, increase in metastases, and the increase of the
+epithelial elements over the stroma.
+
+Brooks[117] in considering the subject of tumors in animals concludes
+that true neoplasms are very rare in wild animals living under natural
+conditions. It should be stated, however, that Brooks refers especially
+to higher mammals such as are found in zoological collections.
+
+
+ TUMORS OF WILD RATS.
+
+A new growth is found approximately once in every thousand rats examined
+in San Francisco. Ninety-two tumors have been examined microscopically.
+Time has been available for the study of but one or at the most two
+sections from each tumor and while in some cases the diagnosis was
+easily made in others there was room for considerable difference of
+opinion as to the nature of the growth. It is obvious that it is hardly
+fair to expect to make a final diagnosis in every case from one or two
+sections taken from one part of the growth, and it is possible that
+further study will throw more light upon the histological nature of some
+of them.
+
+_Location._—The largest number of the tumors have been found in the
+subcutaneous tissue of either the thorax or of the abdomen, and as the
+majority of these have been found in female rats we have assumed that
+they were probably of mammary origin. The growths were occasionally
+located directly under the nipple, but in such cases the nipple was not
+retracted, and it was exceptional to find any ulceration. The tumors
+were very rarely adherent to the surrounding tissue. After the
+subcutaneous tissue tumors were found most frequently in the liver.
+Histologically, the most of these growths were sarcomas and the majority
+of them had a parasite, the _Cysticercus fasciolaris_, in some part of
+the tumor. This parasite, as is well known, is the larval stage of a
+tapeworm found in the cat. These tumors of the liver were frequently
+associated with an enormous number of secondary growths varying in size
+from a millet seed to 1 centimeter in diameter scattered through the
+omentum, mesentery, and other abdominal structures.
+
+Several growths have been found in the kidney, mostly of an epithelial
+nature, one being a particularly well-marked example of a cystic
+papilloma. A few have been found in connection with other parts of the
+genito-urinary tract. A large bloody tumor, which upon microscopical
+examination was found to be an angiosarcoma, replaced a testicle. A
+large growth, apparently an endothelioma, was found near the end of one
+horn of the bicornuate uterus.
+
+
+ METASTASES.
+
+Metastases have been found in a number of cases of sarcoma and a smaller
+number of cases of the epithelial growths. Most frequently the secondary
+tumors were in the liver, the mesentery or the kidney.
+
+_Size._—In proportion to the size of the rat the tumors were quite
+large, scarcely any under 1 centimeter in diameter having been observed,
+and they varied from this to a growth several centimeters in diameter.
+
+
+ HISTOLOGICAL STRUCTURE.
+
+The following tumors may be regarded as of the connective tissue type:
+
+
+ LIPOMATA.
+
+One typical lipoma has been found. It was located in the subcutaneous
+tissue of the thorax and was similar in gross and microscopical
+appearance to the tumors of the same nature in man.
+
+
+ FIBROMATA.
+
+A considerable number of subcutaneous tumors have been typical hard
+fibromas, others were fibromas in which there were a few cell nests that
+led to the suspicion that perhaps a malignant change was taking place in
+the tumor, or that a malignant growth was being converted into one of a
+benign nature.
+
+
+ SARCOMATA.
+
+Typical spindle cell sarcomas have been encountered a number of times. A
+few round cell sarcomas were found in which there were usually a number
+of giant cells, but hardly enough to justify one in designating the
+growths as giant cell sarcomas. Several other growths have been seen
+which gave the impression of being sarcomas but left one in some doubt
+as to whether the tissue might not be of the nature of a granuloma.
+
+Many tumors of the epithelial type were encountered which may be classed
+together.
+
+
+ ADENOMATA AND CARCINOMATA.
+
+Several very typical adenomas and cystic adenomas have been found. A few
+tumors were observed that presented the appearance of carcinomas. A
+large number of growths were observed that apparently stood between the
+adenoma and the carcinoma and there was room for legitimate difference
+of opinion about any one of these, and in fact, different pathologists
+who have examined sections of these tumors have expressed different
+opinions as to the nature of the growths.
+
+
+ REFERENCES.
+
+Endnote 101:
+
+ Hanau (Fortsch. der Med., vol. 7, 1889, May 1, p. 321).
+
+Endnote 102:
+
+ Herzog (Journal Med. Research, 1902, vol. 8, old series, p. 74).
+
+Endnote 103:
+
+ Loeb (Journal Med. Research, 1901, vol. 6, p. 28; also vol. 3, p. 44,
+ and vol. 17, p. 299).
+
+Endnote 104:
+
+ Flexner and Jobling (Journal Am. Med. Assn., 1907, vol. 48, p. 420).
+
+Endnote 105:
+
+ Gaylord and Clowes (Journal Am. Med. Assn., 1907, vol. 48, p. 15).
+
+Endnote 106:
+
+ Tyzzer (Journal Am. Med. Assn., 1906, vol. 47, p. 1237).
+
+Endnote 107:
+
+ Loeb (Univ. of Pa. Med. Bull., 1907, vol. 19, No. 5).
+
+Endnote 108:
+
+ Tyzzer (Journal Med. Research, vol. 17, No. 2, p. 155).
+
+Endnote 109:
+
+ Ehrlich and Apolant (Berl. klin. Woch., 1907, vol. 44, pp. 399 and
+ 1401).
+
+Endnote 110:
+
+ Saul (Centralblatt für Bact., etc., Aug. 27, 1907, vol. 47).
+
+Endnote 111:
+
+ Saul (Centralblatt für Bact., etc., 1909, vol. 49, p. 4).
+
+Endnote 112:
+
+ Tyzzer (Journal Med. Research, vol. 17, No. 2, p. 137).
+
+Endnote 113:
+
+ Simon (International Clinic, vol. 2, 18th series).
+
+Endnote 114:
+
+ Haaland (Berlin, klin. Woch., 1907, vol. 44, p. 73).
+
+Endnote 115:
+
+ Ehrlich, Apolant and Haaland (1906, Berlin, klin. Woch., vol. 43, No.
+ 2).
+
+Endnote 116:
+
+ Gay (1909, Journal Med. Research, Vol. XX, No. 2).
+
+Endnote 117:
+
+ Brooks (1907, Am. Jour. of Med. Sciences, Vol. CXXXIII).
+
+
+
+
+ THE ECTOPARASITES OF THE RAT.
+
+ By NATHAN BANKS,
+
+ _Assistant Entomologist, Bureau of Entomology_.
+
+
+The ectoparasites of the rat fall naturally into three groups, the
+fleas, the lice, and the mites. These three groups are widely separated
+from each other, the mites belonging to the class Arachnida, having four
+pairs of legs, no segmentation to the body, no antennæ, and no compound
+eyes. The fleas and lice belong to the class Insecta. The lice are near
+the order Hemiptera, sucking insects without a complete metamorphosis,
+while the fleas are related to the Diptera and pass through a complete
+metamorphosis. All of these three groups, however, agree in one
+character—they are wingless. The mites and lice have flattened or
+depressed bodies, while the fleas have compressed bodies. All three
+groups have many other species which infest various other animals. Few,
+if any, of these parasites confine themselves to the rat, and all can
+walk or jump in the adult condition, so that they can easily transfer
+their attentions from one rat to another or to some other host. The
+majority of them are known to occur on mice, and several of the fleas
+and mites will readily attack man.
+
+
+ FLEAS—SIPHONAPTERA.
+
+These wingless, compressed insects are known to all, but few have taken
+the trouble to look at them with much care. The adult female flea
+deposits her eggs among the hairs or fur of the host animal, but, unlike
+the eggs of many parasites, these are not fastened to the hairs and fall
+freely to the ground. These eggs are oval, whitish, and smooth, and
+about one-half millimeter long. The larvæ escape from the eggs in two to
+five days. They are enabled to break the eggshell by a slender process
+on the top of the head which disappears after the first molt. This larva
+is a slender, legless, cylindrical creature, whitish or yellowish in
+color, with a head and 13 segments. There are a few scattered hairs or
+bristles on the body and at the tip is a pair of corneous processes. On
+the upper part of the head is a pair of short, slender appendages, the
+antennæ or feelers. At the front of the head is a pair of biting jaws or
+mandibles. These larvæ feed on almost any kind of refuse; some have been
+reared on the sweepings from rooms. There is always some organic matter
+in this refuse, and this is doubtless their nourishment. The larvæ in
+houses usually crawl into cracks or under carpets and feed on the dust
+that occurs in such places. Those that infest wild animals probably feed
+on the refuse in the nests or retreats of these animals. They remain in
+the larval stage from a week to ten days, sometimes two weeks, molting
+the skin three times in this interval. Then they spin flat, white,
+silken cocoons, in which they transform to the pupal stage. Sometimes
+the cocoon is covered with particles of dust. In from five to eight days
+the adult flea emerges from the cocoon. The period of their
+transformation is affected by the temperature and moisture. In warm,
+damp weather a generation may develop in ten days or two weeks, but
+usually about eighteen days to three weeks elapse from the egg to adult.
+Although some moisture seems necessary to their development, an excess
+is apt to destroy the larvæ.
+
+[Illustration:
+
+ FIG. 6.—Flea, showing the various parts.
+]
+
+The leaping ability of adult fleas is familiar to all. No part of the
+leg is particularly enlarged, so that the jump is made by the entire leg
+as in the leaf-hopper insects, and not by the hind part of the leg as in
+grasshoppers and flea-beetles. The size of fleas is not as variable as
+in many insects. Most are about 2 to 3 millimeters long, while the range
+is about 1.5 to 6 millimeters. The adult flea has a hard, strongly
+chitinized body. The head is small, and on each side bears a short
+jointed antenna, which may repose in a groove or depression. Most
+species have a small, simple eye, but several forms are normally without
+eyes. The sides of the head below the antennæ are called the genæ. At
+the lower front end of the head is the mouth and mouth parts. The latter
+consist of a pair of triangular maxillæ with jointed maxillary palpi and
+a beak or proboscis made up of one median and four lateral pieces. The
+outer pair of lateral pieces is the labrum with the imperfectly jointed
+labial palpi. They serve as a sheath for the other organs, which are
+more slender. The inner pair of pieces are considered to be the
+mandibles and the median piece a labrum or hypopharynx. Others call this
+piece the unpaired piercing organ, the lingua, or the syringostome.
+There are other interpretations of the homologies of the mouth parts,
+but the above is the most generally adopted one. The labrum and the
+mandibles are roughened and constitute the piercing organs which the
+flea inserts into the host to tap a blood vessel. On the lower part of
+the head there is frequently a series or comb of stout spines. Similar
+spines sometimes occur on the posterior border of the pronotum. These
+series of spines are called “ctenidia,” and they are of great value in
+classification. Behind the head are three segments, or zoonites, each
+bearing a pair of legs. These together form the thorax. The upper
+surface is called the notum (pronotum, mesonotum, etc.). The sides are
+the pleura—sometimes “epimera” is used; and the ventral part is the
+sternum. Each of the thoracic segments has a spiracle, or a breathing
+pore, on each side. The first segment of the thorax, called the
+“prothorax,” is shorter than the others, and, as above stated,
+frequently has a row of ctenidia, or spines, on its posterior border.
+The next segment is the mesothorax, and the third the metathorax. The
+metathorax usually has some stout bristles in rows on its pleura, which
+are enlarged and called “epiphyses,” formerly called “squama aliforme.”
+The basal one or two segments are sometimes partly covered by the
+epiphyses or the metathorax. These segments consist of a dorsal plate,
+or tergite, and a ventral plate, or sternite. Behind the thorax is the
+abdomen of 9 apparent segments. Seven of these segments have a spiracle
+or breathing pore on the sides. The last segment, or pygidium, bears the
+genital organs; in the male certain processes called “claspers” at each
+side of the genital opening. The anal aperture is at the end of the
+ninth segment between the dorsal and ventral plates. The claspers have a
+main curved part, and a slender backward projection called the
+“manubrium,” and at the apex an articulated clawlike process called “the
+movable finger.” At the tip of the abdomen of the female there is a
+short median piece called the “style.” The legs consist of five parts:
+The coxa, a large basal piece; the trochanter, a minute piece at the end
+of the coxa; the femur, which is usually slightly swollen in the middle;
+the tibia, which usually has stout bristles or spines on its posterior
+side; and the tarsus, which consists of five parts or joints. The basal
+joint is often the longest, and the comparative lengths of these joints
+is expressed by a formula, as 60–45–32–18–30. The last, or fifth, joint
+has been called the “metatarsus,” but this name is better applied to the
+basal joint. At the tip of the last tarsal joint is a pair of stout
+claws. The coxæ of legs II and III show a longitudinal suture.
+
+Fleas as a rule prefer certain hosts, but are not as particular in this
+regard as are many parasites. Those species which are best known are
+found to attack several hosts, including man. This catholicity of taste
+is what makes them dangerous parasites, the possible transmitters not
+only of plague, but also of consumption, leprosy, etc. The fleas are
+treated by various writers under other names, such as _Aphaniptera_, and
+_Suctoria_. About 300 species are described, and perhaps as many more
+will be gathered by collectors. Formerly all fleas were kept in the
+genus _Pulex_; now they are arranged in many genera, and these genera
+grouped into families. No less than eight such families are recognized
+by some authorities on this group. The species that occur on rats belong
+to three families, which may be separated as follows:
+
+ 1. Thoracic segments much shortened and constricted;
+ labial palpi apparently not jointed; third joint
+ of antennæ without subjoints; no ctenidia;
+ abdomen of female becomes more or less swollen _Sarcopsyllidæ_
+
+ Thoracic segments not shortened nor constricted;
+ labial palpi with joints; third joint of antennæ
+ with several more or less distinct subjoints;
+ ctenidia often present; abdomen of female never
+ distinctly swollen 2
+
+ 2. Posterior tibial spines in pairs _Pulicidæ_
+
+ Posterior tibial spines mostly single and more
+ numerous _Ctenopsyllidæ_
+
+
+ CTENOPSYLLIDÆ.
+
+To this family belongs the _Ctenopsylla musculi_ Dugès.
+
+This was formerly placed in the genus _Typhlopsylla_. The head is rather
+acute in front and has four ctenidia each side; the eyes are very small;
+the pronotal comb has 22 spines; each dorsal segment of the body has two
+rows of hairs; the basal row of smaller hairs. The proportions of joints
+in the hind tarsus are: 45–25–17–8–14. Length 1.8 to 2.5 millimeters.
+This species is abundant on rats and mice in Europe and other countries;
+recently it has been taken in California and Florida on rats and mice.
+
+
+ PULICIDÆ.
+
+This family includes the greater number of fleas. They have been
+arranged in many genera, six of which have been taken from rats. These
+are separable as follows:
+
+ 1. Head without ctenidia; eyes distinct 2
+
+ Head and pronotum with ctenidia; last tarsal joint
+ with four pairs of lateral spines 5
+
+ 2. Pronotum with ctenidia; female with one
+ antepygidial bristle on each side _Hoplopsyllus_.
+
+ Pronotum without ctenidia 3
+
+ 3. Last tarsal joint with four pairs of lateral
+ spines; female with one antepygidial bristle each
+ side 4
+
+ Last tarsal joint with five pairs of lateral
+ spines; female with two to five antepygidial
+ bristles each side _Ceratophyllus_.
+
+ 4. Mesosternite very narrow, without internal rod-like
+ incrassation from the insertion of coxa upward _Pulex_.
+
+ Mesosternite with a rod-like internal incrassation
+ from the insertion of coxa upward _Xenopsylla_.
+
+ 5. Eyes rudimentary; female with two to five
+ antepygidial bristles each side _Neopsylla_.
+
+ Eyes distinct; female with but one antepygidial
+ bristle each side _Ctenocephalus_.
+
+_Hoplopsyllus_, one species, described as a _Pulex_.
+
+_Hoplopsyllus anomalus_ Baker.
+
+The mandibles scarcely reach halfway down on the anterior coxæ; upon
+each are two large spines; the pronotal comb has about nine spines each
+side; and each abdominal segment has but a single row of bristles. The
+hind femora have six to eight bristles on the side; the proportions of
+the joints in the hind tarsus are: 26–16–8–5–13. Color, dark reddish
+brown. Female, 2.5 millimeters; male, 1.5 millimeters.
+
+Described from a spermophile from Colorado and recorded by Doctor Fox
+and Professor Doane from _Mus norvegicus_ from California.
+
+_Pulex._—Of this, the typical genus of the family, but one species has
+been recorded from rats.
+
+_Pulex irritans_ Linn.
+
+The mandibles reach about halfway down on the anterior coxæ; the head is
+regularly rounded in front; there are no transverse rows of bristles on
+the vertex, and but one row of bristles on each abdominal tergite. The
+proportions of the joints in the hind tarsus are, 50–30–18–12–32. Color,
+usually yellow brown. Male, 1.6 to 2 millimeters; female, 2 to 3.5
+millimeters.
+
+This, the human flea, is quite cosmopolitan, but more abundant in warm
+countries than elsewhere. It occurs on many domestic animals and has
+frequently been taken from rats in California and elsewhere; it also
+occurs on skunks.
+
+_Xenopsylla._—This genus includes the following species, formerly placed
+in the genus _Lœmopsylla_.
+
+_Xenopsylla cheopis_ Rothschild.
+
+The mandibles reach nearly to the end of the anterior coxæ; there are no
+ctenidia on the head or pronotum; the eyes are distinct; each abdominal
+tergite has but one row of bristles; the hind femur has a row of about
+eight bristles; the proportions of the joints in the hind tarsus are as
+follows: 46–30–16–10–20. Color, light brown. Male, 2.5 to 3.5
+millimeters; female, 4 to 5.5 millimeters.
+
+This is a true rat flea, but will readily bite man, and is the species
+chiefly concerned in transmitting the bubonic plague. It is widely
+distributed, especially in seaport towns.
+
+_Ceratophyllus._—Fleas of this genus are abundant on many kinds of small
+mammals, especially rodents. There are a great many species and some are
+so closely related that it is not easy to identify them. Of the eight
+species recorded from rats, four have been taken in this country. It is
+not practicable to tabulate these eight species, but the four that occur
+in our country may be arranged as follows:
+
+ 1. Hind tarsal joint II with an apical spine much
+ longer than joint III _acutus_.
+
+ Hind tarsal joint II with spines not longer than
+ joint III 2
+
+ 2. Pronotal comb of about 26 spines _niger_.
+
+ Pronotal comb of about 18 or 20 spines _fasciatus_ and
+ _londiniensis_.
+
+_Ceratophyllus niger_ Fox.
+
+This species has the pronotal ctenidia of about 26 spines; there are a
+few hairs on the inner surface of hind femur; apical spines of second
+joint of hind tarsus not longer than third joint; three hairs in front
+of the eye and three in front of these; movable finger of claspers with
+five slender bristles on the outer edge. Color, very dark brown. Length
+3.5 millimeters.
+
+Taken in California from _Mus decumans_ and from man.
+
+_Ceratophyllus acutus_ Baker.
+
+This species is readily known by having a spine at tip of the second
+joint of hind tarsus longer than the third joint and reaching over onto
+the fourth joint; the abdominal tergites have each two rows of bristles;
+the male claspers are very large and long, sickle shaped. Color, pale
+brown. Length, 3 to 3.5 millimeters.
+
+It was described from a spermophile, but Doctor Fox has taken it once
+from a rat in California.
+
+_Ceratophyllus fasciatus_ Bosc.
+
+There are 18 or 20 spines in the pronotal comb; there are three bristles
+in front of eye and in female two, and in male four in front of these;
+there are three or four hairs on the inner surface of the hind femur;
+the proportions of joints in the hind tarsus are 50–33–20–11–21. The
+manubrium of the male claspers is very long and slender, and some of the
+bristles on the movable finger are as long as the joint. Length, male,
+1.8 millimeters; female, 2.5 millimeters.
+
+It has been recorded from California on rats, mice, skunks, and man. It
+is also common in Europe and elsewhere on rats, mice, and other small
+animals.
+
+_Ceratophyllus londiniensis_ Rothschild.
+
+This is allied closely to _C. fasciatus_, and is best separated from
+that species by the shape and armature of the genital parts; the
+manubrium is not as long as in that species, and the bristles on the
+movable finger are shorter; the third joint of the maxillary palpi is
+proportionally longer than in _C. fasciatus_. There are three bristles
+in front of the eyes and four or five in front of these; there are a few
+hairs on the inner surface of the hind femur; the proportions of the
+joints in the hind tarsus are 46–30–18–11–18.
+
+It has been recorded by Doctor Fox from _Mus rattus_ in California, and
+is known from rats and mice from several parts of Europe; the _C.
+italicus_ Tiraboschi is the same species.
+
+The four other species of this genus found on rats and not yet found in
+our country are closely related to _C. fasciatus_, and distinguished
+chiefly by the shape of the male genitalia.
+
+_Ceratophyllus mustelæ_ Wagner.
+
+This species has no series of hairs on the inner surface of the hind
+femur; there are three bristles in front of the eye and six in front of
+these; the pronotal comb has 18 or 20 spines; the proportions of the
+joints in the hind tarsus are 47–37–20–13–20; the movable finger of the
+male clasper has a long process below not seen in other forms. Occurs
+(according to Rothschild) on rats in Europe.
+
+_Ceratophyllus pencilliger_ Grube.
+
+This species also has no hairs on the inner surface of the hind femora.
+The pronotal comb has 18 spines; there are three bristles in front of
+the eye and four in front of these; the proportions of the joints in the
+hind tarsus are 52–36–23–14–24; the outer corner of the movable finger
+of the male clasper has two little rounded processes. It was described
+from Siberia, but according to Rothschild occurs on rats in Europe.
+
+_Ceratophyllus consimilis_ Wagner.
+
+This species is very close to _C. fasciatus_, and has some fine hairs on
+the inner surface of the hind femur; there are but two bristles in front
+of the eye and in front of these a few finer hairs; the proportions of
+the joints in the hind tarsus are 42–30–20–11–19; pronotal spines 18.
+Occurs on rats in Russia.
+
+_Ceratophyllus lagomys_ Wagner.
+
+This species also has a few fine hairs on the inner surface of the hind
+femur; 18 spines in pronotal comb; there are three bristles in front of
+eye and one in front of these; the proportions of the joints in the hind
+tarsus are 53–32–20–11–22; the outer corner of the movable finger of the
+male clasper has two little processes, similar to those on _C.
+pencilliger_. Occurs on rats in Europe.
+
+_Ctenocephalus._—The common fleas on cats and dogs, as well as on man,
+belong to two species long kept under one name (_C. canis_ or _C.
+serraticeps_), but lately shown by Rothschild to be distinct. Both have
+a comb of 8 spines on the head and 16 spines in pronotal comb; the
+proportions of joints in the hind tarsus are 40–24–15–10–24. Both are
+occasionally taken on rats in this country. They may be separated as
+follows:
+
+ 1. In the female the head is fully twice as long as
+ high (seen from side); the first spine of genal
+ comb is two-thirds the length of the second; in
+ male the manubrium of claspers is barely enlarged
+ at tip; and with two rows of hairs on disc of _C. felis_
+ movable finger Bouché.
+
+ In the female the head is less than twice as long
+ as high (seen from side); the first genal spine
+ in the head comb is only about one-half the
+ length of the second; in the male the manubrium
+ of clasper is very distinctly enlarged at tip;
+ but one row of hairs on the disc of the movable _C. canis_
+ finger Curtis.
+
+_Neopsylla._—One species of this genus has been described from the brown
+rat in Europe.
+
+_Neopsylla bidentatiformis_ Wagner.
+
+The eyes are very small; there are 4 pairs of lateral spines beneath the
+last joint of the hind tarsus; the comb on head consists of but 2 stout
+spines, below the middle of the antennæ; the pronotal comb has 18
+spines; the proportions of the joints in the hind tarsus are
+43–33–21–12–21.
+
+Length: Male, 2 to 2.3 millimeters; female, 2.3 to 2.5 millimeters.
+
+Not yet found in the United States; described from Russia.
+
+
+ SARCOPSYLLIDÆ.
+
+The fleas of this family are commonly called “chigoes,” “jiggers,” or
+sand fleas. The head is usually larger proportionally than in the other
+fleas; there are no ctenidia on head or pronotum; the thoracic segments
+are extremely short, and in the female the abdomen enlarges with the
+development of the eggs. They do not hop about as other fleas, but
+remain on the spot to which they have attached until they die.
+Frequently the adjacent skin grows over them, forming a swelling of
+considerable size.
+
+Three species belonging to two genera have been recorded from rats.
+
+ 1. Angle of head acutely produced; fifth tarsal joint
+ of hind legs without heavy spines; few spines on
+ the legs _Sarcopsylla_.
+
+ Angle of head not produced, obtuse; fifth tarsal
+ joint with heavy lateral spines, and other spines
+ on other parts of the legs _Echidnophaga_.
+
+_Echidnophaga._—Two species of this genus are known from rats; one,
+however (_E. gallinacea_), can hardly be called a normal parasite, but
+rather of accidental occurrence. The genus has also been called
+_Argiopsylla_ and _Xestopsylla_.
+
+ 1. Bristles at end of second joint of hind tarsus
+ about as long as next three joints; palpi about _E.
+ one-half the length of mandibles rhynchopsylla_.
+
+ Bristles at end of second joint of hind tarsus
+ about as long as next two joints; palpi about
+ two-thirds the length of the mandibles _E. gallinacea_.
+
+_Echidnophaga rhynchopsylla_ Tiraboschi.
+
+The body is about twice as long as broad and shining brown; there is but
+one hair in front of eye, and four on each metathoracic pleuron;
+mandibles larger than in _E. gallinacea_, and the spiracles are much
+higher up on the sides than in that species. Length, 1.4 to 1.8
+millimeters.
+
+Taken from _Mus rattus_ in Italy.
+
+_Echidnophaga gallinacea_ Westwood.
+
+This species has the body almost as broad as long, and of a red-brown
+color; 1 bristle in front of eye and 6 on each metathoracic pleuron;
+each abdominal tergite has on each side near the median line a single
+hair; the spiracles are situated well down on the sides. Length: Male,
+0.8 to 1.2 millimeters; female, 1 to 1.8 millimeters.
+
+This species is a fairly common pest of poultry and dogs in warm
+countries, and is called the “chicken flea.” It has been taken from rats
+in Italy.
+
+_Sarcopsylla._—This genus includes the _S. penetrans_, which attacks the
+feet of various animals, including man, in the Tropics. This species has
+not yet been recorded from rats, but an allied species is described from
+Brazilian rats.
+
+_Sarcopsylla cæcata_ Enderlein.
+
+Color, clear yellowish. Eyes rudimentary; lower anterior corner of coxæ
+prolonged in a tooth; tarsal joints very short; claws long, but little
+curved, and almost hair like. The body of a swollen female is about 5
+millimeters long.
+
+Taken from _Mus rattus_ in Brazil.
+
+
+ LICE—ANOPLURA.
+
+The insects known as Pediculi, or lice, are parasitic during their
+entire life on various mammals, including man. They are flat, rather
+elongate, wingless insects, with a small head and stout legs, which end
+in a strong claw, opposable to a projection at the tip of the
+penultimate joint. The simple antennæ, three to five jointed, are
+inserted in a concavity on the side of the head. The mouth parts are of
+a very peculiar nature, and not yet homologized with the cibaria of
+other insects. There is a short beak or proboscis in front, with
+recurved spines or hooks on its dorsal and lateral surfaces. Through
+this beak extends a slender stylet, that is formed of three parts; a
+ventral channeled piece, perhaps a labium; a dorsal piece, consisting of
+two pieces fused together, perhaps the maxillæ; and a median tube,
+possibly the hypopharynx. The stylet is used to pierce the skin of the
+host, and the blood is sucked up through it. There are no palpi. On each
+side of the head there is a small, simple eye. The thorax shows only
+incompletely the division into the three parts; there is a large
+spiracle above on each side. The abdomen shows eight segments, six of
+them have a spiracle, or breathing pore, on each side, the basal and
+apical segments being without them. All of the segments bear a few
+simple hairs or bristles; the longest are on the posterior segments. The
+legs are stout and prominent; they consist of a broad coxa, a small
+trochanter, a longer femur, a tibia with an apical process, and a tarsus
+of one joint and a very large terminal claw. At the apex of the tibia,
+just within the projection, is a sucking disc. This, the projection, and
+the claw form the apparatus to hold fast to the hair of the host.
+
+Lice usually walk sideways, but do not travel much, and they keep close
+to one host. The eggs are slightly elongate and fastened to the hair of
+the host. They hatch in about ten to fifteen days, the young coming out
+of the top of the egg. These young do not differ much in structure from
+the adults, but are paler in color. They molt their skin a few times,
+probably four, before they reach the mature condition. The males are
+less numerous than the females, and ordinarily smaller. There are
+several generations each year, dependent doubtless on the temperature;
+but the life history is not thoroughly known for any species. After
+sucking the blood the abdomen of the louse becomes somewhat distended,
+very noticeably so in some species.
+
+The sucking habits of the lice render them dangerous parasites and
+capable of transmitting a disease from one host to another. Fortunately
+they do not readily change hosts so that they can not be considered
+quite as dangerous as some more active parasites. However, several
+species have already been shown to carry diseases in laboratory
+experiments. Therefore it is probable that some of them will be
+connected with the origin and diffusion of certain diseases of animals.
+
+[Illustration:
+
+ FIG. 7.—Louse (_Polyplax spinulosa_).
+]
+
+The Anoplura, or lice, have often been treated in connection with the
+Mallophaga, or biting lice. This is doubtless because they frequently
+occur on the same animal, and have a general resemblance to them.
+However, they have no real affinity to these insects, and the general
+opinion is that they are more or less related to the Hemiptera.
+Sometimes they are treated as a group or section of the Hemiptera, but
+also as a separate order, under various names as Siphunculata,
+Lipognatha, Pseudorhynchota, and Ellipoptera.
+
+There are about 50 or 60 known species which are arranged in 15 genera
+and 4 families. Four species belonging to three different genera have
+been recorded from rats; a number of others are known from mice and
+other rodents, and some of these will probably yet be taken upon rats.
+
+These four forms are separated, as follows:
+
+ 1. Eyes large and distinct; beak very short; thorax _Pediculus
+ plainly longer than broad capitis_.
+
+ Eyes small, beak longer; thorax about as broad as
+ long 2
+
+ 2. In male the pleura of abdominal segments 3 to 6
+ above and below have a prominent tooth-like _Hoplopleura
+ projection; a tooth on the hind femur of female acanthopus_.
+
+ In male the pleura of abdominal segments without
+ such projections; no tooth on hind femur of
+ female 3
+
+ 3. Last joint of antennæ much more slender than those
+ before; an acute tooth at sides of segments 4 to
+ 7; head much narrower in front; antennæ _Polyplax
+ two-thirds as long as head miacantha_.
+
+ Last joint of antennæ not much more slender than
+ others; head quite broad in front; antennæ as _Polyplax
+ long as head spinulosus_.
+
+_Pediculus capitis_ De Geer.
+
+It is pale grayish in color, with faint dark markings at the sides of
+the thorax and abdomen; the last segment of the abdomen in female is
+bilobed. The head is longer than broad and tapers in front. Length, 2
+millimeters. This is the head louse of man, and is said to have been
+taken from rats, and is claimed to be able to transfer plague from rats
+to man. Its occurrence on rats, however, appears to be very uncommon.
+
+_Hopopleura acanthopus_ Burmeister.
+
+In the male the pleura of the abdominal segments 3 to 6, which reach up
+on the dorsum and over on the venter, have at their inner ends a
+prominent projection, toothed in all except the third on dorsum and the
+sixth on venter, which are spine-like. The head is but little longer
+than broad, broad in front; and in the female there is a recurved tooth
+on each hind femur. The last segment of the female abdomen is bilobed
+behind. Length, 1.3 millimeters. It has been taken from rats in Europe,
+but is more common on species of _Microtus_.
+
+_Polyplax spinulosus_ Burmeister.
+
+The sides of the abdominal segments are acute, but the males do not have
+the large tooth-like projection of _Hoplopleura_. The last segment of
+the female is truncate; the head is about as broad in front as behind,
+and the legs are very short and stout; the antennæ are as long as head,
+and the last joint is but little smaller than the others. Color, pale
+yellowish. Length, 1.4 millimeters.
+
+This is the common rat louse, and is probably as widely distributed as
+its host. Specimens have been taken in both the eastern and western
+parts of the United States.
+
+_Polyplax miacantha_ Speiser.
+
+This differs from _P. spinulosus_ in having a longer and narrower
+anterior part of head, in that the last joint of the antennæ is more
+slender, and the antennæ are only two-thirds as long as the head. The
+abdominal segments 4 to 7 show an acute process at the sides. Length,
+1.5 to 1.75 millimeters.
+
+Taken from rats in Abyssinia.
+
+
+ MITES—ACARINA.
+
+The mites (order Acarina, class Arachnida) are readily known from the
+insects (fleas and lice) by having four pairs of legs, no antennæ, and
+the abdomen does not show any segmentation, nor is there usually any
+distinction between head and thorax. In some groups there is a small
+head-like part, called the capitulum. The mouth parts consist of a pair
+of mandibles (often styliform or needle-like), a lip, and a pair of
+palpi. In some forms there is a central piece, called the hypopharynx,
+and in other groups is a plate above the mouth parts, known as the
+epistome. The body usually shows more or less distinctly a division into
+two parts—the anterior, called the cephalothorax, and the posterior the
+abdomen. However, in many mites it is not possible to separate these
+parts, except that it is considered that the legs are borne by the
+cephalothorax. In many forms there is a small, simple eye each side on
+the cephalothorax, but many other forms are blind. Some species have a
+tracheal system, which opens in a pair of spiracles near the hind legs
+or near the anterior end of the body; other species have no definite
+respiratory system. The genital aperture is on the venter, usually
+between the legs. The legs consist of the usual joints—coxa, trochanter,
+femur, tibia, sometimes a metatarsus, and a tarsus. The tarsus
+terminates in a pair of claws, sometimes three or only one, and often a
+sucker or caroncle. Most mites are not parasitic; those species that are
+parasitic are often free in one stage. The parasitic mites suck the
+blood of their host, feed on the hair or dermal scales, or burrow in the
+skin. Some predaceous species inhabit animals to hunt and eat the
+parasitic mites that infest that animal.
+
+The mites that occur parasitically on rats belong to four families:
+Sarcoptidæ, Cheyletidæ, Ixodidæ, and Gamasidæ.
+
+ 1. A distinct spiracle or breathing pore on each side
+ of body near coxæ III or IV 2
+
+ No such spiracle or pore visible 3
+
+ 2. A small, distinct head part in front of the body;
+ palpi three jointed; a granulate area around the
+ spiracle; no sternal plate _Ixodidæ_.
+
+ No such head part; palpi five jointed; no granulate
+ space around spiracle, but a long, chitinized
+ piece reaching forward from it; a more or less
+ distinct sternal plate _Gamasidæ_.
+
+ 3. All legs simple, unmodified, ending in a stalked
+ sucker _Sarcoptidæ_.
+
+ Front legs short, enlarged, and modified for
+ clasping; all legs end in one or two stout claws _Cheyletidæ_.
+
+
+ IXODIDÆ.
+
+The Ixodidæ, or ticks, are rather large, flat, leathery-skinned mites,
+which suck the blood of various animals. In the male the dorsum of the
+body is nearly covered by a corneous shield, while in the female this
+shield occupies only the anterior part of the body. In the female the
+body swells to enormous proportions as she engorges herself on the blood
+of the host. At the posterior margin of the body there are in many forms
+a series of lobes or festoons. There is no species of tick that is
+commonly found on rats, but four species that normally infest other
+animals have been taken from them.
+
+[Illustration:
+
+ FIG. 8.—Mite (_Lælaps echidninus_).
+]
+
+ 1. On the venter is a groove in front of the anus and
+ extending back each side; no festoons to _Ixodes
+ posterior margin of body; palpi rather long ricinus_.
+
+ On the venter there is no groove in front of the
+ anus, but usually one behind; festoons distinct
+ in males and unengorged females 2
+
+ 2. Palpi very short with transverse ridges; shield of
+ female narrowed behind eyes; stigmal plate nearly _Margaropus
+ round annulatus_.
+
+ Palpi short, without transverse ridges; shield of
+ female not narrowed behind eyes; stigmal plate _Rhipicephalus
+ comma shaped sanguineus_.
+
+ Palpi elongate, without ridges; shield of female _Hyalomma
+ broad; stigmal plate oval, aegypticum_.
+
+_Ixodes ricinus_ Linné.
+
+The shield of the female is elliptical, plainly longer than broad, sides
+not suddenly narrowed behind, and there is no eye-spot at each lateral
+corner. The coxa I has a long sharp spine.
+
+This is a common European tick found on sheep, cattle, dogs, etc., and
+it has been taken a few times in this country. Neumann has recorded its
+capture from _Mus decumans_.
+
+_Margaropus annulatus_ Say.
+
+The shield is plainly longer than broad, with a distinct eye-spot at
+each lateral corner, and behind the eye the shield is suddenly narrowed;
+the coxæ of the female are without spines, but the male has 2 on coxæ I.
+This is the common cattle tick of the United States, and disseminates
+the Texas fever. Mr. Hunter has taken it once from a rat in a barn at
+Dallas, Tex.
+
+_Rhipicephalus sanguineus_ Latreille.
+
+The shield of the female is oval, and longer than broad, with an
+eye-spot at each outer corner. Coxa I with 2 teeth; a smaller tooth on
+each of the other coxæ. Stigmal plate long, comma shaped. In the male
+there is a corneous plate each side of the anus, and on middle of
+posterior margin a projection, or short tail.
+
+This species is common in tropical countries, and Nuttall has recorded
+specimens from the black rat in India.
+
+_Hyalomma aegypticum_ Linné.
+
+The shield of the female is as broad as long, and the eye-spot is
+slightly above each outer corner. Coxa I has 2 large teeth, and a small
+tooth on each of the other coxæ. In the male there are 2 corneous plates
+each side of anus, and behind is a pair of small tubercles.
+
+This is a common tick in the warmer parts of the Old World; and Nuttall
+has recorded young specimens on the black rat.
+
+
+ GAMASIDÆ.
+
+The Gamasid mites, although much smaller than the ticks, are large
+enough to be seen by the naked eye. They are active, and most are not
+parasitic, at least for part of their time. The palpi are simple, of 5
+joints; the mandibles are elongate, retractile, and usually chelate at
+tip. There are no eyes. The dorsum and often the venter shows one or
+more corneous shields or plates, frequently a number of them; one or two
+on the dorsum, and on the venter one between the coxæ, called the
+sternal plate; one behind this, the genital plate; one behind the
+latter, the ventral plate; and one surrounding the anus, the anal plate.
+Frequently some of these are absent or united to one of the others.
+
+The legs are slender, usually of 6 joints, with a long tarsus that
+terminates in 2 claws, and often a sucker, or caroncle. The stigmata, or
+spiracles, are lateral above and between coxæ II and IV, and usually
+provided with a slender peritreme reaching forward toward the head.
+Nearly all the Gamasidæ deposit eggs, and the young often differ
+considerably from the adult in structure. There are two, and perhaps
+sometimes three, nymphal stages. In one of these nymphal stages the mite
+is apt to attach itself to an insect for the purpose of being carried to
+a similar locality, where it may feed and mature. The coprophagous and
+xylophagous insects are especially concerned in the diffusion of these
+mites.
+
+There are, however, quite a number of species that are genuine parasites
+of insects and other animals. Those occurring on rats belong to two
+genera, Myonyssus and Lælaps. They can be separated as follows:
+
+ 1. Anal plate small, much smaller than the ventral
+ plate _Lælaps_.
+
+ Anal plate large, larger than the ventral plate _Myonyssus_.
+
+_Myonyssus._—This genus is made by Tiraboschi for one species:
+_Myonyssus decumani_ Tiraboschi.
+
+Body oval; legs short and stout, all tarsi with a large caroncle with
+two short claws; coxæ II have a large tooth on the anterior border, none
+of coxæ with spines; sternal plate much broader than long, with three
+bristles each side; ventro-genital plate much longer than broad,
+broadest behind, bordered with bristles; anal plate very large, nearly
+one and a half times as broad as long; three large spines each side on
+venter. Length, 0.95 millimeter.
+
+Found in Italy on _Mus decumans_.
+
+_Lælaps._—This genus embraces a large number of species, several of
+which occur on small animals, such as the muskrat, ground hog, and
+chipmunk. Three have been recorded from rats, one of these from
+California. The dorsal plate is covered with hairs or bristles, and
+there are usually stout bristles on the margins of the plates on the
+venter. There is also a bristle, or a spine, at the tip of the anal
+plate. The legs are short and stout, with a distinct caroncle, and two
+claws.
+
+ 1. Dorsum with numerous fine hairs; no stout spines on
+ coxæ _L. stabularis_.
+
+ Dorsum with fewer, but stouter spine-like bristles;
+ each coxa has a stout spine 2
+
+ 2. Body but little longer than broad; ventral plate
+ longer than broad _L. agilis_.
+
+ Body much longer than broad; ventral plate about as
+ broad as long _L. echidninus_.
+
+_Lælaps echidninus_ Berlese.
+
+Dorsum of body almost wholly covered with a shield, with rows (six in
+front, eight behind) of stout, curved bristles, a longer pair near front
+margin, and some around lateral and posterior margins. Legs short and
+stout, tarsi about twice as long as preceding joint; each coxa bears a
+stout spine near middle. Palpi very short; sternum with three stout
+bristles or spines each side; ventral plate with four stout bristles
+each side; anal plate with a stout apical bristle, and a small one each
+side. Length, 1 millimeter.
+
+Occurs commonly on rats in warm countries, and known from California. It
+may possibly aid in the transmission of disease.
+
+_Lælaps agilis_ Koch.
+
+Similar in many respects to _L. echidninus_ but differ in the shorter
+and proportionately broader body, barely longer than broad, and in the
+weaker and shorter spines on dorsum and on the ventral plates; there are
+also some small short spines on the general surface of the venter.
+Length, 0.7 millimeter.
+
+Recorded from rats from Europe and Africa.
+
+_Lælaps stabularis_ Koch.
+
+The body is of the same general shape as in _L. echidninus_, but the
+dorsum is clothed with 12 to 18 rows of fine short hairs. The first pair
+of legs is more slender than in the other species, and the hind legs are
+also more elongate; the coxæ do not have the stout spines seen in the
+other species, and the bristles on the sternal and ventral plates are
+much less stout; the general surface of the venter has many hairs, the
+anal plate has a short apical bristle. Length, 1.2 millimeters.
+
+Taken on the brown rat in Italy; also found in manure.
+
+
+ CHEYLETIDÆ.
+
+This family consists of small, soft-bodied mites, that are parasitic or
+predaceous in habits. The palpi are small, three or four jointed; the
+mandibles are styliform and retractile; and the breathing spiracles open
+near the mouth parts. The species that occur on rats belong to the genus
+_Myobia_.
+
+_Myobia._—The body is elongate, fully twice as long as broad, tipped by
+a pair of long, stout bristles. The first pair of legs is enlarged and
+shortened, with a terminal hook to grasp hairs; the other legs are
+short, simple, and far apart. The palpi and mouth parts are very small,
+and the dorsum bears stout bristles. They are supposed to feed on the
+exudations of the skin, but it would seem more probable, from the nature
+of the mandibles, that they pierced the skin to secure food. All are
+very small, not one-half a millimeter long. Of the several species two
+have been recorded from rats.
+
+ 1. Dorsum of female with spines all acute and sharp _M. musculi_.
+
+ Dorsum of female with some of the posterior spines
+ flattened and rather scale like _M. ensifera_.
+
+_Myobia musculi_ Schrank.
+
+This occurs on various mice and moles, and once recorded from the brown
+rat. It has been taken in this country on mice. It lives at the base of
+the hairs.
+
+_Myobia ensifera_ Poppe.
+
+This was described from the brown rat in Europe. The female is separated
+from _M. musculi_ by having about six of the posterior dorsal spines
+flattened and scale like; in the male the six dorsal spines are longer,
+and the small spines much smaller than in _M. musculi_.
+
+
+ SARCOPTIDÆ.
+
+These are the itch and scab mites. The body is soft, rounded, and
+whitish in color. The legs are very short, of five joints, and end in
+one or two claws, and often a pediceled sucker. The palpi are small and
+short, of three joints, but the basal is usually united to the rostrum.
+There are no spiracles, and respiration is therefore through the general
+surface of the skin. The sexes are often quite different in structure.
+The females usually deposit eggs, the larvæ are hexopod, and there are
+two nymphal stages. They are all parasites, mostly on mammals and birds,
+and often burrow in the skin, causing mange, or scabies.
+
+Only one species has been taken on rats; this belongs to the genus
+_Notoedres_.
+
+_Notoedres._—In this genus the third pair of legs of the male and the
+third and fourth of the female have no sucker at the tip. The anal
+opening is on the posterior part of the dorsum. The three known species
+are parasitic on mammals—one on the cat, one on the rabbit, and the
+third on rats.
+
+_Notoedres muris_ Mègnin.
+
+This is a rounded mite, with finely striate skin, a small triangular
+rostrum; in front the four anterior legs project a little beyond the
+body, and each ends in a long pedicellate sucker; the third and fourth
+pairs of legs are not visible from above, and each ends in a long
+bristle. There are a few short hairs around the anal aperture and about
+ten others in front of these. The species measures about 0.3 to 0.4
+millimeter long.
+
+It usually occurs about the ears and the genital organs of the host, and
+has been taken from both the brown and black rat in Europe. The
+_Sarcoptes alepis_ Railliet and Lucet is the same species.
+
+
+ DEMODECIDÆ.
+
+Besides the mites above described, a form of _Demodex_ has been recorded
+from rats, but the species is not given. These mites are very tiny, with
+elongate body, the posterior part annulate, the front part with eight
+very short legs. They inhabit the hair follicles of various mammals.
+That on the rat may have been only an accidental occurrence of some
+species normally on another animal.
+
+
+
+
+THE INTERNAL PARASITES OF RATS AND MICE IN THEIR RELATION TO DISEASES OF
+ MAN.
+
+ By CH. WARDELL STILES, _Chief_, and CHARLES G. CRANE, B. S., _Assistant,
+ Division of Zoology, Hygienic Laboratory, United States Public Health
+ and Marine-Hospital Service_.
+
+
+ SUMMARY.
+
+
+ Rats and mice may harbor 11 species of internal parasites which come
+ into consideration as possible or established parasites of man. From
+ this point of view, 7 of the parasites are of more academic interest
+ than practical importance. The rat may, however, be viewed as the
+ practical, theoretical, and permanent reservoir for one zooparasitic
+ disease (trichinosis) of considerable importance, and of at least one,
+ perhaps two, other zooparasitic infections (“_Lamblia duodenalis_” and
+ _Hymenolepis diminuta_) of much less importance. Its possible future
+ rôle in connection with sleeping sickness should not be entirely
+ ignored.
+
+ From the standpoint of internal zooparasitism, therefore, the present
+ public health interest in rats and mice centers in trichinosis. This
+ disease will probably never be eradicated from man until rats and mice
+ are practically eradicated, and any rational public health campaign
+ directed against trichinosis must take the rat into serious
+ consideration.
+
+ The eradication of rats and mice would be a very substantial
+ contribution toward a reduction and eradication of trichinosis.
+
+
+ INTRODUCTION.
+
+From the habits of rats, it is to be expected that they harbor many
+species of parasites, and on account of their presence in our houses the
+question naturally arises as to whether any of these parasites are
+transmissible, either directly or indirectly, to man.
+
+The species of internal parasites which come especially into
+consideration in this connection are the following:
+
+
+ PROTOZOA: _Chlamydophrys enchelys_ (p. 88), _Lamblia duodenalis_ (p.
+ 89), _Trypanosoma gambiense_ (p. 94).
+
+ TREMATODA: None.
+
+ CESTODA: _Cysticercus cellulosæ_ (p. 95), _C. fasciolaris_ (p. 96),
+ _C. pisiformis_ (p. 95), _H. murina_ Duj. [= _fraterna_] (p. 96),
+ _Hymenolepis diminuta_ (p. 98).
+
+ NEMATODA: _Trichinella spiralis_ (p. 101).
+
+ ACANTHOCEPHALA: _Gigantorhynchus moniliformis_ (p. 108).
+
+ ARACHNOIDEA: _Linguatula denticulata_ (p. 110).
+
+
+Of these 11 species, the trichina worm (sometimes called the flesh worm)
+exceeds all the others combined, both in frequency and importance, as a
+cause of disease in man.
+
+
+ PROTOZOA.
+
+
+ Genus CHLAMYDOPHRYS[U] Cienkowski, 1876.
+
+Footnote U:
+
+ SYNONYM.—_Leydenia_ Schaudinn, 1896.
+
+
+ Species CHLAMYDOPHRYS ENCHELYS[V] (Ehrenberg.)
+
+Footnote V:
+
+ SYNONYMS.—_Difflugia enchelys_ Ehrenberg; _Chlamydophrys stercorea_
+ Cienkowski; _Leydenia gemmipara_ Schaudinn, 1896; _Chl. enchelys_
+ (Ehrenberg) Braun.
+
+A very peculiar organism has been described under the name of _Leydenia
+gemmipara_ Schaudinn, 1896. This was found in fluid, obtained by
+puncture, from two ascites patients in Berlin, Germany. More recently
+Schaudinn has concluded that _Leydenia gemmipara_ represents an abnormal
+condition of a protozoon known as _Chlamydophrys_. The latter passes
+through the intestinal tract of various animals (as man, mice,
+squirrels, rabbits, cattle), and thus is occasionally found in fresh
+human stools. According to Schaudinn, if pathological conditions in the
+colon cause an alkaline reaction of its entire content, the usual shell
+formation in _Chlamydophrys_ fails to take place, the organisms then
+multiply in an atypical manner by division and budding, and the result
+is the structure described as _Leydenia gemmipara_.
+
+
+ Genus LAMBLIA[W] R. Blanchard, 1888.
+
+Footnote W:
+
+ SYNONYMS.—_Dimorphus_ Grassi, 1879 (not Haller, 1878, arachnoid);
+ _Megastoma_ Grassi, 1881 (not de Blainville, mollusk; not Swains.,
+ 1837, bird; not Costa, 1850, fish; not Megerle, mollusk); “_Dimorpha_
+ Grassi” of Senn, 1901 (not _Dimorpha_ Jur., 1807, hymenopteron; not
+ Gray, 1840, mollusk; not Hodgs., 1841, bird); _Megastroma_
+ Schneidemuehl, 1898, misprint.
+
+
+ GENERIC DIAGNOSIS.—_Polymastigidæ_: Body bilaterally symmetrical,
+ pyriform, excavate antero-ventrally to form a sucker; flagella
+ directed posteriorly; 3 pairs inserted on margin of the sucker, 1 pair
+ at posterior end of body. Parasitic in intestine of mammals.
+
+ TYPE SPECIES.—_Lamblia duodenalis_ s. l. (“_L. intestinalis_” of man).
+
+
+Flagellate protozoa belonging to this genus are reported as parasitic in
+the intestinal canal of various species of mammals. At present the forms
+in question are usually looked upon as belonging to the species _L.
+duodenalis_. Evidence is, however, accumulating (p. 92) to the effect
+that there are at least three distinct species of _Lamblia_ (“_L.
+intestinalis_” of man, _L. muris_ of mice, and _L. cuniculi_ (or
+_duodenalis_?) of rabbits). Admitting that there may be three species,
+the intertransmissibility of these forms from one host to another
+remains to be investigated to some extent. It seems thus far definitely
+proved that the form which occurs in man is transmissible to mice,
+rabbits, and guinea pigs, hence mice still remain a source of danger in
+respect to the infection in man. To exactly what extent this fact is of
+academic interest or of practical significance is at present _sub
+judice_.
+
+
+ Species LAMBLIA DUODENALIS[X] (Davaine, 1875) Stiles, 1902, s. l.
+
+Footnote X:
+
+ SYNONYMS.—_Cercomonas intestinalis_ Lambl, 1859, in man (not _Bodo_
+ (_Cercomonas_) _intestinalis_ (Ehrenberg, 1838) Diesing, 1850, in
+ frogs; not _Cercomonas intestinalis_ (Ehrenberg, 1838) Perty, 1852);
+ _Hexamita duodenalis_ Davaine, 1875, in rabbits; _Dimorphus muris_
+ Grassi, 1879, in _Mus_; _Megastoma entericum_ Grassi, 1881 (=
+ _Dimorphus muris_ renamed); _Megastoma intestinale_ (Lambl, 1859) R.
+ Blanchard, 1885; _Lamblia intestinalis_ (Lambl, 1859) R. Blanchard,
+ 1888; “_Megastoma intestinalis_” of Leclerq, 1890; “_Cercomonas
+ intistinalis_ Lambl” of L. Pfeiffer; “_Megastroma entericum_ Grassi,
+ 1881” of Schneidemuehl, 1898; “_Dimorpha muris_ Grassi” of Senn, 1900.
+
+ [Figs. 9 to 15.]
+
+
+ SPECIFIC DIAGNOSIS.—_Lamblia_ (p. 88): Body pyriform, 5 to 16μ (21μ
+ Lambl) long, 4 to 12.5μ (8.6 to 11μ Lambl) broad; flagella 9 to 14μ
+ long; anterior end bluntly rounded, posterior end sharply pointed,
+ dorsum convex, antero-ventrally concave, venter flat to convex;
+ antero-ventral concavity forms a sucker, the margins of which project
+ from the surface and are contractile. Four pairs of ventral
+ posteriorly directed flagella, arranged as follows: 1 pair insert on
+ anterior margin of sucker; 2 pairs on posterior margin of sucker, near
+ median line; 1 pair on posterior extremity. Body membrane (“cuticula”)
+ very delicate, permitting some change of body form; protoplasm finely
+ granular; nucleus dumb-bell shaped, pre-equatorial. Vacuoles not
+ observed. Copulation sucker-to-sucker, followed by an encystation, in
+ which stage complicated nuclear changes occur; cysts 10 by 7μ.
+
+ HABITAT.—Upper portion of small intestine of man (_Homo_); also of the
+ common house mouse (_Mus musculus_), the brown rat (_M. decumanus_),
+ the black rat (_M. rattus_), “_Mus sylvestris_” [=? _M. decumanus_],
+ field mouse (_Microtus arvalis_), water mole (_Arvicola amphibius_),
+ rabbits, guinea pigs, domesticated cats, dogs, and sheep.
+
+ GEOGRAPHICAL DISTRIBUTION.—Europe, Egypt, and United States.
+
+
+This parasite is very common in animals in certain parts of Europe, and
+cases of its presence in man have been reported by a number of authors
+(Lambl, 1859; Grassi, 1881; Perroncito, 1888; Moritz, 1891; Moritz &
+Holzl, 1892; Roos, 1893; Kruse & Pasquale, 1894; Piccardi, 1895;
+Sievers; Mueller; Frshezjesski & Ucke; Stiles, 1902; Braun, 1908; etc.).
+The indications are that it is more common in man than is generally
+assumed.
+
+Possibly man becomes infected through eating food (as bread, etc.) which
+has been soiled by the excrements (containing the encysted stage) of
+mice and rats. Grassi infected himself, Perroncito infected mice and
+rabbits, and Stiles infected guinea pigs by feeding to them human feces
+containing the encysted stage.
+
+The parasite may be present in large numbers. Moritz estimated a
+discharge of 18 milliards within twenty-four hours from one of his
+patients. It has been observed in healthy persons and also in cases of
+various diseases, but especially in children and in cases of
+tuberculosis. It is an inhabitant chiefly of the duodenum and jejunum,
+where it attaches itself (fig. 13) by means of the sucker to the
+epithelial cells. It is rarer in the ileum. In case the stomach is
+alkaline (carcinoma) the parasite may occur in this organ (Cohnheim,
+Zabel). In P. Schmidt’s case the hydrochloric acid was 1 per cent. In
+case the intestinal peristalsis is normal the parasite becomes encysted
+in the colon, so that usually only the encysted stage is found in the
+feces; but in case of increased peristalsis and diarrhea the organisms
+have not time to encyst, so that the free stages are observed in the
+stools. As the parasites become cool motion decreases; when raised to
+high temperature, as 50° C., motion becomes slow, and the organisms die
+at 52° C. or below 0° C.
+
+[Illustration:
+
+ FIG. 9.—Lateral view of encysted _Lamblia duodenalis_.
+
+ FIG. 10.—Cyst from large intestine.
+
+ FIG. 11.—Ventral view of _Lamblia_.
+
+ FIG. 12.—Lateral view.
+
+ FIG. 13.—Epithelial cells of the villous coating of the small
+ intestine infested with _Lamblia_. (After
+ Grassi & Schewiakoff, 1888, pl. 15, figs. 1, 2, 5, 11, 12.)
+]
+
+[Illustration:
+
+ FIG. 14.—An epithelial cell with parasitic _Lamblia_. Greatly
+ enlarged. (After Grassi & Schewiakoff, 1888, pl. 15, fig. 6.)
+]
+
+[Illustration:
+
+ FIG. 15.—An individual in the act of joining an epithelial cell.
+ (After Grassi & Schewiakoff, 1888, pl. 15, fig. 7.)
+]
+
+PATHOGENICITY.—Opinion differs as to the pathogenicity of this organism.
+Perroncito (1902b) reports it as causing a fatal disease in rabbits.
+Braun (1908) is inclined to consider it harmless. From conversation with
+Doctor Hemmeter, we are persuaded that in his case in a child in
+Baltimore the parasite was not without effect. Possibly the question as
+to its pathogenicity is a relative one in that light infections may
+produce no recognizable disturbance, while heavy infections may produce
+recognizable effects. Doctor Hemmeter’s original letter regarding his
+case contained the following notes:
+
+
+ Patient, male, white child, 3 years old, born in Maryland. Had
+ recurrent attacks of colitis all its life; three acute attacks within
+ the last three weeks, accompanied by fever, distended abdomen,
+ sensitive, etc. Stools have always been like putty, containing large
+ amount of mucus, and some blood streaks; fever lasting three days, no
+ pronounced diarrhea, 2 to 3 passages per day; intervals between
+ attacks variable, stools at such times like putty, also with mucus.
+
+
+Later information from Doctor Hemmeter states that the disappearance of
+the parasites from the stools coincided with improvement in the child’s
+condition.
+
+CLINICAL DIAGNOSIS.—The fresh unstained stools should be examined
+microscopically; or the diluted stool may be stained with methylene
+blue, by which nearly all objects become promptly stained, except
+_Lamblia_, which remains grayish white (Roos, 1893) for several hours.
+
+TREATMENT.—Attempts to expel _Lamblia_ have not always met with marked
+success. Among the drugs used are male fern, sulphate of quinine,
+naphthol, calomel, hydrochloric acid, and arsenic. Grassi appears to
+have had success with calcined magnesia.
+
+[Illustration:
+
+ FIG. 16.—“_Lamblia intestinalis_” of man. (After Bensen, 1908, fig.
+ 5.)
+]
+
+[Illustration:
+
+ FIG. 17.—Copulation cyst of “_Lamblia intestinalis_” of man. (After
+ Bensen, 1908, fig. 5.)
+]
+
+THE DIVISION OF _Lamblia duodenalis_ INTO SEPARATE SPECIES.—Bensen
+(1908) has recently divided _Lamblia duodenalis_ s. l. into three
+species: _L. “intestinalis,”_ _L. muris_, and _L. cuniculi_. His
+preliminary paper seems to offer fairly convincing data for the
+correctness of his interpretation, but it may be well to await the
+publication of his more complete paper, in which he promises fuller
+details, before the species are definitely accepted. Several
+nomenclatural points will come up for consideration in this connection.
+
+_Lamblia intestinalis_, which Bensen accepts as name for the species
+(fig. 16) occurring in man, can not be accepted, as this name is based
+on _Cercomonas intestinalis_ Lambl, 1859, which is invalidated by
+_Cercomonas intestinalis_ (Ehrenberg, 1838) Perty, 1852, found in frogs.
+
+_Lamblia muris_ (fig. 18) will probably stand, based on _Dimorphus
+muris_ Grassi, 1879.
+
+_Lamblia cuniculi._—There is some doubt as to the status of this name.
+Davaine (1875a, 128–129) has described from rabbits a protozoon, which
+he designated as _Hexamita duodenalis_ and which Railliet (1893a, 169)
+identifies as a synonym of _Lamblia intestinalis_ (Lambl). On basis of
+the principle that identifications are to be accepted as correct until
+shown to be incorrect, Stiles has accepted _duodenalis_ as name (1902)
+for the form in question. The question now arises as to the relation of
+_cuniculi_ to _duodenalis_. If they are accepted as identical,
+_duodenalis_ will supplant _cuniculi_, and a new name must be given to
+the form found in man. If _duodenalis_ is taken as identical with
+_intestinalis_ Lambl, _duodenalis_ remains as name for the form in man,
+and _cuniculi_ Bensen will stand for the species in rabbits. If
+Railliet’s interpretation of synonymy be shown to be incorrect by
+proving that _duodenalis_ Davaine is not to be considered in connection
+with either form, a new name must be given to _intestinalis_ Lambl.
+
+[Illustration:
+
+ FIG. 18.—_Lamblia muris_ of mice. (After Bensen, 1908, fig. 1.)
+]
+
+[Illustration:
+
+ FIG. 19.—Autogametocyte of _Lamblia muris_. (After Bensen, 1908, fig.
+ 6.)
+]
+
+
+ Genus TRYPANOSOMA s. l.
+
+An extensive group of parasitic protozoa, known as “trypanosomes,” has
+recently been the basis of considerable literature. The genus
+_Trypanosoma_ was originally based upon a species (_T. rotatorium_)
+found in frogs, and while most trypanosomes have been described as
+members of this genus several authors have separated out certain forms
+into separate genera.
+
+Luehe (1906) has recently placed the trypanosomes of mammals in the
+
+
+ Genus TRYPANOZOON Luehe, 1906.
+
+One of these species (_Trypanozoon gambiense_, usually known as
+_Trypanosoma gambiense_) is the cause of “sleeping sickness” in man, and
+has been transmitted in laboratory experiments to rats and mice.
+
+[Illustration:
+
+ FIG. 20.—An isolated pork-measle bladder worm (_Cysticercus
+ cellulosæ_), with extended head. Greatly enlarged. (After Stiles,
+ 1898a, 90, fig. 76.)
+]
+
+Just what practical importance there may be in the ability of the
+parasite to live in rats and mice remains to be seen, but theoretically
+this biological factor may possibly become one of considerable
+magnitude. At present the least conclusion to be drawn is that it adds
+one more to the many arguments in favor of a world-wide destruction of
+rats and mice.
+
+Several trypanosomes, other than _Trypanozoon gambiense_, are
+transmissible by experiment to rats and mice, while one species
+(_Trypanozoon lewisi_) has rats for its normal host, and two other
+species (_Trypanozoon duttoni_ and _Trypanosoma musculi_ Kendall, 1896)
+are reported originally from the mouse.
+
+
+ CESTODA—TAPEWORMS.
+
+Of the five cestodes mentioned as coming into consideration in the
+subject under discussion, only one (_Hymenolepis diminuta_) need be
+considered seriously.
+
+
+ CYSTICERCUS CELLULOSÆ—TÆNIA SOLIUM.
+
+ [Fig. 20.]
+
+The larval cestode known as _Cysticercus cellulosæ_ (which causes
+“measles” in swine) develops (when eaten by man) into a tapeworm which
+is known as _Tænia solium_. This larva is also reported as encysted in
+the peritoneum of _Mus rattus_.
+
+[Illustration:
+
+ FIG. 21.—Portion of mesentery of rabbit infected with _Cysticercus
+ pisiformis_. Natural size. (After Railliet, 1893a, 216, fig. 114.)
+]
+
+Even if it be granted that the specific determination of the specimen in
+question as _Cysticercus cellulosæ_ is correct, the occasional infection
+of rats with this parasite would be of very little practical
+significance in this country from a public health point of view, as we
+do not use rats for food for man. Theoretically it is possible to
+conceive of combinations of circumstances in which such infection in the
+rat might under certain conditions eventually affect man, but the
+chances are so remote as to be negligible, especially when compared with
+the much greater questions which demand attention.
+
+
+ CYSTICERCUS PISIFORMIS—TÆNIA PISIFORMIS.
+
+ [Fig. 21.]
+
+The larval stage of this parasite occurs in rabbits, the adult stage in
+canines. Parona (1901) reports the occurrence of the larval stage in
+_Mus brasiliensis_, and Vital has recorded the presence of the adult
+stage in man.
+
+In view of the fact that Galli-Valerio was unable to infect himself
+experimentally with this species, the specific determination made by
+Vital is open to some question. Even assuming that this tapeworm may
+develop in man, the presence of the larval stage in rats is of such
+little importance as to be negligible.
+
+
+ CYSTICERCUS FASCIOLARIS—TÆNIA TENIÆFORMIS.
+
+ [Fig. 22.]
+
+This encysted larval tapeworm is exceedingly common in the liver of rats
+and mice, and when swallowed by cats it develops into an adult tapeworm.
+
+[Illustration:
+
+ FIG. 22.—Larval stage of _Tænia teniæformis_. Natural size. (After
+ Leuckart, 1880, 450, fig. 202.)
+]
+
+There are two possible points of view in connection with which this
+parasite is of indirect interest in public health matters: (1)
+Occasionally these encysted parasites are mistaken for lesions of
+tuberculosis; (2) Krabbe (1880) relates that in Jutland there exists a
+folk custom of eating chopped raw mice in case of retention of urine,
+and in this connection the point has been raised that the possibility is
+not excluded that such action might eventually give rise to infection of
+man by the parasite in question. No case of such infection in man is as
+yet established.
+
+
+ HYMENOLEPIS MURINA[Y] (Dujardin, 1845) = HYMENOLEPIS NANA FRATERNA[Y]
+ Stiles, 1906.
+
+Footnote Y:
+
+ SYNONYM.—_Tænia murina_ Dujardin, 1845 (not Gmelin, 1790).
+
+ [Figs. 23 and 24.]
+
+Under the name _Tænia murina_, Dujardin (1845) described for rats a
+tapeworm which has been identified by a number of authors (including
+Stiles) as identical with the dwarf tapeworm (_Hymenolepis nana_) of
+man. If this identification be correct, the rats must be considered as
+the great disseminators of this tapeworm. Serious doubts have been
+raised, however, as to whether the tapeworm in man is not in reality
+distinct from that of the rat, and the evidence in favor of such
+conclusion is accumulating. Some slight differences between the two
+forms have been noticed, but by some authors these differences have been
+considered insufficient to hold the two worms apart. Looss has tried to
+infect rats with the dwarf tapeworm found in man in Egypt, but his
+results have been negative. Here in Washington Stiles has repeatedly
+attempted to infect rats with the dwarf tapeworm found in man in the
+United States, but thus far no positive infection has occurred in the
+rodents. In Italy, Grassi attempted to transmit the rat form to six
+persons, and in one case he found tapeworms, but in view of the
+frequency of _H. nana_ in Italy the significance of this one instance
+has been questioned; Grassi was not successful in trying to infect rats
+with _H. nana_ of man.
+
+[Illustration:
+
+ FIG. 23.—Longitudinal section of the intestinal villus of a rat,
+ containing cystic stage of dwarf tapeworm. Enlarged. (After Grassi &
+ Rovelli, 1892a, pl. 3, fig. 25.)
+]
+
+[Illustration:
+
+ FIG. 24.—Adult dwarf tapeworm (_Hymenolepis nana_) of man. Enlarged.
+ (After Leuckart, 1863, p. 393, fig. 112.)
+]
+
+Thus at present the evidence is to the effect that rats and mice are not
+to be viewed as the source or reservoir for the dwarf tapeworm (_H.
+nana_) of man.
+
+
+ HYMENOLEPIS DIMINUTA[Z] (Rudolphi, 1819) R. Blanchard, 1891.
+
+Footnote Z:
+
+ SYNONYMS.—_Tænia diminuta_ Rudolphi, 1819; _T. leptocephala_ Creplin,
+ 1825; _Hymenolepis flavopunctata_ Weinland, 1858; _Tænia (Hymenolepis)
+ flavopunctata_ Weinland, 1859; _H. (Lepidotrias) flavopunctata_
+ Weinland, 1861; _T. flavomaculata_ Leuckart, 1863; _T. “flavopuncta”_
+ Cobbold, 1864 (misprint); _T. “flaviopunctata”_ Vogt, 1878 (misprint);
+ _T. “flavopunktata”_ Stein, 1882; _T. varesina_ E. Parona, 1884; _T.
+ minima_ Grassi, 1886; _T. “septocephala”_ Perroncito and Airoldi, 1888
+ (misprint); _Hymenolepis diminuta_ (Rudolphi, 1819) Blanchard, 1891;
+ _“Hymenolepsis” flavopunctata_ of Osler, 1895, and other authors
+ (misprint); _T. “varerina”_ Huber, 1896 (misprint for _T. varesina_);
+ _T. “flavapunctata”_ Simon, 1896 (misprint); _T. “leptocefala”_
+ Previtera, 1900; _T. “ceptocephala”_ Lussana and Romaro [? date]
+ (misprint); _Tenia flavopunctata_ (Weinland, 1858) Packard, 1900.
+
+ [Figs. 25 to 30.]
+
+[Illustration:
+
+ FIG. 25.—Strobila of _Hymenolepis diminuta_. Natural size. (After
+ Grassi, 1881, pl. 11, fig. 1.)
+]
+
+[Illustration:
+
+ FIG. 26.—Head and anterior portion of _H. diminuta_ from the rat.
+ Enlarged. (After Zschokke, 1889, pl. 1, fig. 21.)
+]
+
+
+ SPECIFIC DIAGNOSIS.—_Hymenolepis_: Strobila 10 to 60 millimeters in
+ length, 2.5 to 4 millimeters in maximum breadth; composed of 800 to
+ 1,300 segments. Head small, almost globular; 200 to 600μ in width;
+ rostellum rudimentary, pyriform, only slightly protractile; hooks
+ absent; suckers globular, near the apical portion of the head, 80 to
+ 160μ in diameter. Neck usually short. Segments throughout strobila
+ broader than long. Genital pores on left margin, near the junction of
+ the anterior and middle thirds of each segment. Three testes in each
+ segment; vas deferens dilates into a prominent seminal vesicle before
+ entering the cirrus pouch, within which also is a vesicle. Gravid
+ uterus occupies most of the proglottids; its cavity is subdivided into
+ a large number of incompletely separated compartments filled with
+ eggs. Eggs round or slightly oval; outer membrane 54 to 86μ in
+ diameter, yellowish in color, may be radially striated; inner membrane
+ 24 by 20μ to 40 by 35μ in diameter, with mammillate projection at each
+ pole often not apparent; between outer and inner membranes a prominent
+ third layer of albuminous substance, often appearing as two delicate
+ smooth membranes, with intervening space filled by a granular
+ coagulum; embryonal hooks 11 to 16μ in length.
+
+
+[Illustration:
+
+ FIG. 27.—Male and female organs of _H. diminuta_: _c. p._, cirrus
+ pouch; _g. p._, genital pore; _ov._, ovary; _rec. sem._,
+ receptaculum seminis; _s. g._, shell gland; _t._, testiculæ; _ut._,
+ uterus; _vag._, vagina; _v. def._, vas deferens; _v. ef._, vas
+ efferens; _ves. sem._, vesicula seminalis; _y. g._, yolk gland.
+ Enlarged. (After Zschokke, 1889, pl. 2, fig. 22.)
+]
+
+[Illustration:
+
+ FIG. 28.—Gravid segment of _H. diminuta_. Enlarged. (After Grassi,
+ 1881, pl. 11, fig. 15.)
+]
+
+[Illustration:
+
+ FIG. 29.—Egg of _H. diminuta_ from man. Greatly enlarged. (After
+ Bizzozero, 1889a, pl. 4, fig. g″.)
+]
+
+
+ HABITAT.—Adults in small intestine of brown or Norway rat (_Mus
+ decumanus_), black rat (_M. rattus_), house mouse (_M. musculus_),
+ Egyptian or roof rat (_M. rattus alexandrinus_), wood or field mouse
+ (_M. sylvaticus_), _Rhipidomys pyrrhorhinus_ [according to Linstow,
+ 1878a, 23], and man (_Homo sapiens_).
+
+ DEVELOPMENT.—The larval stage (_Cercocystis H. diminutæ_) occurs in
+ larval and adult meal moths (_Asopia farinalis_); in young and adult
+ earwigs (_Anisolabis annulipes_); and in adult beetles (_Acis spinosa_
+ and _Scaurus striatus_).
+
+ GEOGRAPHIC DISTRIBUTION.—Massachusetts, Pennsylvania, Nebraska, Iowa,
+ District of Columbia, Maryland, Brazil, Italy, Germany, France,
+ Austria.
+
+
+This parasite is certainly more common in man in this country than has
+heretofore been assumed, but fortunately it seems to be one of the most
+harmless and most easily expelled tapeworms occurring in man.
+
+[Illustration:
+
+ FIG. 30.—Encysted cystic stage of _H. diminuta_: _caud._, caudal
+ appendage; _cyst._, adventitious capsule inclosing the cercocystis.
+ Enlarged. (After Grassi & Rovelli, 1892a, pl. 4, fig. 1.)
+]
+
+From present evidence, the rats and mice are looked upon as the regular
+hosts for this worm, and hence as the natural reservoir of the
+infection. The intermediate host becomes infected from the rodents and
+then transmits the infection to man.
+
+It might be mentioned that as yet no extensive study has been conducted
+in the United States to differentiate clearly the various species of
+_Hymenolepis_ found in our rats and mice. The possibility is therefore
+not entirely excluded that some of our cases of _Hymenolepis diminuta_
+may eventually be shown to be referable to other species of the same
+genus.
+
+
+ NEMATODA—TRUE ROUND WORMS.
+
+
+ Family TRICHINELLIDÆ.[AA]
+
+Footnote AA:
+
+ SYNONYM.—_Trichotrachelidæ._ It becomes necessary under the
+ international code to change the family name; the family name
+ _Trichinellidæ_ is chosen as less likely to lead to confusion than a
+ family name based upon _Trichuris_.
+
+
+ FAMILY DIAGNOSIS.—_Nematoda_: Elongate cylindrical worms; cephalic
+ portion long and very slender, caudal portion more or less swollen.
+ Mouth rounded, without lips. Esophagus relatively very long, composed
+ of a single row of large cells, forming the so-called “cell body” and
+ supporting a narrow esophageal tube; anus terminal or nearly so.
+
+ Male: With a single spicule or without spicule.
+
+ Female: With one ovary; vulva near caudal end of cell body, close to
+ point where body increases in diameter; oviparous or viviparous.
+
+ Eggs: Oviparous species, with thick shell, with opening at each pole,
+ closed by a transparent plug.
+
+ TYPE GENUS.—_Trichinella_ Railliet, 1895.
+
+
+This family furnishes two parasites to man: The whipworm (_Trichuris
+trichiura_) of the colon, and the trichina or flesh worm (_Trichinella
+spiralis_, see p. 101).
+
+
+ Genus TRICHINELLA[AB] Railliet, 1895.
+
+Footnote AB:
+
+ SYNONYMS.—_Trichina_ Owen, 1835 [not Meig., 1830, insect.];
+ _Trichinus_ Fraser, 1881a, for _Trichina_.
+
+
+ GENERIC DIAGNOSIS.—_Trichinellidæ_: Very minute worms, of nearly
+ uniform diameter. Adults in intestine of mammals, larvæ encysted in
+ muscles.
+
+ Male: Without spicules, but with 2 conical appendages on the tail, at
+ side of terminal cloacal opening.
+
+ Female: Vulva about one-fifth the length from anterior end;
+ viviparous.
+
+ TYPE SPECIES.—_Trichinella spiralis_ (Owen, 1835) Railliet, 1895.
+
+
+ TRICHINELLA SPIRALIS (Owen, 1835) Railliet, 1895.
+
+ [Figs. 31 to 51.]
+
+
+ SPECIFIC DIAGNOSIS.—_Trichinella_: Body thread-like, visible to naked
+ eye.
+
+ Male: Length, 1.4 to 1.6 millimeters; diameter, 40μ; distal of cloacal
+ opening, 2 pairs of papillæ, the anterior pair hemispherical,
+ posterior pair conical.
+
+ Female: Length, 3 to 4 millimeters; diameter, 60μ; anus terminal;
+ vulva one-fifth of length of body from the mouth; viviparous.
+
+ HABITAT.—Adults in lumen and wall of small intestine, encysted larvæ
+ in muscles of various mammals, particularly in rats, mice, swine, and
+ man.
+
+ GEOGRAPHIC DISTRIBUTION.—More or less cosmopolitan.
+
+
+SOURCE OF INFECTION.—From the life cycle of this parasite it is clear
+that the permanent reservoir of infection must be some animal with
+cannibalistic tendencies. Of the three most important hosts (man, swine,
+and rats), the rats present ideal conditions in this respect. It is true
+that there are some tribes of man which are cannibalistic, but their
+distribution is restricted. Likewise swine are in so far cannibalistic
+that they eat uncooked swine offal and swill, but this is due to the
+shortsightedness of man rather than to the habits of the swine.
+Accordingly, neither man nor the hog presents the proper theoretical
+conditions for the perpetuation of the parasites and hence to serve as
+reservoir for the disease it causes.
+
+Rats, on the contrary, are cannibalistic, and trichinosis is a common
+disease among them. Hence they may be viewed as the natural reservoir
+for the parasites and for the disease it causes; hence, also, any
+well-directed public health campaign against trichinosis should consider
+the eradication of rats.
+
+Rats become infected by eating each other; by eating scraps of pork
+found on the offal pile of slaughterhouses, or in swill; and by eating
+scraps of human flesh in dissecting rooms of medical schools.
+
+[Illustration:
+
+ FIG. 31.—Female trichina from the intestine; 24 hours after infection.
+ Enlarged. (After Leuckart, 1866a, pl. 1, fig. 1.)
+]
+
+Swine become infected by eating rats, and by eating scraps of pork on
+the offal pile of slaughterhouses, or in swill.
+
+Man becomes infected almost exclusively by eating pork and boar meat.
+The rare infections which occur from eating other meat are almost
+negligible.
+
+MEDICAL SIGNIFICANCE.—_Trichiniasis_ or _trichinosis_ refers to
+infection with the trichina or flesh worm. Normally it occurs only in
+mammals, chiefly carnivorous and omnivorous species, and it is
+transmissible from any infected mammal to any other mammal susceptible
+to it, in case the latter eats the uncooked flesh of the former.
+
+_Symptoms._—In heavy infections there may be three more or less distinct
+periods of the disease, corresponding to the three stages in the life
+cycle of the parasite; but these stages are obscure in light or in
+repeated infections. Profuse sweating may last during the entire attack.
+
+[Illustration:
+
+ FIG. 32.—Gravid adult female trichina. Enlarged. (After Leuckart,
+ 1866a, pl. 1, fig. 2.)
+
+ FIG. 33.—Adult male trichina from the intestine. Enlarged. (After
+ Leuckart, 1866a, pl. 1, fig. 5.)
+
+ FIG. 34.—External genitalia of same. Enlarged. (After Leuckart, 1866a,
+ pl. 1, fig. 7.)
+
+ FIG. 35.—The same with extruded cloaca. Enlarged. (After Leuckart,
+ 1866a, pl. 1, fig. 8.)
+
+ FIG. 36.—Cephalic portion of a trichina showing central nervous system
+ and anterior portion of intestinal canal. Greatly enlarged. (After
+ Leuckart, 1866a, pl. 1, fig. 13.)
+
+ FIG. 37.—Transverse section of a female trichina. Greatly enlarged.
+ (After Leuckart, 1866a, pl. 1, fig. 16.)
+
+ FIG. 38.—Young trichina embryo in a muscle fibre. Greatly enlarged.
+ (After Leuckart, 1866a, pl. 2, fig. 1.)
+]
+
+Period of ingression: The adult parasites are in the intestine, hence
+gastro-intestinal symptoms develop; irregular appetite, nausea, diarrhea
+or constipation, colicky pains; a temporary edema around eyes about the
+eighth day; muscular pains begin.
+
+Period of digression: This begins about the eighth to the fifteenth day,
+sometimes later; young embryos are wandering to and attacking the
+muscles, hence muscular symptoms (myositis) develop; painful tension of
+muscles, especially biceps; members assume semiflexed position;
+movements, chewing, swallowing, breathing, and speech become difficult;
+eyes become fixed; fever.
+
+[Illustration:
+
+ FIGS. 39–42.—Later stages of same; the muscular structure is
+ undergoing changes. (After Leuckart, 1866a, pl. 2, figs. 3, 6, 7,
+ 8.)
+
+ FIGS. 43–45.—Muscle trichinæ, 0.3 mm., 0.4 mm., and 0.6 mm. long.
+ (After Leuckart, 1866a, pl. 2, figs. 10–12.)
+]
+
+Period of regression: The parasites become encysted in muscles. All
+symptoms may increase, then gradually decrease; cachexia and anemia
+resulting from malnutrition; pruritis, miliary cutaneous eruptions;
+desquamation; about twenty-fourth day, a “second” edema develops,
+especially about the face; lungs may become edematous; bronchial
+catarrh, pneumonia, or pleurisy may appear; gradual recovery.
+
+[Illustration:
+
+ FIG. 46.—A female trichina from the muscle. Greatly enlarged. (After
+ Leuckart, 1866a, pl. 1, fig. 12.)
+]
+
+[Illustration:
+
+ FIG. 47.—A piece of pork with encysted trichinæ. Enlarged. (After
+ Braun, 1903, p. 251, fig. 195.)
+]
+
+_Lethality._—The lethality varies from 0 to 100 per cent; it averaged
+5.6 per cent in 14,820 cases collected from literature; it is dependent
+upon amount of infection which remains in the body; low before second
+and after seventh week, highest from fourth to sixth week.
+
+_Prognosis._—Better in cases having severe diarrhea in first stage.
+
+_Complications and sequelæ._—Abortion, menstrual disturbances,
+pneumonia, pleurisy, peritonitis.
+
+[Illustration:
+
+ FIG. 48.—Section through a rat’s muscle; the infected muscle fiber has
+ lost its striation, its nuclei are enlarged and increased in number.
+ Greatly enlarged. (After Hertwig-Graham, see Braun, 1903, p. 284,
+ fig. 212B.)
+
+ FIG. 49.—Portion of an isolated trichina cyst, at the pole of which
+ connective tissue cells have wandered into the thickened sarcolemma.
+ Greatly enlarged. (After Hertwig-Graham, see Braun, 1903, p. 284,
+ fig. 212C.)
+]
+
+_Clinical diagnosis._—Make microscopic examination:
+
+(1) Of pork, if any has been left, to find encysted larvæ; if larvæ are
+found, feed pork immediately to two or three guinea pigs or _white_
+rats, to determine if the encysted larvæ are alive; kill one rat after
+three days and examine intestinal content for adult; kill the second rat
+after two weeks, the third rat after three weeks, and hunt for larvæ in
+muscular portion of diaphragm. Even if live trichinæ are found in
+intestine, an examination of the muscles may show that the worms were
+too weak to reproduce, hence prognosis is favorable.
+
+(2) Of patient’s blood, for increased proportion of eosinophiles.
+
+(3) Of patient’s stools, for discharged adult worms, especially if
+diarrhea is severe; dilute the fecal matter with warm water and pour off
+whatever floats; place remainder in a shallow glass dish so that it will
+not be over one-twelfth of an inch deep; move the dish gently around
+over a dark background (such as dark paper), and hunt for small
+hair-like objects; place these, if found, in a drop of water on a slide,
+cover with a cover slip, and examine under low power. Or, if necessary,
+make a microscopic examination.
+
+(4) Of small excised portion of patient’s deltoid, about three to four
+weeks after infection, for encysted larvæ; cut a small piece parallel to
+muscle fibers, tease this on a slide, add a drop of pure water, or water
+and glycerine, cover with another slide, flatten gently by pressure
+while examining under low power.
+
+[Illustration:
+
+ FIG. 50.—Calcified trichinæ in uncalcified cysts, from pork. Enlarged.
+ (After Ostertag, see Braun, 1903, p. 285, fig. 213.)
+]
+
+Suspect trichinosis especially under following circumstances: Several
+patients in same family or in same neighborhood, usually of North German
+descent, show typhoid-like symptoms shortly after a celebration
+(wedding, birthday party, etc.) at which pork was served.
+
+[Illustration:
+
+ FIG. 51.—Three phases of calcification of trichinæ and their cysts,
+ the changes starting from the poles of the cysts. Enlarged. (After
+ Ostertag, see Braun, 1903, p. 285, fig. 214.)
+]
+
+_Differential diagnosis._—Consider especially typhoid fever and
+rheumatism.
+
+_Treatment._—Purge in early stage to carry away the adult worms and thus
+eventually decrease the amount of muscular infection. No treatment is
+known which can be relied upon to kill the larvæ in the muscles; benzine
+has been suggested. Stimulants may be given to carry patients through
+until the larvæ encyst.
+
+PROPHYLAXIS.—_Kill off rats and mice._—Educate public to eat pork only
+when thoroughly cooked or thoroughly cured. A practical test of cooking
+is the white color of the meat on being cut; if the cut surface is
+reddish and serous, the pork is not sufficiently cooked to kill
+trichinæ.
+
+As a matter of practical experience, the microscopic inspection of pork
+has not given the protection it is generally supposed to give. Of 6,329
+cases with 318 deaths reported for Germany during the years 1881–1898,
+3,388 cases with 132 deaths are directly attributable to faults in the
+inspection. This system directly increases the tendency to eat raw pork,
+gives the public a false sense of security, and does not give practical
+results commensurate with its expense.
+
+
+ ACANTHOCEPHALA—THORN-HEADED WORMS.
+
+
+ Genus GIGANTORHYNCHUS Hamann, 1892.
+
+
+ GENERIC DIAGNOSIS.—_Acanthocephala, Gigantorhynchidæ_: Large worms
+ with annulate round to flat, tape-like body. Hooks with 2 roots and
+ completely covered with transparent chitin. Proboscis sheath a
+ muscular apparatus, without cavity. Central nervous system caudad of
+ equator of proboscis sheath and eccentric. Lemnisci long, cylindrical,
+ with central canal.
+
+ TYPE SPECIES.—_Gigantorhynchus echinodiscus_ (Diesing, 1851).
+
+
+ The Moniliform Thorn-headed Worm—GIGANTORHYNCHUS MONILIFORMIS
+
+ (Bremser, 1819).
+
+ [Figs. 52 to 58.]
+
+
+ SPECIFIC DIAGNOSIS.—_Gigantorhynchus_ (p. 108): Body attenuated
+ anteriorly, with fine transverse striæ or rings, or even constrictions
+ which give the appearance of a series of beads, except in the caudal
+ fourth of body, which is nearly smooth and cylindrical. Proboscis 425
+ to 450μ long, 176 to 190μ in diameter, armed with feeble, very curved,
+ 26μ long, hooks arranged more or less in quincunx and forming at most
+ 15 transverse and about 12 longitudinal rows. Lemnisci more than a
+ centimeter in length, cylindrical, undulated posteriorly.
+
+ Male: Length 4 to 4.5 centimeters long; bursa campaniform.
+
+ Female: Length 7 to 8 centimeters (to 27 centimeters after Westrumb).
+
+ Eggs: Ellipsoidal, 85 by 45μ; external envelope thin, yellowish;
+ middle envelope very thick, colorless, homogeneous; inner envelope
+ less thick, colorless, and quite pliant. Embryo striated transversely
+ in posterior two-thirds, and covered with spines which increase in
+ size toward anterior end of embryo, the anterior spines being
+ transformed into hooklets with prong and base.
+
+ Development: With beetles (_Blaps mucronata_) as intermediate host.
+
+ HABITAT.—Small intestine of various small mammals; brown rat (_Mus
+ decumanus_); white rat (_Mus norvegicus albus_); _M. fuscirostris_;
+ hamster (_Cricetus frumentarius_); dormice (_Myoxus quercinus_ or
+ _glis_); field mole (_Arvicola arvalis_ or _agrestris_?); _Lemnus
+ arvalis_; and _Mustela putorius_. It can also develop in man, as has
+ been shown experimentally by Grassi and Calandruccio (1888, 521–525).
+
+
+MEDICAL SIGNIFICANCE.—Grassi and Calandruccio report a doubtful case of
+infection in a girl near Catania. Calandruccio infected himself
+experimentally by swallowing the young worms taken from a Blaps. Twenty
+days later he was seized with severe pains which increased on pressure;
+diarrhea followed, with ringing in the ears, fatigue, and somnolence.
+Seventeen days later the characteristic eggs were found in his stools,
+and twelve days later the symptoms became so severe that he took 8 grams
+of extract of male fern; one to two hours later he passed 53 of the
+parasites. For two days the symptoms continued, on the second day fever
+developed, but all symptoms disappeared on the third day.
+
+[Illustration:
+
+ FIG. 52.—_Gigantorhynchus moniliformis_, female. ×2. (After Grassi &
+ Calandruccio, 1888, p. 523, fig. 1.)
+
+ FIG. 53.—_G. moniliformis_, male. ×2. (After Grassi & Calandruccio,
+ 1888, p. 523, fig. 2.)
+
+ FIG. 54.—Rostellum of _G. moniliformis_. Greatly enlarged. (After
+ Grassi & Calandruccio, 1888,
+ p. 523, fig. 3.)
+
+ FIG. 55.—Hooks from same. Greatly enlarged. (After Grassi &
+ Calandruccio, 1888, p. 523, fig. 4.)
+
+ FIG. 56.—Eggs of _G. moniliformis_, with embryo. Greatly enlarged.
+ (After Grassi & Calandruccio,
+ 1888, p. 523, fig. 5.)
+
+ FIG. 57.—Egg very greatly enlarged. (After Grassi & Calandruccio,
+ 1888, p. 524, fig. 6.)
+
+ FIG. 58.—A young larva of _G. moniliformis_ in a _Blaps_; the
+ rostellum is invaginated and the larva is
+ surrounded by a thick inner jelly-like and thin outer cuticular
+ covering. Enlarged. (After Grassi &
+ Calandruccio, 1888, p. 524, fig. 7.)
+]
+
+
+ ARACHNOIDEA.
+
+
+ Genus LINGUATULA Frœhlich, 1789.—Tongue worms.
+
+
+ Species LINGUATULA SERRATA Frœhlich, 1789.
+
+The larva of this parasite is found encysted in the entrails of rabbits,
+cattle, and certain other animals, and it becomes mature in the nasal
+cavities of canines.
+
+Both the larva and the adult have been reported for man, and the larva
+has been reported as occurring in _Mus decumanus_.
+
+As canines are not fond of eating rats, the presence of the larval
+tongue worm in the latter is of more academic interest than practical
+importance, and although the theoretical possibility must be admitted
+that a dog by eating rats might become infected with tongue worms and
+eventually might transmit the infection to man, these possibilities seem
+somewhat remote. Remote possibilities must also be admitted to the
+effect that if a person ate a rat infected with tongue worms this person
+might become infected.
+
+
+
+
+ COMPENDIUM OF ANIMAL PARASITES REPORTED FOR RATS AND MICE (GENUS MUS).
+
+ By CH. WARDELL STILES, Ph. D., _Public Health and Marine-Hospital
+ Service_,
+
+ and
+
+ ALBERT HASSALL, M. R. C. V. S., _Assistant, Division of Zoology, United
+ States Bureau of Animal Industry_.
+
+
+The following list of parasites is prepared from the detailed host
+catalogues of the zoological divisions of the Public Health and
+Marine-Hospital Service and the Bureau of Animal Industry.
+
+The species of hosts and parasites are taken as given by the various
+authors. It is needless to say that no list of this kind can ever lay
+claim to being complete.
+
+
+ Genus MUS Linneaus, 1758.
+
+ [_Mus musculus_ should be the type species.]
+
+
+ MUS AGRARIUS.—Harvest Mouse.
+
+
+ CESTODA:
+
+ _murina_ Dujardin: Hymenolepis.—Small intestine. [See fraterna.]
+
+ NEMATODA:
+
+ _obvelata_: Oxyuris.—Intestine.
+
+ ARACHNOIDEA:
+
+ _acuminatus_ Neumann: Ixodes.—External.
+
+ INSECTA:
+
+ _fasciatus_ Bosc: Ceratophyllus.—External.
+ _musculi_ Dugès: Ctenopsyllus, Ctenopsylla.—External.
+
+
+ MUS ALBIPES.
+
+
+ INSECTA:
+
+ _pallidus_ Taschenberg: Pulex.—External.
+
+
+ MUS ALEXANDRINUS.—Roof Rat.
+
+ [See also _Mus rattus alexandrinus_.]
+
+
+ CESTODA:
+
+ _diminuta_ Rudolphi, 1819: Tænia, Hymenolepis.—Small intestine.
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+ _leptocephala_: Tænia.—Small intestine.
+ _murina_ Dujardin: Hymenolepis.—Small intestine. [See fraterna.]
+
+
+ MUS ALEXANDRINUS ALBIVENTRIS.
+
+
+ CESTODA:
+
+ _diminuta_ Rudolphi: Hymenolepis.—Small intestine.
+
+
+ MUS AMPHIBIUS.
+
+
+ _Dubium_ Rudolphi.—Inguinal gland.
+
+ CESTODA:
+
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+ _omphalodes_ Hermann: Tænia, Anoplocephala.—Intestine.
+
+ NEMATODA:
+
+ _nodosus_: Trichocephalus.—Cecum.
+ _obvelata_: Ascaris.
+
+
+ MUS ARVALIS.
+
+
+ CESTODA:
+
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+ _longicollis_: Cysticercus.
+ _omphalodes_ Hermann: Tænia, Anoplocephala.—Intestine.
+
+ NEMATODA:
+
+ _nodosus_: Trichocephalus.
+ _obvelata_: Ascaris.
+
+ ACANTHOCEPHALA:
+
+ _moniliformis_: Echinorhynchus.
+
+
+ MUS BARBARUS.
+
+ [See also _barbatus_ Enderl.]
+
+
+ INSECTA:
+
+ _spiculifer_ Gerv.: Hæmatopinus, Polyplax.—External.
+
+
+ MUS BRASILIENSIS Geoffr.
+
+ [See also _Holochilus brasiliensis_.]
+
+
+ CESTODA:
+
+ _pisiformis_ Zeder: Cysticercus.
+
+ NEMATODA:
+
+ _muris brasiliensis_ Diesing: Physaloptera.
+ _obvelata_ Bremser: Oxyuris.
+
+
+ MUS CAPENSIS.
+
+
+ CESTODA:
+
+ _muris capensis_: Tænia.—Intestine.
+
+ NEMATODA:
+
+ _contortus_ Rudolphi: Trichocephalus.—Cecum.
+
+
+ MUS CRICETUS.
+
+
+ CESTODA:
+
+ _straminea_ Gœze: Tænia.—Intestine.
+
+
+ MUS DECUMANUS Pallas.—Brown or Norway Rat; German Wanderratte.
+
+
+ PROTOZOA:
+
+ ? _balfouri_: Hæmogregarina.—Blood.
+ _intestinalis_ Lambl, 1859: Lamblia.—Intestine. [See duodenalis.]
+ _lewisi_ Saville-Kent: Herpetomonas, Trichomonas, Trypanosoma.—Blood.
+ species Siebold: Sarcocystis.—Muscles.
+
+ TREMATODA:
+
+ _armata_: Cercaria.
+ _muris_: Distomum.
+ _spiculator_ Dujardin, 1845: Distoma, Echinostoma, Distomum,
+ Echinostomum.—Small intestine.
+
+ CESTODA:
+
+ _brachydera_ Diesing: Tænia.—Small intestine.
+ _contracta_ Janicki: Hymenolepis.—Intestine.
+ _crassa_ Janicki: Hymenolepis.—Intestine.
+ _diminuta_ Rudolphi: Tænia, Hymenolepis.—Small intestine.
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+ _horrida_ Linstow, 1901: Tænia, Hymenolepis.—Intestine.
+ _microstoma_ Dujardin: Tænia, Hymenolepis.—Small intestine.
+ _murina_ Dujardin, 1845: Tænia, Hymenolepis.—Small intestine. [See
+ fraterna.]
+ _nana_ Siebold: Hymenolepis.—Small intestine. [See fraterna, murina.]
+ _pusilla_ Gœze: Tænia, Catenotænia.—Small intestine.
+ _ratti_: Tænia.—Intestine.
+ _relicta_ Zschokke, 1888: Tænia, Hymenolepis.—Small intestine.
+ species Janicki: Hymenolepis.
+ species: Hymenolepis.—Small intestine.
+
+ NEMATODA:
+
+ _annulosum_ Dujardin: Trichosoma, Trichosomum, Calodium.—Duodenum,
+ small intestine.
+ _anulosum_ see annulosum Dujardin: Trichosoma.
+ _circumflexa_ Polonio: Trichina.—Encysted in peritoneum.
+ _crassicauda_ Bellingham, 1840: Trichodes, Trichosoma.—Urinary
+ bladder, ureter, kidneys, intestine.
+ _hepaticum_ Bauer: Trichosoma.—Liver.
+ _hepaticum_ Railliet, 1891: Trichosoma.—Liver.
+ _hepaticus_ Bancroft: Trichocephalus.—Liver.
+ _longus_ Grassi & Segrè: Strongyloides, Rhabdonema.—Intestine.
+ _minimum_ Molin: Gongylonema.
+ _murina_ Leuckart: Spiroptera.—Stomach. [See obtusa.]
+ _muris_ Gmelin: Filaria.—Stomach.
+ _obtusa_ Rudolphi: Filaria, Spiroptera.—Stomach. [See murina.]
+ _obvelata_ Bremser: Oxyuris.—Large intestine.
+ _papillosum_ Polonio: Trichosoma.—Urinary bladder.
+ _rhytipleuritis_ Deslongchamps: Filaria.—Stomach.
+ _schmidtii_ Linstow: Trichosoma.—Urinary bladder.
+ species Davaine: Filaria [embryo].—Blood.
+ species: Heterakis.—Large intestine.
+ species undetermined: Oxyuris.
+ species Gerstæcker: Spiroptera.—Encapsuled in wall of stomach and
+ intestine.
+ species Bakody: Spiroptera.—Encapsuled in walls of alimentary canal
+ and muscles.
+ species: Spiroptera.—Encapsuled in wall of stomach and intestine.
+ species Parona: Strongyloides.
+ species Lutz, 1894: Strongylus.—Small intestine.
+ ? species Railliet: Trichosoma.
+ _spiralis_ Owen, 1835: Trichina, Trichinella.—Adult in intestine,
+ larva in muscles.
+ _spumosa_ Schneider: Heterakis.—Cœcum and large intestine.
+ ? _tenuissimum_ Leidy, 1891: Trichosomum.—Liver. [See hepaticum.]
+
+ ACANTHOCEPHALA:
+
+ _moniliformis_ Bremser: Echinorhynchus, Gigantorhynchus.
+
+ ARACHNOIDEA:
+
+ _agilis_ Koch: Lælaps.—External [See echidninus, musculi.]
+ _alepis_ Railliet & Lucet, 1893: Sarcoptes, Notoedres.—External, ears,
+ genitalia.
+ _complanatus_ Kramer: Gamasus.—External. [See stabularis, fenilis.]
+
+ _decumani_ Tiraboschi: Myonyssus.
+ _echidninus_ Berlese: Lælaps.—External.
+ _ensifera_ Poppe: Myobia.—External.
+ _fenilis_ Mègnin: Gamasus.—[See stabularis, complanatus.]
+ _musculi_ Schrank: Pediculus, Myobia.—External, head.
+ _musculi_ Mègnin: Hæmomyson.—External. [See echidninus, agilis.]
+ _musculi_ Schrank: Myobia.—External.
+ _ricinus_ Linné: Acarus, Ixodes.—External. [See rufus, sulcatus,
+ sciuri.]
+ _rufus_ Koch: Ixodes.—External. [See ricinus.]
+ _sciuri_ Koch: Ixodes.—External. [See ricinus.]
+ sp. n. Banks: Lælaps.—External.
+ _stabularis_ Koch: Gamasus, Hypoaspis, Lælaps.—External. [See
+ complanatus, fenilis.]
+ _sulcatus_ Koch: Ixodes.—External. [See ricinus.]
+ _tænioides_ Lamark (larva): Linguatula. [See serrata.]
+
+ INSECTA:
+
+ _acanthopus_ Denny: Hæmatopinus, Hoplopleura.—External.
+ _bidentatiformis_ Wagner: Neopsylla.—External.
+ _brasiliensis_ Baker: Pulex.—External.
+ _canis_ Curtis: Ctenocephalus, Ceratophyllus.—External.
+ _cheopis_ Roth.: Pulex, Læmopsylla.—External.
+ _consimilis_ Wagner: Ceratophyllus.—External.
+ _fasciatus_ Bosc: Pulex, Ceratophyllus. External.
+ _felis_ Bouché: Ctenocephalus.—External.
+ _irritans_ Linné: Pulex.—External.
+ _lagomys_ Wagner: Ceratophyllus.—External.
+ _londiniensis_ Roth.: Ceratophyllus.—External.
+ _musculi_ Dugès: Ctenopsylla.—External.
+ _mustelæ_ Wagner: Ceratophyllus.—External.
+ _penicilliger_ Grube: Ceratophyllus.—External.
+ _philippinensis_ Herzog: Pulex.—External.
+ _serraticeps_ Gervais: Pulex.—External.
+ _spinulosus_ Burmeister: Hæmatopinus, Polyplax.—External.
+
+
+ MUS DECUMANUS × MUS NORVEGICUS ALBUS.
+
+
+ PROTOZOA:
+
+ undetermined.—Small intestine.
+
+ CESTODA:
+
+ _fasciolaris_: Cysticercus.—Liver.
+ species: Hymenolepis.—Intestine.
+
+ NEMATODA:
+
+ _spiralis_ Owen: Trichinella.—Artificial infection.
+
+
+ MUS DOMESTICUS = MUS MUSCULUS ALBUS.
+
+
+ ARACHNOIDEA:
+
+ _crotali_ Humboldt (larva): Porocephalus.—Encysted in various organs,
+ experimental.
+
+
+ MUS FERCULINUS.
+
+
+ INSECTA:
+
+ _thomasi_ Rothschild: Stephanocircus.—External.
+
+
+ MUS FLAVIDUS.
+
+
+ CESTODA:
+
+ ? _gracilis_ Janicki: Davainea.—Intestine.
+
+
+ MUS FULIGINOSUS.
+
+
+ ARACHNOIDEA:
+
+ _crotali_ Humboldt: Porocephalus.—Encysted in various organs.
+
+
+ MUS FURCIROSTRIS Wagner.
+
+
+ ACANTHOCEPHALA:
+
+ _moniliformis_ Bremser: Echinorhynchus.—Intestine.
+
+
+ MUS GENTILIS.
+
+
+ INSECTA:
+
+ _cheopis_ Rothschild: Pulex.—External.
+
+
+ MUS LEMMUS.
+
+
+ CESTODA:
+
+ _lemmi_: Tænia.—Intestine. [See muris lemmi.]
+ _muris lemmi_: Tænia.—Intestine. [See lemmi.]
+
+
+ MUS MEYERI.
+
+
+ CESTODA:
+
+ _celebensis_ Janicki, 1902: Davainea.—Intestine.
+
+
+ MUS MINIMUS Ptrs.
+
+
+ NEMATODA:
+
+ species Linstow, 1901: Spiroptera.—Stomach.
+
+
+ MUS MINUTUS Pallas.—German Zwergmaus.
+
+
+ NEMATODA:
+
+ _obvelata_ Bremser: Oxyuris.—Cecum.
+ _oxyura_ Nitzsch, 1821: Ascaris.—[See obvelata.]
+
+
+ MUS MUSCHENBROCKI.
+
+
+ CESTODA:
+
+ _polycalceola_ Janicki: Davainea.—Intestine.
+
+
+ MUS MUSCULUS[AC] Linné, 1758.—House Mouse.
+
+Footnote AC:
+
+ In laboratory experiments the white mouse is used more than the
+ ordinary form, but the host is frequently reported simply as “the
+ mouse.”
+
+
+ ——:
+
+ _Dubium_ Rudolphi, 1819.—Inguinal gland.
+
+ PROTOZOA:
+
+ _brucei_: Trypanosoma, Trypanozoon.—Blood, artificial infection.
+ _dimorphon_: Trypanosoma, Trypanozoon.—Blood.
+ _duttoni_ Thiroux, 1905: Trypanosoma, Trypanozoon.—Blood.
+ _equinum_: Trypanosoma, Trypanozoon.—Blood, artificial infection.
+ _equiperdum_: Trypanosoma, Trypanozoon.—Blood, artificial infection.
+ _evansi_: Trypansoma, Trypanozoon.—Blood, artificial infection.
+ _falciforme_ Schneider: Coccidium, Eimeria.—Intestine.
+ flagellate, something like Herpetomonas bütschlii.
+ _gambiense_: Trypanosoma, Trypanozoon.—Blood, artificial infection.
+ _intestinalis_ Lambl, 1859: Lamblia, Megastoma.—Intestine. [See
+ duodenalis, muris.]
+ _muris_ Grassi: Amœba.
+ _muris_ Bensen, 1908: Lamblia.—Intestine. [See intestinalis.]
+ _muris_ Schuberg: Coccidium.—Intestine.
+ _muris_ Smith & Johnson, 1902a: Klossiella.—Renal epithelium.
+
+ _muris_ Balfour: Leucocytozoon.—Blood.
+ _muris_ R. Blanchard: Miescheria, Sarcocystis.—Striated muscle.
+ _musculi_ Kendall: Trypanosoma.—Blood.
+ _schubergi_ Labbé: Pfeifferella.—Intestine.
+ species Th. Smith: Eimeria.—Kidney.
+ species J. J. Clarke: Pfeifferella.—Intestine.
+ species Miescher: Sarcocystis.—Muscles.
+ _stercorea_ Cienkowski: Chlamydophrys.—Intestine.
+
+ TREMATODA:
+
+ _armata_: Cercaria.
+ _muris_ Ercolani, 1882: Distomum.
+ _musculi_ Rudolphi, 1819: Distoma, Distomum.—Intestine.
+ _recurvum_ Dujardin, 1845: Distoma, Distomum.—Intestine.
+
+ CESTODA:
+
+ _canis lagopodis_ Viborg: Tænia.—Intestine. [See lineata.]
+ _contracta_ Janicki: Hymenolepis.—Intestine.
+ _crassa_ Janicki, 1904: Hymenolepis.—Intestine.
+ _diminuta_ Rudolphi: Tænia, Hymenolepis.—Intestine.
+ _echinococcus._ [See Devé, 1904, October 28; 264.]
+ _fasciolaris_ Rudolphi, 1819: Cysticercus.—Liver.
+ _imbricata_ Diesing: Tænia.—Small intestine.
+ _leptocephala_ Creplin, 1849: Tænia.—Small intestine.
+ _lineata_ Gœze: Tænia, Mesocestoides, Ptychophysa. [See canis
+ lagopodis.]
+ _microstoma_ Dujardin, 1845: Tænia.—Intestine.
+ _murina_ Dujardin, 1845: Tænia, Hymenolepis.—Intestine. [See
+ fraterna.]
+ _muris capensis_: Tænia.
+ _muris hepatica_ Rœderer, 1762: Fasciola.—Liver. [See fasciolaris.]
+ _musculi_ Rudolphi, 1810: Tænia.—Abdominal cavity.
+ _pisiformis_ Zeder: Cysticercus.—Liver.
+ _pusilla_ Gœze, 1782: Tænia.—Intestine.
+ species Janicki: Hymenolepis.—Intestine.
+ species Merrem, 1781: Fasciola.—Liver. [See fasciolaris.]
+ _tenella_ Pallas, 1781 pars: Tænia.—Abdominal cavity. [See musculi.]
+ _umbonata_ Molin, 1858: Tænia.—Intestine.
+
+ NEMATODA:
+
+ _bacillatum_ Eberth: Trichosoma.—Esophagus.
+ _hepaticum_ Railliet, 1889: Trichosoma.—Liver.
+ _minimum_ Molin: Gongylonema.—On stomach, liver.
+ _muris_ Gmelin: Filaria.
+ _muris_ Werner: Lumbricus, Ascaris, Fusaria. [See obtusa Frœlich.]
+ _muris musculi_ Creplin, 1849: Trichosoma.—Large intestine.
+ _musculi_ Rudolphi: Filaria, Gongylonema.—Abdomen.
+ _nodosus_ Rudolphi: Trichocephalus.—Intestine, cecum.
+ _oxyura_ Nitzsch, 1821: Ascaris.—[See obvelata.]
+ _obvelata_ Rudolphi: Oxyuris.—Cecum.
+ _obtusa_ Rudolphi: Filaria, Spiroptera.—Stomach.
+ _obtusa_ Frœlich, 1791: Ascaris.—Stomach. [See muris Werner.]
+ _quadrialata_ Molin: Spiroptera.—Stomach.
+ _semilanceolata_ Molin, 1858: Oxyuris.—Cecum. [See tetraptera.]
+ _spiralis_ Owen, 1835: Trichina, Trichinella.—Adult in intestine,
+ larva in muscles.
+ _tetraptera_ Nitzsch: Oxyuris.—Cecum. [See semilanceolata.]
+ _tricuspis_ Leuckart: Ollulanus.—Muscles.
+
+ ACANTHOCEPHALA:
+
+ _muris_ Zeder: Echinorhynchus.—Stomach.
+
+ ARACHNOIDEA:
+
+ _coarctata_ Heyden: Myobia.—External. [See musculi Schrank.]
+ _musculi_ Oudemans: Demodex.—Hair follicles. [See folliculorum
+ musculi.]
+ _musculi_ Schrank: Pediculus, Myobia.—External, head.
+ _musculinus_ Galli-Valerio: Myocoptes.—External.
+ _simplex_ Tyrrell: Psorergates.—External.
+
+ INSECTA:
+
+ _acanthopus_ Burmeister, 1838: Hoplopleura, Hæmatopinus.—External.
+ _agyrtes_ Heller: Typhlopsylla.—External.
+ _assimilis_ Taschenberg: Typhlopsylla.—External.
+ _charlottensis_ Baker: Odontopsyllus.—External.
+ _fasciatus_ Bosc: Ceratophyllus.—External.
+ _italicus_ Tiraboschi: Ceratophyllus.—External.
+ _londiniensis_ Roth.: Ceratophyllus.—External.
+ _musculi_ Dugès: Ctenopsyllus, Ctenopsylla, Typhlopsylla.—External.
+ _serratus_ Burm., 1838: Hæmatopinus.—External.
+ _serraticeps_ Taschenberg: Ctenocephalus.—External.
+ larva of a dipteron, gen. sp.?
+ _taschenbergi_ Wagner: Ctenopsyllus.—External.
+ _tripectinata_ Tiraboschi: Hystrichopsylla.—External.
+ _walkeri_ Roth.: Ceratophyllus.—External.
+
+
+ MUS MUSCULUS ALBUS.—White Mice.
+
+
+ CESTODA:
+
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+
+ ARACHNOIDEA:
+
+ _crotali_ Humboldt (larva): Porocephalus.—Encysted in various organs.
+ _proboscideum_: Pentastomum. [See crotali.]
+
+
+ MUS NAVALIS.
+
+
+ NEMATODA:
+
+ _labiodentata_ Linstow: Spiroptera.—Intestine.
+
+
+ MUS NORVEGICUS Erxl.—Norway Rat.
+
+ [See also _Mus decumanus_.]
+
+
+ PROTOZOA:
+
+ _lewisi_: Trypanosoma, Trypanozoon.—Blood.
+
+ INSECTA:
+
+ _bidentatiformis_ Wagner: Ctenophthalmus.—External.
+ _brasiliensis_ Baker: Pulex.—External.
+ _fasciatus_ Bosc: Ceratophyllus.—External.
+ _italicus_ Tiraboschi: Ceratophyllus.—External.
+ _murinus_ Tiraboschi: Pulex.—External.
+ _musculi_ Dugès: Ctenopsyllus.—External.
+
+
+ MUS [NORVEGICUS] ALBUS.—White Rat.
+
+
+ PROTOZOA:
+
+ _muris_ Fantham: Piroplasma.—Blood.
+ _perniciosum_ Miller: Hepatozoon.—Liver, blood.
+
+ CESTODA:
+
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+
+ NEMATODA:
+
+ _hepaticum_: Trichosoma.—Liver.
+ _spiralis_ Owen, 1835: Trichinella.—Adult in intestine, larva in
+ muscle.
+
+ ARACHNOIDEA:
+
+ _ensifera_ Poppe: Myobia.
+
+
+ MUS PUMILIS Dujardin.—Little Mouse.
+
+
+ CESTODA:
+
+ _murina_ Dujardin, 1845: Tænia, Hymenolepis.—Intestine. [See
+ fraterna.]
+
+
+ MUS PYRRHORHINUS Neuwied.
+
+ [See also _Hesperomys pyrrhorhinus_.]
+
+
+ CESTODA:
+
+ _diminuta_: Tænia.—Intestine.
+
+ ARACHNOIDEA:
+
+ _crotali_ Humboldt: Porocephalus.—Encysted in various organs.
+ _subcylindricum_: Pentastomum.—Liver.
+
+
+ MUS RAJAH.
+
+
+ CESTODA:
+
+ _blanchardi_ Parona: Davainea.
+
+
+ MUS RATTUS Linné.—German Hausratte.
+
+
+ PROTOZOA:
+
+ “amibes.”
+ _intestinalis_ Lambl, 1859: Lamblia.—Intestine. [See duodenalis,
+ muris.]
+ _lewisi_ Saville-Kent, 1880: Trypanosoma.—Blood.
+ species Siebold: Sarcocystis.—Muscles.
+
+ TREMATODA:
+
+ _spiculator_: Distomum.
+
+ CESTODA:
+
+ _cellulosæ_ Rudolphi: Cysticercus.—Peritoneum.
+ _diminuta_ Rudolphi, 1819: Tænia, Hymenolepis.—Small intestine.
+ _fasciolaris_ Rudolphi: Cysticercus.—Liver.
+ _microstoma_ Dujardin: Tænia, Hymenolepis.—Small intestine.
+ _minima_: Tænia. [See diminuta.]
+ _murina_ Dujardin, 1845: Tænia, Hymenolepis.—Small intestine. [See
+ fraterna.]
+ _pusilla_ Gœze, 1782: Tænia, Catenotænia.—Small intestine.
+ _ratti_ Rudolphi: Tænia.—Small intestine.
+ _ratticola_ Linstow: Bothriocephalus.—Liver.
+ species Eber: Tænia.—Intestine.
+ _umbonata_ Molin: Tænia.—Intestine.
+ _varesina_ Parona: Tænia.—[See diminuta.]
+
+ NEMATODA:
+
+ _annulosum_ Dujardin: Trichosoma, Calodium.—Intestine.
+ _anulosum_: Trichosoma. [See annulosum.]
+ _brauni_ Linstow: Spiroptera.
+ _circularis_ Linstow: Physaloptera.—Stomach.
+ _circumflexa_ Polonio: Trichina.—Encysted in peritoneum.
+ _nodosus_ Rudolphi: Trichocephalus.—Cecum.
+ _obvelata_ Bremser: Oxyuris.—Cecum.
+ _oxyura_ Nitzsch, 1821: Ascaris. [See obvelata.]
+ _ratti_ Diesing: Spiroptera.—Urinary bladder.
+ _rhytipleuritis_ Deslongchamps: Filaria.—Stomach.
+ species Gerstæcker: Spiroptera.—Wall of stomach and intestine.
+ species Bakody: Spiroptera.—Encapsuled in wall of intestine, muscles.
+ _spumosa_ Schneider: Heterakis.—Cecum, colon.
+
+ ACANTHOCEPHALA:
+
+ _moniliformis_ Bremser: Echinorhynchus, Gigantorhynchus.—Intestine.
+
+ ARACHNOIDEA:
+
+ _ægyptium_ Linné: Acarus, Ixodes, Hyalomma.—External. [See
+ marginatum.]
+ _agilis_ Koch: Lælaps.—External. [See echidninus, musculi.]
+ _alepis_ Railliet & Lucet, 1893; Sarcoptes, Notoedres.—External, ears,
+ genitalia.
+ _echidninus_ Berlese: Lælaps.—External. [See agilis, musculi.]
+ _marginatum_ Koch: Hyalomma.—External. [See ægyptium.]
+ _muris_ Can., 1894: Notoedres.—External. [See alepis.]
+ _musculi_ Mègnin: Hæmomyson.—External. [See agilis, echidninus.]
+ _serratum_: Pentastomum.—Thoracic cavity.
+
+ INSECTA:
+
+ _brasiliensis_ Baker: Pulex.—External. [See cheopis.]
+ _cæcata_ Enderlein: Dermatophilus, Rhynchoprion.—External.
+ _cheopis_ Rothschild, 1903: Lœmopsylla.—External. [See brasiliensis,
+ murinus, pallidus, philippinensis.]
+ _fasciatus_: Ceratophyllus.—External.
+ _gallinacea_ Westwood: Echidnophaga, Argopsylla.—External.
+ _irritans_ Linné: Pulex.—External.
+ _italicus_ Tiraboschi: Ceratophyllus. External.
+ _londiniensis_ Rothschild: Ceratophyllus.—External.
+ _mexicanus_ Baker: Ctenopsyllus.—External.
+ _murinus_ Tirab.: Pulex.—External. [See cheopis, pallidus,
+ brasiliensis, philippinensis.]
+ _musculi_ Dugès: Ctenopysllus.—External.
+ _pallidus_ Taschenberg: Pulex.—External. [See brasiliensis, cheopis,
+ murinus, philippinensis.]
+ _philippinensis_ Herzog: Pulex.—External. [See brasiliensis, cheopis,
+ murinus, pallidus.]
+ _rhynchopsylla_ Tiraboschi: Echidnophaga.—External.
+
+
+ MUS RATTUS ALEXANDRINUS.
+
+ [See also _Mus Alexandrinus_.]
+
+
+ INSECTA:
+
+ _brasiliensis_ Baker: Pulex.—External.
+ _cæcata_ End: Dermatophilus.—External.
+ _canis_ Curtis: Ctenocephalus.—External.
+ _cheopis_ Roth.: Pulex.—External.
+ _fasciatus_ Bosc: Ceratophyllus.—External.
+ _felis_ Bouché: Ctenocephalus.—External.
+ _gallinacea_ Westwood: Echidnophaga.—External.
+ _irritans_ Linné: Pulex.—External.
+ _londiniensis_ Roth.: Ceratophyllus.—External.
+ _murinus_ Tiraboschi: Pulex.—External.
+ _musculi_ Dugès: Ctenopsylla.—External.
+ _philippinensis_ Herzog: Pulex.—External.
+ _rhynchopsylla_ Tiraboschi: Echidnophaga, Argopsylla.—External.
+
+
+ MUS RUFESCENS Gray.
+
+
+ PROTOZOA:
+
+ _lewisi_ Saville-Kent, 1880: Trypanosoma, Trypanozoon.—Blood.
+
+
+ MUS SIPORANUS.
+
+
+ CESTODA:
+
+ _blanchardi_ Parona: Davainea.—Intestine.
+
+
+ MUS SURIFER.
+
+
+ NEMATODA:
+
+ _muricola_: Spiroptera.—Subcutaneous.
+
+
+ MUS SYLVATICUS Linné.—German Waldmaus.
+
+
+ TREMATODA:
+
+ _recurvum_ Dujardin, 1845: Distoma, Distomum, D.
+ (Brachylaimus).—Intestine.
+ _vitta_ Dujardin, 1845: Distoma, Distomum, D.
+ (Brachylaimus).—Intestine.
+
+ CESTODA:
+
+ _muris sylvatici_ Rudolphi: Tænia.—Intestine.
+ _pusilla_ Gœze: Tænia.—Intestine.
+
+ NEMATODA:
+
+ _cristatum_ Rudolphi: Ophiostomum, Rictularia.—Intestine.
+ _lævis_ Dujardin: Strongylus, Metastrongylus.—Intestine.
+ _minutus_ Dujardin: Strongylus, Metastrongylus.—Intestine.
+ _muris sylvatici_ Dujardin: Trichosoma.—Intestine.
+ _nodosus_ Rudolphi: Trichocephalus.—Intestine, cecum.
+ _obtusa_ Rudolphi: Spiroptera.
+ _obvelata_ Bremser: Oxyuris.—Cecum.
+ _oxyura_ Nitzsch, 1821: Ascaris. [See obvelata.]
+ _polygyrus_ Dujardin: Strongylus, Metastrongylus.—Intestine.
+ _spirogyrus_ Leuckart: Strongylus.—Intestine.
+ _stroma_ Linstow, 1884: Oxyuris.—Intestine.
+ _tetraptera_ Nitzsch: Oxyuris.—Intestine.
+
+ ARACHNOIDEA:
+
+ _simplex_ Tyrell: Psorergates.—Skin.
+
+ INSECTA:
+
+ _agyrtes_ Heller: Ctenophthalmus, Typhlopsylla.—External.
+ _assimilis_ Taschenberg: Typhlopsylla.—External.
+ _fasciatus_ Bosc: Ceratophyllus.—External.
+ _gallinæ_ Schrank: Ceratophyllus.—External.
+ _italicus_ Tiraboschi: Ceratophyllus.—External.
+ _londiniensis_ Rothschild: Ceratophyllus.—External.
+ _musculi_ Dugès: Ctenopsyllus, Ctenopsylla.—External.
+ _obtusiceps_ Ritsema: Hystrichopsylla.—External.
+ _pentacanthus_ Rothschild: Neopsylla, Ctenophthalmus.—External.
+ _poppei_ Wagner: Typhloceras, Typhlocerus.—External.
+ _proxima_ Wagner: Typhlopsylla, Ctenopthalmus.—External.
+ _talpæ_ Curtis: Hystrichopsylla.—External.
+ _taschenbergi_ Wagner: Ctenopsylla.—External.
+
+
+ MUS SYLVESTRIS.
+
+
+ PROTOZOA:
+
+ _intestinalis_ Lambl, 1859: Lamblia.—Intestine. [See muris.]
+
+
+ MUS TECTORUM Sari.
+
+
+ CESTODA:
+
+ _fasciolaris_: Cysticercus.—Liver.
+
+
+ MUS VARIEGATUS.
+
+
+ CESTODA:
+
+ _muris variegati_ Janicki: Hymenolepis.—Intestine.
+ _trapezoides_ Janicki: Davainea.—Intestine.
+
+
+ MUS VELUTINUS Balser, 1905.
+
+
+ INSECTA:
+
+ _dasyuri_ Skuse: Stephanocircus.—External.
+ _hercules_ Roth.: Macropsylla.—External.
+ _simpsoni_ Rothschild: Stephanocircus.—External.
+ _simsoni_. [See simpsoni.]
+
+
+ MUS in the sense of “rats.”
+
+The following parasites are reported either from “rats” or from “_Mus_”
+in the sense of “rats:”
+
+
+ PROTOZOA:
+
+ _brucei_: Trypanosoma, Trypanozoon.—Blood.
+ _dimorphon_: Trypanosoma, Trypanozoon.—Blood.
+ _equiperdum_: Trypanosoma, Trypanozoon.—Blood.
+ _evansi_: Trypanosoma, Trypanozoon.—Blood.
+ _evansii_: Trypanosoma. [See evansi.]
+ _gambiense_: Trypanosoma, Trypanozoon.—Blood, artificial infection.
+ _intestinale_ R. Blanchard, 1885: Megastoma.—Intestine. [See muris.]
+ _muris_ Grassi: Amœba.
+
+ CESTODA:
+
+ _fasciolaris_: Cysticercus.
+
+ NEMATODA:
+
+ _hepaticum_ Railliet, 1889: Trichosoma.—Liver.
+ _hepaticus_: Trichocephalus.
+ species Davaine: Filaria.—Blood.
+
+ GORDIACEA:
+
+ _Gordius._ By error Cerruti & Camerano (1888b, 6) have interpreted a
+ title by
+ Leidy (1879) as meaning that he found _Gordius_ in a rat.
+
+ ARACHNOIDEA:
+
+ _sanguineus_ Latreille: Rhipicephalus.—External.
+
+ INSECTA:
+
+ _capitis_ Nitzsch: Pediculus.—External.
+ _canis_ Curtis: Ctenocephalus.—External.
+ _præcisus_: Hæmatopinus.—External.
+
+
+ MUS species.
+
+ Under various “_Mus_ sp.” entries, the following parasites are
+ reported:
+
+
+ PROTOZOA:
+
+ _gambiense_: Trypanosoma.—Blood, artificial injection.
+
+ INSECTA:
+
+ _aganippes_ Roth.: Ctenopsylla.—External.
+ _agyrtes_ Heller: Typhlopsylla.—External.
+ _colossus_ Roth.: Pygiopsylla.—External.
+ _ellobius_ Roth.: Ctenopsylla.—External.
+ _hercules_ Roth.: Macropsylla.—External.
+ _miacantha_: Polyplax.—Hair.
+ _pinnatus_ Wagn.: Ceratophyllus.—External.
+ _præcisus_ Neum., 1902: Hæmatopinus.—External.
+
+
+ WATER RAT.
+
+ [See also _Mus amphibius_.]
+
+
+ CESTODA:
+
+ _longicollis_: Cysticercus.—Axillary space.
+
+ INSECTA:
+
+ _spiniger_ Burm., 1838: Hæmatopinus.
+
+
+ MUS.
+
+ The following parasites are recorded under “_Mus._:”
+
+
+ PROTOZOA:
+
+ _falciformis_: Eimeria.—Intestine.
+
+ TREMATODA:
+
+ _migrans_: Dist.
+
+ CESTODA:
+
+ _blanchardi_ Parona: Davainea.
+ _celebensis_ Janicki: Davainea.
+ _gracilis_ Janicki: Davainea.
+ _muris variegati_ Janicki: Hymenolepis.
+ _nana_ Siebold: Hymenolepis. [See fraterna.]
+ _polycalceola_ Janicki: Davainea.
+ _relicta_ Zschokke: Hymenolepis.
+ _trapezoides_ Janicki: Davainea.
+
+ NEMATODA:
+
+ _hepaticum_ Railliet: Trichosoma.
+ _obvelata_ Bremser: Oxyuris.—Intestine.
+
+ ARACHNOIDEA:
+
+ _musculi_ Oudemans: Demodex.
+
+ INSECTA:
+
+ _cheopis_ Roth.: Lœmopsylla.—External.
+ _felis_ Bouché: Ctenocephalus.
+
+
+ MUS.—A Field Mouse.
+
+
+ CESTODA:
+
+ _longicollis_: Cysticercus.—Thoracic cavity.
+
+
+
+
+ THE FLEA AND ITS RELATION TO PLAGUE.
+
+ By Passed Assistant Surgeon CARROLL FOX,
+
+ _United States Public Health and Marine-Hospital Service_.
+
+
+ THEORIES AS TO TRANSMISSION OF PLAGUE.
+
+ 1. Direct contagion from man to man.
+
+ 2. Through slight abrasions of the skin, mucous membranes of mouth,
+ tonsils, nose, and conjunctiva receiving contaminated material.
+
+ 3. Through the respiratory tract, from air contaminated with dried
+ infectious sputum or dejecta. (Possibly the cause of primary pneumonic
+ plague.)
+
+ 4. Through the alimentary tract from food contaminated with saliva or
+ excretions from plague patients, or dejecta or the feet of insects
+ that have fed on plague material. In the case of rats, from eating the
+ carcasses of infected rats.
+
+ 5. Infected clothes, soil, or houses.
+
+ 6. Through the bites of insects, especially the flea.
+
+ It has been noticed for many years that an epidemic of plague in man
+ was associated with an epizootic of high mortality among rats, but it
+ was not until Yersin discovered the _Bacillus pestis_ in 1894 that the
+ disease in man and rats was shown to be identical. The first five
+ theories are not satisfactory in explaining the epidemiology of
+ plague, and in 1897 Simond advanced the theory that plague was carried
+ by means of fleas. Hankin in 1898 also suggested an insect as an
+ intermediate host. This theory has been developed by Ashburton
+ Thompson, Gauthier and Raybaud, Liston, Verjbitski, and others, and
+ finally by the last Indian Plague Commission, whose work makes a
+ distinct advance in our knowledge of this subject. The reader is
+ referred to the work of this commission for a review of the subject,
+ which has been liberally used in the preparation of this paper.[AD]
+
+Footnote AD:
+
+ Journal of Hygiene (Vol. VI, No. 4; Vol. VII, No. 3; Vol. VII, No.
+ 6; Vol. VIII, No. 2).
+
+
+ INSECTS THAT HAVE BEEN SUSPECTED IN THE TRANSMISSION OF PLAGUE.
+
+ It is probable that all insects capable of sucking blood will take the
+ _Bacillus pestis_ into their alimentary canal if they feed on a
+ septicæmic plague animal. Ogata suggested that not only the flea but
+ the mosquito also may be responsible for the transmission of plague.
+ Yersin, Hankin, and Nuttall have each demonstrated the presence of
+ _Bacillus pestis_ in the dejecta of flies and ants; and Nuttall and
+ Verjbitski in the stomach and dejecta of the bedbug. Hertzog found the
+ bacilli in the _Pediculus capitis_ taken from a child which died of
+ plague, and McCoy[201] has found the organism in lice, _Hæmatopinus
+ columbianus_, taken from a plague-infected squirrel. The plague
+ bacilli have been frequently demonstrated in rat fleas taken from
+ plague rats, and McCoy has shown its presence in the flea
+ (_Ceratophyllus acutus_) of the California ground squirrel (_Citellus
+ beecheyi_). The cockroach has also been thought to be instrumental in
+ spreading the infection by contaminating food. The presence of bacilli
+ in the stomach and dejecta of insects has not only been proven
+ microscopically but by animal inoculation as well.
+
+ Assuming that the relation between rat plague and human plague has
+ been proven without a doubt—that is, that an outbreak of human plague
+ is associated with an infection in rats, or, in other words, that
+ plague is primarily a disease of rats and secondarily a disease of
+ man—the theory that it is conveyed through an intermediate parasitic
+ host is the only one which will fulfill all the requirements, and
+ after a study of their habits we are able to exclude all of the
+ parasites but the flea as the active agent in its transmission.
+
+ Plague is rarely or never contracted either in rat or in man by eating
+ contaminated food. Therefore those insects like flies and cockroaches,
+ which are supposed to spread the infection by contaminating food with
+ their dejecta, need not be considered.
+
+ The habits of the domestic mosquitoes are such that while they
+ occasionally do bite animals they usually feed on the blood of man,
+ and are not known to feed where there is much hair, as there is on the
+ rat. This also applies to the bedbug. Verjbitski has shown
+ experimentally that bedbugs would not feed on rats until the animals
+ were shaved.
+
+ Pediculi are degenerate insects, their powers of locomotion being
+ limited. Their eggs are laid on and are attached to the hair of the
+ host. They are born, live, and die on the same host, and rarely pass
+ from one animal to another of a different species. It can not be
+ denied, however, that this parasite occasionally may be instrumental
+ in spreading plague from rat to rat. The _Pediculus capitis_, if
+ placed on a rat, will feed with avidity, but these insects are rarely
+ found upon rats in nature.
+
+ We have no record of plague bacilli having been demonstrated in mites
+ commonly found on rats, but no doubt if search be made they could be
+ found after feeding on a septicæmic plague rat. These mites, however,
+ always confine themselves closely to their particular host and are not
+ known to bite man. The tiny itch mite (_Notoedres alepis_, Railliet
+ and Lucet) producing rat scabies has, according to Schumann,[202] been
+ known to cause a cutaneous lesion in man, but this mite need not be
+ considered from a plague standpoint.
+
+ The flea, on the other hand, lives but part of the time on its host,
+ its eggs developing in the nests or runs of the animal. Again, this
+ insect does not confine itself to one particular species of host only,
+ as frequently the flea of one animal is found on an animal of an
+ entirely different species. Unlike the lice, they are very active and
+ can readily move from place to place. Not only that, but it has been
+ frequently demonstrated that the fleas of rats and of other animals
+ would readily take to man, especially if their natural host was
+ scarce. That rat fleas will bite man has been demonstrated by Gauthier
+ and Raybaud, working with the _Leomopsylla cheopis_; Tidswell,
+ _Lœmopsylla cheopis_ and _Ceratophyllus fasciatus_; Liston,
+ _Lœmopsylla cheopis_; Tiraboschi, _Lœmopsylla cheopis_; Indian Plague
+ Commission, _Lœmopsylla cheopis_; and McCoy and Mitzmain[203],
+ _Lœmopsylla cheopis_, _Ceratophyllus fasciatus_, and _Ctenopsyllus
+ musculi_. It has generally been considered that the _Ctenopsyllus
+ musculi_, above all others, would not bite man, but the last-named
+ observers showed that it would occasionally feed, although it would
+ not live long, in captivity. One of the fleas, a _Ceratophyllus
+ fasciatus_, was kept alive by Mitzmain for over four months on man’s
+ blood alone.
+
+
+ EXPERIMENTS PROVING THAT FLEAS CAN TRANSMIT PLAGUE.
+
+ By a series of experiments carried out in specially constructed cages
+ and go-downs where healthy rats in the absence of fleas were brought
+ in contact with plague-infected rats, the Indian Plague Commission
+ showed that the healthy rats would not contract the disease,
+ notwithstanding the fact that they were not only in intimate contact
+ with the sick rats, but also with the contaminated food and excreta of
+ the sick rats. They then showed that if fleas were introduced the
+ healthy rats would contract plague, the rate of progress of the
+ epizootic being in direct proportion to the number of fleas present.
+ By hanging cages containing healthy rats in cages holding infected
+ rats, but above the jumping distance of a flea, it was shown that the
+ healthy rats would remain well, while those in cages hung within 2
+ inches from the ground would contract plague. Thus they excluded
+ aerial infection. They also found that if fleas were excluded young
+ rats could suckle a plague-infected mother without contracting the
+ disease.
+
+ Guinea pigs were allowed to run in houses where cases of human and of
+ rat plague were known to have occurred and where many fleas were
+ present. These rodents served as good traps for the fleas and 29 per
+ cent of them contracted plague.
+
+ Most of the experiments of the Indian Plague Commission were done with
+ the Indian rat flea, the _Lœmopsylla cheopis_, but they also performed
+ 27 experiments with the cat flea, _Ctenocephalus felis_, with negative
+ results; 35 experiments with the human flea, _Pulex irritans_, 3 of
+ which were successful; and 2 experiments with the _Ceratophyllus
+ fasciatus_, the common rat flea of Europe and North America, both of
+ which were successful.
+
+ In San Francisco a few experiments under purely experimental
+ conditions have been carried on by McCoy to determine the ability of
+ the squirrel flea, the _Ceratophyllus acutus_, to transmit plague.
+ Fleas that had been previously fed on the blood of a septicæmic
+ plague-infected squirrel were then allowed to feed from test tubes on
+ healthy guinea pigs. While the feces of some of these fleas up to four
+ days, when inoculated into guinea pigs, were proven to be infective,
+ none of those guinea pigs on which the fleas were allowed to feed
+ contracted plague. It might be said, however, that in no case were
+ they seen to eject feces while feeding, the significance of which will
+ be apparent later.
+
+
+ THE BACILLUS IN THE FLEA.
+
+ The Indian Plague Commission found that the average capacity of the
+ rat flea’s stomach (_Leomopsylla cheopis_) was 0.5 cubic millimeter,
+ and that it might receive as many as 5,000 germs while imbibing blood
+ from a plague rat. They further found that the bacillus would multiply
+ in the stomach of a flea and that the percentage of fleas with bacilli
+ in the stomach varied with the season of the year. In the epidemic
+ season the percentage was greatest for the first four days, and on one
+ occasion the stomach was found filled with _Bacillus pestis_ on the
+ twentieth day. In the nonepidemic season no plague bacilli were found
+ in the stomach after the seventh day. They also found that in the
+ epidemic season fleas might remain infective up to fifteen days, while
+ in the nonepidemic season but seven days, and in the latter case the
+ percentage of infection in animals was much less than in the epidemic
+ season. They showed that while one flea was occasionally able to carry
+ the infection this was not usual. It was found that both the males and
+ the females were capable of transmitting the disease.
+
+ After a number of dissections they were unable to demonstrate the
+ presence of bacilli anywhere but in the stomach and rectum. At no time
+ was anything found in the body cavity or salivary glands and but
+ rarely in the œsophagus, and then only when the flea was killed
+ immediately after feeding.
+
+ We have in San Francisco examined quite a number of serial sections of
+ plague-infected fleas with the same result as obtained by the Indian
+ Plague Commission. The bacilli are readily demonstrated, sometimes in
+ enormous numbers, in the gizzard, stomach, and in the rectum, but at
+ no time have they been found in the body cavity, the salivary glands,
+ or the ovary. In fact, as we are dealing with a vegetable organism and
+ not an animal organism, like the _Plasmodium malariæ_, we could hardly
+ expect to find any biologic change, except simple multiplication,
+ occurring in the intermediate host.
+
+
+ HOW THE FLEA CLEARS ITSELF OF BACILLI.
+
+ Some explanation is necessary as to why the bacilli eventually
+ disappear from the flea, although they seem to multiply during the
+ first few days. It is evident that the peristaltic action of the
+ stomach during the course of digestion forcing the blood at the proper
+ time into the rectum, finally to be ejected from the body, would in
+ itself cause many bacilli to be discharged, but naturally a few would
+ remain to multiply indefinitely. The bacteriacidal action of the blood
+ is soon lost after entering the flea’s stomach, but it has been shown
+ by proper staining that the leucocytes after the first feeding with
+ healthy blood contain numbers of _Bacillus pestis_, and it seems
+ probable that this phagocytic action is important in the cleansing
+ process. It has been shown that after successive feedings on the blood
+ of noninfected animals the power of phagocytosis is increased, and
+ that successive feedings on the fresh blood of animals that have been
+ immunized against plague still further assists and hastens the
+ process. When there is a frequent introduction of fresh normal or
+ immunized blood its bactericidal action is also instrumental in the
+ cleansing process.
+
+
+ REGIONAL DISTRIBUTION OF FLEAS ON RATS.
+
+ The location of the primary bubo in a case of plague, human or rodent,
+ depends upon the site of inoculation, for that group of glands will
+ first enlarge which has direct lymphatic connection with the area
+ through which the _Bacillus pestis_ enters the animal organism. The
+ British Indian Plague Commission found that 72 per cent of their
+ naturally infected rats and 61 per cent of the rats experimentally
+ infected by fleas had cervical buboes, while in no instance in over
+ 5,000 plague rats was a mesenteric bubo encountered. On the other
+ hand, where plague was induced through feeding healthy rats with the
+ carcasses of plague rats a mesenteric bubo was found in 74.5 per cent
+ of those infected and a cervical bubo in 36 per cent. In San Francisco
+ in naturally infected rats a primary mesenteric bubo has never been
+ seen, and a cervical bubo has been seen but once. These figures show
+ conclusively that naturally infected rats are not infected by feeding.
+ It is curious, as has been pointed out by McCoy[204], that such a
+ large percentage of cervical buboes should be found in India, while a
+ cervical bubo has been seen but once in naturally infected animals in
+ San Francisco. Here the axillary and inguinal buboes are the rule. The
+ Indian Commission found that the commonest situation to find fleas on
+ guinea pigs was the head and neck. They combed 53 guinea pigs to
+ determine the regional distribution of fleas, and found that 65.3 per
+ cent were taken from the neck and head. This would account for the
+ preponderance of cervical buboes in guinea pigs observed in their
+ work, and inferentially for the preponderance of cervical buboes found
+ in naturally infected rats. Thinking that the predominating rat flea
+ in San Francisco, the _Ceratophyllus fasciatus_, might be the carrier
+ of the infection and that it might prefer a different part of the body
+ than the _Lœmopsylla cheopis_, McCoy and Mitzmain carried on a series
+ of investigations to determine the regional distribution of fleas on
+ the rat’s body, but this has shown that while the _Ctenopsyllus
+ musculi_ seems to be generally confined to the head and neck, the
+ _Ceratophyllus fasciatus_ and _Lœmopsylla cheopis_ are almost
+ invariably taken from the body, especially from the pelvic region.
+
+
+ ANATOMY OF THE MOUTH PARTS OF THE CERATOPHYLLUS FASCIATUS.
+
+ The following description differs somewhat from that given by
+ Wagner[205] and the description found in the Journal of Hygiene, both
+ of which, however, refer to different species of Siphonaptera.
+
+ The mouth parts may be divided into those inside and those outside of
+ the head.
+
+
+ OUTSIDE THE HEAD.
+
+ The epipharynx, or pricker, is a long, slender, hollow organ. Its
+ cavity is closed distally, and proximally connects with the hoemocoel.
+ It is made up of a dorsal and a ventral portion. Its dorsal portion
+ ends just within the head. Its ventral portion is grooved and is
+ continuous with the posterior wall of the aspiratory pharynx. Its
+ distal extremity is slightly expanded, forming a stylet for piercing,
+ while the little papillæ seen along the anterior surface in many
+ species are absent in this one. Laterally there is a membranous
+ expansion which interlocks with a similar expansion on the mandibles,
+ forming a tube, through which the blood is sucked.
+
+ The mandibles are two in number, articulating just within the head, so
+ that they are capable, of independent movement. They are serrated at
+ their distal extremities. Above, within the head, the anterior portion
+ of the mandibles ends just behind the beginning of the hypopharynx, to
+ which it is connected, becoming practically continuous with that
+ organ. The posterior portion is attached to its basal element. Each
+ mandible contains a groove, forming practically a closed canal, which
+ becomes continuous with the exit duct of the salivary pump.
+
+ The rostrum (labial palpi) forms a protection and guide to the
+ mandibles and epipharynx. Its first portion is unpaired and
+ articulates within the head, with its basal element. At the apex of
+ its first portion it bifurcates, forming a paired organ, which is
+ divided into a varying number of pseudojoints, depending on the
+ species of the flea. As it is a chitinous structure, these
+ pseudojoints, areas in which there is little chitin, enable it to
+ double up as the mandibles and epipharynx are inserted into the skin.
+ At the apex of the rostrum are some tactile hairs.
+
+ The maxillæ are triangular chitinous plates situated on either side of
+ that portion of the head where the biting organs emerge. These
+ structures serve to protect the origin of the epipharynx and
+ mandibles, rest upon the cutaneous surface in the act of biting,
+ thereby steadying the head and serving as a fulcrum when the flea
+ withdraws its biting apparatus when through feeding. The maxillæ have
+ their palpi, which are four jointed, paired organs coming out at the
+ anterior lower angle of the head. Their function is sensory.
+
+
+ INSIDE THE HEAD.
+
+ The hypopharynx is a chitinous plate forming part of the floor of the
+ aspiratory canal. To its under surface are attached the muscles which
+ operate the salivary pump. Its lower portion is connected to the
+ mandibles, while its upper portion is connected to the posterior
+ portion of the floor of the aspiratory pharynx by a membranous
+ ligament.
+
+ The aspiratory pharynx extends from the connection of the hypopharynx
+ with the mandibles to the œsophageal commissure. In a general way it
+ first passes upward and then turns, passing backward. Its roof is
+ formed by the continuation of the ventral surface of the epipharynx,
+ while its floor is formed by the hypopharynx below and above by the
+ chitinous layer which is continuous with the œsophagus. The anterior
+ end of this particular portion curves strongly downward, where it is
+ attached to the upper portion of the hypopharynx by a membranous
+ ligament. In a general way it may be divided into a vertical and
+ longitudinal portion. The longitudinal portion expands laterally, so
+ that its capacity is greatly increased when dilated. Into the floor of
+ this longitudinal portion empties the vertical part of the aspiratory
+ pharynx, and at the junction of the two there seems to be a valvular
+ arrangement, preventing blood from escaping after it has entered the
+ upper part of the aspiratory canal. The œsophagus starts at the
+ œsophageal commissure and ends in the gizzard. It is not expanded as
+ in some insects, forming a gullet, but is practically the same
+ diameter throughout its entire extent. It is lined with chitin,
+ surrounded by a delicate basement membrane.
+
+ The gizzard is a mushroom-shaped organ, opening into the stomach and
+ receiving the contents of the œsophagus and the aspiratory pharynx.
+ From its anterior concave inner surface project a number of
+ finger-like processes that arise from a basement membrane. They are
+ lined with chitin, and each one near its base contains an elongated
+ nucleus. These processes reach to the center of the gizzard and in a
+ general way point towards the opening into the stomach. The gizzard is
+ surrounded by circular bands of muscle fibers. Its function is not
+ entirely understood. Wagner[205] has pointed out that these processes
+ may act as whips to defibrinate the blood. It is more probable that
+ their action is mainly valvular, preventing regurgitation of blood
+ from the stomach.
+
+ The stomach of a flea is large and is capable of great distention. It
+ is composed of a layer of secretory cells, resting on a basement
+ membrane, the organ being surrounded by muscle fibers passing in
+ different directions. The epithelial surface is thrown into little
+ projections like villi. As absorption occurs in the stomach, these
+ villi, or projections of the epithelial cells, may serve to increase
+ the absorptive surface as well as serving a glandular function. At the
+ anterior end of the stomach are the cecal glands.
+
+ The intestine is short, receives the excretion from the Malpighian
+ tubules, and ends in the rectum. In the rectum may be seen the
+ so-called “rectal glands.” All of the alimentary canal, with the
+ exception of the stomach, is lined with chitin. The stomach and the
+ rectum are capable of peristaltic movement.
+
+ The salivary glands, four in number, two on each side of the anterior
+ part of the stomach, are simple acinous glands, lined with a single
+ layer of secreting cells. The lumen of the glands is large and acts as
+ a reservoir for the salivary secretion. The ducts from these glands
+ unite to form a single duct which passes beneath the subœsophagal
+ ganglion and empties into the salivary pump. This duct is lined on its
+ inner surface by a spiral arrangement of chitin, giving it a very
+ characteristic appearance.
+
+
+ DESCRIPTION OF FIGURE SHOWING MOUTH PARTS.
+
+ 1. Epipharynx.
+
+ 2. Mandibles.
+
+ 3. Rostrum, paired portion.
+
+ 4. Rostrum, unpaired portion.
+
+ 5. Maxilla.
+
+ 6. Maxillary palpus.
+
+ 7. Salivary grooves.
+
+ 8. Basal element of rostrum.
+
+ 9. Basal element of mandibles.
+
+ 10. Salivary pump.
+
+ 11. Salivary duct.
+
+ 12. Vertical portion, aspiratory canal.
+
+ 13. Longitudinal portion, aspiratory canal.
+
+ 14. Œsophagus.
+
+ 15. Œsophageal ganglia.
+
+ 16. Muscles operating aspiratory canal.
+
+ 17. Hypopharynx.
+
+ 18. Muscles operating salivary pump.
+
+ 19. Ligament connecting hypopharynx with floor of aspiratory canal.
+
+[Illustration:
+
+ PLATE I.
+
+ MOUTH PARTS OF CERATOPHYLLUS FASCIATUS.
+]
+
+
+ THE ACT OF BITING.
+
+ The epipharynx, or pricker, makes an opening into the skin, through
+ which the mandibles are inserted. These organs, by means of their
+ serrations and independent movement, then enlarge the opening as with
+ a saw, permitting them, with the epipharynx, to pass deeper and deeper
+ until the points of the maxilla rest upon the cutaneous surface. The
+ labial palpi serve as a protective case when the organs are not in
+ action. When in action they serve as a guide to the piercing organs,
+ but are not inserted into the skin. They double up like a bow, on each
+ side, the bend of the bow becoming greater and greater as the biting
+ apparatus passes deeper and deeper. Mitzmain[206] has pointed out that
+ the spring-like action of this bow may assist the flea to withdraw the
+ mandibles and epipharynx.
+
+ During the process of penetration the salivary pump receives saliva
+ from the salivary glands and pumps it down, through the channel in the
+ mandibles, into the wound. It will be seen that the hypopharynx, being
+ attached above by a membranous ligament and connected intimately with
+ the mandibles below, moves downward with these organs as they pass
+ through the skin. At the same time the muscles attached to its under
+ surface and the salivary pump contract, enlarging the lumen of the
+ pump. When the mandibles are retracted the salivary pump collapses,
+ thereby forcing the saliva out with the movement upward of the
+ mandibles. At the proper time the muscles operating the aspiratory
+ pharynx contract, drawing the canal open and aspirating blood through
+ the canal made by the approximation of the epipharynx and mandibles
+ and into the aspiratory pharynx. When full, the muscles relax from
+ before backward and the pharynx, by means of the elastic reaction of
+ its chitinous lining, contracts and forces the blood backward through
+ the gizzard and into the stomach. It has already been pointed out that
+ the finger-like processes in the gizzard probably act as valves to
+ prevent regurgitation from the stomach.
+
+
+ HOW THE FLEA INFECTS ITS HOST.
+
+ The exact method by which the flea can transmit plague from animal to
+ animal has, in our opinion, never been satisfactorily explained. There
+ have been several explanations offered: First, that the rat may eat
+ the flea. Miller[207] has found that the _Hepatazoon perniciosum_ is
+ transmitted from rat to rat through the rat eating the mite, _Lelaps
+ echidninus_, which acts as the intermediate host. We know, however,
+ that when a rat is fed on plague material a mesenteric bubo is the
+ rule, while in naturally infected rats a mesenteric bubo is a rare
+ condition. This, then, negatives the possibility of plague being
+ contracted through eating the flea.
+
+ Another explanation is that the infection comes from the saliva
+ injected at the time of biting. We have already stated that after
+ repeated examinations, both by dissecting out the salivary glands and
+ by serial sections of the entire flea, plague bacilli have never been
+ demonstrated in these glands or anywhere outside of the alimentary
+ tract.
+
+ Another explanation has been advanced, that the bacillus is introduced
+ by the contaminated mandibles. It is not possible to exclude this as a
+ means of infection, although the Indian Plague Commission made
+ numerous investigations and was unable to demonstrate the bacillus on
+ the mandibles.
+
+ The possibility of infection taking place by regurgitation from the
+ stomach has also been considered. As the stomach is guarded by the
+ finger-like processes in the gizzard which seem to act as competent
+ valves, and as the movement of the blood aspirated by reason of the
+ mechanism already explained is in a backward direction, it would seem
+ improbable that there is any regurgitation from the stomach.
+
+ The most plausible explanation that has been advanced has been based
+ on an observation that blood-sucking insects at the time of biting
+ frequently eject a drop of blood from the rectum. We know that the
+ rectum may contain numerous plague bacilli, and it is supposed that
+ this blood ejected in the vicinity of the bite is either brought in
+ contact with the slight wound by the feet or mandibles of the flea
+ itself or is rubbed in as a result of scratching. Verjbitski has shown
+ that an emulsion of the feces of fleas or any plague material when
+ placed upon the bitten part before the expiration of twenty-four hours
+ is sufficient to give the animal plague. After twenty-four hours the
+ animals did not develop plague, it being supposed that the slight
+ wound in the skin made by the biting apparatus had healed. It is
+ probable that this ejection of blood is purely accidental and does not
+ necessarily occur at the time of biting, but it is likely that the
+ insect had just previously had a full meal, which had been digested
+ and passed into the rectum. In the many biting experiments done by
+ McCoy and Mitzmain they report never having seen this ejection of
+ rectal contents taking place. It might also be stated that where they
+ used plague-infected fleas none of the animals developed plague after
+ being bitten.
+
+
+ ENUMERATION OF FLEAS THAT HAVE BEEN FOUND ON RATS.
+
+ Various writers have reported the following fleas taken off rats:
+
+
+ Family SARCOPSYLLIDÆ Taschenberg.
+
+ Genus DERMATOPHILUS.
+
+ 1. _Dermatophilus cæcata_ Enderlein.—Seventeen specimens (females)
+ were found by Doctor Enderlein on the skin behind the ears of a
+ specimen of _Mus rattus_ from Saopaulo, Brazil.
+
+
+ Genus ECHIDNOPHAGA Olliff.
+
+ 2. _Echidnophaga gallinacea_ Westwood.—Tiraboschi has found this flea
+ on the _Mus rattus_ in Italy.
+
+ 3. _Echidnophaga rhynchopsylla_ Tiraboschi.—This flea has been taken
+ in Italy from _Mus rattus_ and _Mus alexandrinus_. It has been
+ described by Rothschild under the name of _Echidnophaga murina_.
+
+
+ Family PULICIDÆ Taschenberg.
+
+ Genus CERATOPHYLLUS Curtis.
+
+ 4. _Ceratophyllus fasciatus_ Bosc.—This is the common rat flea of
+ Europe and the United States. It has also been found in Cape Town,
+ Australia, and is occasionally found on rats in India.
+
+ 5. _Ceratophyllus londiniensis_ Rothschild.—This flea has been taken
+ off mice in England; off rats in Italy (_Ceratophyllus italicus_
+ Tiraboschi) and has been found once on _Mus rattus_ in San Francisco,
+ Cal.
+
+ 6. _Ceratophyllus acutus_ Baker.—This is the common flea of the
+ California ground squirrel; and has been taken off _Mus norvegicus_ in
+ San Francisco, Cal.
+
+ 7. _Ceratophyllus anisus_ Rothschild.—This flea has been described by
+ Rothschild from Yokohama, Japan, taken off _Felis_ sp. One specimen
+ was found in San Francisco, Cal., taken off _Mus norvegicus_.
+
+ 8. _Ceratophyllus niger_ Fox.—This flea is commonly found in San
+ Francisco, Cal., in chicken yards and sparrows’ nests and has also
+ been found on rats, _Mus norvegicus_, and on man.
+
+ 9. _Ceratophyllus consimilis_ Wagner.
+
+ 10. _Ceratophyllus lagomys_ Wagner.
+
+ 11. _Ceratophyllus mustelæ_ Wagner.
+
+ 12. _Ceratophyllus penicilliger_ Grube.
+
+ These fleas have been taken off _Mus norvegicus_ in Europe.
+
+
+ Genus PULEX Linn.
+
+ 13. _Pulex irritans_ Linn.—This flea is widely distributed throughout
+ the world, and while essentially the human flea has been found on many
+ different species of animals and has frequently been encountered on
+ rats. A very large number of specimens have been taken off rats in San
+ Francisco, Cal.
+
+
+ Genus LŒMOPSYLLA Rothschild.
+
+ 14. _Lœmopsylla cheopis_ Rothschild.—This is the common rat flea in
+ tropical and subtropical countries. It has also been found in seaports
+ of the temperate zone, where it has been brought by ship rats.
+ Ninety-eight per cent of the rat fleas in India are of this species.
+ It has been found in Australia, where it was described by Tidswell
+ under the name of _Pulex pallidus_. In the Philippine Islands, where
+ it was described by Hertzog as the _Pulex philippinensis_. It has been
+ found in Brazil, where it was described by Baker as _Pulex
+ brasiliensis_, and Tiraboschi has found it in Italy, where it has been
+ described as the _Pulex murinus_. This flea has been frequently found
+ on man in India.
+
+
+ Genus CTENOCEPHALUS Kolenati.
+
+ 15. _Ctenocephalus canis_ Curtis.—This is the common dog flea found in
+ many parts of the world and is frequently taken off rats.
+
+ 16. _Ctenocephalus felis_ Bouché.—This is the common cat flea and is
+ also a widely distributed species. Frequently taken off rats.
+
+
+ Genus CTENOPSYLLUS Kolenati.
+
+ 17. _Ctenopsyllus musculi_ Dugés.—In England this flea is commonly
+ found on the domestic mouse. It has a wide distribution and has been
+ found on rats and mice in Europe, South Africa, India, Australia,
+ Mexico, and other places, and has been taken off _Mus norvegicus_,
+ _Mus rattus_, and _Mus musculus_ in San Francisco, Cal.
+
+
+ Genus NEOPSYLLA Wagner.
+
+ 18. _Neopsylla bidentatiformis_ Wagner.—This flea has been taken off
+ _Mus norvegicus_ in the Crimea.
+
+
+ Genus HOPLOPSYLLUS Baker.
+
+ 19. _Hoplopsyllus anomalus_ Baker.—This is one of the common
+ groundsquirrel fleas of California and has been found on _Mus
+ norvegicus_ in San Francisco and Palo Alto, Cal. That these squirrel
+ fleas are occasionally found on rats is interesting from the fact that
+ plague has been demonstrated both in rats and the ground squirrel in
+ California.
+
+
+ Genus HYSTRICHOPSYLLA Taschenberg.
+
+ 20. _Hystrichopsylla tripectinata_ Tiraboschi.—Reported by Tiraboschi
+ from _Mus musculus_ in Italy.
+
+
+ Genus CTENOPTHALMUS Kolenati.
+
+ 21. _Ctenopthalmus agyrtes_ Heller.—Taken off _Mus Norvegicus_ in
+ England.
+
+ _The results of the identification of 19,768 fleas in San Francisco
+ and Oakland, Cal._
+
+ SAN FRANCISCO, 1908.
+ Host: MUS NORVEGICUS.
+ ───────────┬───────────┬───────────┬───────────┬───────────┬───────────
+ Month. │ C. │L. cheopis.│ P. │ Cten. │ Cten.
+ │fasciatus. │ │ irritans. │ musculi. │ felis,
+ │ │ │ │ │ Cten.
+ │ │ │ │ │ canis.
+ ───────────┼─────┬─────┼─────┬─────┼─────┬─────┼─────┬─────┼─────┬─────
+ „ │Male.│ Fe- │Male.│ Fe- │Male.│ Fe- │Male.│ Fe- │Male.│ Fe-
+ │ │male.│ │male.│ │male.│ │male.│ │male.
+ ───────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────
+ April to │1,343│2,510│ 485│ 837│ 31│ 76│ 78│ 211│ 16│ 31
+ July 31 │ │ │ │ │ │ │ │ │ │
+ August │ 489│ 883│ 145│ 228│ 156│ 206│ 27│ 90│ 17│ 22
+ September │ 543│1,180│ 655│ 930│ 339│ 387│ 33│ 109│ 46│ 119
+ October │ 254│ 435│ 509│ 652│ 59│ 64│ 9│ 45│ 6│ 18
+ November │ 129│ 252│ 256│ 288│ 52│ 69│ 20│ 54│ 6│ 6
+ ───────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────
+ │2,758│5,260│2,050│2,935│ 637│ 802│ 167│ 509│ 91│ 196
+ ───────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────
+ Host: MUS RATTUS.
+ ───────────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────
+ │ 23│ 43│ 3│ 3│ 0│ 0│ 17│ 16│ 1│ 0
+ │ 4│ 7│ 1│ 0│ 9│ 16│ 3│ 3│ 0│ 0
+ ───────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────
+ │ 27│ 50│ 4│ 3│ 9│ 16│ 20│ 19│ 1│ 0
+ ───────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────
+ Host: MUS MUSCULUS.
+ ───────────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────
+ │ 4│ 10│ 1│ 0│ 0│ 0│ 2│ 10│ 0│ 0
+ │ 11│ 10│ 1│ 6│ 4│ 4│ 0│ 3│ 1│ 1
+ ───────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────
+ │ 15│ 20│ 2│ 6│ 4│ 4│ 2│ 13│ 1│ 1
+ ───────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────
+ OAKLAND, CAL., 1909.
+ Host: MUS NORVEGICUS.
+ ───────────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────
+ February │ 135│ 304│ 166│ 178│ 1│ 1│ 229│ 506│ 1│ 3
+ March │ 253│ 456│ 167│ 215│ 2│ 5│ 125│ 243│ 1│ 2
+ April │ 227│ 479│ 105│ 129│ 0│ 1│ 62│ 143│ 0│ 1
+ ───────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────
+ │ 615│1,239│ 438│ 522│ 3│ 7│ 416│ 892│ 2│ 6
+ ───────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────
+ Host: MUS ALEXANDRINUS.
+ ───────────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────
+ April │ 1│ 5│ 0│ 0│ 0│ 0│ 0│ 0│ 0│ 0
+ ───────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────
+
+ This does not include a few other specimens of different species taken
+ from _Mus rattus_ and _Mus norvegicus_, which have been included under
+ the heading of “Enumeration of fleas which have been found on rats.”
+
+
+ SYNOPSIS OF FLEAS COMMONLY FOUND ON RATS.
+
+ A. WITHOUT A COMB OF SPINES ON THE PROTHORAX OR THE HEAD.
+ 1. Two bristles on the gena, an ocular bristle placed
+ below the eye, an oral bristle placed just above
+ root of maxilla. Mesothorax not divided by an
+ internal incrassation. Claspers in male forming
+ prominent hump, claw like and covered by hairy
+ flap. An irregular row of about 10 teeth on inner _Pulex
+ side of hind coxa irritans_.
+
+ 2. Two bristles on gena, an ocular placed in front of
+ and just above middle of eye, an oral bristle
+ placed just above root of maxilla. Mesothorax
+ divided by internal incrassation, claspers not
+ forming prominent hump, not claw like, not
+ covered by hairy flap. A regular row of about six _Lœmopsylla
+ teeth on inner side of hind coxa, cheopis_.
+
+ AA. WITH A COMB OF SPINES ON PROTHORAX BUT NOT ON HEAD.
+ 3. Three bristles on lower genal row, upper genal row
+ represented by three or four small bristles
+ running along anterior margin of antennal groove.
+ Eye present, about five hairs on second joint of
+ antenna, not as long as third joint. Maxillary
+ palpi not as long as labial palpi. Labial palpi
+ reach to apex of fore coxa. Spines on posterior
+ tibia in pairs of about five groups. Head of male _Ceratophyllus
+ flattened on top, fasciatus_.
+
+ AAA. WITH A COMB OF SPINES ON THE PROTHORAX AND ON THE HEAD.
+ 4. Eye present, seven spines on lower margin of gena. _Ctenocephalus
+ Spines on posterior border of tibia in pairs canis_ or
+ _felis_.
+
+ 5. Eye absent, four spines on hind margin of gena.
+ Spines on posterior tibia single and in a close _Ctenopsyllus
+ set row musculi_.
+
+ DESCRIPTION OF PLATE II.
+ ────────────────────────────────────────────┬──────────────────────
+ Fig. 1. Clasping organs of male. │P Process.
+ „ │F Finger.
+ „ │M Manubrium.
+ „ │IX St Ninth Sternite.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 2. Head of female. │
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 3. Terminal abdominal segments, female.│8 T Eighth Tergite.
+ „ │8 St Eighth Sternite.
+ „ │10 T Tenth Tergite.
+ „ │10 St Tenth Sternite.
+ „ │Sp Spermatheca.
+ „ │Sty Stylet.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 4. Hind tibia. │
+
+
+ CERATOPHYLLUS FASCIATUS Bosc.
+
+ [Plate II.]
+
+ _Head._—Evenly and gently rounded in the female, flattened on top in
+ the male. Frontal notch distinct. Eye present, placed low down in
+ head. Gena acutely pointed posteriorly. Maxilla triangular. Maxillary
+ palpi not as long as the labial palpi. Labial palpi reach to apex of
+ anterior coxa, 5-jointed. Antennal groove in the male reaches to top
+ of head, in the female to within one-third. There are 3 bristles on
+ the lower genal row, the middle of which is the smallest, while the
+ upper genal row is represented by 3 small bristles, extending along
+ the edge of the antennal groove. In the male the lowermost bristle is
+ frequently paired. There are several fine hairs above the eye. The
+ occiput contains the normal row of apical bristles, the lowest of
+ which is the largest. There is one bristle back of the middle of the
+ antennal groove and a number of fine hairs along the posterior margin
+ of the antennal groove. The antenna is 3-jointed, the first joint
+ contains a row of about 5 very short fine hairs, while the second
+ joint contains about 5 not as long as the third joint.
+
+[Illustration:
+
+ PLATE II.
+
+ CERATOPHVLLUS FASCIATUS, BOSC.
+]
+
+ _Thorax._—The pronotum has one row of about 10 bristles, and a
+ ctenidium composed of about 16 or 18 spines. The mesonotum has a
+ posterior row of about 10 long bristles and there is an anterior row
+ of more numerous smaller ones. The metanotum has also a posterior row
+ of about 10 large bristles, with an anterior row of more numerous
+ smaller ones, while still anterior to this there are 5 or 6 still
+ smaller bristles. The metathorax contains 8 or 10 bristles which are
+ small anteriorly, larger posteriorly. On the sternum of the metathorax
+ there are 2 large bristles, while the episternum has 3 smaller ones.
+ On the epimerum are 2 bristles placed anteriorly and 3 or 4
+ posteriorly, one of which is on the apical margin.
+
+ _Abdomen._—The first stigma is nearly in line with those of the other
+ abdominal segments. There are two rows of bristles on the abdominal
+ tergites, a posterior of about 12 or 14 and an anterior of smaller,
+ less numerous bristles. The antipygidial bristles in the female are 3
+ in number on each side, of which the middle is the longest, and the
+ inner one the smallest. The male has but 2 antipygidial bristles on
+ each side. The sternites from the third to the sixth have a single row
+ of about 10 bristles, while the seventh has about 12. The metanotum
+ has 2 teeth on each side, as have the first and second abdominal
+ tergites. The third and fourth abdominal tergites have 1 tooth on each
+ side.
+
+ _Legs._—The fore coxæ are normally clothed. The fore femur has on the
+ outer side 11 or 12 fine bristles irregularly disposed, while on the
+ mid femur there is a row of about 3 to 5 bristles on the inner
+ surface. The hind coxa has no patch of spines on the inner side, while
+ on the inner surface of the hind femur there is a row of about 5 to 7
+ bristles. The spines on the posterior tibia are in pairs of six
+ groups, while on the outer surface there is a row of about 7 bristles.
+ None of the apical bristles of the tarsi are as long as the next
+ succeeding joint. The fifth tarsal joints on all the legs have 5
+ lateral spines.
+
+ Length of joints of tarsi:
+
+ Mid tarsi (♂) 8 7 4½ 3 7
+ Hind tarsi 18 11 7 4 8
+ Mid tarsi (♀) 8 7 5 3½ 7
+ Hind tarsi 21 13 8 5 8
+
+ _Modified segments._—(♂). The manubrium of the claspers is straight
+ and narrow, while the process extends upward as a short, blunt cone,
+ where at the tip there are several fine hairs. The lower margin is
+ evenly and gently rounded. The finger is short, extending but a little
+ above the process. It is concave on its anterior surface and convex on
+ its posterior, and from the posterior margin there are 2 large and 2
+ small bristles alternating. Two long heavy bristles arise from the
+ process below the insertion of the finger. The ninth sternite is
+ broad, with a deep sinus in its posterior border. Its lateral surface
+ contains numerous fine hairs, these hairs being somewhat larger just
+ beneath the sinus. Along the dorsal border of the tenth sternite there
+ are 3 heavy bristles in line. At the tip of the tenth tergite there is
+ one heavy bristle. Besides these heavy bristles in this segment there
+ are numerous fine hairs.
+
+ (♀) The eighth tergite contains just anterior to the sensory plate
+ about 12 small hairs while just beneath the sensory plate there are 2
+ long bristles. Lower down there is a patch of about 6 bristles and on
+ the apical margin 4 to 6. The stylet is short, cylindrical, slightly
+ larger at the base than at the tip, where there is a long bristle. On
+ the under surface arises a fine hair. Substylar flap (tenth sternite)
+ has along its margin numerous hairs.
+
+ DESCRIPTION OF PLATE III.
+ ────────────────────────────────────────────┬──────────────────────
+ Fig. 1. Clasping organs of male. │P Process.
+ „ │M Manubrium.
+ „ │F Finger.
+ „ │IX St Ninth Sternite.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 2. Head of female. │
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 3. Terminal abdominal segments, female.│8 T Eighth Tergite.
+ „ │8 St Eighth Sternite.
+ „ │10 T Tenth Tergite.
+ „ │10 St Tenth Sternite.
+ „ │Sp Spermatheca.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 4. Hind coxa inner surface. │
+
+
+ LŒMOPSYLLA CHEOPIS Rothschild.
+
+ [Plate III.]
+
+ _Head._—Abruptly rounded. Flattened on top in ♂. Eye present. No
+ ctenidia on head. Antennal groove in the ♀ reaches to within one-third
+ of the top of the head. In ♂ reaches to top of head. Gena obtusely
+ pointed posteriorly. Maxilla triangular. Maxillary palpi are not as
+ long as labial palpi. Labial palpi reach to apex of fore coxæ,
+ 4-jointed. Anterior edge of antennal groove overlapped by chitinous
+ flap. On posterior edge of antennal groove are a number of small
+ bristles, these being most distinct in the male. The first antennal
+ joint in the male contains 4 or 5 hairs at its outer edge, while
+ transversely there is a row of several fine hairs. The second joint
+ has a row of fine hairs not as long as the third joint. Divisions
+ marking separations of third joint most pronounced on dorsal edge. Two
+ bristles on gena. The oral bristle placed low down just above the base
+ of the maxilla; the ocular bristle in front and just above the middle
+ of the eye. Six bristles on the posterior margin of the occiput on
+ each side with 2 back of the antennal groove.
+
+[Illustration:
+
+ PLATE III.
+
+ LŒMOPSYLLA CHEOPIS, ROTHSCHILD.
+]
+
+ _Thorax._—The pronotum is without a ctenidial comb, and has one row of
+ about 14 bristles. The mesonotum, the broadest of the three thoracic
+ nota, also has a single row of about 12 bristles. The metanotum has a
+ single row of about the same number. The mesosternite contains about 5
+ bristles. The pleura of the metathorax is normally divided. The
+ sternum contains 2 bristles, 1 anterior and 1 posterior. The
+ episternum contains 1 bristle, and the epimerum contains 2 rows of
+ bristles, an anterior row of 7 and an apical row of the same number.
+
+ _Abdomen._—The first abdominal tergite contains 2 rows of bristles, an
+ anterior and a posterior of about 6 bristles each, while the next 6
+ contains but a single row of about 14 bristles each, the lowest placed
+ just below the stigma. From the seventh tergite springs a single
+ antipygidial bristle. The sternites contain a single row of 8 or 10
+ bristles.
+
+ _Legs._—The fore coxa is normally clothed. The fore femur has on its
+ outer surface about 8 fine bristles. The mid femur has a single row of
+ about 6 bristles, while the hind femur has a row of the same number.
+ The hind coxa has on its inner surface a regular row of about 6 teeth.
+ The hind tibia has on its posterior border 5 groups of spines in
+ pairs, while on its outer surface there are about 8 small bristles in
+ a row. The apical bristle on the second tarsal joint of the hind leg
+ reaches to about the middle of the fifth tarsal article. The fifth
+ tarsal article on all of the legs has 4 lateral spines and a subapical
+ pair of hairs.
+
+ _Modified segments._—(♂) The manubrium of the claspers is short and
+ narrow. There are two free processes, the upper one, the finger, being
+ broadest and wider at the tip than at the base, its upper border being
+ more convex than the lower border and containing a number of bristles.
+ The ninth sternite is club-shaped, is nearly straight on its dorsal
+ margin, and the ventral margin contains a row of fine bristles from
+ base to apex.
+
+ (♀) No bristles in front of the sensory plate. Along its apical margin
+ externally there is a row of about 12 long bristles, and internally a
+ row of less numerous, shorter bristles. Laterally there is a more or
+ less regular row of about 8 bristles, and between this row and the
+ apical row 3 or 4 more.
+
+ DESCRIPTION OF PLATE IV.
+ ────────────────────────────────────────────┬──────────────────────
+ Fig. 1. Clasping organs, male. │10 T Tenth Tergite.
+ „ │10 St Tenth Sternite.
+ „ │P Process.
+ „ │F Finger.
+ „ │M Manubrium.
+ „ │IX St Ninth Sternite.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 2. Head of female. │
+ Fig. 3. Last tarsal joint of hind leg. │
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 4. Terminal abdominal segments, female.│8 T Eighth Tergite.
+ „ │8 St Eighth Sternite.
+ „ │10 T Tenth Tergite.
+ „ │10 St Tenth Sternite.
+ „ │Sp Spermatheca.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 5. Hind tibia. │
+
+
+ CTENOPSYLLUS MUSCULI Dugés.
+
+ [Plate IV.]
+
+ _Head._—The frons is prominent anteriorly, giving the head somewhat
+ the shape of a fez. There are 4 spines on the posterior border of the
+ gena. The antennal groove reaches to the top of the head. The
+ maxillary palpi are shorter than the labial palpi, which reach to
+ about two-thirds of the fore coxa and are 5-jointed. Maxilla
+ triangular. Eyes absent. At the most prominent part of the frons
+ anteriorly there are two short thick spines, while below these,
+ running along the anterior margin, there are 5 bristles. Above there
+ is an oblique row of 4 bristles, with 1 more placed near the top of
+ the antennal groove. Between this oblique row and lower bristles there
+ are numerous fine hairs. On the occiput there is a subapical row of
+ about 7 bristles on each side, while in front of this are 3 oblique
+ rows of bristles, the first containing 3, the second 4, and the third
+ 5. On the posterior margin of the antennal groove there are several
+ small hairs. On the first joint of the antenna there are about 3
+ hairs, while on the second joint there are 4 or 5, the longest
+ somewhat longer than the third joint.
+
+ _Thorax._—The pronotum has an anterior row of about 10 bristles, and a
+ ctenidium of about 24 spines. The mesonotum contains about 4 rows of
+ bristles, more or less regularly disposed, each row consisting of
+ about 8 or 9 bristles. The metanotum has 2 rows of bristles, a
+ posterior row of about 10 bristles, and an anterior of the same
+ number, while there are several smaller bristles in front of this. The
+ mesothorax contains about 10 bristles. The episternum of the
+ metathorax has 2 bristles, and on the sternum there is 1 large one.
+ The epimerum has 2 rows of 4 bristles each, with 1 large one at the
+ apical margin.
+
+[Illustration:
+
+ PLATE IV.
+
+ CTENOPSYLLUS MUSCULI, DUGES.
+]
+
+ _Abdomen._—The first abdominal tergite has 2 rows of 10 bristles each,
+ the posterior being comprised of the larger bristles. The next 6
+ tergites have 2 rows of bristles each, a posterior of large bristles,
+ about 12 in number, and an anterior of smaller bristles, also 12 in
+ number. On the apical edge of the metanotum there are 2 small teeth on
+ each side. The first abdominal tergite contains 3 such teeth while the
+ second and third have 1 each on each side. At the apex of the seventh
+ tergite in the female there are 4 antipygidial bristles, sometimes 5.
+ The male has but 3 antipygidial bristles. The abdominal sternites from
+ the third to the sixth have a single row of 6 bristles. The seventh
+ has a row of about 16 bristles.
+
+ _Legs._—The fore coxa has about 32 large bristles more or less
+ regularly disposed in 6 oblique rows. The hind coxa is without teeth
+ on the inner surface. The mid femur is without bristles on its lateral
+ surfaces. The hind femur is also without a row of bristles on its
+ lateral surfaces. The spines on the posterior border of the tibia are
+ single and in a close set row. The apical spines of the second tarsal
+ joint of the hind legs are shorter than the third joint. The last
+ tarsal joint on all the legs contains 4 lateral spines and a subbasal
+ pair situated between the first lateral pair.
+
+ _Modified segments._—(♀) Just beneath the pygidium is 1 long bristle.
+ On the eighth tergite there is a patch of hairs, 6 of which are on the
+ apical margin and about 5 or 7 anterior to these. The stylet is short,
+ almost as wide at the base as at the tip, where there is a long hair.
+ Posteriorly to this bristle there springs another one from the under
+ surface.
+
+ (♂) Manubrium of the claspers is narrow, curved at the tip. The finger
+ reaches to the level of the process, has a stout pedicle, is flat on
+ its anterior border, and is decidedly convex on its posterior border,
+ where there are 4 bristles. The shape of the ninth sternite is shown
+ in the figure.
+
+ DESCRIPTION OF PLATE V.
+ ────────────────────────────────────────────┬──────────────────────
+ Fig. 1. Clasping organs of male │P Process.
+ „ │F Finger.
+ „ │M Manubrium.
+ „ │IX St Ninth Sternite.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 2. Head of female. │
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 3. Terminal abdominal segments, females│8 T Eighth Tergite.
+ „ │8 St Eighth Sternite.
+ „ │10 T Tenth Tergite.
+ „ │10 St Tenth Sternite.
+ „ │Sty Stylet.
+ „ │Sp Spermatheca.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 4. Hind coxa, inner surface. │
+
+
+ PULEX IRRITANS Linnæus.
+
+ [Plate V.]
+
+ _Head._—Evenly and abruptly rounded in both sexes. Frontal notch
+ absent. Eye large. Maxillary palpi longer than the labial palpi.
+ Labial palpi reach to about half the length of the anterior coxa and
+ are 4-jointed. The mandibles are broad and markedly serrate. Maxillæ
+ triangular. Antennal groove short and wide, closed behind, thickened
+ on edges, and reaches to top of head in both sexes by chitinous
+ thickening. Second joint contains 8 or 9 fine hairs, shorter than the
+ third joint. Division of the third joint only to be seen on dorsal
+ surface. Two bristles on the gena, one placed low down just above the
+ maxilla, the other below the eye. From the lower margin of the gena
+ occasionally may be seen a small tooth. One bristle on the occiput
+ near the posterior lower angle. A few fine hairs on the posterior edge
+ of the antennal groove.
+
+ _Thorax._—The thoracic nota each contain a single row of about 10 or
+ 12 bristles. There is no ctenidium on the pronotum. The mesosternite
+ is narrow and is not divided by an internal incrassation. The
+ episternum of the metathorax is large and contains about 2 or 3
+ bristles and is not quite separated from the sternum anteriorly. The
+ epimerum has an anterior row of about 7 or 8 bristles and an apical
+ row of about 6.
+
+ _Abdomen._—Each of the abdominal tergites, with the exception of the
+ first, has a single row of 8 or 10 bristles. The first has 2 rows of
+ about 4 each. The sternites from third to seventh have a single row of
+ about 6 bristles. There is one short antipygidial bristle on each
+ side.
+
+ _Legs._—The hind coxa has on its inner surface posteriorly a number of
+ fine hairs, while anteriorly there are 10 or 12 teeth in an irregular
+ line. The hind femur has on its inner surface a row of about 8 or 9
+ bristles. The spines on the posterior tibia are in pairs, and there
+ are about 7 bristles in a line on its outer lateral surface. The
+ apical bristle of the second tarsal joint of the hind leg reaches to
+ about the middle of the fifth joint. The last tarsal joints of all the
+ legs contain 4 lateral spines and a subapical pair, and between the
+ third and last lateral spine there is a hair.
+
+ _Modified segments._—(♀) The eighth tergite has no bristles above the
+ pygidium but has numerous short stout bristles laterally and on and
+ close to the apical margin. The stylet is short and stout and has at
+ its tip a long hair. The tenth sternite and tergite contain numerous
+ fine hairs, those on the sternite confined to the apical edge.
+
+ (♂) The male claspers are quite characteristic. The manubrium is large
+ and curved and points ventrally. The claspers have two processes, the
+ lower of which, with the finger, form together a kind of claw which is
+ covered by the other process forming a flap, quite hairy on its upper
+ margin. The ninth sternite is described very well by Rothschild[208]
+ as “boomerang” shaped. The eighth tergite has a small manubrium.
+
+[Illustration:
+
+ PLATE V.
+
+ PULEX IRRITANS, LINNÆUS.
+]
+
+ DESCRIPTION OF PLATE VI.
+ ────────────────────────────────────────────┬──────────────────────
+ Fig. 1. Clasping organs of male │F Finger.
+ „ │M Manubrium.
+ „ │IX St Ninth Sternite.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 2. Head of male. │
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 3. Terminal abdominal segments, female │8 T Eighth Tergite.
+ „ │8 St Eighth Sternite.
+ ────────────────────────────────────────────┼──────────────────────
+ Fig. 4. Hind coxa and femur, inner surface. │
+
+
+ CTENOCEPHALUS CANIS Curtis.
+
+ [Plate VI.]
+
+ _Head._—Strongly and evenly rounded in both sexes. Eye large. Maxilla
+ triangular. Maxillary palpi about as long as labial palpi. Labial
+ palpi reach to two-thirds of anterior coxæ, 4-jointed. Seven spines
+ along the lower margin of the gena. The posterior angle of the gena
+ ends in a small tooth. Occasionally this may be absent. Antennal
+ groove in the female reaches to within one-third of the top of head
+ and is prolonged upwards by a chitinous thickening and in the male
+ reaches almost to top of head. Two bristles on the gena, one placed
+ well toward the anterior lower angle and the other in front of the
+ eye. Usual number of bristles on posterior margin of the head, with 2
+ large ones back of the antennal groove. About 8 hairs on the second
+ joint of the antenna nearly as long as the third joint.
+
+ _Thorax._—A row of about 10 bristles on the pronotum, with a ctenidium
+ of about 14 to 16 spines. Two rows of bristles on the mesonotum, a
+ posterior of about 12, another of more numerous smaller bristles
+ placed well anteriorly. The metanotum contains a single row of about
+ 10 or 12 bristles. The episternum of the metathorax has 3 or 4 stout
+ bristles, while the epimerum contains an anterior row of about 10
+ bristles and a posterior row of about 9.
+
+ _Abdomen._—The first abdominal tergite contains 2 rows of about 4
+ bristles each, while the other tergites to the seventh contain a
+ single row of from 12 to 16 bristles. The stigmata are large. There is
+ a single antipygidial bristle on each side. The sternites from third
+ to seventh have a single row of 4 bristles each.
+
+ _Legs._—The hind coxa has on its inner side a patch of from 6 to 12
+ spines, while the hind femur has a row of 10 or 12 bristles on its
+ inner surface. The spines on the posterior border of the hind tibia,
+ with the exception of the apical, are in pairs, while in the apical
+ group are about 3 stout bristles. The apical spine of the second joint
+ of the hind leg reaches to nearly the middle of the fifth joint. On
+ the fifth joint of all the legs there are 4 lateral spines and a
+ subapical pair, and between the third and fourth lateral spines there
+ is a hair.
+
+ _Modified segments._—(♀) The eighth tergite has no hairs back of the
+ stigma. The apical margin is rounded at the apex and contains 8 or 10
+ bristles. The stylet is short and wide and contains at its tip a long
+ and a short bristle.
+
+ (♂) The manubrium is short and narrow. The movable finger of the
+ clasper is short, thick, swollen at its middle, bluntly rounded at its
+ extremity, and contains on its upper border numerous hairs and a few
+ on its lower border.
+
+ Rothschild[209] has pointed out certain differences between the
+ _Ctenocephalus canis_ and _Ctenocephalus felis_. The differences are
+ that in the female of the felis the head is longer and more pointed.
+ This difference is not so pronounced in the male. Also certain
+ differences in the shape of the claspers and the number of bristles in
+ the episternum and epimerum of the metathorax and the hind femur,
+ those in the _C. canis_ being more numerous. Also that group of
+ bristles on the posterior border of the hind tibia between the fifth
+ pair and the apical bristles consists of two in the _Ctenocephalus
+ canis_, while there is but a single bristle with a small hair in the
+ _Ctenocephalus felis_.
+
+
+ REFERENCES.
+
+Endnote 201:
+
+ 1909, McCoy.—“Plague Bacilli in Ectoparasites of Squirrels.” Public
+ Health Reports, Vol. XXIV, No. 16.
+
+Endnote 202:
+
+ 1908, Schumann.—“A Disease of Rats Caused by Mites.” Centralblatt f.
+ Bact., Oct. 30th.
+
+Endnote 203:
+
+ 1909, McCoy and Mitzmain.—“An Experimental Investigation of the
+ Biting of Man by Fleas Taken from Rats and Squirrels.” Public Health
+ Reports, Vol. XXIV, No. 8.
+
+Endnote 204:
+
+ 1908, McCoy.—“A Report on Laboratory Work in Relation to the
+ Examination of Rats for Plague at San Francisco, California.” Public
+ Health Reports, Vol. XXIII, No. 30.
+
+Endnote 205:
+
+ Wagner.—Aphanipterologische Studien aus dem zootomischen
+ laboratorium der Universität zu St. Petersburg.
+
+Endnote 206:
+
+ 1908, Mitzmain.—“How a Hungry Flea Feeds.” Entomological News,
+ December.
+
+Endnote 207:
+
+ 1908, Miller.—“Hepatazoon Perniciosum (N. G. N. SP.). A
+ Hæmogregarine Pathogenic for White Rats; With a Description of the
+ Sexual Cycle in the Intermediate Host; A Mite (Lælaps Echidninus).”
+ Bull. No. 46, Hyg. Lab. U. S. Pub. Health and Mar. Hosp. Serv.,
+ Wash.
+
+Endnote 208:
+
+ 1908, Jordan and Rothschild.—“Revision of Non-Combed Eyed
+ Siphonaptera.” Parasitology, Vol. I, No. 1.
+
+Endnote 209:
+
+ 1901, Rothschild.—“Notes on Pulex canis, Curtis, and Pulex felis,
+ Bouché.” Entomologist’s Record, Vol. XIII, No. 4.
+
+ 1905, Rothschild.—“Some Further Notes on Pulex canis, Curtis, and
+ Pulex felis, Bouché.” Novitates Zoologicae, Vol. XII.
+
+[Illustration:
+
+ PLATE VI.
+
+ CTENOCEPHALUS CANIS, CURTIS.
+]
+
+
+
+
+ RODENTS IN RELATION TO THE TRANSMISSION OF BUBONIC PLAGUE.
+
+ By Surgeon RUPERT BLUE,
+
+ _United States Public Health and Marine-Hospital Service_.
+
+
+ Man has associated the rat with bubonic plague since the dawn of
+ history. The monuments and coins of the earliest times yield abundant
+ evidence of this association. Æsculapius, the god of the healing art,
+ is represented by the Greeks with a rat at his feet. An early
+ scriptural reference may be found in the first Book of Samuel in the
+ fifth and sixth chapters. The historian records therein the occurrence
+ of a fatal epidemic of “emerods” in the land of the Philistines
+ coincident with an invasion of “mice.”
+
+ The inhabitants of southern China in recent times have learned to look
+ upon the finding of sick and dead rats in their homes as a harbinger
+ of evil, in fact, as a forerunner of that dread scourge—“wan-yick,” or
+ plague. In the villages and cities of the Kwantung and Kwangsi
+ provinces, as recorded by medical missionaries, epizootic plague
+ almost invariably precedes an outbreak among human beings. So well is
+ this fact known to the common people that many seek safety in flight,
+ feeling assured that in a short time “yang-tzu” or “wan-yick” will
+ claim a harvest of victims among those who remain.
+
+ Doctor Mahē, sanitary officer for the port of Constantinople, in 1889,
+ called attention to the fact that epidemics of plague were always
+ announced by a great mortality among rats and mice. In 1894 Yersin
+ reported the fatal epizootic among rats then prevailing in Canton and
+ Hongkong coincident with the outbreak of plague among the Chinese.
+ Recent researches have confirmed these observations and a great deal
+ has been added to the literature of plague, especially in relation to
+ its mode of transmission. Indeed, it should be said that wherever the
+ disease has prevailed in recent years the relation of rats to its
+ spread has been observed, and that since the discovery of the specific
+ bacillus by Yersin and Kitasato, in 1894, bacteriological
+ investigations have shown that there is no difference morphologically
+ or culturally between the bacilli of human and rat plague. Moreover,
+ the gross and microscopic lesions in the lymph nodes are practically
+ the same, and the _B. pestis_ recovered in both fulfills the
+ postulates of Koch.
+
+ Nothing was definitely known, however, of the mode of transmission of
+ the disease from rat to rat or from rat to man until the completion of
+ the experimental work of the Indian Plague Commission. Simond, Ogata,
+ Thompson, and Koch each expressed the belief that the infection was
+ transferred by the rat flea. Nuttall (1897) and Simond (1898)
+ demonstrated the presence of _B. pestis_ in the bodies of bugs
+ (_Cimex_) and fleas which had been taken from plague-sick rats, and
+ the latter observer, in the same year, succeeded in transmitting the
+ disease from rat to rat without contact.
+
+ The work of the Indian Plague Commission was undertaken (1905) with a
+ view to establishing the exact relationship between epizootics among
+ rats and epidemics among men, and included both field and laboratory
+ observations. The experiments of Gauthier and Raybaud (1903) and of
+ Simond were repeated on a larger scale and greatly improved in that
+ all rats and fleas used were first identified as to species. The
+ findings of the commission may be briefly summarized as follows: That
+ fleas and bugs taken from plague-sick rats contain _B. pestis_, and
+ that some of them remain alive in the bodies of the insects from five
+ to sixteen days; that plague is conveyed by the bites of fleas which
+ have previously fed on the blood of animals suffering with the
+ disease; that rat fleas bite man; that under experimental conditions
+ the infection is not transferred from rat to rat in the absence of
+ fleas.
+
+ A careful study of the findings of the workers in India justifies the
+ assumption that plague is a disease of the rodent primarily and
+ accidentally, and secondarily a disease of man. An analysis of the
+ epidemiological facts collected in San Francisco leads to the same
+ conclusion. As a result our practice with regard to suppressive
+ measures and quarantine procedure has undergone a radical change in
+ the last decade. If the infection is flea-borne from rat to man in the
+ majority of cases, then the extermination of the rat should be the
+ first principle upon which to base a campaign. In the former
+ contribution on the subject (1907) I stated that “if we destroy the
+ host there is no longer danger of infecting the parasite.” This basic
+ principle has been recognized and successfully applied in two
+ campaigns against plague in San Francisco. First in the outbreak in
+ Chinatown in 1903–4, and again in the larger epidemic of 1907.
+
+ The outbreak of 1907 began May 27, a little over a year after the
+ great fire and earthquake, but no cases were discovered between that
+ time and mid-August when the disease began to appear in various parts
+ of the city. The source of infection was, in all probability, a
+ recrudescence from a focus which was not destroyed in the campaign of
+ 1903–4. There occurred 160 cases with 77 deaths, the last case
+ appearing January 30, 1908. The following table shows the incidence of
+ human plague:
+
+ ─────────────────────┬───────┬───────
+ Year. │Cases. │Deaths.
+ ─────────────────────┼───────┼───────
+ 1907. │ │
+ May │ 1│ 1
+ August │ 13│ 6
+ September │ 56│ 25
+ October │ 34│ 25
+ November │ 41│ 12
+ December │ 13│ 7
+ 1908. │ │
+ January │ 2│ 1
+ ─────────────────────┼───────┼───────
+ Total │ 160│ 77
+ ─────────────────────┴───────┴───────
+
+
+ EPIDEMIOLOGICAL OBSERVATIONS IN SAN FRANCISCO.
+
+ Abundant epidemiological data associating the rat[AE] with plague have
+ been collected in San Francisco. For the purpose of illustration a
+ detailed reference to a few cases will be made. Two small boys
+ (October, 1907) while playing in an unused cellar found the body of a
+ dead rat. The corpse was buried with unusual funeral honors. In
+ forty-eight hours both were ill with bubonic plague. A laborer finding
+ a sick rat on the wharf picked it up with the naked hand and threw it
+ into the bay. He was seized three days later with plague. Doctor C.
+ and family lived in a second-story flat over a grocery store in the
+ residence section. Being annoyed for some days by a foul odor the
+ doctor caused the wainscoting around the plumbing to be removed. One
+ or two rat cadavers were found in the hollow wall. In two or three
+ days the two members of the family who used the room sickened, one
+ dying on the fifth day of cervical bubonic plague. It is probable that
+ infected rat fleas were set free by the removal of the wainscoting.
+
+Footnote AE:
+
+ _M. norvegicus_ and _M. rattus_.
+
+ Dead rats were frequently found in or near houses where plague had
+ occurred. Immediately upon the discovery of a case of plague trained
+ men were sent into the neighborhood and a thorough search made for
+ rats. This work consisted in the removal of defective wooden floors
+ and walls of insanitary buildings and other harboring places.
+ Extensive rat catacombs were frequently found in these operations. In
+ the yard of a house in which 4 cases had occurred 20 cadavers were
+ found under the board covering. In the walls of a Chinese restaurant
+ 87 dead rats were uncovered.
+
+ Very little can be said of the relation of mice (_M. musculus_) to the
+ epidemic. While many thousands were trapped, only a few hundred were
+ examined microscopically and in these no infection was found. They are
+ nonmigratory in habit and for this reason are not considered of much
+ importance from an epizoological standpoint.
+
+ Transmission from man to man was observed in but a small percentage of
+ cases, 3 per cent to be exact. In these the probability of
+ transference by fleas (_P. irritans_) or by bugs (_Cimex_) must be
+ admitted. When more than one case occurred in a house a common source
+ of infection was indicated, such cases occurring simultaneously or
+ within from forty-eight to seventy-two hours after the first.
+ Deratization was the measure mainly relied upon. After an infected
+ house was rat proofed, and the harboring places in the block
+ destroyed, no further cases occurred.
+
+ The course of epizootic plague was not interrupted at any time by
+ climatic conditions, there being as many cases in proportion to the
+ rat population in the winter of 1908 as there were at the height of
+ the epidemic. The last case of human plague occurred January 30, 1908,
+ but the infection remained active among rats for eight months longer,
+ or until October 21, 1908. (See following table.)
+
+ ─────────┬─────────┬─────────┬─────┬────────────┬────────┬─────────────
+ Month. │ Number │ Number │ Per │ Average │Rainfall│Character of
+ │examined.│infected.│cent.│temperature.│ in │ days.
+ │ │ │ │ │inches. │
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ 1907. │ │ │ │ °F. │ │{Clear, 13.
+ September│ 1,002│ 27│ 2.69│ 60.6│ 0.11│{Part cloudy,
+ │ │ │ │ │ │15.
+ │ │ │ │ │ │{Cloudy, 2.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 10.
+ October │ 2,679│ 23│ .86│ 60.6│ 1.36│{Part cloudy,
+ │ │ │ │ │ │10.
+ │ │ │ │ │ │{Cloudy, 11.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 14.
+ November │ 3,954│ 36│ .88│ 57.8│ .04│{Part cloudy,
+ │ │ │ │ │ │13.
+ │ │ │ │ │ │{Cloudy, 3.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 6.
+ December │ 4,308│ 48│ 1.11│ 52.4│ 3.66│{Part cloudy,
+ │ │ │ │ │ │11.
+ │ │ │ │ │ │{Cloudy, 14.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ 1908. │ │ │ │ │ │{Clear, 5.
+ January │ 6,622│ 70│ 1.05│ 50.8│ 4.88│{Part cloudy,
+ │ │ │ │ │ │11.
+ │ │ │ │ │ │{Cloudy, 15.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 11.
+ February │ 11,700│ 45│ .38│ 51.0│ 5.39│{Part cloudy,
+ │ │ │ │ │ │12.
+ │ │ │ │ │ │{Cloudy, 6.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 20.
+ March │ 19,263│ 52│ .26│ 54.8│ .90│{Part cloudy,
+ │ │ │ │ │ │10.
+ │ │ │ │ │ │{Cloudy, 1.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 17.
+ April │ 15,524│ 34│ .21│ 56.3│ .22│{Part cloudy,
+ │ │ │ │ │ │10.
+ │ │ │ │ │ │{Cloudy, 3.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 17.
+ May │ 11,311│ 20│ .13│ 55.4│ .76│{Part cloudy,
+ │ │ │ │ │ │12.
+ │ │ │ │ │ │{Cloudy, 2.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 16.
+ June │ 13,624│ 4│ 0.02│ 55.3│ 0.01│{Part cloudy,
+ │ │ │ │ │ │9.
+ │ │ │ │ │ │{Cloudy, 5.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 11.
+ July │ 11,204│ 2│ .017│ 57.4│ .02│{Part cloudy,
+ │ │ │ │ │ │17.
+ │ │ │ │ │ │{Cloudy, 3.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 11.
+ August │ 10,988│ 0│ .0│ 57.3│ .01│{Part cloudy,
+ │ │ │ │ │ │10.
+ │ │ │ │ │ │{Cloudy, 10.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 16.
+ September│ 15,902│ 0│ .0│ 59.3│ .29│{Part cloudy,
+ │ │ │ │ │ │9.
+ │ │ │ │ │ │{Cloudy, 5.
+ ─────────┼─────────┼─────────┼─────┼────────────┼────────┼─────────────
+ │ │ │ │ │ │{Clear, 16.
+ October │ 10,178│ 2│ .019│ 58.8│ .061│{Part cloudy,
+ │ │ │ │ │ │7.
+ │ │ │ │ │ │{Cloudy, 8.
+ ─────────┴─────────┴─────────┴─────┴────────────┴────────┴─────────────
+
+ The rats examined for September, 1907, were very largely collected
+ from the badly infected districts; the remaining months give a truer
+ picture of the extent of the epizootic in the entire rat population.
+
+
+ THEORIES AS TO THE CAUSE OF SEASONAL PREVALENCE.
+
+ The marked seasonal prevalence of plague in man in San Francisco may
+ be given as additional proof of the association of the rat with its
+ spread. In the cold, rainy season, from December to April, the
+ epidemic ceases while the epizootic is apparently not influenced. The
+ anomaly is accounted for when we remember that the rat and its
+ parasites are very susceptible to cold and rain. It is then that the
+ animal seeks a warm, comfortable place from which it does not venture
+ until driven thence by dire necessity. In other words, the association
+ of the rat with man is not so intimate in winter, while the reverse is
+ true of the relation of rat with rat. The rains, while interrupting
+ the overground migrations and domiciliary visits of rats, drive them
+ to overcrowded burrows and harboring places. Another factor should be
+ mentioned in this connection. Human fleas (_P. irritans_), and
+ probably rat fleas also, are markedly reduced in numbers at that
+ season of the year. We must conclude, therefore, that the seasonal
+ prevalence of plague in man is due to the effect of climatic
+ conditions upon the habits of rats and the life history of the insect
+ carriers of the bacilli.
+
+ An examination of the foregoing should convince everyone that all
+ former theories as to the prolonged viability of _B. pestis_ in
+ contaminated soil or in polluted streams, and of the periodical spread
+ of the infection therefrom, are no longer tenable. It may also be
+ stated that insanitary conditions, except in so far as they furnish
+ food and shelter to rats and other vermin, play no important rôle in
+ the continuance of plague. This general revision has also eliminated
+ overcrowding as an important factor. In the absence pneumonic cases,
+ and of suctorial insects, this _bête noire_ of the sanitarian may be
+ disregarded.
+
+
+ THE OCCURRENCE OF PLAGUE IN THE MARMOT OF ASIA AND THE GROUND SQUIRREL
+ OF CALIFORNIA.
+
+ Rudenko (1900) first pointed out the possibility of contagion by the
+ “Tarbagan,” a species of the _arctomyinæ_ found in Siberia. He
+ observed a connection in 1894 between this rodent and an outbreak of
+ plague in a Cossack family of Soktuewsk. According to Beliatsky and
+ Zabolotny, each having been an observer in the same field, the natives
+ of Siberia and Mongolia often acquire plague in this manner. Le Dantec
+ and other writers have called attention to the probable susceptibility
+ of the marmot (_Arctomys bobac_), a hibernating rodent of India and
+ China. The marmot of Thibet, in the opinion of this writer, is the
+ natural animal host and purveyor of the virus. The literature of the
+ subject presents no bacteriological evidence, however, of such a
+ relationship, and plague in the _arctomyinæ_ of Asia is merely an
+ hypothesis. There is positive evidence though of the susceptibility of
+ the tree squirrel (_Sciurinæ_) to plague infection. Dr. Alice Corthorn
+ (1898) reported the finding of a plague-infected squirrel in one of
+ the outbreaks in the Bombay Presidency.
+
+
+ PLAGUE INFECTION IN GROUND SQUIRRELS.[AF]
+
+Footnote AF:
+
+ Genus Citellus, Oken; subgenus Otospermophilus. “California
+ Mammals,” Frank Stephens.
+
+ The demonstration of natural plague in the California ground squirrel
+ (_Otospermophilus beecheyi_) is perhaps the most important observation
+ of the antiplague work of the service in 1908. The existence of a
+ plague epizootic in Contra Costa County was suspected as early as the
+ summer of 1903, and efforts were made at that time to collect sick and
+ dead rodents for bacteriological examination. In August (1903) two
+ fatal cases of human infection occurred in widely separated sections
+ of the county. The investigation which followed failed to connect
+ either with a previous case of human plague, but showed an association
+ with ground squirrels. These deaths occurred during a fatal epizootic
+ among ground squirrels and suggested a connection which unfortunately
+ was not confirmed.
+
+ None of the circumstances were forgotten, however, and in the second
+ campaign, begun in September, 1907, in San Francisco, inspectors were
+ detailed to examine all persons dying in the area under suspicion. No
+ plague was reported that autumn and winter. Fatal cases occurred and
+ were reported by the inspectors in July, 1908, as follows: A boy (J.
+ F.) died July 15, near Concord, and a young woman (M. P.) died July
+ 28, on a ranch 10 miles from Martinez. The two were not associated. An
+ investigation was ordered at once and a force of trappers was hurried
+ to the scene with instructions to collect squirrels from the ranches
+ in the vicinity. The first plague-infected squirrel was found August 5
+ on the ranch where the boy had died July 15. Of 425 squirrels
+ collected from August 1 to October 12, 4 showed the gross and
+ microscopic lesions of natural plague.
+
+ A lad (F. M.) sickened August 5, 1908, in Los Angeles, Cal., after
+ being bitten by a sick ground squirrel. A polyadenitis, which
+ afterwards proved to be plague, developed in a few days. A dead
+ squirrel was found nearby and pathological specimens taken from it
+ were sent to the United States Plague Laboratory in San Francisco.
+ McCoy recovered _B. pestis_ from the tissue of the animal. This was
+ the only case of plague reported in Los Angeles. In order to complete
+ the list of those who contracted plague in the country, two other
+ cases should be mentioned. F. S., a pregnant woman, died of
+ bubosepticæmic plague near Concord, Cal., February 29, 1904. The _B.
+ pestis_ was recovered in pure culture from the axillary glands. In
+ April, 1906, a school boy of east Oakland developed a multiple plague
+ adenitis. Investigation showed that he had shot and handled ground
+ squirrels in the country four or five days before his illness.
+
+
+ THE NATURAL HABITAT OF PLAGUE.
+
+ The location of the natural habitat of plague has concerned
+ sanitarians for many years. Not a few have settled upon India as the
+ endemic center, while others associate China with the epidemics which
+ have devastated Europe from remote times. Le Dantec, a recent writer,
+ suggests the “lofty mountains” between India, Thibet, and China as the
+ exact location, and selects the rodent (marmot) of that region as the
+ natural enzootic host.
+
+ A panzootic leaves in its wake enzootics of plague in various
+ countries which persist until the rodents upon which they thrive are
+ either exterminated or rendered immune. At varying intervals epidemics
+ spring from them and finally cease with the exhaustion or destruction
+ of the enzootic foci. Plague disappears in time from these temporary
+ abodes and retires to its original habitat in India or China.
+
+ Of serious import in this connection is the fact that all the
+ conditions necessary for the establishment of a permanent focus of
+ plague exist on the Pacific coast of the United States. The broad
+ valleys and lofty mountains of this region are rich in the
+ _arctomyinæ_, there being no less than 12 species in California alone.
+ In the high Sierras the marmot (_Marmota flaviventer_),[AG] a species
+ of the natural enzootic host of Le Dantec, is found in great numbers.
+ The ground squirrel infests the valleys and foothills in an unbroken
+ chain from Oregon to the Mexican border. Once planted in this ideal
+ soil, infection may never be uprooted or its growth and extension
+ controlled. Small outbreaks will occur here and there, and periodical
+ visitations of greater magnitude may be expected in cities where a
+ combination of epidemiological factors is permitted.
+
+Footnote AG:
+
+ “California Mammals,” Frank Stephens.
+
+ The facts as set forth in this paper have caused grave apprehension in
+ the minds of those who have been at all conversant with the conditions
+ in the transbay counties since 1903. At that time the writer
+ recognized the probability of the establishment of a permanent focus
+ of plague in that locality, and subsequent discoveries have proven the
+ correctness of the assumption. This changes the aspect of the problem
+ from that of a local infection to one of national importance. Once
+ established in such a rural community, plague is dislodged with
+ difficulty and only after a campaign covering a considerable length of
+ time. Being a national problem it can be best solved by the Federal
+ Government.
+
+
+ REFERENCES.
+
+ The Croonian Lectures on Plague, W. J. Simpson; Journal of Hygiene,
+ Volume VI, No. 4; Volume VII, No. 6; Volume VIII, No. 2; Plague among
+ the Ground Squirrels of California, W. B. Wherry, Journal Infectious
+ Diseases, Volume V, No. 5; California Mammals, Frank Stephens.
+
+
+
+
+ RODENT EXTERMINATION.
+
+ By Passed Asst. Surg. WILLIAM COLBY RUCKER,
+
+ _United States Public Health and Marine-Hospital Service_.
+
+
+ It should be remembered that rodents are extremely wily creatures and
+ that any campaign against them is a contest between the wit of man on
+ the one hand and acute animal instinct on the other. The rat, by his
+ constant association with man, has become extremely wary, and is
+ frightened by anything in the least out of the ordinary. They will eat
+ the bread on which poison is spread so carefully that they will leave
+ behind the poison and take practically all the bread; they will open
+ traps by pressing down the pan, and they have been known to repeat
+ this operation several times within an hour, entering the trap, eating
+ the bait, and then liberating themselves. At other times they will
+ enter the trap and stand on the pan with their hind legs, eat the
+ cheese, then carefully turn around and back out. This, of course, is
+ not possible with snap traps, but they have been known to spring them
+ by causing pieces of wood to fall upon them, after which the bait
+ would be eaten. Rats are found wherever food exists in abundance or
+ where they can find suitable breeding and nesting places.
+
+ Rodent extermination is a problem, with difficulties arising from the
+ animal’s highly developed regard for self-preservation. In main, the
+ rat requires two conditions for life. He needs plentiful food and
+ places suitable for nesting and breeding. Eliminate either of these
+ elements and you drive away your rats. Yet the problem remains far
+ more difficult than shown in the simple terms of the above equation.
+ The fabulous speed at which rats multiply will baffle all but the most
+ determined and efficient efforts to exterminate them. Under normal
+ conditions each female bears 3 litters a year and each litter produces
+ 10 young. Under conditions ideally favorable, it has been computed
+ that 1 pair of rats will in five years, providing all can live so
+ long, increase to 940,369,969,152. Such a result is, of course,
+ impossible in nature, for it means that every rat born of the original
+ pair survive five years; that every litter of 10 contains 5 males and
+ 5 females; and that the ideally favorable conditions persist. On the
+ other hand, rodent existence is an unending struggle in which an
+ enormous percentage succumbs; the ratio of half males and half females
+ does not hold; and ordinary conditions of life are hardly even
+ favorable. Nevertheless, the above proves emphatically that no rat
+ eradication can be effective unless the breeding is curtailed. Any
+ campaign against rodents must aim (_a_) to slaughter the greatest
+ possible number of those already living and (_b_) to prevent the
+ possibility of further breeding.
+
+ The existing rats are best attacked by trapping, by poisoning, and by
+ their natural enemies. Traps and poisons alone have been found
+ insufficient to keep pace with the rat’s speed of multiplication. The
+ surest of the rat’s enemies are his natural ones, and once they have
+ been loosed upon him his chance of escape is reduced. The cat, dog,
+ skunk, and other rodent foes, given a fair chance, quickly drive out
+ rats. But these animals do not eradicate the pest. The rats will
+ probably migrate to some other shelter, returning when their natural
+ enemies have quieted down. Absolute extermination is reached only when
+ conditions make the continuation of species impossible for the rat.
+
+ The size and frequency of rodent litters decreases proportionately
+ with every cutting off of food supplies. Separate the rat from his
+ pabulum and he will not breed so freely nor so often as when he is
+ well fed. Destroy rat habitations and make it impossible for them to
+ find new nesting places, and breeding will virtually cease, since the
+ unsheltered progeny can no longer survive, and since the starving
+ parent rats are driven to cannibalism in the struggle for existence.
+
+ Campaigns against rodents must cover five directions: (1) Trapping,
+ (2) poisoning, (3) exposing them to natural enemies, (4) cutting off
+ food supply, and (5) destroying existing nests at the same time that
+ the making of new ones is prevented.
+
+ Parenthetically, it may be noted that while these principles apply
+ equally to the extermination of rats in cities and in country
+ districts, their application must vary according to the place.
+
+
+ TRAPPING.
+
+ The kind of traps to be used varies with the rodent to be captured and
+ the locality which it infests.
+
+
+ CAGE TRAPS.
+
+ The large 19-inch French cage trap gives good results where rats are
+ plentiful. It should be made of stiff, heavy wire and well reenforced,
+ as a large, strong rat will force his head between the wires in a weak
+ trap and thus escape. Before setting, the lever on the trap should be
+ tested to see that it works properly. The trap should be placed on a
+ hard surface, with the rear end a little higher than the entrance, so
+ that the trap will close promptly. When setting the trap in the open
+ it should be fastened to a board on which about an inch of soft dirt
+ has been spread. Place the trap where the rat usually goes for food or
+ in a runway and disturb the surroundings as little as possible. It is
+ sometimes well to place the trap near where there is dripping water,
+ as the rats come there to drink. If the trap is set in hay or straw or
+ wood it should be covered (with the exception of the entrance) with
+ this material. When this is not possible it should be covered with a
+ piece of sacking or placed in a dark corner or beneath the floors.
+ When setting the traps in the sewer a dry place should be chosen.
+
+ The rat is more or less of an epicure, therefore the bait should be
+ changed at frequent intervals. Also he should be given food which he
+ is not in the habit of getting. For example: In a meat market
+ vegetables are the best bait, while in a location where vegetables are
+ plentiful fresh liver and fish heads, or a little grain, are best. The
+ following may be suggested as good bait to be used: Fish, fish heads,
+ raw meat, cheese, smoked fish, fresh liver, cooked corn beef, fried
+ bacon, pine nuts, apples, carrots, and corn. When trapping in chicken
+ yards a small chick or duckling is remarkably good. When a large
+ number of rats are caught in one trap, search for the female and leave
+ her alive in the trap, as she may call in the young or the males. The
+ bait should be fastened to the inner side of the top of the trap with
+ a piece of fine wire so that the first rat in can not force the bait
+ underneath the pan and thus prevent the entrance of other rats. A few
+ grains of barley should be scattered near the entrance of the trap and
+ a small piece of cheese or meat fastened to the pan with a piece of
+ wire. It is often well to touch the pan with a feather which has been
+ dipped in oil of anise or oil of rhodium. Before leaving the trap it
+ should be smoked with a piece of burning newspaper to kill the smell
+ of the human hands or the rats which have been in it. Do not handle
+ the trap after burning it out. When trapping in a neighborhood where
+ rats are known to exist the traps should not be moved for three or
+ four days unless they have rats in them, as it is well for the rats to
+ become accustomed to seeing them and thus careless about entering. It
+ is not wise to kill rats where they are caught, as the squealing may
+ frighten the other rats away.
+
+
+ SNAP TRAPS.
+
+ Snap or spring traps are best for use in houses and stores, with the
+ exception of fish and meat markets. Snap traps are best for use in
+ runways, beams, and shelves. It is sometimes well to disguise the trap
+ by covering its floor with a little sawdust or dirt. They should be
+ first tested to see that they work properly and that the staples are
+ secure. New traps should be smoked or stained to render them an
+ inconspicuous color.
+
+ The bait should consist of some firm material, such as fried bacon or
+ tough meat, and should be tied on so that the rat will be obliged to
+ pull on it and thus spring the trap. The trap should be placed in a
+ corner or close to the wall on a flat, hard surface, so that the rat
+ can not spring it with his tail or by walking on it.
+
+
+ BARREL TRAPS.
+
+ In warehouses and granaries large numbers of rats may frequently be
+ trapped by using a barrel or garbage can having a metal top which is
+ carefully balanced. Large pieces of strong cheese are placed in the
+ middle of the cover and a plank laid from the floor to the edge of the
+ barrel. The rat runs up the plank onto the smooth metallic lid which
+ tips and the rat is precipitated into the barrel.
+
+ In cities trapping is one of the most effective of the three methods
+ to slaughter rodents. The rat highways are easily discovered and in
+ them traps capture great numbers of the unwary. In the country one can
+ not so readily determine the rat highway. This difficulty diminishes
+ the effectiveness of trapping. To make up for what is thus lost
+ shooting has been resorted to with good results. In Honolulu, where a
+ vigorous campaign against rodents is being waged, a very large
+ proportion of the captured rats (_Mus rattus_ and _M. alexandrinus_)
+ have been shot from trees. In Contra Costa County, Cal., where ground
+ squirrels are being exterminated, it has been found that rodents
+ possess an instinctive suspicion of traps and that during the summer
+ months shooting is not only the most practical but also about the only
+ effective means of attacking them. Shotguns are the weapons to use. A
+ rifle requires the hunter to be a better shot than is ordinarily
+ obtainable for such work, and, furthermore, the danger from its longer
+ range and from ricocheting bullets menaces cattle and farm hands who
+ may be working in the vicinity. As to the shot and the powder charge
+ for shells hunters differ. It is a different problem for every
+ shotgun, depending upon the gun’s caliber and choke. The principle is
+ to put the greatest number of the largest shot the gun will carry into
+ the rodent body. Thus in 10 and 12 gauge guns shoot No. 8 shot and in
+ 16-gauge guns shoot No. 9 shot, but this varies with each individual
+ gun. The use of soft lead or chilled shot seems a matter for personal
+ preference. The charge must be as much as the gun will carry. In the
+ country smokeless powder becomes a necessity during summer months
+ since black powder is liable to ignite the dry grass and stubble.
+
+
+ POISONING.
+
+
+ PLASTER FLOUR.
+
+ Plaster flour is prepared by mixing one part dry plaster of Paris with
+ two parts flour or meal. When this is taken in sufficient quantity by
+ the rodent it produces death by the formation of enteroliths, death
+ occurring in from four to eight days. This is a poison of uncertain
+ value and is recommended chiefly on account of its cheapness and small
+ danger to children and domestic animals. It can not be used in wet
+ weather, and judging from the small number of rats found dead with
+ plaster casts in the alimentary canal it is not believed to be very
+ efficacious.
+
+
+ PHOSPHORUS PASTE.
+
+ Phosphorus paste is prepared by mixing crude phosphorus in the
+ proportion of one-half to 10 per cent in a suitable base. The latter
+ may consist of cheese, sugar, and oil of anise mixed together and
+ heated to the consistency of sirup, the phosphorus being added after
+ the fire has been withdrawn and the mixture begun to cool. Other bases
+ are cheese, corn meal, and oil of rhodium; cheese, ground fish, or
+ meat and oil of valerian, glucose, and a small quantity of flour.
+ Glucose makes an exceptionally good base, as when properly mixed the
+ poison thus prepared is noninflammable even when heated. The liability
+ to spontaneous combustion of phosphorus mixtures eliminates their use
+ in hay, grain, or other warehouses or places where there is danger of
+ fire or the invalidation of insurance. It should not be forgotten that
+ phosphorus deteriorates very rapidly, especially when it is exposed to
+ the sun.
+
+
+ ARSENIC PASTE.
+
+ This consists of arsenious acid combined with a base of cheese, meal,
+ or macerated fish. It may be placed on raisins or prunes and is to be
+ recommended on account of its stability, the ease with which it is
+ handled, and the absence of danger from fire. It should, however, be
+ distributed with great care, every precaution being used to place it
+ where it is inaccessible to children and domestic animals.
+
+
+ BARIUM CARBONATE.
+
+ This has not proven an effective poison owing to the fact that it is
+ easily decomposed by the vegetable acids, especially lactic and oleic
+ acid found in cheese and oil. The poisonous effect is not greatly
+ altered by this change. A disagreeable metallic taste is produced and
+ the rats will not take it.
+
+
+ STRYCHNINE.
+
+ Strychnine is prepared as a poison by soaking wheat over night in
+ water and subsequently pouring off the excess fluid and placing the
+ wheat in a caldron containing hot glucose and strychnia sulphate, the
+ latter in the proportion of one-tenth of 1 per cent. After carefully
+ stirring so that each grain is thoroughly coated it is dried in
+ shallow iron pans over a slow fire with constant agitation of the
+ grain, or by exposure on sheets or canvas to the rays of the sun. This
+ mixture may be made much more efficient by the addition of cyanide of
+ potassium in the proportion one-half of 1 per cent. Poisoned grain has
+ not been found efficient in the destruction of rats, as its bitter
+ taste causes them to eat little or none of it. It is, however,
+ particularly efficient in poisoning squirrels, as it is taken readily
+ by them. The chief objections to its use are its cost, difficulties of
+ preparation, and liability to its being taken by chickens.
+
+
+ CARBON BISULPHIDE.
+
+ Carbon bisulphide is not a poison so much as an asphyxiant. As the
+ name indicates, it is a two-to-one mixture of sulphur and carbon. The
+ resulting liquid preparation should be kept in air-tight cans, since
+ it evaporates quickly. The principle of its efficacy against rodents
+ is that the fumes are heavier than air and, sinking into a rat or
+ squirrel hole, drive out the necessary oxygen. To use bisulphide
+ saturate a small pad of some absorbent cotton, jute, wool, or flannel
+ material with the liquid, thrust this into the rodents’ burrow, and
+ carefully stop all apertures through which the fumes might escape.
+ Animal life of every sort in that burrow is quickly asphyxiated. In
+ buildings the use of carbon bisulphide is greatly hampered by the
+ difficulty to confine the gas by stopping all cracks and other
+ openings. Also the odors of decomposition in animals so killed stand
+ against its use anywhere but in the country.
+
+ Against rats and squirrels in country places carbon bisulphide has
+ proved one of the best of all weapons. Where it kills, it kills whole
+ families at a time, not one by one, as must ever be the case with
+ other poisons and with traps or shotguns. Not only does it kill the
+ rodent but it also destroys the rodent’s fleas and vermin, which is
+ most important. A dead infected rat is still a menace, since its fleas
+ may inoculate other rats and human beings with the infection. Destroy
+ the fleas and that greatest danger is removed. The recent campaigns
+ against rodents in the United States have been waged because rats and
+ squirrels were infected with bubonic plague; hence the added value of
+ carbon bisulphide. Unfortunately, though this asphyxiant proved so
+ effective in the work against squirrels in Contra Costa County, Cal.,
+ it proved to be well-nigh useless during the summer season when dry
+ heat checks the adobe and makes the ground generally porous.
+ Nevertheless, the value of carbon bisulphide, especially for sanitary
+ purposes, can not be easily overestimated for work in the country
+ during the fall, winter, and spring seasons.
+
+ Fumigants in general are effective. They possess no marked or peculiar
+ advantages as special weapons against rodents. Their use is limited
+ chiefly to warehouses, elevators, and ship holds. They are deadly to
+ rats in the same way that they are fatal to every sort of life. Many
+ difficulties and some dangers stand in the way of their use. It is
+ safe to advise that no one unacquainted with their action should ever
+ employ fumigants.
+
+
+ NATURAL ENEMIES.
+
+ The war upon rats carried on in San Francisco has proved the great
+ value of cats and dogs as natural enemies of the rat. That city now
+ has a law requiring all structures of 800 or less square feet and
+ outside certain limits to be raised high enough above the ground to
+ allow access to cats and dogs. (All other buildings in the city must
+ be rat proof.) An index to the worth of rodent foes in their
+ extermination points from what happened during the great London
+ plague. At that time the disease was supposed to be air carried; any
+ furry material might hold and spread infection. The magistrates
+ decreed that all cats and dogs should be killed to prevent plague from
+ lodging and traveling in their hair. Rats were thus free to live and
+ breed unmolested, and live and breed they did until the plague killed
+ them off; then and then only did the disease cease its ravages among
+ human beings.
+
+
+ DOGS.
+
+ Slight training will make excellent ratters of Fox, Irish, or Scotch
+ terriers. Fox terriers have proved especially valuable as retrievers
+ when shooting squirrels, which in one case out of five will escape to
+ their burrows unless sharply retrieved.
+
+
+ CATS.
+
+ Cats are little less valuable than dogs against rats, while they are
+ useless against squirrels. The ordinary cat is too well fed to attack
+ large rats and goes, almost solely, after mice.
+
+ All other animals naturally preying upon rodents class with wild
+ life—weazels, ferrets, badgers, skunks, and minks. These can be used
+ only in country places, where, however, their raiding of chicken coops
+ tends to counterbalance their value as ratters. The skunk alone is an
+ infrequent slayer of fowl, whereas he harvests innumerable farm pests
+ from worms to crickets. Yet an insurmountable prejudice against skunks
+ stands in the way of realizing his full usefulness against rodents. In
+ addition, various hawks and most owls kill off rats. Since rats come
+ out chiefly in the nighttime, owls have the better chance to be
+ serviceable in their destruction. The efficiency of these birds in
+ rural districts quite equals that of a dog against rats, while besides
+ dogs we have not as yet found a safe natural foe of ground squirrels.
+
+ But all such attacks upon rats fail of absolute eradication. One must
+ make it impossible for them to find sustenance and must destroy not
+ only all existing rat houses, but also all chance of their digging or
+ finding new ones.
+
+
+ CUTTING OFF THE RAT’S FOOD SUPPLY.
+
+ This is important not alone for its effect in a campaign upon rodents,
+ but equally because it necessitates sanitary care and cleanliness in
+ handling foodstuffs intended for humans and garbage coming therefrom.
+ Abattoirs and places where cattle and hogs are fattened perhaps
+ furnish the greatest number of rats. Stables, food-supply stores,
+ groceries, meat, fish and vegetable markets, restaurants, bakeries,
+ and the various places where food is prepared for human consumption
+ are usually infested. In each of the places the barriers vary
+ according to the nature of the premises. Rat-proof receptacles for the
+ foodstuffs must be installed wherever practical. In San Francisco an
+ ordinance requires every stable to have metal lined feed bins. Markets
+ and places where eatables are constantly being shifted about must be
+ properly screened against rats. Screening should be of heavy wire and
+ sufficient fineness, not larger than halfinch mesh. In all places the
+ food has to be raised such a height above floorings as to be beyond
+ the rat’s reach. This applies also to corn and grain cribs in the
+ country. Yet, no matter how carefully the bulk of the food may be kept
+ from rats, negligence in handling it, in spilling or scattering small
+ amounts upon floors or the ground, will nullify every precaution.
+
+ No less painstaking must be the disposition of garbage. Ordinance now
+ requires that all premises in San Francisco be provided with “sanitary
+ garbage cans.” Preferably these should be of zinc or galvanized iron
+ and fitted with tight covers. Under no circumstances should the cover
+ be allowed to remain off its can. Garbage is to be placed in a can
+ without delay and care must prevent the dropping of it upon the
+ ground. Rats once served communities as scavengers; wherever the
+ scavenger work is laxly done, rats are welcomed. Finally, garbage must
+ never be allowed to accumulate and should be removed daily, not less
+ often than every other day.
+
+ Special conditions, closely related to the next topic, are encountered
+ in large warehouses and grain sheds. Places where large quantities of
+ food may be stored for a length of time should be constructed of
+ reenforced concrete to be rat proof. Then, again, where vessels are
+ changing cargoes, rat-proof compounds should be erected for the
+ temporary storage of freights. The water fronts of seaports are
+ invariably rat ridden; and in San Francisco a compound for freight
+ held in transit was found invaluable. No effort can be spared in
+ keeping rats from their food if their extermination is to be
+ accomplished.
+
+ With regard to ground squirrels, the use of poisoned wheat very
+ properly enters here. With the changing season ground squirrels change
+ their habitat and food. During early spring these rodents come down
+ from their winter dwellings in the hills and seek burrows in meadow
+ lands and cultivated spots. Months have passed since the squirrel
+ tasted wheat; his fickle appetite betrays him. From the first spring
+ months until harvest time one can kill thousands of ground squirrels
+ by tempting them with poisoned wheat. But so soon as harvest time
+ comes, they seek new growing green stuffs to eat and thereafter, on
+ through winter, poisoned wheat is ineffective.
+
+
+ BUILDING THE RAT OUT OF EXISTENCE.
+
+ Most certain of all methods to get rid of rodents is to allow them no
+ place in which to live. San Francisco effects this result through its
+ ordinance, which requires small houses outside certain city limits to
+ be raised so high from the ground that dogs and cats can drive out
+ rats from under them, and which requires all other buildings in the
+ city to be rat proofed with cement or concrete. The latter
+ contemplates foundation walls of concrete or brick sunk at least 1
+ foot to 18 inches to 2 feet above that surface; the whole ground area
+ inclosed by their foundation walls must be covered with concrete at
+ least 1½ inches in thickness. Thus the entrance of burrowing rodents
+ is prevented. Even where buildings stand upon rock or hardpan, these
+ requirements should be enforced. Rock may crack, gradual weather decay
+ may cause crevices to be found in it unseen crannies may be found by
+ rodents, and once the rat lodges in rock his nest is virtually
+ unassailable. With hardpan it is even worse, for the rats can burrow
+ in it, with some difficulty, truly, but when nests are impossible
+ elsewhere, necessity will drive rats to find shelter in hardpan, which
+ will protect them quite as well as rock. In the main, these two points
+ of building rats out of existence, though modified, will apply to any
+ structure.
+
+ Yet any negligence will overthrow these safeguards. The principle is
+ to allow no opening within which rodents may nest. Plank sidewalks and
+ back yards will continue the rat nuisance even though buildings are
+ amply protected. Carelessness in throwing old boxes into basements or
+ piling old lumber or refuse within reach will supply shelter for rats
+ despite concreted ground area. The precaution must be constant and
+ consistent.
+
+ Another important phase is to cut off the rodent migrations. Prevent
+ rats from moving from place to place. Their time-honored highway is
+ through sewers. Modern sewers afford no protection, inviting rodents
+ to live in them as formerly. Scarcely less important, access should be
+ stopped. Catch-basin feeding sewers should be constructed so that rats
+ can not slip through into the mains, or having once gotten in, they
+ can not escape, and hence must drown. Farms are frequently protected
+ against rodent migrations by tin or zinc sheeting sunk into the ground
+ about a foot and a half and standing about the same height above the
+ surface along the fence line.
+
+ Finally, as the progress of rodents from place to place within
+ communities must be hindered, so must they be stopped from entering
+ new communities. Railroads and seagoing vessels carry great numbers of
+ rats in freight. The rat-proof compounds above described serve well
+ enough so far as railroads are concerned. With vessels it is a
+ different matter, and one demanding special attention, since the
+ rodent is only too likely to import infection from foreign harbors.
+ All hawsers thrown out to make boats fast should be provided with
+ traps to catch any rat seeking to land along the hawser. San
+ Francisco, about to possess a rat-proof water front, is now building
+ concrete wharves to prevent the landing of rodents. Every port should
+ be safeguarded by stone, concrete, or iron wharves and piers. As a
+ further protection, all ships should have permanent devices, as is now
+ proposed for naval construction. Levy’s system of metal conduits built
+ into vessels promises much in the present world-wide war upon rodents.
+ Rodents must be “built out of existence,” and to eradicate rats for
+ all time we must erect wide systems of municipal fortifications.
+
+
+
+
+ NATURAL ENEMIES OF THE RAT.
+
+ By DAVID E. LANTZ,
+
+ _Assistant Biologist, United States Department of Agriculture_.
+
+
+ INTRODUCTION.
+
+ Undoubtedly the great increase of rodent pests throughout North
+ America is in large part due to a general scarcity of the animals that
+ habitually prey upon them. Since the early settlement of the country
+ persistent warfare has been made on birds and mammals of prey on the
+ plea that they are enemies of poultry, game, and insectivorous birds.
+ Efforts to destroy the predaceous birds and mammals have been greatly
+ stimulated by the payment of municipal, county, and state bounties,
+ and the destruction has gone on until in many sections these animals
+ have nearly disappeared.
+
+ The effect of killing off the natural enemies of rodents has been to
+ disturb natural conditions. Rodents multiply so rapidly that they
+ derive an undue advantage in the struggle for existence when their
+ natural enemies are destroyed. The result is noticeable in the
+ increased depredations of rats, field mice, rabbits, and other pests.
+
+ The destruction of carnivorous wild mammals and birds by the farmer,
+ hunter, or game preserver is often due to misapprehension. Because one
+ kind of hawk preys on the farmer’s poultry is not sufficient reason
+ for exterminating all hawks. Nor does the fact that occasionally an
+ owl or a skunk destroys a chicken or a game bird justify warfare on
+ all owls and skunks. It is the occasional individual and not the
+ species that offends.
+
+
+ ANIMALS THAT DESTROY RATS.
+
+ The usefulness of the natural enemies of the rat must not be
+ overlooked in plans for its repression. Among the more important are
+ the larger hawks and owls, skunks, foxes, coyotes, weasels, minks, and
+ a few other wild mammals; as well as cats, dogs, and ferrets among
+ domestic animals, and snakes and alligators among reptiles.
+
+
+ HAWKS.
+
+ Most of the larger hawks destroy rats. Feeding only in the daytime,
+ they seldom find their quarry near houses and barns, where rats do not
+ venture out until after sunset. Besides, owing to persecution by
+ farmers, hawks generally keep away from farm buildings. In the open
+ fields, however, where rats feed in early morning and late afternoon,
+ hawks find many of the rodents.
+
+ The species of hawks that more commonly feed on rats are the buzzard
+ hawks, including the red-tailed (_Buteo borealis_ and sub-species),
+ the red-shouldered (_B. lineatus_), the broad-winged (_B.
+ platypterus_), and the Swainson (_B. swainsoni_); the rough-legged
+ hawks (_Archibuteo_), two species; and, to a less extent, the marsh
+ harrier (_Circus hudsonius_), and a few other species.
+
+ The writer has several times found the remains of rats about the nest
+ of the red-tailed hawk. Of the 562 stomachs of this species examined
+ by Dr. A. K. Fisher, of the Biological Survey, less than 10 per cent
+ contained poultry or game, while more than 70 per cent contained
+ injurious rodents.[AH] Most of the other species of buzzard hawks made
+ a better showing even than this, especially the Swainson hawk, which
+ had fed entirely on harmful rodents and insects. The stomachs of
+ rough-legged hawks examined nearly all contained harmful rodents and
+ none of them contained remains of birds of any sort.
+
+Footnote AH:
+
+ Hawks and Owls of the United States, p. 62, 1893.
+
+ A few months ago, while walking on the Potomac flats near Washington,
+ the writer met some boys who had just shot a red-tailed hawk. Its crop
+ was greatly distended, and later examination showed that the bird had
+ recently eaten an enormous brown rat. Although the shooting was
+ contrary to law, when it was reported to the nearest policeman, his
+ comment was, “Oh, a hawk! Why, it’s a good thing to shoot a hawk.” The
+ incident illustrates the general popular prejudice against all hawks.
+
+
+ OWLS.
+
+ Because they hunt by twilight and at night, owls are more efficient
+ than hawks in destroying rats. All American owls, except the more
+ diminutive species, prey on the common rat. Even the little screech
+ owl (_Otus asio_) feeds on young rats.
+
+ Of all our species, the barn owl (_Aluco pratincola_) is preeminent as
+ a destroyer of rats. It lives commonly about farm buildings, sometimes
+ even making its nest and rearing its young in the pigeon loft without
+ molesting the pigeons. In such surroundings its opportunities for
+ securing rats are excellent, and no other wild bird is so useful on
+ the farm. The late Henry Newman once stated that every barn owl is
+ worth £5 a year to the British nation, and the value of the bird to
+ the American farmer is not less.
+
+ Owls, hawks, and other birds of prey that swallow their quarry whole
+ or in large pieces do not digest the bones, fur, and feathers. They
+ eject these indigestible parts in the form of large pellets, in which
+ the fur or feathers surround the bones. The contents of these casts
+ are an excellent index of the food of owls. Dr. A. K. Fisher, of the
+ Biological Survey, has examined 987 pellets of a pair of barn owls
+ that live in a tower of the Smithsonian building in Washington, and in
+ them found the skulls of no fewer than 192 rats (_Mus norvegicus_),
+ together with those of 554 common mice and 1,508 field mice (_Microtus
+ pennsylvanicus_).
+
+ Dr. John I. Northrop found a nest of the barn owl on Andros Island,
+ Bahamas. It contained two young owls and the remains of a black rat
+ (_Mus rattus_). The ground about the nest was covered with pellets
+ which contained remains of the black rat and no other species.[AI]
+
+Footnote AI:
+
+ The Auk, vol. 8, p. 75, 1891.
+
+ The great horned owl (_Bubo virginianus_) is the largest of our
+ resident owls. It feeds mainly on rodents, though occasionally it
+ takes a fowl found roosting in an exposed situation, as on a fence or
+ in a tree. While it occasionally destroys game birds, the rats it
+ captures would probably destroy ten times as much game as the owl.
+ Charles Dury, of Ohio, in 1886 published a letter from O. E. Niles in
+ which it was stated that he counted 113 dead rats at one time under a
+ nest of this bird.[AJ]
+
+Footnote AJ:
+
+ Jour. Cincinnati Soc. Nat. Hist., vol. 8, p. 63, 1886.
+
+ The snowy owl (_Nyctea nyctea_) is a rather rare winter visitor in the
+ northern United States. It usually arrives when the ground is covered
+ with snow and ordinary food is scarce. Near barns, outbuildings, and
+ stacks it finds its chief subsistence in the common rat; and, if
+ undisturbed, will stay for several weeks in the same locality,
+ destroying many of the pests. Unfortunately, mounted specimens of this
+ beautiful owl are so much in demand that the majority of them fall a
+ prey to the specimen hunter and the taxidermist. The destruction of
+ this bird should be prohibited under heavy penalties.
+
+ The barred owl (_Strix varia_), the long-eared owl (_Asio
+ wilsonianus_), and the short-eared owl (_Asio flammeus_) all destroy
+ some rats; but as they do not generally nest or live in the vicinity
+ of farm buildings, the rodents they capture are taken chiefly from the
+ fields. Occasionally a short-eared or a long-eared owl makes its
+ winter home in a group of evergreens near the farm buildings, and does
+ excellent service in clearing the premises of rats and mice.
+ Evergreens are desirable about a country place, if for no other reason
+ than that they attract owls.
+
+ The practice of indiscriminately destroying hawks and owls should be
+ discouraged. Game preservers especially should realize that the birds
+ of prey they kill would, if allowed to live, destroy rats, which in
+ the course of a year do many times as much harm to game as the
+ supposed offenders do. Besides, the birds would destroy also large
+ numbers of mice and injurious insects.
+
+ The farmer and the poultry grower may easily learn to recognize the
+ few harmful species of hawks, and should confine their warfare to
+ these. The practice of setting pole traps for hawks and owls is
+ exceedingly reprehensible, as it results chiefly in the destruction of
+ our beneficial owls when they come about the premises at night in
+ search of rats. Furthermore, the beneficial hawks and owls should have
+ legal protection. The larger hawks, nearly all of which are
+ beneficial, are slow of wing and much more likely to be shot than the
+ swifter and more harmful falcons.
+
+
+ NATIVE WILD MAMMALS.
+
+ Not many species of wild carnivorous mammals live where the common rat
+ is abundant. Coyotes, foxes, and a few others occasionally find a rat
+ in the fields, but for the most part they depend for food on native
+ wild rodents and other animals. Chief among the mammals that do good
+ work in destroying rats are skunks, minks, and weasels.
+
+
+ SKUNKS.
+
+ Skunks are excellent ratters, and when they take up their abode on the
+ premises of the farmer, they speedily destroy or drive away all rats
+ and mice. This statement applies equally to the large skunks
+ (_Mephitis_) and the little spotted skunks (_Spilogale_).
+ Unfortunately, skunks are seldom allowed to tenant the premises
+ without being molested by either dogs or men. When undisturbed, they
+ are inoffensive, and will stay about the farm buildings or stacks
+ until rats and mice are no longer to be had for food.
+
+ Skunks usually hunt by night, and hence poultry properly housed is
+ safe from them. The larger skunks do not climb, and can capture only
+ fowls that roost on the ground. Indeed, so few skunks ever learn to
+ kill poultry that there is no good reason for warfare on the skunk
+ family. Besides destroying mice and rats, the animals are invaluable
+ as consumers of noxious insects, especially cutworms, army worms,
+ white grubs, May beetles, grasshoppers, crickets, and sphinx moths.
+
+
+ WEASELS.
+
+ Weasels are good ratters and mousers. Several of our species come
+ about buildings, and often perform excellent service in destroying
+ rats and mice. They are more likely than the skunk to attack poultry,
+ for they can enter the poultry house through smaller openings. At
+ times weasels seem to kill for the mere love of killing, and while
+ occasionally this trait makes them formidable in the poultry house, it
+ also renders them more efficient as destroyers of rodents. A small
+ weasel can follow a rat into all its retreats, and will soon clear a
+ stackyard or shed of all rodents.
+
+ Our largest weasel, the black-footed ferret (_Putorius nigripes_),
+ occasionally deserts its wild haunts on the plains and comes about
+ buildings in search of rats and mice. In 1905, while the writer was at
+ Hays, Kans., one of these ferrets took up its quarters under a board
+ sidewalk in the business part of the village. The squealing of the
+ rats it killed was often heard.
+
+ As regards the destruction of poultry by weasels, the same care
+ necessary to exclude the rat from a poultry house will keep out the
+ weasel also. When so excluded, a weasel will do no harm about the
+ premises, but may be depended upon to drive out or kill all the rats
+ and mice.
+
+
+ MINKS.
+
+ Minks are excellent ratters, but as enemies of poultry are worse than
+ weasels. They destroy fish also. The great demand for mink fur causes
+ close trapping of these animals, and in the future they are not likely
+ to influence greatly the numbers of rodent pests.
+
+
+ DOMESTIC ANIMALS.
+
+ Among the enemies of rodents often employed as aids to rat destruction
+ are the dog, cat, and ferret.
+
+
+ DOGS.
+
+ The value of dogs as ratters can not be appreciated by those who have
+ had no experience with trained animals. The ordinary cur and the
+ larger breeds of dogs seldom make useful ratters. Small Irish, Scotch,
+ and fox terriers, when well trained, are superior to most other breeds
+ as ratters, and under favorable circumstances may be depended on to
+ keep premises free from rodents. Much, too, may be done by the farmer
+ or householder to increase the effectiveness of his dogs by removing
+ obstructions to their work. Corncribs and outbuildings, when of wood,
+ should not have floors close to the ground, but should have ample room
+ below to permit dogs to move about freely.
+
+ With a little preliminary training, most terriers learn to hunt rats
+ independently, and they thus become doubly useful on farms and in
+ warehouses.
+
+
+ CATS.
+
+ When the black rat was the dominant species in Europe and America,
+ cats were the chief dependence of the householder against rats; but
+ comparatively few cats will venture to capture a full-grown brown rat.
+ Then, too, the ordinary house cat is too well fed and consequently too
+ lazy to be an efficient ratter.
+
+ Occasionally, however, one meets with rat-killing cats whose work in
+ destroying the brown rat has decided value. These cats are rarely of
+ the fine breeds, but generally of the common “tabby” variety, kept in
+ barns or warehouses, fed on milk, and left to forage for their own
+ meat. Managed in this way, cats are far less objectionable on sanitary
+ grounds than when kept in the house as pets. In the country, on the
+ other hand, barn cats are far more likely than the house-kept ones to
+ run at large and prey upon birds and young poultry. Aside from the rat
+ itself, we have no more serious enemy of birds and game than half-wild
+ cats, many of which have been abandoned in fields and woods by the
+ thoughtless. All things considered, cats do not rank high as
+ destroyers of the common brown rat.
+
+
+ FERRETS.
+
+ Tame ferrets, like weasels, are inveterate foes of rats, and can
+ follow them into their retreats. Under favorable circumstances ferrets
+ are useful aids to the rat catcher, but their value is often greatly
+ overestimated. They require experienced handling and the additional
+ services of a well-trained dog or two to do effective work. Dogs and
+ ferrets must be thoroughly accustomed to each other. A noisy or
+ excitable dog is useless in ferreting. The ferret should be used only
+ to drive out the rats, which are then killed by the dogs. If an
+ unmuzzled ferret is sent into rat retreats under floors, it is apt to
+ lie up after killing a rat and sucking its blood. Sometimes the ferret
+ will remain for hours in a rat burrow or escape by unguarded exits and
+ be lost.
+
+ Such experiences often discourage the amateur ferreter. Besides,
+ ferrets are subject to diseases and require the greatest of care as to
+ their food. For these reasons the use of ferrets to destroy rats,
+ except in the hands of the experienced, is generally expensive and
+ disappointing.
+
+
+ OTHER ANIMALS.
+
+
+ MONGOOSE.
+
+ The various species of mongoose (_Herpestes_ and _Mongos_) are
+ destroyers of rats, and their importation into this country has often
+ been urged. Many years ago they were introduced into Jamaica and
+ Hawaii to save the sugar plantations from ravages by rats. The
+ mongoose has, however, proved very destructive to native birds and
+ poultry in the islands, and its introduction is now generally
+ regretted. Its importation into the United States is prohibited by
+ law.
+
+
+ ALLIGATORS.
+
+ In the South the alligator is said to destroy many rats along levees
+ and banks of streams, and its protection has been urged on this
+ account.
+
+
+ SNAKES.
+
+ Our larger snakes are beneficial in destroying rats, mice, prairie
+ squirrels, and pocket gophers. As most of the food of snakes is
+ obtained remote from human abodes, only a small percentage consists of
+ rats.
+
+
+ BOUNTIES ON PREDATORY ANIMALS.
+
+ Whatever may be said in favor of bounties on the larger beasts of
+ prey, those on hawks, owls, and the smaller fur-bearing animals can
+ not be justified. Payments of this sort should cease, and laws should
+ be enacted to protect species which careful investigations have shown
+ to be mainly beneficial.
+
+ A few States still pay bounties for the destruction of foxes, weasels,
+ skunks, minks, and raccoons. All of these, except the southern
+ weasels, have valuable fur, and hence should be protected as a source
+ of wealth. In addition they do far more good by destroying rats, mice,
+ and other field pests than harm to game and poultry.
+
+ The payment of bounties on hawks of any kind is open to the objection
+ that officials hardly ever discriminate between the harmful and the
+ useful kinds, even when the statutes do so. Since the beneficial kinds
+ are the more easily captured, public money is often paid out to reward
+ what really injures the community. The bounty on owls is still more
+ reprehensible, since owls are a more decided check to rodent increase.
+
+ The natural enemies of the rat exercise a steady, cumulative effect in
+ restricting the numbers of the pest. That the effect is not greater is
+ largely our own fault, since instead of protecting the birds and
+ mammals that prey on the rat, we destroy them, sometimes even offering
+ bounties on their heads. In future our aim should be to increase their
+ numbers and to protect them in every way possible.
+
+
+
+
+ RAT PROOFING AS AN ANTIPLAGUE MEASURE.
+
+ By RICHARD H. CREEL,
+
+ _Passed Assistant Surgeon, United States Public Health and
+ Marine-Hospital Service_.
+
+
+ To appreciate the great importance and absolute necessity of rat
+ proofing as an antiplague measure, it is only necessary to consider
+ the results that have followed its use as compared with other measures
+ that have been relied on in recent years in combating this disease.
+ These were, briefly, disinfection, evacuation, or destruction of
+ buildings in infected areas, preventive inoculations, and destruction
+ of rats either by poison or by trapping.
+
+ Plague was formerly believed to be communicable by aerial transmission
+ and through the agency of fomites. Sanitarians have, therefore, put
+ great faith in disinfection procedures, but the results have never
+ been satisfactory, and it is only necessary to consider the method of
+ transmission of plague to perceive the fatuity of bactericidal
+ measures. Measures intended for the destruction of fleas are also of
+ relatively small value. It is well worth while to destroy all fleas
+ possible, but if those infesting the rat population escape, the
+ efforts will have had little effect in preventing the spread of
+ plague. It is only those fleas that infest rats and their habitats
+ that are of importance in relation to the transmission of disease, and
+ it is only by rat proofing that their destruction in rat burrows and
+ runs can be accomplished.
+
+ Rat-proofing of individual buildings is of no recent date, but new
+ emphasis was laid on rat-proofing as a separate and distinct
+ antiplague measure by Passed Assistant Surgeon Mark J. White in an
+ article written in the fall of 1907.[AK]
+
+Footnote AK:
+
+ Journal American Medical Association October 19, 1907.
+
+ Disinfecting procedures must be regarded as of minor importance in
+ plague prevention, except in pneumonic cases where its use is
+ imperative. It is not intended to depreciate the value of
+ disinfection, but rather to estimate its exact value as an antipest
+ measure. Time and money should not be wasted nor a feeling of false
+ security engendered by using an ineffective measure when others, as
+ rat proofing, of much greater value are at hand. As an example of this
+ might be cited an outbreak of plague in one of the refugee camps
+ during the recent epidemic of the disease in San Francisco. This camp
+ covered several blocks and housed between two and three thousand
+ people. The camp grounds throughout and the houses were disinfected
+ and disinfected well. At the same time, every effort was made to
+ poison and trap rats. Notwithstanding these precautions, cases
+ continued to occur, but when the houses were elevated there followed
+ an immediate cessation of plague cases in the camp.
+
+ Another case of infected premises proved equally refractory to
+ disinfection. The place was a large two-story frame dwelling located
+ in the center of the city and in a good neighborhood. The yard was
+ planked, as was also a part of the basement, the latter being used as
+ a storeroom. On November 1 there occurred in this dwelling a fatal
+ case of human plague, and plague rats were found at the same time. The
+ place was disinfected in the usual manner and thorough measures were
+ taken to trap and poison rats with apparent subsidence of infection,
+ but on January 22 a plague rat was trapped, followed by another on
+ January 31, after which the occupant of the building vacated it in
+ great alarm. All planking was then removed from the yard and basement
+ and concrete substituted by the owner, the place thereby being
+ rendered thoroughly rat proof, and no plague rats were subsequently
+ taken from that dwelling or in its immediate neighborhood.
+
+ In 1902 the plague outbreak was almost wholly confined to the Chinese
+ colony. Chinatown was made the battle ground, and among other measures
+ rat proofing was enforced, with the result that after the fire it was
+ by far the most sanitary district in the city of San Francisco from a
+ structural point of view. The buildings when erected were made rat
+ proof from cellar to garret. The Chinese had had their lesson, and to
+ their credit it must be stated that they responded with a greater show
+ of intelligence than did some of the residents in surrounding
+ districts.
+
+ Adjacent to the Chinese colony is the Latin quarter. In the rebuilding
+ of this section, no attention was paid to rat proofing; consequently
+ many of the buildings consisted of small shacks set on the ground or
+ abutting some insanitary stable, and were therefore ideal rat harbors.
+ On account of these conditions the natural results followed.
+ Chinatown, on the other hand, which had contributed in the previous
+ epidemic almost the entire number of plague cases during the epidemic
+ of 1907, did not furnish more than two or three of the plague cases
+ reported; that is, less than 2 per cent of the total cases reported,
+ while the Italian colony, including North Beach district, probably
+ furnished over 50 per cent of the total.
+
+ The evacuation or burning of buildings can hardly be called a
+ successful measure any more than a retreat can be styled a victory;
+ moreover, there can be no question from an economic standpoint as to
+ the value of rat proofing over abandonment except in a few isolated
+ cases of dilapidated insanitary property.
+
+ Schemes and plans for demurization, total or partial, have been as
+ numerous and varied as they have been unsuccessful. Traps and poisons
+ have been the agencies of destruction, but until some highly
+ communicable epizootic peculiar to rodents shall have been discovered,
+ absolute eradication of the rat can be considered as nothing less than
+ impossible.
+
+ A recognized authority on plague, Major Morehead, of the Indian
+ Medical Service, states that “rat destruction is of doubtful value,”
+ referring, of course, to trapping and poisoning when those measures
+ are used solely without auxiliary measures. He agrees with Japanese
+ authorities in their arguments that as rat populations decrease, the
+ breeding rate among survivors increases, due, obviously, in part at
+ least, to increased food supply and harboring facilities. Such a
+ result is assured where rat proofing is not accomplished at the same
+ time. This latter procedure, by destroying rat harborages and cutting
+ off food supplies bring about conditions unfavorable to breeding.
+
+ The total eradication of rats in a locality is not absolutely
+ necessary, however, to the eradication of plague. If the rat
+ population is kept within fairly low limits, rat centers destroyed,
+ and such rat population as does exist well scattered and not
+ congested, it is ventured that rat plague will disappear from a
+ locality. Plague among rats in San Francisco ceased to appear when the
+ number of rodents was reduced some 50 per cent, but such reduction was
+ accomplished only after six months of ceaseless endeavor, which
+ included also the rat proofing of the bakeries, stables, and markets
+ in the city.
+
+ It is a logical supposition that close contact is just as essential
+ for the propagation of plague among rats as it is for the spread of
+ certain communicable diseases among human beings, the increase of
+ cases being in direct proportion to the density of population and
+ closeness of contact.
+
+
+ RAT PROOFING OF PRIMARY IMPORTANCE.
+
+ Without the general enforcement of rat proofing antiplague measures
+ are bound to be more or less temporary and decidedly unsatisfactory.
+ This subject is of immense importance to the public, both from a
+ sanitary and a commercial standpoint, but the latter aspect of the
+ question is more apt to prove of interest to most communities.
+
+ The measures necessary to render buildings rat proof are the same,
+ however, whether they be instituted for sanitary or for commercial
+ reasons. Rat proofing will, therefore, be considered entirely from a
+ sanitary standpoint; but it can be understood that granaries,
+ bakeries, butcher shops, packing houses, dwellings, and other places,
+ if rat proofed for sanitary reasons, are just as much protected from
+ depredation of the rat as though the work had been performed for
+ commercial reasons alone.
+
+ Rat proofing has a twofold objective. It serves as a protection to the
+ inmates of a building, and excludes rodents from sources of food
+ supplies and harboring places. While rat proofing should be enforced
+ as a general measure in all plague-infected localities, it is
+ imperatively demanded in premises whereon have occurred cases of human
+ or rodent plague.
+
+ Plague-infected localities or places that contain food must be
+ rendered impervious to rats in order to insure the success of other
+ preventive measures. Rats can be trapped or poisoned only when other
+ food supply is excluded. A rat will enter a trap for food or will eat
+ poisoned preparations not because of their greater attractiveness, but
+ because of their greater availability. It therefore follows that rat
+ proofing of food supplies is a prerequisite to success in rat
+ eradication. The food depots requiring attention in the order of
+ importance are stables, meat markets, bakeries, restaurants,
+ groceries, warehouses, and private dwellings.
+
+ It is logical to suppose that the most common mode of infection is by
+ reason of plague rats dying in the walls, roofs, or floorings of human
+ habitations. As soon as the rat’s body is cold the fleas abandon it
+ for another rat, some domestic animal, or human being. The risk to
+ human inmates in such infected houses, therefore, is evident.
+
+ That rat proofing is a valuable measure is shown by the reports of the
+ British Plague Commission where are mentioned the results following
+ the use of rat-proof “go-downs” and those not so constructed.
+ Additional evidence is presented by the fact that appalling epidemics
+ of plague have ravaged India and the China coast, whereas in the
+ Philippine Islands but few people die of the disease. It would appear
+ that the comparatively few cases in the Philippine Islands were due to
+ the fact that most Philippine dwellings are rat proof by reason of
+ being elevated from the ground and the fact that the walls are thin
+ and offer no refuge whatever to rats.
+
+
+ RAT PROOFING IS EXPENSIVE.
+
+ The almost insuperable obstacle that will usually confront the
+ sanitary authorities in such work will be either the financial
+ inability of the unfortunate community or the sordid unwillingness to
+ make any expenditure that does not promise personal gain.
+
+ When the influence of the mosquito in the transmission of yellow fever
+ was proven, recourse was had to mosquito proofing of both the sick and
+ the well as a preventive measure. Rat proofing in plague is just as
+ rational and necessary, but the financial expenditure contemplated
+ thereby has been of such proportion as to cause the majority of
+ sanitary authorities in different parts of the world to dismiss the
+ idea as impossible.
+
+ To properly rat proof a city undeniably requires enormous
+ expenditures, but no antiplague campaign was ever waged without an
+ immense outlay of both money and labor. If allowed to progress
+ unchecked, however, plague, either through ravages of the population
+ or through commercial interference, is ruinous. To fight plague,
+ therefore, is the only alternative, and a costly campaign should be
+ anticipated and prepared for in advance. To merely put out traps and
+ poisons without the preliminary rat proofing required can be
+ productive of little good and no permanency. Such a plan of campaign
+ may be attractive because of its relative cheapness, but any city or
+ country that relies wholly on such measures is practicing false
+ economy and deferring the day of reckoning.
+
+ It becomes evident, therefore, that rat proofing is of the greatest
+ value as an antiplague measure, and that practical results to be
+ expected are much greater than with any other method.
+
+ As has already been stated, the individual premises on which plague
+ either among rodents or human beings has occurred demand first and
+ immediate attention. The work should be extended as rapidly as
+ possible from the point of infection so as to include the entire block
+ and neighboring blocks.
+
+ While the chief energies should be centered on plague-infected foci,
+ similar work should be carried on simultaneously throughout the city.
+
+
+ METHODS OF RAT PROOFING.
+
+ If plague occurs in the grounds of dwellings the following course
+ should be pursued: All planked-over areas, including sidewalks, that
+ might possibly shelter a rat should be removed, leaving either bare
+ ground or, at the option of the owner, gravel or concrete used, the
+ gravel being preferable. Small sheds should be elevated, or their
+ ground floors concreted. Wood sheds should probably be left without
+ flooring, wood kindling or other contents being piled on elevated
+ platforms provided for the purpose. Stables on the premises should be
+ treated as indicated in a subsequent paragraph relating to these
+ structures.
+
+ The garbage depository must be given most careful attention. It should
+ be a metal receptacle, preferably a galvanized can, water-tight to
+ prevent seepage which would attract rats, and there should be a
+ closely fitting lid. A can 2 feet in height without cover will not be
+ proof against the incursion of rats.
+
+ The rat proofing of chicken yards is a difficult task as most chickens
+ in private families are fed on table scraps, thereby attracting and
+ supporting a fair quota of rats. The entire inclosure should be
+ protected by wire fencing 6 feet high and of a mesh not larger than a
+ half inch. Ordinary poultry netting is inadequate, the mesh being too
+ large. The edge of the yard should be of concrete construction, the
+ concrete extending 1 foot upward and 2 feet inward. If, on any
+ subsequent inspection, rats have been found to have burrowed into the
+ inclosure, the entire area should be concreted, sand or earth being
+ allowed as a top dressing.
+
+ It would seem sufficient to confine these specifications to a feeding
+ pen, but in practice this will not suffice, as a mere pretext of such
+ a place would be built, and the housewife would continue to throw
+ scraps into the unprotected yard.
+
+ The dwelling house itself should receive the most careful attention.
+ If it is a small frame structure the cheapest and most effective means
+ of rendering it free from rats is by elevating it, the minimum height
+ being 1½ feet, measured from the most dependent joist. At the same
+ time, all underpinning should be freed of rubbish or other material.
+ It is not sufficient to raise the structure a few inches so as to
+ permit the entrance of cats and other enemies of the rat. Such height
+ and exposure must be secured as to deprive all rodents of cover.
+
+ If the house is of more substantial structure, and always if it has a
+ cellar or basement, concrete or some other rat-proof material should
+ be adopted. If sound foundation walls of stone or brick exist, then
+ only the addition of a concrete floor is necessary. The stopping up of
+ rat holes in any substance pervious to rats is at best a poor
+ expedient.
+
+ The grounds must be rendered rat proof by piling all loose materials
+ at such an elevation as will preclude rat harborage. All rubbish
+ should be burned or otherwise destroyed. All basement windows should
+ be properly protected against the ingress of rats, and if the _Mus
+ rattus_ be present, even second and third story windows should not be
+ considered too high to afford them entrance.
+
+ All loose materials on the premises should be properly piled, even
+ though they are in a rat-proof cellar. It is not probable that the
+ _Mus decumanus_ would remain or breed in any place where it could not
+ burrow; but no encouragement should be offered to any rodent let in by
+ carelessly left open doors. There have been cases where the black rat
+ has lived, increased, and overrun a house which was structurally rat
+ proof, but in which there was allowed easy access through open windows
+ and doors, and great piles of loose materials and dunnage furnish
+ harborage.
+
+ Stables are of twofold importance because they provide a source of
+ food supply for rats and furnish harborage. All grain must be kept in
+ a metal lined box or granary. A small stable is sufficiently rat proof
+ if it has an elevation of 2 feet with clear underpinning, provided the
+ floor is rendered impervious to falling grain. Barns of larger extent
+ are best made rat proof by concrete flooring tight on the ground, and
+ the area walls should be of concrete 1 foot high or of galvanized iron
+ of standard thickness. The ingredients of concrete should be specified
+ as to quality and quantity.
+
+ The windows of stables should be screened, especially if black rats be
+ present. To render a large livery stable rat proof, however, is hardly
+ practicable, owing to doors being open almost continuously, but rat
+ proofing even in such buildings will destroy rat harborage and limit
+ rat invasions to an occasional migratory rodent. With concrete
+ flooring and protected feed pens it should be an easy task to keep
+ such a building free from rats.
+
+ Finally, manure pens should be rat proof or the manure thrown into the
+ corner of the rat-proof stable, provided there is frequent cartage.
+
+
+ RAT-PROOFING ORDINANCES SHOULD BE SPECIFIC.
+
+ Any law or ordinance providing for rat proofing should specifically
+ state the minimum thickness of concrete and cement. Concrete 4 inches
+ deep with one-half inch dressing of cement or 1-inch asphalt answers
+ very well. Area walls if of concrete should be 6 inches thick, and the
+ floors should have sufficient slant to allow drainage.
+
+ Any expedient as galvanized iron sunk into the ground and made flush
+ with the flooring will not prove of practical value, as it allows
+ rat-harboring space to exist beneath the flooring, and sooner or later
+ rats will gain access thereto by burrowing under the iron gratings or
+ through the wooden flooring.
+
+ Meat markets should have concrete floors with cement or asphalt
+ dressing, the floors to be close on the ground and surrounded by
+ properly constructed foundation walls of stone or brick in cement.
+ Water-tight metal cans should be provided for all scraps, and
+ especially for the sawdust with its admixture of fine pieces of meat.
+
+ Bakeries and restaurant kitchens should be treated in the same way as
+ meat markets. Packing houses, slaughter pens, warehouses, and food
+ depots in general should be concreted.
+
+ The water front demands the greatest attention. The piers and wharves
+ should be of concrete or steel construction. The shipping should be
+ shored off from the dock, and all lines properly rat guarded. When not
+ in use, gang planks should be lifted. Notwithstanding these
+ precautions, rats will be imported from time to time, and the only
+ practical way to prevent their getting ashore will be the systematic
+ and routine fumigation of ships by the quarantine authorities.
+
+ The rat proofing of sewers is open to argument. Of all places in a
+ city the sewer is certainly the one where rats can die with the least
+ danger to the human population. For this reason the sewer should be
+ the last structure in a municipality to be made rat proof. The
+ movements and migrations of rats should be controlled to the extent of
+ making corner catch basins their sole means of entrance and exit to
+ sewers. The small and large iron-pipe mains require no attention in
+ this respect, but where mains are constructed of brick, and especially
+ where they are old and in bad repair, they should be repaired, all rat
+ runs leading from the sewer walls being stopped up and all blind
+ sewers being closed. By this means there will be prevented the
+ breeding of rats in these areas.
+
+ The rat proofing of catch basins by any method that would not also
+ block the entrance to the basin seems hardly possible. Properly
+ trapped basins, however, will be found almost as effective and just as
+ desirable.
+
+ To attain efficient rat proofing requires necessary laws or ordinances
+ and public sentiment favoring their enforcement. Dead-letter laws that
+ form no small part of many city statutes attest the fact that
+ favorable public opinion is almost indispensable to their enforcement.
+ However, well-drafted laws, clear and specific in requirement and
+ impartially and consistently enforced, inevitably lessen and destroy
+ opposition.
+
+ In the foregoing are contained general principles necessary to rat
+ proofing in the case of an outbreak of plague. Due allowance will have
+ to be made, however, for local conditions, and special considerations
+ as they arise, as no unvarying plan will be practical of application
+ in every instance.
+
+
+ CHOICE OF ARCHITECTURE AND BUILDING MATERIALS.
+
+ Cities and countries have from time to time wholly revolutionized
+ their type of buildings and constructive materials for either
+ commercial or æsthetic reasons. It is suggested that ports having
+ trade relations with countries where plague prevails should bear in
+ mind the advisability of taking advantage of this fact and revise
+ their building laws with the view to rendering all new buildings rat
+ proof.
+
+ Concrete has been advocated for purposes of rat proofing because of
+ its durability and relative cheapness. Concrete flooring or side walls
+ can be made more durable, however, by embedding therein steel netting
+ of 1 or 2 inch mesh. By this method the cost of construction will
+ probably be reduced, as a thinner layer of concrete would be
+ sufficient, and the metal would be protected, thereby adding
+ stability. Such construction at the same time would be doubly rat
+ proof.
+
+
+
+
+ THE INEFFICIENCY OF BACTERIAL VIRUSES IN THE EXTERMINATION OF RATS.
+
+ By M. J. ROSENAU,
+
+ _Surgeon, U. S. Public Health and Marine-Hospital Service, Washington,
+ D. C., now Professor of Preventive Medicine, Harvard University
+ Medical School_.
+
+
+ INTRODUCTION.
+
+ Rats are notoriously resistant to bacterial infections. About the only
+ exception is the plague bacillus. Plague among rats occurs both in
+ endemic and epidemic form. When we recall that this virulent disease,
+ which spreads readily from rat to rat, neither eradicates these
+ rodents nor, as a rule, makes any appreciable inroads on the number of
+ rats, we can hardly expect that an artificially induced bacterial
+ disease would be successful. No other known bacterial infection has
+ such a virulence for rats as the plague bacillus has maintained.
+ Epizootics of bacterial nature, therefore, can not be classed among
+ the natural enemies of the rat. Despite this fact persistent efforts
+ have been made to create artificial epizootics to combat these
+ dangerous and destructive rodents, but with little success.
+
+ The bacterial viruses that have been used for the destruction of rats
+ and mice belong to the colon-typhoid group[AL] and excite enteritis of
+ different characters and a septicemia.
+
+Footnote AL:
+
+ More particularly the hog-cholera group, which includes the
+ para-typhoid organisms.
+
+ In 1889 Loeffler discovered and described a bacillus which he called
+ the bacillus of mouse typhoid (_B. typhi murium_). He isolated this
+ organism from a spontaneous epidemic which occurred among white mice
+ in the Hygienic Institute at Griefswald.[AM] He determined that this
+ bacillus not only caused the death of his mice in the laboratory, but
+ also that the infection was taken into the system of the mouse by
+ ingestion. He found the cultures to be especially virulent for field
+ mice (_Arvicola arvalis_). Loeffler gives a complete description of
+ the bacillus which, from a biologic standpoint, is the parent stock of
+ almost all subsequent work along this line. The bacillus used by
+ Danysz and other workers is either identical with or very closely
+ allied to Loeffler’s bacillus of mouse typhoid.
+
+Footnote AM:
+
+ Loeffler, F.: Ueber Epidemieen unter den im hygienischen Institute
+ zu Griefswald gehalten Mäusen und über die Bekämpfung der
+ Feldmausplage. Centblt. f. Bakt., Orig., vol. 11, 1892, pp. 129–141.
+
+ In 1892 Loeffler[AN] personally undertook a campaign against the field
+ mice in Thessaly and reported satisfactory results. The depredations
+ carried on by the mice were checked within eight to nine days.
+
+Footnote AN:
+
+ Loeffler, F.: Die Feldmausplage in Thessalien und ihre erfolgreiche
+ Bekämpfung mittels des _Bacillus typhi murium_. Centblt. f. Bakt.,
+ Orig., vol. 12, 1892, p. 1.
+
+ The English commission[AO] threw doubt upon the Thessaly operations
+ and concluded that the bacillus as a means of destruction of mice has
+ no value. They found the method to be expensive, affecting only one
+ species of mice; further, that the epidemic-like spread of the disease
+ in the fields was not sufficiently investigated, and that the infected
+ material retains its virulence only for eight days and does not permit
+ of being used in continued bad weather.
+
+Footnote AO:
+
+ Wien. landw. Zeit. 1894, p. 783.
+
+ Loeffler’s optimistic report, however, stimulated many similar trials
+ with varying success. Practically all these efforts were directed
+ against mice, until 1900, when Danysz took up the subject from the
+ standpoint of the rat and plague.
+
+ Danysz found that Loeffler’s _Bacillus typhi murium_ proved to be
+ pathogenic for ordinary mice (_Mus musculus_) and for field or harvest
+ mice (_Mus arvicolis_), but not for rats.
+
+ The culture isolated by Laser[AP] in 1892 was pathogenic for field
+ mice (_Mus agrarius_); this organism killed 70 of the 76 mice which
+ were used as experiment animals at the Hygienic Institute at
+ Königsberg.
+
+Footnote AP:
+
+ Laser, Hugo: Ein neuer für Versuchsthiere pathogener Bacillus aus
+ der Gruppe der Frettschen-Schweinseuche. Centblt. f. Bakt., Orig.,
+ vol. 11, 1892, p. 184.
+
+ Mereshkowsky[AQ] in June, 1893, isolated an organism belonging to this
+ group from a ground squirrel known as the Zisel (_Spermophilus
+ musicus_). This culture killed domestic and field mice when placed in
+ their food, but was not pathogenic for rats.
+
+Footnote AQ:
+
+ Mereshkowsky, S. S.: Ein aus Zieselmäusen ausgeschiedener und zur
+ Vertilgung von Feld-resp. Hausmäusen geeigneter Bacillus. Centblt.
+ f. Bakt., Orig., vol. 17, 1895, p. 742.
+
+ The Japanese investigator Issatchenko,[AR] in 1898, briefly described
+ a bacillus obtained by him from gray [white?] rats, which proved
+ virulent for rats and mice.
+
+Footnote AR:
+
+ Issatchenko, B.: Untersuchungen mit dem für Ratten pathogenen
+ Bacillus. Centblt. f. Bakt., Orig., vol. 31, 1902, p. 26.
+
+ Each of these various bacilli is of such variable virulence that it
+ could not be used for the destruction of all species of these rodents.
+
+ Danysz[AS] therefore conceived the notion that it would be of great
+ interest first to extend the field of action of one of these organisms
+ by increasing its virulence so that it would attack other species of
+ rodents, and then maintain this increased virulence at its highest
+ point.
+
+Footnote AS:
+
+ Danysz, J.: Un microbe pathogène pour les rats (_Mus decumanus_ et
+ _Mus rattus_) et son application à la destruction de ces animaux.
+ Ann. Inst. Pasteur, vol. 14, 1900, p. 193.
+
+ In 1900 Danysz isolated a bacillus from a spontaneous epidemic among
+ harvest mice. This organism was a cocco-bacillus presenting the
+ general characteristics of the colon-typhoid group and resembling the
+ bacillus of Loeffler—_B. typhi murium_. From the first this bacillus
+ showed a slight pathogenicity for gray rats (_M. decumanus_). Out of
+ 10 animals fed with a culture of this microbe 2 or 3 would die;
+ several others would sicken and recover; others appeared completely
+ refractory. The fact that a certain number of the rats fed with these
+ cultures always succumbed led to the hope that it would be possible to
+ increase the virulence of this particular microbe by the generally
+ accepted methods—that is to say, by a certain number of passages from
+ rat to rat.
+
+ Danysz first tried to increase the virulence of the organism by this
+ means, but he found that successive passages from rat to rat, whether
+ by feeding or by subcutaneous injection, ended by enfeebling rather
+ than increasing the virulence of the microbe. He found that it was
+ rarely possible to go beyond 10 to 12 passages. Sometimes the series
+ was stopped at the fifth passage, or even sooner, by the survival of
+ all the animals undergoing experiment. The result was exactly the same
+ if, instead of alternating each passage through the animal by a
+ culture in bouillon or agar, the bodies of animals dead of a preceding
+ passage were fed to others.
+
+ It was therefore plain that in the evolution of an epidemic caused by
+ this microbe it was necessary to take account of the indisputable
+ diminution of the virulence of the microbe, as well as the natural
+ resistance of the survivors.
+
+ Passage of cultures in collodion sacs inclosed in the peritoneal
+ cavities of rats was tried, both in interrupted series and by
+ alternating each sac culture with a culture in bouillon or on agar,
+ but the end was invariably a notable diminution of virulence when
+ administered by the digestive tract.
+
+ Finally, after long and painstaking procedures, Danysz obtained a very
+ virulent culture that, contained in flasks and kept from the influence
+ of light and air, preserved its virulence for several months. Planted
+ on agar it preserved its virulence without appreciable diminution for
+ two months under laboratory conditions. In bouillon, in flasks, or in
+ tubes stoppered with cotton it altered very rapidly.
+
+
+ DESCRIPTION OF THE ORGANISM.
+
+ A culture of Danysz’s virus obtained from the Pasteur Institute had
+ the following characteristics:
+
+ The organism is a cocco-bacillus showing distinct motility. Stains
+ well by the ordinary stains, but does not stain by Gram’s method.
+
+ It grows well at ordinary room temperature, also in the incubator, and
+ on all the ordinary media. In bouillon it produces a uniform
+ cloudiness in twenty-four hours. A slight scum forms after several
+ days’ growth, which falls to the bottom when shaken. In Dunham’s
+ solution it grows well, but produces no indol in twenty-four hours’
+ growth.
+
+ It does not coagulate milk.
+
+ It grows the whole length of the stab in gelatin, forming small
+ whitish colonies in the deeper portions of the tube. It does not grow
+ over the entire surface of the gelatin tube; does not liquefy gelatin.
+
+ It grows under anærobic conditions.
+
+ It ferments glucose bouillon, but not lactose bouillon. In glucose
+ bouillon it produces 1-CO_{2}, 5-H. It also produces H_{2}S.
+
+ From a general biological standpoint it is plain that this bacillus
+ belongs to the para-typhoid group, and is very similar to the bacillus
+ of hog cholera as well as the _Bacillus icteroides_, also _B.
+ enteritidis_, so far as its morphological and cultural characteristics
+ are concerned.
+
+ In the following table the fermentations produced by various members
+ of this group upon certain carbohydrates are shown:
+
+ ─────────────┬────────┬───────────┬────────┬────────┬────────┬─────────
+ Organism. │Lactose.│Saccharose.│Maltose.│Mannete.│Glucose.│Levulose.
+ ─────────────┼────────┼───────────┼────────┼────────┼────────┼─────────
+ B. typhosus │ − │ − │ − │ − │ − │ −
+ B. dysenteriæ│ − │ − │ − │ − │ − │ [AT]
+ Shiga │ │ │ │ │ │
+ B. dysenteriæ│ − │ − │ − │ − │ − │ [AT]
+ Kruse │ │ │ │ │ │
+ B. │ │ │ │ │ │
+ para-typhosus│ − │ − │ + │ + │ + │ +
+ A │ │ │ │ │ │
+ B. │ │ │ │ │ │
+ para-typhosus│ − │ − │ + │ + │ + │ +
+ B │ │ │ │ │ │
+ B. para colon│ − │ − │ + │ + │ + │ +
+ B. acidi │ + │ − │ + │ + │ + │ +
+ lactici │ │ │ │ │ │
+ B. hog │ − │ − │ + │ + │ + │ +
+ cholera │ │ │ │ │ │
+ B. typhi │ − │ − │ + │ + │ + │ +
+ murium Danysz│ │ │ │ │ │
+ B. icteroides│ − │ − │ + │ + │ + │ +
+ B. │ − │ − │ + │ + │ + │ +
+ enteritidis │ │ │ │ │ │
+ B. coli │ + │ + │ + │ + │ + │ +
+ communis │ │ │ │ │ │
+ ─────────────┴────────┴───────────┴────────┴────────┴────────┴─────────
+
+Footnote AT:
+
+ Or bubble.
+
+
+ EXPERIMENTS UPON RAT VIRUS IN THE HYGIENIC LABORATORY.
+
+ In 1901 I made an investigation of this pathogenic microbe (_B. typhi
+ murium_) applied to the destruction of rats under laboratory
+ conditions.[AU] One hundred and fifteen rats were fed with the
+ cultures in various ways during the course of these experiments with
+ the virus. Of these, 46 died—less than half.
+
+Footnote AU:
+
+ Rosenau, M. J.: An investigation of a pathogenic microbe (_B. typhi
+ murium_ Danysz) applied to the destruction of rats. Bull. No. 5 of
+ the Hygienic Laboratory, U. S. Mar. Hosp. Serv., Washington, 1901,
+ 11 p.
+
+ Most of the rats used were the gray rat (_M. decumanus_ or
+ _norvegicus_) and the tame white rat. A few (8) of the wild black or
+ house rats (_M. rattus_) were used.
+
+ The virus is in reality pathogenic for these three kinds of rats when
+ ingested. No special difference was noted in its effects upon the
+ various species.
+
+ As the work progressed it soon became evident to me that the result
+ depended largely upon the amount of the culture ingested. By starving
+ rats for a day or two and then giving them all they could be induced
+ to eat and drink of the cultures, a very positive result was obtained.
+ In one instance of 27 rats so fed all died within a week. If the rats
+ are given a small amount the effect is uncertain—only a few die. In
+ one instance I fed 70 rats with 4 agar tubes and only 7 died. Feeding
+ them a second time with very large quantities 9 more died. The
+ survivors were then fed with all they could be induced to eat every
+ day for a week without effect.
+
+ It seems plain, therefore, that a large primary dose proves fatal, and
+ a small dose is not only uncertain, but produces an immunity. This is
+ a very important factor, for it is likely that in the wild state rats
+ would often partake of an amount too small to cause death. Such rats
+ may then subsequently eat large amounts of the culture with impunity.
+
+ It would seem then that, after all, the virus is not so different from
+ the laying of a chemical poison, depending as it does for its effect
+ upon the amount ingested. A chemical poison, however, does not possess
+ the disadvantage of producing an immunity. Another disadvantage
+ possessed by the virus is the rapid deterioration in virulence which
+ occurs when it is exposed to the action of air and light, or when it
+ becomes dry, as is very apt to happen when laid out for rats in the
+ wild state.
+
+ Since these early experiments, tests have been made of various rat
+ viruses in the Hygienic Laboratory, and the results are given in the
+ following pages:
+
+
+ AZOA.
+
+ Series 1. Single feeding of azoa in oatmeal. Rats starved twenty-four
+ hours before feeding. Three out of eight animals died in four, five,
+ and seven days, respectively. Micro-organisms resembling the
+ predominant one of azoa could not be isolated from their hearts’
+ blood. The organs of these dead rats were fed to fresh rats with the
+ result that one of the three died. It must be mentioned that the
+ mortality among our fresh rats was nearly as high as that in the
+ experimental animals from a disease probably due to infection with an
+ animal parasite.
+
+ Series 2. Daily feedings with azoa in oatmeal. Five white rats fed
+ with the mixture, a constant supply being kept in the cage. These
+ animals were picked rats freshly obtained from the dealer. One rat
+ died after seven days. It was heavily infested with lice. The azoa
+ organism could not be found in the blood. The rest remained well after
+ twenty-five days.
+
+ Series 3. Black tame mice, daily feedings. One of the five died after
+ seven days. The rest remained well after fourteen days.
+
+ These experiments indicate that azoa is not pathogenic for white rats
+ and black tame mice to a degree rendering it applicable for vermin
+ extermination on a practical scale, provided that its action is no
+ more pathogenic for the wild than for the tame species.
+
+
+ RATITE.
+
+ The manufacturers recommend a single feeding of this substance rather
+ than a continued exhibition of the virus.
+
+ Series 1. Five white rats starved twenty-four hours and then fed with
+ a mixture of ratite and oatmeal. Subsequent daily feedings with plain
+ oatmeal. Picked animals fresh from the dealer. One animal died after
+ twelve days; too much putrefied for further examination; had been
+ heavily infested with lice. The remaining rats are well after
+ twenty-five days.
+
+ Series 2. Five black tame mice fed as above. Three were found dead
+ after eighteen days and the other two after nineteen days. Further
+ experiments were not made, as putrefaction was too far advanced when
+ they were found. The room in which they were kept had been unusually
+ cold just before their death owing to a sudden and unexpected drop in
+ the external temperature.
+
+ Ratite does not appear to be very pathogenic for white rats. All the
+ five mice fed with ratite died in eighteen to nineteen days (much
+ longer than the advertised incubation period of the infection), but
+ their death could be reasonably attributed to unusual cold. This part
+ of the test is therefore invalidated except that the animals lived
+ considerably longer than would be expected from the literature
+ furnished by the manufacturers, which says that the effects of laying
+ the virus will be apparent in eight to ten days.
+
+
+ DANYSZ VIRUS.
+
+ Twelve tubes of Danysz virus were sent to the laboratory for
+ examination April 7 by the Independent Chemical Company, agent for
+ Danysz Virus Company (Limited). The label stated “Keep in a cool place
+ and at above temperature; use before May 15, 1909.”
+
+ The virus was kept at 15° C. until April 13, when it was turned over
+ to Passed Asst. Surg. W. H. Frost, who made the following tests:
+
+ One tube opened. Cultures made on two agar tubes were found to
+ correspond in cultural characteristics with the bacillus of Danysz
+ virus as generally described. The remainder of the tube prepared
+ according to directions in accompanying circular, using stale dry
+ bread 2 ounces and suspension of the culture in normal salt solution.
+
+ Series 1. Approximately equal parts, then fed to six white rats in
+ individual cages, they having not been fed for twenty-four hours
+ previously. Rats all ate greater part of infected food.
+
+ Five rats of series 1 died within five to seven days and were partly
+ eaten before being removed from the cage. The pathological changes in
+ all cases were chiefly enlargement and congestion of spleen and liver,
+ and in some cases inflammation of small intestine. In each case an
+ organism was obtained, usually in pure culture, from one or more
+ organs, corresponding culturally and morphologically with cultures
+ taken from original tube.
+
+ Series 2. April 14: Rats all ate greater part of infected food.
+ Transferred to large cage containing nine other white rats. Nine other
+ white rats exposed to infection by being placed in a large cage with
+ the rats of series 1. Four of the nine rats of this series died in
+ four to seven days after eating infected rats.
+
+ Pathological changes and results of cultures from internal organs the
+ same as with series 1. Autopsy and cultures impossible in one case,
+ where body was almost completely devoured.
+
+ Series 3. May 5: Three of the six surviving rats (one from series 1,
+ two from series 2) were placed in individual cages, deprived of food
+ for twenty-four hours, then fed each with one-third agar tube cultures
+ of Danysz virus (the same used in the original feeding). All three ate
+ practically all the virus given.
+
+ All three of these rats remain alive and well after two months.
+
+ Summary.—Series 1. Six rats each fed one-twelfth to one-sixteenth agar
+ culture Danysz virus. Five died within five to seven days.
+
+ Series 2. Nine rats exposed to infection by being placed in cage with
+ series 1. Four died within eight to twelve days after death of first
+ rat of series 1.
+
+ Series 3. Three of the surviving rats (1 from series 1 and 2 from
+ series 2) fed each with one-third agar tube of original Danysz virus
+ as used in series 1. None died.
+
+
+ TRANSATLANTIC RATIN.
+
+ A can of this substance labeled “Transatlantic ratin” was furnished by
+ the American agents representing the Bacteriological Laboratory,
+ Copenhagen, Denmark. The can bore the date January 26, 1909, and was
+ stated to be “effective for six months from date of production.”
+
+ On April 13, 1909, this sample was given to Passed Asst. Surg. W. H.
+ Frost for examination, and he obtained the following results:
+
+ April 13, 1909: Can of ratin opened with aseptic precautions. Contents
+ mixed with about equal bulk of clean fresh lard.
+
+ A portion of this about equal to one tablespoonful fed to each of six
+ white rats previously deprived of food for twenty-four hours. All the
+ rats ate some of the bait at once. Feeding at 2 p. m.
+
+ April 14: Five rats very sick, having convulsions; partially
+ paralyzed. One dead.
+
+ April 15: Three more rats found dead. Remaining 2 recovering.
+
+ The pathological change in all the above cases consisted chiefly of
+ intense congestion of intestines, both large and small.
+
+ Cultures from the original case of ratin, on agar, bouillon, and in
+ fermentation tubes, negative except staphylococcus in one tube.
+
+ Cultures taken from heart’s blood and other organs of the 4 dead rats
+ all negative, except in one case a growth of a staphylococcus
+ resembling _S. pyogenes citreus_.
+
+ April 20: Two rats fed on half agar slant culture of the
+ staphylococcus obtained from heart’s blood of rat No. 1. Result of
+ feeding negative after several weeks.
+
+
+ NOTE. The absence of a colon-like organism in this virus and the
+ rapid death of the animals with convulsions suggested a chemical
+ poison, which it is believed this can contained.—M. J. R.
+
+
+ EXPERIMENTS WITH MICRO-ORGANISMS FOR DESTROYING RATS, CONDUCTED BY THE
+ UNITED STATES BIOLOGICAL SURVEY.[AV]
+
+Footnote AV:
+
+ This report was furnished by Dr. A. Hart Merriam, Director of the
+ Biological Survey.
+
+
+ RATIN.
+
+ The Biological Survey, Department of Agriculture, in cooperation with
+ the Bureau of Animal Industry, has experimented with “ratin.” The
+ material (ratin No. 2—labeled “Transatlantic ratin”) was furnished by
+ the American agents in New York. Although the agent claimed that this
+ was a bacterial preparation and that “it would kill for six
+ generations,” it proved to be a glucoside poison (probably squills)
+ and contained no bacteria of any kind. A number of experiments were
+ made with it, and it proved to be an effective rat poison. In some
+ instances the animals died within two hours after eating it, and in
+ two experiments all the animals fed died within twelve hours. In other
+ experiments, however, a considerable percentage of the affected rats
+ recovered, and subsequent attempts to kill them with ratin No. 2
+ failed. Some were immune to its effects and others too wise to eat it
+ a second time. More than a hundred rats were used in the experiments;
+ but the main object—to test the communicability of the disease caused
+ by ratin bacteria in healthy rats—failed, of course, since, as above
+ stated, the preparation experimented with contained no bacteria, but
+ was merely a vegetable poison. Before its character was fully
+ determined, 15 rats killed in the experiments were eaten by 5 healthy
+ rats; the latter were unaffected.
+
+ It should be noted that the labels on the tins containing
+ transatlantic ratin were misleading. The user was warned to open the
+ packages in dim light and to allow no moisture to come in contact with
+ the contents, as the bacteria were very sensitive to light and
+ moisture. The contents of the can were to be used at once. As a matter
+ of fact the contents of one can were exposed to severe drying in heat
+ and sunlight for four days and then soaked in water for two days.
+ Afterwards the preparation was fed to different rats for a further
+ period of four days, and its virulence was retained to the last.
+
+ The transatlantic ratin is in a solid medium, apparently bread and
+ molasses. Its keeping qualities are excellent, and it is an effective
+ poison for rats, but far too expensive for extensive use. A can
+ costing $1.50 is enough for only 15 baits.
+
+ Its harmfulness to domestic animals was not fully tested. Dogs and
+ cats refused to eat it and vomited it when it was forced upon them.
+ Several animals, including a dog, were killed by injections of the
+ poison in concentrated form.
+
+ A shipment of ratin No. 1 (the solid bacterial ratin, said to retain
+ its virulence for two months) was received June 4, 1909. This
+ preparation was dated May 8 and should have been still virulent. The
+ contents of a can mixed with milk was fed to 8 adult rats on June 7.
+ All of the baits were eaten, but no result followed. Cultures of the
+ bacteria showed strong growths of new colonies.
+
+ On July 6 the contents of another can were fed to 1 adult and 16 young
+ rats. One of the young was found dead on the morning of July 14.
+ Cultures were made from the dead rat, but the bacillus was not
+ recovered. Up to July 28 none of the other rats have been affected.
+
+
+ AZOA.
+
+ Several trials of azoa for the destruction of rats have come under the
+ observation of members of the Biological Survey. Experiments made in
+ the building occupied by the Interstate Commerce Commission were at
+ first promising, but from a second invoice of the virus no results
+ were obtained. In the buildings of the National Zoological Park 72
+ bottles of azoa were used, but the results were for the most part
+ negative. In a store in south Washington where this preparation had
+ been used the stench of dead rats was very strong, showing a measure
+ of success.
+
+
+ DANYSZ BACILLUS.
+
+ Some three years ago the Biological Survey, assisted by the Bureau of
+ Animal Industry, tested the efficiency of Danysz virus. In the
+ laboratory from 10 to 50 per cent of rats fed on the virus died. In
+ the field, however, results obtained were unsatisfactory. Only 1 dead
+ rat was found from which the bacillus was recovered. Experiments with
+ field mice gave better results. All the mice fed in confinement died,
+ and field experiments resulted in many dead mice from which the
+ bacillus was recovered.
+
+
+ EXPERIMENTS DURING THE SAN FRANCISCO PLAGUE OUTBREAK.[AW]
+
+Footnote AW:
+
+ These experiments were made by Passed Asst. Surg. G. W. McCoy,
+ United States Public Health and Marine-Hospital Service, in 1907–8
+ during the plague campaign in San Francisco and here published for
+ the first time.
+
+ Several proprietary biological products sold as rat exterminators were
+ made the subject of seven experiments on wild San Francisco rats, for
+ the purpose of ascertaining whether they were efficient for the
+ purpose for which they were sold. Seventy-six rats were used in these
+ experiments. About 10 per cent died within a month and there was
+ considerable doubt as to whether all of the deaths that occurred were
+ due to the agent used.
+
+ The following is a brief statement of the work done with these agents.
+ In each case the rats used were wild _Mus norvegicus_, caught in San
+ Francisco.
+
+
+ RATIN NO. 1.
+
+ Made by the Bakteriologik Laboratorium, Copenhagen, marked: “Effective
+ two months from April 28, 1908.” The preparation comes ready for use
+ in the form of a moist, mealy mass. On May 28, about 6 ounces of the
+ material was fed to 12 rats. They all remained well until thirty days
+ after feeding them when the experiment was regarded as terminated.
+
+
+ DANYSZ VIRUS.
+
+ The Danysz Virus Company (Limited), of London, furnished a preparation
+ in the form of a culture on a slant of solid medium, said to be
+ gelatine. The tube was marked: “To be used before June 1, 1908.” The
+ contents of the tube, mixed with bread, according to directions, was
+ fed to 6 rats. On the twenty-first day but 4 rats remained, 2 having
+ died and been devoured by their companions. The 4 that remained were
+ chloroformed, as the cage was needed for other purposes. Post-mortem
+ examination showed them to be entirely normal.
+
+
+ RATITE.
+
+ Furnished by the Pasteur Vaccine Company, Chicago. This preparation is
+ in the form of a culture in a liquid medium, presumably broth. The
+ bottle was dated April 10, 1908, and the label stated that it should
+ be used within twenty days from date of preparation. On April 29,
+ 1908, 9 rats were fed with about 6 ounces of the preparation, mixed
+ according to directions. The rats all remained alive and well, and
+ when chloroformed on June 1, 1908, presented no abnormality on
+ post-mortem examination. In another experiment the contents of a
+ bottle of ratite was fed to 6 medium-sized _Mus norvegicus_. None of
+ the animals died from the effects of the agent, and when they were
+ killed on the fifty-fifth day after the feeding were found to present
+ no lesions.
+
+ The remaining work was done with rat virus, sometimes called
+ “Mouratus.” It is made by the same concern that makes the ratite. The
+ rat virus comes in the form of a culture on a solid medium. The
+ contents of three tubes was fed to 6 rats on May 26, 1908. Three of
+ these rats died within thirty days. Only one was secured for
+ examination before it had been mutilated beyond the possibility of
+ making a satisfactory examination. This rat had a large yellow liver
+ and a very large, dark, firm spleen. These appearances were probably
+ due to the agent used and it is not unlikely that these 3 rats died
+ from its effect. It will be observed that a very large dose was given.
+ On another occasion four tubes of Mouratus were used for feeding 6
+ _Mus norvegicus_. One of the rats died on the fifteenth day, showing
+ at autopsy an enlarged granular spleen and a granular liver. The other
+ rats were alive and well at the end of thirty-four days when the
+ experiment was discontinued.
+
+ Subcultures on broth were made from this preparation on three
+ occasions, always well within the time limit on the label. The
+ cultures were incubated in the dark, at room temperature, for forty
+ hours on each occasion. Liberal amounts of the subculture were fed to
+ a total of 31 rats. At the end of thirty days, it was found that only
+ 2 of these rats had died. The others were alive and apparently well.
+
+ One objection to these agents which I have not seen stated is the
+ following: The lesions caused by at least some of these members of the
+ paracolon group may readily be mistaken for the lesions of plague, or
+ it will perhaps be more accurate to say they give rise to lesions that
+ create in one’s mind a suspicion of plague infection, and I have had
+ to put many a rat to the guinea-pig test in order to make certain that
+ a Danysz infection was not associated with the infection of plague, or
+ that a Danysz rat was not a plague rat. Of course, this is of no
+ consequence except in a community where antiplague measures are being
+ taken, and an observer of limited experience who did not put a rat to
+ a pretty rigid test would probably call some plague infected when in
+ reality such is not the case.
+
+ In addition to the data set forth in this report, I have on several
+ occasions fed the tissue of rats dead of Danysz infection to other
+ rats, but have never succeeded in reproducing the disease. In other
+ words, I have had no success whatever in raising the virulence by
+ passage through animals.
+
+
+ OPINIONS OF OTHERS.
+
+ Kitasato,[AX] 1906, states that the typhoid bacillus of the rat, which
+ has been effectively used for killing field mice, has been found
+ useless for house rats (_Mus rattus_) and therefore they no longer
+ employ it.
+
+Footnote AX:
+
+ Kitasato, S.: Combating plague in Japan. Philippine Journ. Sci.,
+ vol. 1, 1906, p. 465.
+
+ Melvin,[AY] 1908, reports that recently several new rat viruses were
+ investigated in the Bureau of Animal Industry, with the result that
+ the experiments clearly demonstrated the ineffectiveness and
+ unreliability of the preparations tested.
+
+Footnote AY:
+
+ Melvin, A. D.: Report of the Chief of the Bureau of Animal Industry
+ for 1908. Washington, 1908.
+
+ Räbiger and Schwinning,[AZ] 1906, tested the culture discovered by G.
+ Neumann and prepared by the joint stock company “Ratin” at Copenhagen
+ by applying it to rat destruction. Of house rats 90 per cent died;
+ black rats 42.9 per cent; while horses, dogs, goats, sheep, fowls, and
+ pigeons suffered no harm. Of seven experiments practically carried
+ out, six showed very good results; in one favorable results were
+ absent, which agrees with the experiments made in Denmark. There it
+ was likewise found that in individual locally limited places the rats
+ were able absolutely to withstand the infection of ratin.
+
+Footnote AZ:
+
+ Räbiger and Schwinning: Versuche mit Ratin, einem neuen Ratten
+ tötenden Bacillus. Mitth. d. deutsch. Landw.-Gesellsch., 1906, No.
+ 18. Rev. by Ehrenberg in Centblt. f. Bakt., 2. Abt., vol. 18, 1907,
+ p. 375.
+
+ Räbiger,[BA] 1905, states that experiments with Loeffler’s mouse
+ typhus bacillus and the bacillus of Danysz virus have been carried to
+ the conclusion that these bacterial preparations must be characterized
+ as practically worthless.
+
+Footnote BA:
+
+ Räbiger, H.: Ueber Versuche zur Vertilgung der Ratten durch
+ Bakterien. Landw. Woch. f. d. Prov. Sach., 1905, p. 142. Rev. by
+ Stift in Centblt. f. Eakt., 2 Abt., vol. 15, 1905, p. 86.
+
+ In 1903 Neumann discovered in Denmark a rat-killing bacillus, which
+ has been placed on the market by a society under scientific control
+ under the name of “ratin.” Feeding experiments with this bacillus were
+ tried under conditions as nearly natural as possible upon white mice,
+ gray house mice, long-tailed field mice, and gray rats. The experiment
+ animals were fed with cubes of white bread impregnated with virulent
+ cultures. White mice show the least power of resistance, since they
+ die within six days; house mice died in six to nine days; the greater
+ part of the rats died from the sixth to the sixteenth day after
+ feeding; a small percentage lived. The long-tailed field mice, which
+ are shown to be insusceptible to Loeffler’s bacillus, also remained
+ perfectly healthy after repeated feedings with bread infected with
+ ratin.
+
+ Brooks,[BB] 1908, reports the results of tests made with azoa on rats
+ and mice, both in captivity and at large, but without any apparent
+ discomfort to the animals. One of the tests is described as follows:
+
+Footnote BB:
+
+ Brooks, Fred E.: Notes on the habits of mice, moles, and shrews. A
+ preliminary report. Bull. 113, W. Va. Univ. Agric. Exper. Sta.,
+ Morgantown, W. Va., Jan., 1908.
+
+
+ A supply of the azoa was obtained direct from the laboratories of
+ the manufacturers. On July 27, 1907, while the material was yet
+ fresh, three young Norway rats were caught and kept confined in a
+ large wire rat trap. Beginning with the date given, and for a period
+ of forty days thereafter, azoa was fed to the rats at intervals of a
+ few days until ten 75-cent bottles had been consumed. The rats ate
+ the cracked grain with which the virus was mixed very readily, and
+ other food was denied them each time the azoa was given until every
+ particle was eaten. At the end of the forty days the rats were still
+ apparently in a healthy condition, and were removed from the trap
+ and killed with a club.
+
+
+ Thompson,[BC] 1906, states that three laboratory attempts have been
+ made to destroy rats with imported strains of Danysz rat virus without
+ success. Danysz having arrived at Sydney to study a similar method of
+ destroying rabbits, the opportunity was taken of making a further
+ attempt under his supervision with virus which had been imported and
+ subsequently increased to the requisite degree of virulence, and had
+ been placed at Thompson’s disposition. The grounds of the Gladesville
+ Asylum, a large institute for the insane, were chosen for the tests,
+ which were conducted by Dr. R. J. Millard.
+
+Footnote BC:
+
+ Thompson, J. Ashburton: Report of the Board of Health on plague in
+ New South Wales, 1906. On a sixth outbreak of plague at Sydney,
+ 1906. Legislative assembly, N. S. W., 1907.
+
+ Millard summarized his result by stating that they can not be
+ considered a satisfactory demonstration of the efficacy claimed for
+ the Danysz virus. The results indicate a rapid loss of virulence,
+ which must be obviated if this virus is to be of utility for rat
+ destruction.
+
+ Again, in 1907, during the seventh outbreak of plague in Sydney,
+ Thompson[BD] had Millard test the preparations known as azoa and
+ ratin. The laboratory results with these preparations were similar to
+ those made by other investigators. Experiments made upon the ship
+ _Hartfield_ with azoa produced no considerable epizootic. The fatality
+ among such rats as were infected was small. The practical tests with
+ azoa upon several areas along the harbor front also resulted in
+ disappointment.
+
+Footnote BD:
+
+ Thompson, J. Ashburton: Report of the board of health on plague in
+ New South Wales, 1907. On a seventh outbreak of plague at Sydney,
+ 1907. Legislative Assembly, N. S. W., 1908.
+
+ The tests made with ratin upon the bark _Quilpe_ produced no epizootic
+ among the rats, and of the rats caught none of them showed infection;
+ and the field experiment at Gladesville also resulted negatively so
+ far as dead or sick rats were concerned. Nevertheless, there was
+ apparently considerable diminution in the rat population of this area.
+
+ Foster,[BE] 1908, reports unfavorably upon the results of tests made
+ of some of these rat viruses. Laboratories were opened for the use of
+ different parties who wished to make tests. The tests were conducted
+ under their own supervision. The rats which were not fed on anything
+ but grain died as freely as those that had been fed on azoa. So far as
+ this preparation is concerned Foster states that it is absolutely
+ useless to depend upon it.
+
+Footnote BE:
+
+ Foster, N. K.: The danger of a general plague infection in the
+ United States. Proc. Confer. State and Prov. Boards of Health of N.
+ America, 1908, p. 15.
+
+ Several reports are found in print in which the rat virus was laid out
+ in certain localities and shortly afterwards the rats disappeared—at
+ least no more were noticed. Such observations are apt to be
+ misleading, for rats are migratory. They come and go, especially when
+ disturbed. Further, it is doubtful, as far as plague is concerned,
+ whether it is desirable to drive the rats away, for they may thus
+ scatter the infection.
+
+ S. S. Mereshkowsky and E. Sarin[BF] have recently studied ratin II,
+ put out by a Copenhagen firm—“Bakteriologisches Laboratorium Ratin.”
+ The label upon the can of ratin II states that it is a bacterial
+ culture, which produces in rats an infectious and fatal disease,
+ killing them in two to eight days. The samples used by the authors
+ were obtained as needed from the St. Petersburg representative of the
+ firm. Feeding experiments carried out with gray rats (_Mus decumanus_)
+ showed that the rapidity and severity of the symptoms was proportional
+ to the amount ingested. No positive results were obtained from the
+ bacteriological examination of the bodies.
+
+Footnote BF:
+
+ Ueber das Ratin II. Centralb. für Bakt. Parstk. u. Infectsk.
+ Originale. Bd. 51. Heft 1. July 17, 1909, p. 6.
+
+ The ratin itself was sometimes found to be sterile, sometimes found to
+ contain several varieties of bacteria and fungi, but no one variety
+ was constantly present.
+
+ The potency of the ratin was not altered by exposure to 100° C. for
+ one hour or 120° C. for five minutes. It was destroyed, however, by
+ burning to an ash.
+
+ Identical poisonous results were obtained upon rats by feeding them
+ with “Scilla maritina cum bulbo rubro.”
+
+ Microscopical examination disclosed a small portion of a lamella,
+ identified as belonging to the Liliaciæ, to which family squill
+ belongs.
+
+ The authors conclude that ratin II is not a bacterial culture, but a
+ poison rendered more dangerous to persons and domestic animals by the
+ misleading statements of its makers.
+
+
+ PATHOGENICITY FOR MAN.
+
+ Loeffler[BG] rather took it for granted at first that his _Bacillus
+ typhi murium_ was harmless for man. In order to remove the fears of
+ the peasants in his campaign against the field mice in Thessaly he fed
+ pieces of bread impregnated with the cultures to chickens, pigeons,
+ dogs, hogs, horses, asses, sheep, and goats. No ill effects resulted.
+ Further, some of the men who were distributing the prepared virus ate
+ pieces of the infected bread in the presence of all and, it appears,
+ suffered no ill effects.
+
+Footnote BG:
+
+ Loeffler, F.: Die Feldmausplage in Thessalien und ihre erfolgreiche
+ Bekämpfung mittels des Bacillus typhi murium. Centblt. f. Bakt.,
+ vol. 12, 1892, p. 1.
+
+ Up to this time Loeffler had made no human experiments, but thought it
+ improbable that his bacillus was harmful to man. He considered this
+ view confirmed by the fact that he and his companions and still more
+ so the peasants, handled large quantities of the virus without
+ thorough disinfection of their hands and suffered no untoward effects.
+
+ Since that time, however, several mishaps have occurred. Instances of
+ serious sickness and even death have been attributed to infection with
+ the bacterial virus used for the destruction of rats.
+
+ Further, there is practically no difference between the _Bacillus
+ typhi murium_ and the para-typhoid bacillus which is the well-known
+ cause of meat poisoning, and the _Bacillus enteridion_ of Jarbues,
+ which is associated with intestinal disorders.
+
+ It is true that persons have purposely partaken of the rat virus to
+ prove that it is harmless to man; but it must be remembered that
+ persons have partaken of cultures of cholera, typhoid, and other
+ bacteria without apparent injury to themselves. The flora and
+ condition of the gastro-intestinal tract, the amount and virulence of
+ the infection, and other conditions (“Y” and “Z” of Pettenkofer) play
+ an important rôle in the production of these diseases.
+
+ The following references from the literature give the instances in
+ which the _B. typhi murium_, or similar rat viruses, have been held
+ responsible for the disease in man:
+
+ Trommsdorff[BH] carefully studied 13 suspected cases near Munich in
+ early May, 1903. Nine of these came into direct contact with the
+ virus, three ate and associated with these, and the remaining one only
+ smelled of the virus. One died from vomiting and severe diarrhea. The
+ illness, which set in usually two days after contact with the virus,
+ was for the most part simple diarrhea of two to seven days’ duration
+ (two to eight stools daily); in only three or four cases was there
+ vomiting. The one fatal case seemed due to a confusing chain of
+ circumstances, gross dietetic and alcoholic excesses in a weak,
+ emaciated, presumably phthisical man whose three brothers had died of
+ phthisis. One man, case No. 2 in the table, known to have eaten three
+ pieces of infected bread, suffered only with a mild diarrhea.
+
+Footnote BH:
+
+ Trommsdorff, R.: Ueber Pathogenität des Löfflerschen
+ Mäustyphusbazillus beim Menschen. Münch. med. Woch., vol. 50, 1903,
+ p. 2092.
+
+ In all cases errors of diet could be proven, and diarrhea was not
+ uncommon at that season. The same physician attended during this
+ period ten other cases of similar diarrhea in the vicinity having
+ nothing to do with rat virus. The stools, however, did not have the
+ same pathogenicity for mice, guinea pigs, or rabbits.
+
+ Trommsdorff specially points out the fact that the bacillus of mouse
+ typhoid can multiply vigorously in the human intestine. It demands
+ greater caution in the application of the cultures and more careful
+ supervision over their use.
+
+ Finally, attention is invited to the fact that, contrary to the usual
+ custom, the cultures of rat virus here used had been grown on milk,
+ which might account for the increased virulence.
+
+ The following table gives a brief summary of ten cases with the
+ results of the agglutination tests:
+
+ _Agglutination tests with serum of recovered cases, May 17, 1908._
+ ──────┬─────────────────────────┬────────┬─────────────────────────────
+ Case. │ How infected; symptoms. │Strains.│ Serum dilutions.
+ „ │„ │„ │¹⁄₂₀ │¹⁄₄₀ │¹⁄₆₀ │¹⁄₁₀₀│¹⁄₂₀₀
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 1 B. │(From this case stool 2.)│A │ + │ + │ + │ ± │ 0
+ K. │ Laid rat poison │ │ │ │ │ │
+ │ 5–2,5–5; some days │ │ │ │ │ │
+ │ later diarrhea; later │ │ │ │ │ │
+ │ vomiting; convalescence│ │ │ │ │ │
+ │ and recovery May 10. │ │ │ │ │ │
+ „ │„ │B │ + │ + │ + │ ± │ 0
+ „ │„ │C │ + │ + │ + │ ± │ 0
+ „ │„ │D │ + │ + │ + │ + │ ±
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 2 K. │Ate three pieces of │A │ + │ 0 │ 0 │ 0 │ 0
+ E. │ infected bread May 2; │ │ │ │ │ │
+ │ mild diarrhea several │ │ │ │ │ │
+ │ days. │ │ │ │ │ │
+ „ │„ │B │ + │ ± │ 0 │ 0 │ 0
+ „ │„ │C │ 0 │ 0 │ 0 │ 0 │ 0
+ „ │„ │D │ + │ ± │ 0 │ 0 │ 0
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 3 H. │Brought the virus April │A │ + │ 0 │ │ │
+ B. │ 28; perhaps touched it;│ │ │ │ │ │
+ │ next day diarrhea and │ │ │ │ │ │
+ │ vomiting; recovery │ │ │ │ │ │
+ │ after several days. │ │ │ │ │ │
+ „ │„ │B │ + │ 0 │ │ │
+ „ │„ │C │ + │ 0 │ │ │
+ „ │„ │D │ − │ − │ − │ − │ −
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 4 G. │Father of man that died; │A │ + │ + │ + │ + │ 0
+ S. │ laid virus; two days │ │ │ │ │ │
+ │ later mild diarrhea for│ │ │ │ │ │
+ │ one or two days. │ │ │ │ │ │
+ „ │„ │B │ + │ + │ + │ + │ 0
+ „ │„ │C │ + │ + │ + │ 0 │ 0
+ „ │„ │D │ + │ + │ + │ + │ ±
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 5 J. │On April 27 laid virus; 2│A │ ± │ 0 │ 0 │ 0 │ 0
+ K. │ days later diarrhea for│ │ │ │ │ │
+ │ several days. │ │ │ │ │ │
+ „ │„ │B │ ± │ 0 │ 0 │ 0 │ 0
+ „ │„ │C │ ± │ 0 │ 0 │ 0 │ 0
+ „ │„ │D │ − │ 0 │ 0 │ 0 │ 0
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 6 J. │Laid virus April 27; two │A │ 0 │ 0 │ 0 │ 0 │
+ N. │ days later had diarrhea│ │ │ │ │ │
+ │ for several days. │ │ │ │ │ │
+ „ │„ │B │ + │ + │ + │ ± │
+ „ │„ │C │ 0 │ 0 │ 0 │ 0 │
+ „ │„ │D │ + │ + │ + │ ± │
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 7 G. │“Held” the virus April │A │ + │ + │ + │ + │ ±
+ I. │ 28. Next day diarrhea │ │ │ │ │ │
+ │ for four days. │ │ │ │ │ │
+ „ │„ │B │ + │ + │ + │ + │ ±
+ „ │„ │C │ + │ + │ + │ + │ ±
+ „ │„ │D │ − │ − │ − │ − │ −
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 8 H. │Ate and associated with │A │ + │ + │ 0 │ │
+ R. │ persons who handled │ │ │ │ │ │
+ │ virus; diarrhea several│ │ │ │ │ │
+ │ days. │ │ │ │ │ │
+ „ │„ │B │ + │ − │ 0 │ │
+ „ │„ │C │ + │ ± │ 0 │ │
+ „ │„ │D │ − │ − │ − │ │
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 9 K. │Associations as case 8; │A │ + │ + │ + │ + │
+ S. │ headache several days │ │ │ │ │ │
+ │ and loss of appetite. │ │ │ │ │ │
+ „ │„ │B │ + │ + │ + │ + │
+ „ │„ │C │ + │ ± │ 0 │ │
+ „ │„ │D │ − │ − │ − │ − │ −
+ ──────┼─────────────────────────┼────────┼─────┼─────┼─────┼─────┼─────
+ 10 │Associations as case 8; │A │ 0 │ 0 │ 0 │ 0 │
+ │ diarrhea for eight │ │ │ │ │ │
+ │ days; vomiting several │ │ │ │ │ │
+ │ days. │ │ │ │ │ │
+ „ │„ │B │ + │ + │ + │ ± │
+ „ │„ │C │ 0 │ 0 │ 0 │ 0 │
+ „ │„ │D │ + │ + │ + │ ± │
+ ──────┴─────────────────────────┴────────┴─────┴─────┴─────┴─────┴─────
+ A = Strain from Loeffler.
+ B = Strain from market virus.
+ C = Strain from stool 1 (fatal case).
+ D = Strain from stool 2 (case 1 of table).
+ − = No test made.
+ 0 = Negative.
+ ± = Slight.
+ Controls = Serum of five normal persons tested as above; gave in no
+ case agglutination higher than 1 : 20.
+
+ The attending physician, noting that most of his patients had come
+ into recent contact with rat virus (_B. typhi murium_) and suspecting
+ that to be responsible, sent specimens of stools to the Hygienic
+ Institute at Munich, where they were carefully examined with reference
+ to this subject.
+
+ Organisms identical with Loeffler’s _B. typhi murium_ were isolated
+ from the two stools examined and these cultures were compared with and
+ conformed with a culture of _B. typhi murium_ obtained from Loeffler
+ and also a culture from the virus on the local market.
+
+ Two guinea pigs injected with cultures from the two stools gave, after
+ the second injection, serum which agglutinated all the above organisms
+ 1:200. A mouse typhoid serum obtained from Loeffler agglutinated all
+ the above strains distinctly in dilutions 1:640 and slightly in
+ 1:1280.
+
+ In conclusion, the author considers three possibilities: 1. The mouse
+ typhoid bacillus was the cause of the illness. 2. The bacillus was
+ accidentally present, having no part in the production of the
+ symptoms. 3. The bacillus was able to multiply only in case
+ pre-existing intestinal trouble; then, however, causing the
+ inflammation.
+
+ The case of Mayer, who became infected during the course of some
+ laboratory experiments, is particularly instructive.
+
+ During an epidemic of mouse typhoid among his laboratory mice,
+ evidently spread from some inoculated mice by ants, Mayer[BI] who had
+ personally handled the infected mice and their cages, became sick July
+ 15, just seven days after the first appearance of the ants and after
+ the observed rise in virulence of the mouse typhoid among the mice.
+ His clinical history is as follows:
+
+Footnote BI:
+
+ Mayer, Georg: Ueber die Verschleppung typhöser Krankheiten durch
+ Ameisen und die Pathogenität des Loeffler’schen Mäusetyphusbazillus
+ für den Menschen. Münch. med. Woch., vol. 52, 1905, p. 2261.
+
+ July 15: Weakness, epigastric pain, obstipation, temperature 37.7,
+ pulse 90.
+
+ July 16: Slight diarrhea, increase of pain in region of trans-colon,
+ temperature 38.3, pulse 98.
+
+ July 17: Diarrhea continued, pains increased—severe, chill in evening,
+ temperature 39.1, pulse 102.
+
+ July 18: Obstipation, symptoms worse, chill again in evening,
+ temperature 39.4, pulse 104.
+
+ July 19: Symptoms better, stools from purgative, evening temperature
+ 36.9, pulse 68.
+
+ July 20: Left bed. Temperature and pulse normal, but weakness and
+ slight epigastric pains continued till August 7.
+
+ Patient’s serum agglutinated as follows:
+
+ ──────────────────────────┬──────────────┬──────────────┬──────────────
+ │ Typhoid. │ Paratyphoid. │Mouse-typhoid.
+ ──────────────────────────┼──────────────┼──────────────┼──────────────
+ July 23 │ 1–50+│ 1–50+│ 1–250+
+ August 7 │ 1–50+│ 1–50+│ [BJ]1–100+
+ August 16 │ 1–50+│ 1–50+│ 1–50 +
+ ──────────────────────────┴──────────────┴──────────────┴──────────────
+
+Footnote BJ:
+
+ Slight
+
+ The bacillus of mouse typhoid was isolated from the patient’s stools
+ July 21 and 23. Negative results thereafter. Examinations continued a
+ month.
+
+ Same organism isolated from urine July 21. Negative thereafter.
+
+ The author concludes that the _B. typhi murium_ is able to cause in
+ man a rather severe acute illness of short duration.
+
+ Shibayama[BK] gives the following report of outbreaks of human
+ infection that have come to his knowledge in Japan, where
+ mouse-typhoid virus has been used in considerable quantities.
+
+Footnote BK:
+
+ Shibayama, G.: Ueber Pathogenität der Mäusetyphusbazillen für den
+ Menschen. Münch. med. Woch., May, 1907, p. 979.
+
+ _Outbreak 1._ In April, 1905, in a village of the Province of Saitama,
+ 30 people became ill and 2 died with severe gastro-intestinal
+ symptoms. Outbreak investigated by Dr. H. Sezuki, district medical
+ officer, formerly of the Tokio Institute for Infectious Diseases.
+
+ It was found that all the 30 people had partaken of a dish of cooked
+ vegetables served at a meeting of the town council, and that for
+ application of sauce to these vegetables (after cooking) a wooden
+ vessel had been used which two days before had been used for mixing
+ mouse-typhoid virus with meal, without subsequent cleansing or
+ sterilization.
+
+ The symptoms came on within twelve to forty-eight hours thereafter
+ (usually twenty hours), chill or chilly sensations, rise of
+ temperature to 38° or 39° C., or even to 40° C.; face flushed; pulse
+ accelerated; great weakness; thirst, nausea, colicky pains in abdomen
+ followed by severe diarrhea and vomiting. In general, the fever and
+ diarrhea lasted two or three days; but malaise, anorexia, weakness,
+ and mucous stools persisted for several days. The more severe cases
+ showed choleraic symptoms of collapse. Two persons died in spite of
+ medical treatment—a 6-year old boy and a man of 43, on the second and
+ third day, respectively.
+
+ From the intestinal contents of these two cases, from the stools of
+ several other cases, and from the remnants of the dish of vegetables
+ in the wooden bowl an organism was isolated, which was demonstrated to
+ be identical with the bacillus of mouse typhoid.
+
+ These results were confirmed at the Tokio Institute for Infectious
+ Diseases by Shibayama, by biological and immunizing tests.
+
+ _Outbreak 2._ On December 7, 1905, a peasant of a village in the
+ Province of Miyaki brought home some mouse virus mixed with meal in
+ cakes. This being mistaken for “mochi” was eaten about 2 p. m. the
+ next day by two little girls, 3 and 8 years old, respectively, and
+ their grandfather, 61 years old.
+
+ The man and the 8-year-old girl became sick at 9 p. m. the same day
+ and the other child at about 3 p. m. on December 9. The symptoms in
+ all cases were those of severe gastro-enteritis, as described under
+ outbreak 1.
+
+ The man died December 12, the 8-year-old child died on the 10th; the
+ 3-year-old child recovered after several days’ illness. These three
+ alone ate of the virus and no other persons in the house became sick.
+
+ No bacteriological examination was practicable.
+
+ _Outbreak 3._—In a village of the Province of Iskawa, on April 22,
+ 1906, a lot of rat poison was prepared by mixing agar cultures of the
+ mouse-typhoid bacillus with meal and water in a large wooden bowl.
+
+ On April 24 there was a festival in the village at which about 170
+ persons were served with 240 pounds of rice, which, after being
+ cooked, was kneaded into cakes in a wooden bowl. About 80 pounds of
+ this rice was so kneaded in the bowl previously used for preparing the
+ rat poison. Twenty to twenty-four hours later 120 people who had eaten
+ of the rice became ill with the already described symptoms of
+ gastro-enteritis, of mild type among the strong but severe among the
+ children and old people. Eighty-nine cases came under medical
+ treatment. There were no deaths, but a number of cases were confined
+ to bed for a week or more; mild cases recovered in one to three days.
+
+ No bacteriological examination was made, but the physicians and town
+ officials were unanimously of the opinion that the rat virus was the
+ cause of the outbreak.
+
+ _Outbreak 4._—A peasant of the province of Niigata brought home on May
+ 14, 1906, some rat virus (cultures of mouse-typhoid bacilli mixed with
+ meal) which he laid away. Two of his grandchildren—a boy of 5 and a
+ girl of 7—together with the 4-year-old daughter of a neighbor, found
+ and ate the rat virus. The next day all three children became ill with
+ severe gastro-enteritis, of which the 4-year-old child died on the
+ third day. The others recovered after several days of medical
+ treatment.
+
+ _Outbreak 5._—On May 16, 1906, a peasant in the province of Jamagata
+ brought home some rat virus (6 c. c. cultures of mouse-typhoid
+ bacillus mixed with meal), which was accidentally mixed with the feed
+ given to a healthy horse next morning. The same evening the horse
+ showed loss of appetite and appearance of sickness. Within two days he
+ developed a severe enteritis, of which he died on the seventh day. The
+ body was buried, but was dug up in the night by a laborer who cut off
+ the hind quarters, took them home, and distributed the meat among
+ friends and neighbors.
+
+ Within three days 34 persons who had eaten of this meat became ill
+ with symptoms of severe gastro-enteritis. A 72-year-old man died after
+ five days; the others recovered in three to eleven days.
+
+ This outbreak was investigated by Dr. H. Segawa, a medical officer of
+ the province and former member of the institute at Tokyo, who isolated
+ from the remains of the horseflesh by plate cultures and animal
+ inoculations, an organism identical with the bacillus of mouse
+ typhoid. A culture was sent to Shibayama, who carefully verified it
+ (details not given).
+
+ Shibayama concludes: In all cases the close relationship between the
+ bacillus of mouse typhoid and the illness was established; and he
+ thinks this organism must be accepted as the direct cause of the
+ outbreaks.
+
+ Referring to Loeffler’s uniformly negative human experiments, he calls
+ attention to known cases where men have taken virulent cultures of
+ typhoid, diphtheria, etc., without infection. According to many
+ bacteriological investigations, _B. typhi murium_ is identical with
+ the bacillus of enteritis. If it is proven that the latter is a cause
+ of acute gastro-enteritis then the conclusion is likewise justified
+ that the _B. typhi murium_ is frequently pathogenic for man, causing
+ an acute gastro-enteritis.
+
+ Fleischanderl[BL] a reports six cases of illness—three severe and
+ three mild—occurring in his practice in the latter part of April,
+ 1908, presenting the following symptoms: Onset with rapidly increasing
+ body pains, followed in a few hours by diarrhea, rise of temperature,
+ and general prostration; in the next two or three days aggravation of
+ the symptoms, fever (39° to 40° C.), copious diarrhea, vomiting (in
+ one case), severe body pains, vertigo, and considerable prostration.
+ Symptoms abated quickly in a few days, leaving considerable
+ prostration, convalescence requiring two weeks in one case. In the
+ less severe cases there was no fever, and the other symptoms were
+ generally milder.
+
+Footnote BL:
+
+ Fleischanderl, Fritz: Mitteilung über einige Krankheitsfälle,
+ hervorgerufen durch Mäustyphusbazillen. Munch. med. Woch., vol. 56,
+ Feb., 1909, p. 392.
+
+ The simultaneous appearance of these and other similar rumored mild
+ cases among the neighbors (about 20 in all) pointed to a common cause.
+ It was found that three of the six cases were in people who had
+ handled mouse-typhoid cultures the day before their illness, taking no
+ precautions to avoid infection.
+
+ The other three occurred in a family which, on the day before the
+ onset of the illness, had drunk raw milk obtained from a house where
+ the rat virus had been used shortly before, and only three members of
+ the family who drank the milk became ill.
+
+ In order to prove the etiology of these cases Fleischanderl, who had
+ never suffered any intestinal troubles, had had nothing to do with any
+ case of typhoid fever for a year, and was in excellent health, took a
+ culture of the mouse-typhoid bacillus as used in the neighborhood,
+ rubbed a glass rod over the surface, washed it off in a glass of
+ water, and drank this before breakfast on the morning of May 3.
+
+ In twenty-two hours he experienced mild, increasing body pains,
+ followed within a few hours by diarrhea, and a few hours later by
+ slight chill, rise of temperature to 38.2, pulse 106, severe pains in
+ body, and feeling of great weakness.
+
+ May 4, 9 p. m.: Temperature 39.2° C., pulse 120. Height of symptoms.
+
+ May 5: Temperature 38.2° to 38.5° C., pulse 106 to 120. Other symptoms
+ continued.
+
+ May 6: Temperature and pulse normal. All symptoms disappeared except
+ weakness, which lasted two days.
+
+ Bacteriological investigations conducted by Herbert Berger in the K.
+ K. Serotherapeutischen Institut and by Doctor Reichel, assistant in
+ the Hygienic Institute of the University of Vienna, follow:
+
+ From the stools of one of the patients infected from milk an organism
+ was isolated which, injected into mice (1 c. c. emulsion of
+ forty-eight-hour culture), killed them in two to five hours. Mice
+ infected by eating these dead mice died in thirty to forty-eight
+ hours.
+
+ Control mice inoculated similarly with a culture of the market
+ mouse-typhoid virus died in twenty to thirty hours, while the mice
+ infected through eating these died after three to four days.
+
+ The following strains were used for cultural agglutination tests:
+
+ A. From stools of patient infected from milk.
+
+ B1. Market virus used in injecting mice.
+
+ B2. Market virus taken by author.
+
+ C25. From stools of author twenty-five hours after infection.
+
+ C55. From stools of author fifty-five hours after infection.
+
+ LL. Stock culture of Loeffler’s mouse-typhoid bacillus.
+
+ LP. Stock culture of para-typhoid bacillus.
+
+ All organisms (A-C55) were demonstrated as motile bacilli, not
+ liquefying gelatine, not forming lactic acid, and forming gas from
+ dextrose.
+
+ The serum of a rabbit after two injections of LL agglutinated LL and
+ LP in dilution of 1:1280, did not agglutinate A, B1, B2, C25, and C55.
+
+ Serum of rabbit after one injection of B2 agglutinated in 1:320
+ dilution A, B1, B2, C25, C55, and LL; did not agglutinate LP.
+
+ Serum of rabbit after one injection of C25 gave exactly similar
+ results.
+
+ Doctor Reichel considers it proven that the organisms A to C55 are
+ undoubtedly identical with Loeffler’s bacillus of mouse typhoid, and
+ distinct from para-typhoid bacilli. The author considers it proven
+ that this bacillus was the sole cause of the cases of enteritis
+ observed.
+
+ Recently Mallory and Ordway[BM], in a paper read before the American
+ Association of Pathologists and Bacteriologists held in Boston,
+ reported that lesions analogous to the early stages of typhoid lesions
+ may be produced in rats by the use of Danysz virus.
+
+Footnote BM:
+
+ Mallory, F. B., & Ordway, T.: Lesions produced in the rat by a
+ typhoid-like organism (Danysz virus). Journ. Am. med. assn., vol.
+ 52, May 1, 1909, p. 1455.
+
+ In view of these facts the statements of some of the advertising
+ matter of certain rat viruses call for revision.
+
+
+ REFERENCES TO THE LITERATURE.
+
+ Loeffler,[BN] 1889, gives an account of two spontaneous outbreaks
+ among the mice kept at the Hygienic Institute at Griefswald. It was
+ from these animals that he obtained and described the original _B.
+ typhi murium_. He determined that the infection was by ingestion and
+ that the organism was especially virulent for field mice. He described
+ the organism in detail and also the lesions.
+
+Footnote BN:
+
+ Loeffler, F.: Ueber Epidemieen unter den im hygienischen Institute
+ zu Griefswald gehalten Mäusen und über die Bekämpfung der
+ Feldmäusplage. Centblt. f. Bakt., Orig., vol. 11, 1898, p. 129.
+
+ Laser,[BO] 1892, reports that on the morning of February 6, 1892, 70
+ of the 76 field mice (_Mus agrarius_) used as experiment animals in
+ the Hygienic Institut at Königsberg were found dead. A small bacillus
+ twice as long as broad, displaying a very lively specific motility,
+ was isolated from the spleen. It was tested upon animals and all the
+ results compared with Eisenberg’s tables and found to be closely
+ allied to the bacillus of ferret plague (Ebert-Schummelbusch), to the
+ bacillus of American swine plague (Billings), and to that of French
+ swine plague (Chantamesse and Cornil).
+
+Footnote BO:
+
+ Laser, Hugo: Ein neuer für Versuchsthiere pathogener Bacillus aus
+ der Gruppe der Frettschen-Schweinseuche. Centblt. f. Bakt., Orig.,
+ vol. 11, 1892, p. 184.
+
+ Mereshkowsky,[BP] 1893, isolated an organism at the Royal
+ Bacteriological Institute at St. Petersburg from a stock of Zisel
+ (_Spermophilus musicus_) among which a spontaneous epizootic had
+ occurred. The author found this culture to be virulent for domestic
+ and field mice.
+
+Footnote BP:
+
+ Mereshkowsky, S. S.: Ein aus Zieselmäusen ausgeschiedener und zur
+ Vertilgung von Feld-resp. Mäusen, geeigneter Bacillus. Centblt. f.
+ Bakt., Orig., vol. 17, 1895, p. 742.
+
+ Zupnik,[BQ] 1897, states that Joseph, of the Agricultural Institute of
+ Breslau, in 1882 originated the use of favus fungus for the
+ destruction of mice. Zupnik tested _B. typhi murium_ and Danysz virus
+ upon mice. No experiments with rats.
+
+Footnote BQ:
+
+ Zupnik, Leo: Ueber die pratische Verwendbarkeit der Mäuse bacillen
+ inbesondere des Loeffler’schen _Bacillus typhi murium_. Centblt. f.
+ Bakt., Orig., vol. 21, 1897, p. 446.
+
+ Issatschenko,[BR] in 1898, described briefly a bacillus obtained by
+ him from gray rats. Recent investigation showed this bacillus to be
+ very virulent for rats and mice, but harmless for the different
+ species of domestic animals. Four hundred and forty-three experiments
+ were made upon rats with pure cultures of the bacillus combined with
+ dough and fed to the rats. He gives a table showing that the mortality
+ occurred in 431 rats at an average of ten and one-half days. The
+ greatest mortality occurred during the first fifteen days (84.2 per
+ cent), with the greatest number on the seventh day (20.1 per cent).
+
+Footnote BR:
+
+ Issatschenko, B.: Untersuchungen mit dem für Ratten pathogenen
+ Bacillus. Centblt. f. Bakt., Orig., vol. 31, 1902, p. 26.
+
+ Danysz,[BS] 1900, isolated a cocco-bacillus during an outbreak of
+ spontaneous disease amongst field mice which presented the general
+ characteristics of the colon bacillus and to this extent resembled
+ Loeffler’s bacillus (_B. typhi murium_), and which from the beginning
+ exhibited some pathogenicity for gray rats (_M. decumanus_). Of ten
+ such rats fed upon a culture of this organism, two or three died,
+ while others that had fallen sick recovered and the same remained
+ well. This small mortality offered some hope that it would be possible
+ to increase the virulence of the bacillus by ordinary methods; that
+ is, passing it from rat to rat. It was found, however, that the
+ opposite was true; the virulence was always weakened by this process
+ regardless of the method of administration. Thus in every series the
+ first culture killed the animals in seven to twelve days; occasionally
+ after one or two passages five to seven days; but subsequent passages
+ decreased the virulence so that none died.
+
+Footnote BS:
+
+ Danysz, J.: Un microbe pathogène pour les rats (_Mus decumanus_ et
+ _Mus rattus_) et son application à la destruction de ces animaux.
+ Ann. Inst. Pasteur, 1900, vol. 14, p. 193.
+
+ The general result is that it is difficult to maintain the virulence
+ of the cocco-bacillus of the rat or to increase it when it is found to
+ be small. It can only be effected by constantly making a large number
+ of experiments and frequently testing the virulence of the culture.
+ Danysz succeeded in keeping up a supply of cultures of sufficient
+ strength for eight years. In 60 per cent of the operations where this
+ culture has been used it has been successful in causing the absolute
+ disappearance of the rats. In 15 per cent the result was entirely
+ negative, and in the remaining 25 per cent there was a large
+ diminution.
+
+ Oettinger,[BT] in 1903, increased the virulence of the Danysz bacillus
+ by growth in an egg rendered alkaline after the method previously
+ introduced by Wiener.
+
+Footnote BT:
+
+ Oettinger, M.: Ueber die Wienersche Methode zur Virulenzsteigerung
+ der Danysz Bazillen. Munch. med. Woch., vol. 1, 1903, p. 324.
+
+ Pfreimbtner,[BU] 1904, sees the reason for a partial failure in the
+ application of Loeffler’s bacillus to the destruction of field mice.
+ In the use of a solid medium (agar-agar), upon which the bacterial
+ cultures only grow upon the surface, too few bacteria are transferred
+ to the pieces of bread, and consequently too few virulent bacteria are
+ consumed by the mice. An active infection depends not upon the
+ existence of virulent bacteria, but rather upon the entrance of a
+ definite number of virulent bacilli.
+
+Footnote BU:
+
+ Pfreimbtner, J.: Erfahrung über des Loeffler’schen
+ Infektionsverfahren zur Bekämpfung der Mäuseplage in einer neuen Art
+ der Anwendung. Fühlung’s landw. Zeit., 1904, p. 619. Rev. by
+ Schander in Centblt. f. Bakt., 2. Abt., vol. 15, 1905, p. 502.
+
+ The author used skimmed milk as a nutrient medium and describes a
+ series of 9 experiments and gives an estimate of the cost of the
+ process with the use of milk instead of agar. The advantage of the use
+ of milk is in the greater certainty of the results and cheapness as
+ compared with other methods. The bread cubes impregnated with skimmed
+ milk were well taken by the mice and desiccation of the cultures,
+ which not infrequently occurs in the use of more solid media, is
+ excluded. Notwithstanding the excessive thinning, the liquid still
+ contains many virulent bacilli. The washing out of bacilli after rain
+ is slightly less possible as in the use of the more solid media. The
+ action of light, where the bread cubes contain many bacilli, is
+ insignificant, and hence the carrying out of the process in the
+ daytime is made possible. Milk is easily obtained and the thinning and
+ application less bothersome. Finally the author expresses himself
+ against the view that the _B. typhi murium_ causes serious diseases in
+ man.
+
+ Teichert,[BV] 1905, speaks of Loeffler’s mice typhus bacillus and
+ Pfreimbtner’s method of growing it upon sterilized skimmed milk. A
+ number of experiments carried out at the bacteriological laboratory of
+ the Vreschen experiment station shows the utility of Loeffler’s
+ bacillus for the destruction of house and field mice. The long-tailed
+ field mouse was, on the other hand, not harmed by it.
+
+Footnote BV:
+
+ Teichert: Die mechanischen, chemischen und bacteriellen Kampfmittel
+ gegen Ratten und Mäuse. 2. Teil: Die Bekämpfung der Mäuse. Fühlung’s
+ landw. Zeit., 1905, No. 16. Rev. by Ehrenberg in Centblt. f. Bakt.,
+ 2. Abt., vol. 15, 1905, p. 503.
+
+ Bahr,[BW] 1905, gives a complete and satisfactory summary of the
+ literature upon the subject of the destruction of rats and mice with
+ bacteria, including original work of his own.
+
+Footnote BW:
+
+ Bahr, L.: Ueber die zur Vertilgung von Ratten und Mäusen benutzten
+ Bakterien. Centblt. f. Bakt., Orig., vol. 39, 1905, p. 263.
+
+ Zielander,[BX] 1908, obtained fairly good results with Danysz virus in
+ the laboratory, also with ratin. No fixed tests were recorded.
+
+Footnote BX:
+
+ Zielander: Der Rattenbacillus als Rattenvertilgungsmittel. Arb. a.
+ d. k. Gesndhtsmte., Berl., vol. 28, 1908, p. 145.
+
+
+ RÉSUMÉ.
+
+ Rats are notoriously resistant to bacterial infection. Even plague
+ usually fails markedly to diminish their prevalence. An epizootic of
+ bacterial nature, therefore, can not be classed with the natural
+ enemies of the rat. We are not surprised, then, to learn that the
+ bacterial viruses have signally failed to accomplish their mission.
+
+ These bacterial viruses belong to the colon-typhoid group of
+ organisms. They are either identical with or closely related to the
+ original bacillus of mouse typhoid discovered by Loeffler, or the
+ para-typhoid bacillus type B, which is frequently the cause of meat
+ poisoning, or the _Bacillus enteritidis_ of Gærtner, which has been
+ associated with gastro-intestinal disorders.
+
+ The claim that these rat viruses are harmless to man needs revision,
+ in view of the instances of sickness and death reported by various
+ observers. The pathogenicity for man depends upon the virulence of the
+ culture, the amount ingested, the nature of the medium in which it
+ grows, and many other factors.
+
+ Danysz virus is pathogenic for rats under laboratory conditions, but
+ has feeble powers of propagating itself from rat to rat. It rapidly
+ loses its virulence, especially when exposed to light and air. The
+ result depends largely upon the amount ingested. The other viruses
+ have proven even less satisfactory.
+
+ Under natural conditions these rat viruses may be likened to a
+ chemical poison, with the great disadvantage that they rapidly lose
+ their virulence and are comparatively expensive. They also have the
+ further disadvantage that chemical poisons do not possess of rendering
+ animals immune by the ingestion of amounts that are insufficient to
+ kill or by the ingestion of cultures that have lost their virulence.
+
+
+
+
+ PLAGUE ERADICATION IN CITIES BY SECTIONAL EXTERMINATION OF RATS AND
+ GENERAL RAT PROOFING.
+
+ By VICTOR G. HEISER,
+
+ _Passed assistant surgeon, U. S. Public Health and Marine-Hospital
+ Service, chief quarantine officer and director of health for the
+ Philippine Islands_.
+
+
+ The health officials of the city of Manila, P. I., for the five-year
+ period from 1900 to 1905 made most valiant efforts to destroy the rats
+ of the city; approximately $15,000 were paid in rat bounties and
+ $325,000 in salaries and wages and other expenses for rat catching,
+ but at the end of that time the rats were apparently as plentiful as
+ before and the plague was still present. The experience in Tokio and
+ Osaka had been practically the same. Professor Kitasato expressed the
+ opinion that a given city could only have up to a certain number
+ anyhow, because further increase was limited by the amount of
+ available food, and when the limit had been reached the rats commenced
+ to eat one another, which prevented more than a certain number ever
+ being present, and that the increase by breeding was about as rapid as
+ any method of destruction which had yet been tried.
+
+ The following plan was then tried, and the plague among human beings
+ soon disappeared, there being no cases since April, 1906; and it has
+ been eradicated among rats each time that it has made its appearance.
+
+ A list of the places at which plague-infected rats were found was
+ made. Each was regarded as a center of infection. Radiating lines,
+ usually five in number, were prolonged from this center, evenly spaced
+ like the spokes of a wheel. Rats were caught along these lines and
+ examined. Plague rats were seldom found more than a few blocks away.
+ The furthermost points at which infected rats were found were then
+ connected with a line, as is roughly shown in the diagram on page 206
+ (Fig. 59.)
+
+ The space inclosed by the dotted line was regarded as the section of
+ infection. The entire rat-catching force, which had heretofore been
+ employed throughout the city, was then concentrated along the border
+ of the infected section; that is, along the dotted line. They then
+ commenced to move toward the center, catching the rats as they closed
+ in. Behind them thorough rat proofing was carried out. One section
+ after another was treated in this way until they had all been wiped
+ out. Once weekly thereafter rats were caught in the previously
+ infected sections and at other places which were insanitary and which
+ had been infected in years gone by. This was continued for one year.
+
+ The city was then divided as is shown in the diagram facing this page,
+ and rats are caught once weekly at each point at which the lines
+ intersect and sent to the laboratory for examination.
+
+[Illustration:
+
+ FIG. 59.—Isolated plague-infested center, Manila, P. I.
+]
+
+ In addition, sanitary inspectors are instructed to bring in dead rats
+ which have evidently died of disease, and more detailed rat catchings
+ are made along the water front.
+
+ It is understood of course that rat proofing of the entire city should
+ be thoroughly carried out and constantly maintained.
+
+
+ CONCLUSIONS.
+
+ 1. Since the above system was adopted plague has disappeared in the
+ city of Manila; among human beings in 1906; among rats in 1907, and it
+ has not reappeared since.
+
+ 2. That the cost is only a small fraction of that of general rat
+ extermination.
+
+ 3. That the plan is thoroughly practical for any kind of a city.
+
+[Illustration:
+
+ FIG. 60.—General Scheme for testing plague rat infection, City of Manila.
+ Sanitary Map Bureau of Health. _Escala 1:38,500_
+]
+
+
+
+
+ THE RAT IN RELATION TO SHIPPING.
+
+ By WILLIAM C. HOBDY,
+
+ _Passed Assistant Surgeon, Public Health and Marine-Hospital Service_.
+
+
+ Since men first went down to the sea in ships the rat’s voyage-making
+ tendencies have been known, and their fecundity is as well established
+ as their fondness for travel. The record does not state that there
+ were more than a pair on the ark at the beginning of her voyage, but
+ the chances are better than even that her skipper began that voyage
+ with more rats than his manifest showed; but whether he did or not, we
+ can be sure he had more at the end of the voyage than at the
+ beginning. Whether or not succeeding generations inherited from their
+ forbears on the ark this well-known wanderlust is undetermined, but it
+ is a fact that the intimacy and companionship established and begun
+ then have been persistently maintained by the rat ever since. His
+ travels have been coextensive with man’s, until to-day there is not a
+ port on earth where the rat is not present. Any exception to this
+ statement simply proves the rule. The rat is cute; he knows when he is
+ well off and his absence from a port does not prove that he has not
+ been there, but that he has been too intelligent to follow man ashore.
+ In establishing this shipboard intimacy there has been no “by your
+ leave” courtesy on his part either; he goes without consent—against
+ orders, even—and man’s ingenuity has as yet discovered no effective
+ means of keeping him off. This is not surprising when the rat’s
+ ability as a rope walker is considered. I have seen a rat gallop with
+ all appearance of enjoyment along an inclined electric cable from a
+ church steeple on one side of a street into the second story of a
+ hotel on the other. Others have been seen traveling along the
+ telephone wires from house to house, and on shipboard they frequently
+ have runways on small pipes along which they scurry in perfect
+ security. When a ship is fended off 6 feet from the dock and her gang
+ plank is lifted or guarded she is still freely accessible, because all
+ her mooring lines are only so many highways along which rats can and
+ do pass with ease and in perfect safety.
+
+ This fondness for ships and sea travel is shared by the various
+ species of the rat family, but the _Mus norvegicus_ has earned the
+ reputation of being the greatest traveler of them all. He almost
+ invariably predominated among those killed by fumigation on shipboard.
+ That he finds life on shipboard easy and the conditions satisfactory
+ is proved by the numbers that are destroyed from time to time by
+ fumigation. While in charge of the outgoing quarantine work in San
+ Francisco the chief engineer of a small lumber carrier called to book
+ his vessel for fumigation. The vessel was small, only 260 tons, and
+ carried nothing but lumber and her own ship’s stores, but the chief
+ declared she was overrun with rats, and to prove it showed where they
+ had eaten the patches from his shoes. He declared they robbed him of
+ his sandwich when he came off watch, and requested me to give her a
+ thorough fumigation. This was done. The next morning the agent of the
+ vessel phoned to ask how I measured rats, stating that on this vessel
+ they had collected “a barrelful and seven.” Three hundred and ten on a
+ little vessel of only 260 tons burthen.
+
+ On another vessel after one fumigation 100 were collected immediately
+ after fumigation, but a few days later, when the vessel was undergoing
+ extensive repairs, 425 others were found—a total of 525 on one small
+ vessel. These numbers are small, however, when compared with the
+ results obtained on others, i. e., on grain-carrying vessels. For
+ instance, a vessel was fumigated some years since in Bombay where
+ 1,300 were destroyed at one time, and the _Minnehaha_, a new vessel
+ only nine months in commission, on fumigation in London, England, in
+ May, 1901, yielded a bag of 1,700 rats.
+
+
+ ADAPTABILITY OF THE RAT TO HIS SURROUNDINGS.
+
+ In addition to his qualities as a sailor and tight-rope walker, the
+ rat has the power of adapting himself to most unusual conditions and
+ surroundings. At the beginning of the outgoing work in San Francisco
+ it was urged that rats either could not or would not live on any part
+ of tank ships engaged exclusively in carrying oil, owing to the fumes
+ and vapors that permeated the entire vessel. This statement was
+ unquestionably correct for those compartments in which the oil itself
+ was stored or carried. It was not true, however, for the
+ superstructure of these vessels, for on one of the oil carriers 60
+ rats were found after one fumigation, and of the thirty or more
+ vessels of this class that were regularly fumigated in San Francisco,
+ although the odors of oil or gasoline were quite strong in the living
+ compartments, not one was found that did not harbor rats. Still more
+ remarkable, as illustrating the rat’s adaptability, was the fact that
+ from the large refrigerating plants which some vessels carried and in
+ which fumigation had not been practiced for a long time rats were
+ obtained that had grown a fur an inch and a half long to protect
+ themselves from the cold.
+
+
+ DAMAGE TO CARGO.
+
+ That rats on shipboard in any such numbers as mentioned above must do
+ much damage to cargo can not be doubted.
+
+ Inquiry as to the extent of this damage showed that there were no data
+ on the subject. That such damage was common and considerable, however,
+ was revealed by the fact, elicited by these inquiries, that nearly
+ every steamship company on both the Atlantic and Pacific took
+ precautions both to keep rats from getting on board and to destroy
+ them after they did. One example will show what damage may occur. The
+ British steamer _Gadsby_, on a voyage from India to Antwerp, covering
+ a period of twenty-nine days, had 44,000 out of 46,000 bags of wheat
+ cut by rats, with an estimated damage of $2,200.
+
+ The constant and almost universal presence, then, of rats on shipboard
+ can not be doubted, and if it could the results of fumigation,
+ wherever practiced with SO_{2}, would serve to settle the question,
+ for they are found under all conditions, even on the most unlikely
+ vessels.
+
+ How do these rodents gain access to a vessel? It has been the custom
+ to assume that they came on board from the docks over the side when
+ this was possible, and when it was not, as when the vessel was fended
+ off or stood too high out of the water, that they made use of the
+ gangways, mooring lines, hawsers, etc., as avenues of communication.
+ It is still the practice, therefore, in enforcing antirat precautions,
+ to compel the ship to fend off 6 feet from the dock, to wear fat
+ funnels on all lines, and to raise the gangway from the dock at night.
+ Just a word as to these precautions. The most practical fender is a
+ floating one made of heavy timbers either bolted together into a solid
+ frame, with the necessary cross braces bolted in, or made up of logs
+ or spars chained together. They should be long enough to distribute
+ the pressure of the vessel as the tide moves over a number of piers or
+ piles so that the weight does not bear, through the medium of these
+ fenders, on just one or two of the wharf foundations. Such a fender
+ will stay in position, will do no damage to the vessel, and no matter
+ how great the amplitude of the tide may be, will always remain below
+ the ship’s gunwale and can not therefore be utilized by rats as a
+ means to get on board. Large vessels require at least two. Small ones
+ need but one, and it was found in San Francisco, in the case of those
+ vessels changing their mooring several times daily, that this one
+ could be carried from wharf to wharf by the vessel without trouble or
+ delay simply by lashing it edgewise outside on top of the guard.
+
+ Funnels should be of heavy galvanized iron, circular in shape, and not
+ less than 36 inches in diameter. The spout of the funnel should be 3
+ inches in diameter and should be at least 18 inches long. The flange
+ of the funnel should be soldered to this 18-inch pipe at its middle so
+ that the spout projects 9 inches out of the funnel and 9 inches into
+ it. When the two halves of the funnel are brought together this spout
+ or tube is occupied by the line or hawser to be protected, and by
+ lashing this tube to the hawser the funnel is held in position and
+ prevented from lying down. Such a funnel should be put on every line
+ from the vessel to the dock, and when the tube does not fit the line
+ the latter should be parceled before the tube is lashed to it.
+
+ These, together with raising the gang plank from the dock at night,
+ make up the precautions ordinarily taken to prevent the rats from
+ getting on ships. As stated above, they are based on the assumption
+ that these are the common avenues of entrance. That these precautions
+ do much good can not be doubted, but in the writer’s opinion they do
+ not entirely cover the case, for there remains one other road of
+ ingress, one of the important, if not the most important, which these
+ precautions do not and can not block and through which rats constantly
+ get on board, and that is through the medium of the cargo itself.
+ There is at present nothing to prevent access in this manner to a
+ vessel and the route is so easy that there can be no doubt that whole
+ families of rats are carried on board in this way. In fact some
+ articles of cargo offer inviting harbors and homes to rats,
+ particularly when these articles have been stored for a time in
+ rat-infested warehouses. Among such articles of cargo may be mentioned
+ crockery or china packed in hay or straw or excelsior and loosely
+ crated; various articles of furniture packed in excelsior, wrapped in
+ gunny, and loosely crated; wheat, corn, oats, peanuts, or barley when
+ shipped in bags; and matting in hollow rolls when sewed up in gunny.
+ Any of these articles could easily become the home of even an entire
+ rat family after having been stored for a time prior to shipment in a
+ rat-infested warehouse. As a matter of fact, the last plague rat
+ discovered in San Francisco was found in a bag of peanuts on the third
+ floor of a warehouse.
+
+ That rats are thus carried on board is absolutely certain in my
+ opinion. In the recent antiplague campaign at San Francisco there were
+ ample opportunities for observations along this line, and in no other
+ way can the presence of rats in troublesome numbers on board certain
+ vessels be explained. These vessels were new, were freed from rats by
+ careful and repeated fumigation, and between these acts touched at no
+ wharves save in Honolulu and San Francisco, where constant antirat
+ precautions were observed. And yet on their second trip (about five
+ months after the fumigation had been discontinued) they were badly
+ rat-infested. Of course, by no means had all these rats been carried
+ on board in cargo, but the original patriarchs of the colony had,
+ after which, as is probably the case in all rat-infested ships, their
+ natural prolific characteristics did the rest.
+
+ In the same way, too, rats are carried from ship to shore and the
+ truth of Kitasatso’s aphorism that “wherever ships go, plague will
+ go,” at once becomes apparent, and any regulations to prevent the
+ introduction of such vermin and the plague which they may carry to be
+ effective must include the inspection of cargo to insure its freedom
+ from rats, this inspection to be made just before it goes on board.
+
+ The relation these rodents bear to plague and the part they play in
+ its transmission have been thoroughly discussed and set forth in
+ another article in this work. The work of Ashburton Thompson in
+ Australia and of the British Medical Commission in India was a
+ scientific demonstration that plague was primarily a rat disease
+ transmitted by fleas, while McCoy in the United States has gone
+ further probably than anyone else in demonstrating the manner in which
+ the flea does this work. The importance of this relation is emphasized
+ and the difficulty of ridding a port of pest infection is explained by
+ a fact, first observed so far as I know by Klein, of London, that rats
+ suffer from a chronic form of pest, not fatal, at least for a long
+ time, and during the course of which the rat may exhibit practically
+ his normal activity. This fact then, that plague is primarily a rat
+ disease and that it may occur in the rat in a chronic form, shows how
+ great the danger may be from their presence on shipboard, explains why
+ it is that where ships go plague will go, and emphasizes the
+ importance of destroying them on shipboard apart from the damage and
+ loss which their presence entails.
+
+ So important is this and so preeminent is the rôle played by the rat
+ in plague transmission and propagation that I believe regulations
+ should demand that all ships be disinfected at least three times, and
+ better still, four times, a year, for the destruction of rats. If this
+ precaution were taken, and if to it were added an inspection of cargo
+ at the port of embarkation to insure its freedom from rats, I believe
+ the disinfection of cargo could be entirely dispensed with. It is
+ infectious only in so far as it harbors rats, and if these are not
+ present disinfection, in my opinion, does as little good in preventing
+ plague as dipping ballast did in preventing yellow fever.
+
+
+ FUMIGATION.
+
+ Once the rat has gained access to a vessel, what is the best method of
+ getting rid of him?
+
+ There are several methods, all of which are effective if properly
+ used, and all of which depend on sulphur dioxide as the destructive
+ agent. The following are mentioned: Pot and pan, sulphur furnace,
+ Clayton system, and Marot system. A choice of one of these methods
+ will be determined by the cost, the rapidity of fumigation desired,
+ and the condition of the vessel, whether empty or loaded. No matter
+ which method is selected, to be effective the sulphur dioxide must be
+ simultaneously delivered to or generated in every compartment on the
+ vessel.
+
+ For an empty vessel nothing is so satisfactory as the pot and pan
+ method of generating the gas. It has the following advantages; is more
+ rapid than any other, is cheaper, is more effective, and is equally
+ applicable to the largest and the smallest vessel afloat. With a
+ sufficient number of pots and pans 3,500 pounds of sulphur can be
+ burned just as quickly as 100. Ten pounds of sulphur in each of 350
+ pots will be consumed just as quickly as will 10 pounds in any one of
+ that number, namely, in less than five hours, a fact which was
+ demonstrated over and over in the outgoing work in San Francisco.
+
+ At the beginning of this work it was thought a 2½ per cent gas with
+ three hours’ exposure would be sufficient. Practice proved, however,
+ that this was not effective and the strength of gas was increased to 3
+ per cent and the exposure to five hours which a test, extending over
+ twelve months and embracing over 3,000 vessels, proved to be ample.
+
+ The best pot in which to burn sulphur is 6 inches deep, has a flare of
+ 6 inches—that is, the diameter at the top exceeds the diameter at the
+ bottom by that much, is from 16 inches to 24 inches in diameter at the
+ top and has four hemispherical legs about the size of half a billiard
+ ball. These pots when in use are set in a galvanized iron tub. These
+ tubs contain a little water, and are of a diameter 6 inches greater
+ than the top of the pot. The hemispherical legs of these pots will not
+ punch holes into the tub. The pots are filled with sulphur, which is
+ hollowed out into a little crater at the top, into which crater from 4
+ to 6 ounces of alcohol are poured and when all are ready a lighted
+ match is dropped into each little crater and the compartment is
+ closed.
+
+ In actual practice it was found that an exposure of five hours to a 3
+ per cent gas would not destroy all the rats in absolutely every case.
+ Some ships afford better hiding places than others, and on these an
+ occasional rat would escape. It was the custom, however, to fumigate
+ all vessels every thirty days and after the third fumigation, on
+ vessels that did not carry general cargo, no more rats were obtained,
+ though the fumigations were continued for a number of months.
+
+ On those vessels that carried miscellaneous general cargoes a few rats
+ were found after almost every fumigation. These vessels touched no
+ wharf from the time they left San Francisco until their return, except
+ for a short time in Honolulu, where adequate precautions were
+ observed, and it is difficult to understand how these rats got on
+ board if they were not carried on in cargo.
+
+ For vessels with cargo in their holds the pot and pan method is
+ dangerous owing to the possibility of fire. For these vessels one of
+ the other methods of generating the sulphur gas must be used. This
+ involves the use of an expensive plant consisting of a furnace,
+ cooling chamber, blower, or fan, and a system of mains and delivery
+ pipes by means of which the gas is delivered to the various holds and
+ compartments of the vessel. To be at all effective the gas must be 4½
+ per cent strength, with at least twenty-four hours exposure. The one
+ recommendation of such a system is its freedom from danger by fire. It
+ is too slow; the pipes, even where 6 inches in diameter, are liable to
+ clogging with sublimed sulphur, an inevitable result if the fans are
+ driven too rapidly, and it is not possible to do more than one or at
+ most two ships at a time. The inadequacy of such a method when
+ compared to the work done in San Francisco where we averaged over nine
+ vessels every day for almost fourteen months is at once apparent. Many
+ ships now carry their own disinfecting plants, by means of which not
+ only is sulphur dioxide generated and pumped into a compartment, but
+ at the same time also the air of this space is sucked out. This
+ principle is excellent, but in its application the machines used are
+ wholly inadequate, having a very limited sulphur capacity per hour and
+ equipped with delivery pipes in many instances only 2 or 3 inches in
+ diameter. It would be a matter of days to disinfect some of these
+ ships with the machines they carry. In San Francisco we again and
+ again used pots and pans to fumigate these vessels, including the very
+ compartments in which their own machines sat doing nothing.
+
+ The Marot system of generating the gas from compressed liquid sulphur
+ dioxide has in this country been found too expensive to apply to
+ vessels. Probably no system will effectually destroy all the rats on a
+ cargo-laden vessel.
+
+
+ SUMMARY.
+
+ To summarize then:
+
+ 1. The rat is found on all vessels, sometimes in enormous numbers, and
+ is able to adapt himself to all sorts of conditions. He either gets on
+ board himself or is carried on in cargo. Owing to his seagoing
+ tendency, his distribution is world-wide.
+
+ 2. On shipboard, to live he must do damage to either cargo or stores,
+ or both.
+
+ 3. Plague is primarily a rat disease; it may exist in the rat in a
+ chronic form. Hence where ships go plague will go sooner or later.
+
+ 4. To prevent the ingress of rats and the consequent spread of plague,
+ ships should observe antirat precautions, and cargo inspection should
+ be included in these.
+
+ 5. At stated intervals, three or, better still, four times a year, all
+ vessels should be fumigated for the destruction of rats.
+
+ 6. On empty vessels this can best be done by generating sulphur by the
+ pot and pan method.
+
+ 7. On laden vessels some special apparatus must be used to generate
+ the gas. A longer exposure is required, at least twenty-four hours,
+ and the gas should be 4½ per cent strength instead of 3 percent. It is
+ extremely difficult by any method to kill all the rats on a
+ cargo-laden vessel.
+
+
+
+
+ THE RAT AS AN ECONOMIC FACTOR.
+
+ By DAVID E. LANTZ,
+
+ _Assistant Biologist, United States Department of Agriculture_.
+
+
+ INTRODUCTION.
+
+ The world has rightly learned to dread rats as disseminators of
+ disease, and recent efforts to rid cities of the pests have resulted
+ chiefly from sanitary considerations. Yet the material losses due to
+ depredations of rats are now, and always have been, a sufficient
+ argument for their destruction. The requirements of sanitation and
+ public health are slowly bringing to pass what economic interests
+ failed to accomplish, namely, a general recognition of the fact that
+ the rat is a standing menace to prosperity. To point out some of the
+ many ways in which rats inflict injury and the extent to which they
+ drain the resources of the people is the object of the present
+ chapter.
+
+
+ UTILITY OF THE RAT.
+
+ Do rats serve any useful purpose? With very slight reservation, the
+ question may be answered in the negative. There have been times and
+ places in which the rat’s work as a scavenger accomplished good, but
+ modern methods of garbage disposal are superseding the feeding it to
+ rats.
+
+ It was Robert Southey, the poet, who, nearly a century ago, humorously
+ suggested as the first three steps to eradicate rats—first,
+ introducing them as a table delicacy; second, utilizing the skins; and
+ third, inoculating them with a contagious disease.[BY] The last of
+ these plans is now receiving considerable attention from
+ bacteriologists, but the others, for obvious reasons, have been
+ neglected.
+
+Footnote BY:
+
+ Omniana, vol. 1, p. 25, 1812.
+
+ It is true that under exceptional circumstances the rat has been a
+ source of human food. The principal instances on record were during
+ the siege of Paris in 1870, and during the siege of the French
+ garrison at Malta, 1798–1800, when food was so scarce that rat
+ carcasses brought high prices. Another was on board the ship _Advance_
+ during an arctic winter, when Doctor Kane attributed his entire
+ immunity from scurvy to his diet of fresh rats, of which none of the
+ other members of the party would partake.[BZ]
+
+Footnote BZ:
+
+ Second Grinnell Expedition, vol. 1, p. 393, 1856.
+
+ The statement is often made in newspapers, and even in encyclopedias,
+ that in Europe, and especially in France, rat skins are extensively
+ used in the manufacture of gloves. The late Frank T. Buckland, about a
+ half century ago, made diligent inquiry in London, and through friends
+ in Paris and other places on the Continent, but found no confirmation
+ of such statement. He concluded that either rat skins were not used
+ for making gloves or the manufacturers were unwilling to acknowledge
+ such a use.[CA] Personally, the writer has been unable to learn of any
+ demand or market for rat skins at the present time. They are not
+ strong, and the fur is of inferior quality. The occasional finding of
+ one or more rat skins in the fur lining of coats is probably to be
+ explained by the fact that they are sometimes included in lots of
+ small muskrat skins (“kitts”) and overlooked by the buyer.
+
+Footnote CA:
+
+ Curiosities of Natural History, first series, p. 83, 1857 (Reprint
+ 1900).
+
+
+ DESTRUCTIVENESS OF THE RAT.
+
+ Rats inflict injury in a surprising number of ways, and before an
+ attempt is made to consider the magnitude of the losses due to these
+ animals a statement of the nature of their depredations should be
+ made.
+
+
+ DAMAGE TO GRAINS.
+
+ Cultivated grains are the favorite food of rats. The animals begin
+ their depredations by digging up the newly-sown seed. They eat the
+ tender sprouts when they first appear, and continue destroying the
+ plants until the crop matures. They then attack the grain itself, and
+ after harvest take toll from shock, stack, mow, crib, granary,
+ elevator, mill, and warehouse. When rats are abundant their
+ depredations amount to an appreciable percentage of the entire yield
+ of grain, and in exceptional cases whole crops have been ruined.
+
+
+ INDIAN CORN.
+
+ Probably this crop suffers greater injury from rats than any other in
+ the United States. To some extent the animals dig up newly planted
+ corn, but their injury to the maturing grain is far greater. They are
+ especially fond of corn in the milk stage, and often climb the upright
+ stalks and strip the cobs bare. In this way sometimes whole fields are
+ destroyed.
+
+ Corn in the shock is often attacked by rats, especially in parts of
+ fields adjacent to hedges, drains, or embankments that afford shelter
+ for the animals. A pair of rats often make a corn shock their home,
+ and soon destroy both grain and fodder.
+
+ Corn in cribs is often damaged by rats. Many cribs are built close to
+ the ground, and rats take up their abode under the floor. They soon
+ gnaw through the wooden barrier and have free access to the grain.
+ They shell the corn and eat the soft part of the kernels, wasting much
+ more than they eat. They carry the grain into underground burrows and
+ bring up moist soil from below, which in contact with the grain makes
+ it moldy and unfit for market or for feeding to stock. A number of
+ farmers have reported the loss by rat depredations of from a fifth to
+ a half of the contents of a large corn crib during a single winter.
+
+ An Iowa farmer, writing to an agricultural journal, relates the
+ following experience:
+
+
+ We had about 2,000 bushels of corn in three cribs to which rats ran,
+ and they ate and destroyed about one-fourth of the corn. Much of it
+ was too dirty to put through the grinder until it had been cleaned
+ an ear at a time. All the time we were poisoning and trapping the
+ rats. We killed as high as 300 rats in two days and could hardly
+ miss them. They destroyed more than enough corn to pay taxes on 400
+ acres of land.[CB]
+
+
+Footnote CB:
+
+ Missouri Valley Farmer, April, 1907.
+
+ Throughout the United States, but especially in the West and South,
+ corn is often stored for months in rail or other open pens, to which
+ rats have free access. Often the loss in a single season would pay for
+ the construction of rat-proof cribs, or at least for wire netting,
+ that would fully protect the crop.
+
+
+ SMALL GRAINS.
+
+ Much has been written about the rat as a house and barn pest, but its
+ depredations in the fields have usually been overlooked. In some
+ localities the common rat, as well as the house mouse, swarms in the
+ fields, especially in summer, and subsists entirely upon the farmers’
+ crops.
+
+ Stacked grain is peculiarly exposed to rat depredations. In the United
+ States, although the cost of protection is small, rats are seldom
+ fenced away from stacks, and, if threshing is delayed, serious loss
+ results. Often, at the removal of a stack, large numbers of rats are
+ discovered, which have been living at the expense of the farmer. As
+ early as 1832 a farmer in Frederick County, Md., with the help of men
+ and dogs, killed 217 large brown rats from one stack of rye.[CC] In
+ England instances are on record of the killing of over a thousand rats
+ from one stack of wheat.
+
+Footnote CC:
+
+ Am. Turf. Register, vol. 3, p. 632, August, 1832.
+
+ The destruction of feed by rats is a serious loss not only on the farm
+ but also in city and village. The feed bin or barrel is often left
+ uncovered and rats swarm to the banquet thus exposed. Small feeders
+ suffer greater proportional losses, for managers of larger barns
+ recognize the enormous drain and usually provide rat-proof bins, if
+ not rat-proof stables. When rats have access to a stable they take a
+ good share of the feed directly from the mangers, but the loss is
+ seldom noticed.
+
+ Rats are exceedingly fond of malt, and in malt houses and breweries
+ constant watchfulness is needed to prevent losses. Mills, elevators,
+ and warehouses in which grain and feed stuffs are stored are subject
+ to constant invasion by rats and mice.
+
+ A full-grown rat consumes about 2 ounces of grain daily. A half-grown
+ rat eats nearly as much as an adult. Fed on grain, therefore, a rat
+ eats from 45 to 50 pounds a year. The cost depends somewhat on the
+ kind of grain. If wheat, the value is 60 to 75 cents; if oatmeal,
+ about $1.80 to $2. Several feeders of horses in Washington, D. C.,
+ estimated the cost of keeping each rat on their premises at $1 a year.
+ Even though half the grain eaten is waste, the direct loss from this
+ source to feeders is enormous.
+
+
+ MERCHANDISE IN STORES AND WAREHOUSES.
+
+ The loss from depredations of rats on miscellaneous merchandise in
+ stores, markets, and warehouses, is second only to the losses on
+ grains. Not only are food materials of every kind subject to attack,
+ but the destruction of dry goods, clothing, books, leather goods, and
+ so on is equally serious. Merchandise other than foodstuffs is usually
+ destroyed for making nests, but books and pamphlets, especially the
+ newly bound, and some other articles, furnish food in the glue, paste,
+ oils, or paraffin used in their manufacture. Some kinds of leather
+ have a peculiar attraction for rats, while others are never touched.
+ Shoes are seldom gnawed unless they have cloth uppers or are made of
+ kid. New harnesses are not often attacked, except collars, which
+ contain straw, and cruppers, which are stuffed with flaxseed. Old
+ harness leather is salty from the perspiration of horses, and rats and
+ mice gnaw it for this reason. Kid gloves and other articles made of
+ similar leather are often destroyed by rats.
+
+ Lace curtains, silk handkerchiefs, linens, carpets, mattings, and
+ other dry goods in stores are often attacked by rats. Some of the
+ stuffs contain starch, which serves as food, but most of them furnish
+ nesting materials only. A slight injury makes these articles
+ unsalable; this is especially true of white goods, which are easily
+ ruined by soiling. Nearly all large dry goods and department stores
+ suffer heavy losses from rats. Grocers, druggists, confectioners, and
+ other merchants also have similar experiences, and to the direct
+ losses must be added the sums expended in fighting the pests.
+
+
+ MERCHANDISE IN TRANSIT.
+
+ Merchandise billed for shipment often lies for days in stations and
+ warehouses or on wharves, where depredations of rats and mice cause
+ heavy losses to shippers and consignees. Similar losses occur on boats
+ carrying merchandise from port to port.
+
+ Fruits and vegetables in transit on steamboats are often destroyed or
+ damaged by rats. Tomatoes, cucumbers, sweet potatoes, bananas,
+ oranges, grape fruit, peanuts, and similar produce shipped by water
+ from the South, especially in winter, reach northern markets with a
+ large percentage of loss.
+
+ In view of the practicability of destroying rats on ships by
+ fumigation, and the ease with which rat-proof compartments for stowing
+ produce can be constructed, it would seem that losses of this nature
+ should be entirely prevented.
+
+
+ POULTRY AND EGGS.
+
+ Aside from disease, the greatest enemy of poultry is the rat. The loss
+ from rats varies with their abundance and the care taken to exclude
+ them from the poultry yard. The magnitude of the damage is not
+ generally known, because much of it is blamed on other animals,
+ particularly minks, skunks, and weasels. Much of the injury occurs at
+ night, and the actual culprit is seldom detected. Farmers have heard
+ that minks, skunks, and weasels prey upon poultry. What more natural
+ than to conclude that one of these animals is doing the mischief,
+ especially if one has been seen about the premises?
+
+ Rats often prey upon small chicks, capturing them in the nests at
+ night or even about the coops in the daytime. The writer has known
+ rats to take nearly all the chicks on a large poultry ranch, and over
+ a large section of country to destroy nearly half of a season’s
+ hatching. Young ducks, turkeys, and pigeons are equally liable to
+ attack, and when rats are numerous, are safe only in rat-proof yards.
+
+ A writer in a western agricultural journal states that in 1904 rats
+ robbed him of an entire summer’s hatching of three or four hundred
+ chicks.[CD] A correspondent of another newspaper says, “Rats destroyed
+ enough grain and poultry on this place in one season to pay our taxes
+ for three years.”[CE] When it is remembered that the poultry and eggs
+ marketed each year in the United States have a farm value of over
+ $600,000,000, it will be seen that a small percentage of loss
+ represents an enormous sum.
+
+Footnote CD:
+
+ Homemaker (Des Moines, Iowa), May 27, 1907.
+
+Footnote CE:
+
+ Missouri Valley Farmer, April, 1907.
+
+ The destruction of eggs by rats is great, not only on the farms where
+ they are produced, but also in the markets. Commission men and grocers
+ complain of depredations upon packed eggs. The animals break and eat a
+ few eggs at the top of a case and the broken yolks run down and soil
+ the eggs below. Then, too, rats carry away unbroken eggs, displaying
+ much ingenuity in getting them over obstacles, as up or down a
+ stairway.
+
+ A commission merchant in Washington, D. C., states that he once stored
+ 100 dozen eggs in a wooden tub in his warehouse and left them for
+ nearly two weeks. He then found that rats had gnawed a hole through
+ the tub, just under the cover, and had carried away 71½ dozen, leaving
+ neither pieces of shell nor stains to show that any had been broken.
+
+ Besides their destruction of eggs and young fowls, rats eat much of
+ the food put out for poultry. They are destructive also to tame
+ pigeons and their eggs, but particularly to young squabs. They climb
+ the wire netting and gain entrance to the cages through the same
+ openings by which the pigeons come and go. Fanciers are often put to
+ great trouble to protect their pigeons from rats, and because of these
+ pests some of them have abandoned the business.
+
+
+ GAME AND WILD BIRDS.
+
+ The rat is the most serious pest in European game preserves. A writer
+ in Chambers’s Journal says:
+
+
+ In a closely preserved country at the end of an average year the
+ game suffers more from the outlying rats of the lordship than from
+ the foxes and mustelines together. The solitary rats, whether males
+ or females, are the curse of a game country. They are most difficult
+ to detect, for in a majority of cases their special work is supposed
+ to be done by hedgehog, weasels, or stoat.[CF]
+
+
+Footnote CF:
+
+ Chambers’s Journal, vol. 82, p. 64, January, 1905.
+
+ The propagation of game birds is becoming a promising industry in the
+ United States. The difficulties of the business are not yet fully
+ known, but the rat is an enemy with which the raiser of game will have
+ to contend. The animal has already proved itself a foe in American
+ pheasantries.
+
+ Our wild native game birds are less subject to rat depredations than
+ birds kept in confinement. The nests of ruffed grouse are in
+ woodlands; those of the prairie hen and related species are on plains
+ remote from the haunts of rats. The quail, however, often makes its
+ nest within the summer range of rats, which destroy many of its eggs.
+
+ Rats are said often to destroy the nests of wild ducks, woodcock, and
+ other marsh birds. Terns have been entirely driven from their nesting
+ grounds in this way. In England the common tern was extirpated from
+ the Thames marshes; and on Loggerhead Key, Tortugas Islands, off the
+ Florida coast, rats recently nearly exterminated a colony of least
+ terns by destroying the eggs.
+
+ The nests of many ground-nesting and other song birds are robbed by
+ rats. Crows, jays, snakes, and skunks are blamed for most of the
+ destruction and the actual offender seldom suspected. While the other
+ animals named do part of the mischief, the rat is a more serious foe
+ of song and game birds than any of these.
+
+
+ FRUITS AND VEGETABLES.
+
+ A well-known form of damage by rats is the destruction of fruits and
+ vegetables in cellars and pits. Apparently no garden vegetable or
+ common fruit is exempt from attack. But the rat does not confine its
+ depredations to stored fruits and vegetables. It attacks ripe
+ tomatoes, melons, cantaloupes, squashes, pumpkins, sweet corn, and
+ many other vegetables in the field; and often the depredations are
+ attributed to rabbits or other animals, which may or may not be
+ concerned in the mischief.
+
+ Rats are fond of the small fruits, eating not only the fallen but
+ climbing vines and canes to obtain the ripe grapes or berries. They
+ eat also apples, pears, cherries, and other fruits. The brown rat,
+ while not so expert as the black or the roof rat, readily climbs trees
+ and obtains fruit even at the extremities of the branches.
+
+ Among tropical fruits injured by rats are oranges, bananas, figs,
+ dates, cocoanuts, and especially the pods of cacao (_Theobroma
+ cacao_), from which chocolate is manufactured. H. N. Riddey, writing
+ of his experiences on the island of Fernando do Noronha, South
+ America, mentions the destructiveness of rats in this penal colony.
+ They climb the cocoanut palms and papaw trees to devour the fruit, and
+ do mischief in melon patches. To lessen the evil, each convict was
+ required to bring in a certain number of dead rats, and battues were
+ held monthly to satisfy the requirement. Sometimes the number killed
+ in a single hunt reached 20,000.[CG]
+
+Footnote CG:
+
+ Zoologist, vol. 46, p. 46, 1888.
+
+ Fruits and vegetables grown under glass are subject to injury by rats.
+ The animals usually find entrance to greenhouses by way of openings
+ for pipes or drains.
+
+
+ FLOWERS AND BULBS.
+
+ Rats attack seeds, bulbs, and the leaves, stems, and flowers of
+ growing plants, whether in the greenhouse, propagating pits, or
+ elsewhere. Of flowering bulbs, the tulip suffers most from rats.
+ Hyacinths also are eaten; but, probably because they are slightly
+ poisonous, narcissus and daffodil bulbs escape injury. Rats eat pinks,
+ carnations, and roses, cutting the stems off clean. They denude
+ geraniums of both flowers and leaves. They attack the choicest blooms
+ of chrysanthemums and carnations in markets, stores, and exhibition
+ rooms, causing heavy losses.
+
+
+ FIRES.
+
+ Rats and mice cause many fires. Several specific instances have been
+ reported by the fire department of the city of Washington within the
+ past two or three years. It is likely that some of these fires are
+ caused by rats gnawing matches. The animals are fond of paraffin,
+ which is often used to protect match heads. They carry the matches to
+ their nests, which are composed of paper and other combustible
+ materials, and the conditions for a conflagration are ready. Since the
+ heads of matches contain from 14 to 17 per cent of phosphorus, actual
+ gnawing is not required to ignite them, but heat or friction from any
+ cause may suffice.
+
+ Fires in mills or warehouses have sometimes been traced to the
+ spontaneous ignition of oily or fatty rags and waste carried under
+ floors by rats. Cotton and woolen mills are said to be peculiarly
+ subject to fires of this kind.
+
+ Sometimes rats cause fires by gnawing through the lead pipes leading
+ to the gas meter. Workmen or others, searching for the leak,
+ accidentally ignite the gas. Phillips’s warehouse, London, was twice
+ badly damaged by fires originating in this way, and in several
+ instances the sleeping inmates of houses have been in danger of
+ asphyxiation by gas freed in this manner.
+
+ The most common way in which rats and mice cause fires is by the
+ destruction of the covering of electric light wires under floors or in
+ partition walls. A considerable percentage of the enormous fire losses
+ in the United States is caused by defective insulation of wires. After
+ wires are once in position rats are the chief agents in impairing the
+ insulation. These animals do much mischief also by gnawing off the
+ coverings of telephone wires. In the case of electric light wires the
+ covering is probably used by the rats for nesting material, but
+ frequently the paraffin in the insulation is the object of attack.
+
+
+ BUILDINGS AND FURNITURE.
+
+ Rats seem to be able to gnaw through almost any common material except
+ stone, hard brick, cement, glass, and iron; neither wood nor mortar
+ suffice to keep them out of bins or rooms. They sometimes gnaw through
+ walls or doors in a single night. In the same way they enter chests,
+ wardrobes, bookcases, closets, barrels, and boxes. Almost every old
+ dwelling bears evidence of its present or former occupancy by rats.
+ Often the depreciation of houses and furniture is largely due to marks
+ left upon them by rats—marks that paint and varnish can not hide.
+
+ Damage to dwellings by rats is a large item. The decay of sills and
+ floors is hastened by contact with moist soil brought up from rat
+ burrows. Ceilings, wall decorations, and floor coverings are flooded
+ by leaks in lead pipes or wooden tanks gnawed by rats. Bricked areas
+ and even foundations are undermined and ruined by rats. All this is
+ real waste and a constant drain on the resources of the country.
+
+
+ MISCELLANEOUS.
+
+ A few instances of miscellaneous damage by rats may be mentioned to
+ show the great variety of mischief chargeable to the animals.
+
+ A Washington, D. C., merchant reported that at one time rats in his
+ store destroyed 50 dozen brooms worth $2.50 a dozen. In another store,
+ in a single night, they broke $500 worth of fine chinaware on shelves
+ and tables. A dealer in harness reported the loss of $400 worth of
+ collars in one season. The manager of a restaurant complained of an
+ average loss of $30 a month in table linen ruined by rats and mice. A
+ hotel reported the destruction of $75 worth of linen in a month.
+
+ At Mobile, Ala., in March, 1908, lost jewelry worth $400 was recovered
+ from a rat’s nest in the home of Señor Viada.
+
+ In London rats at one time killed all but 11 out of an aviary of 366
+ birds.
+
+ At Hamburg, Germany, Carl Hagenbeck once had to kill three young
+ African elephants because rats had gnawed their feet, inflicting
+ incurable wounds.
+
+ Rats often gnaw the hoofs of horses until they bleed. They kill young
+ lambs and pigs, and have been known to gnaw holes in the bodies of
+ very fat swine, causing death.
+
+ Like the muskrat, the brown rat often burrows into embankments and
+ dams, causing serious breaks.
+
+ The rat is one of the greatest enemies with which the sugar planter
+ has to contend, destroying acres of growing cane.
+
+ In rice plantations rats not only break down and destroy the growing
+ crops, but burrow into the dikes and flood the fields at the wrong
+ season.
+
+ On the London docks and on shipboard ivory is often badly damaged by
+ rats. They select for attack the greenest tusks, which are the more
+ valuable.
+
+ Mail sacks and other kinds of bagging are greatly injured by rats. The
+ consequent loss and necessary outlay for repairs are a large item in
+ post-office expenditures and in mills and other places where bagging
+ is used.
+
+ About the year 1616 rats caused a two years’ famine in the Bermudas.
+ In the southern Deccan and Mahratta districts of India rats ate a
+ large part of the scant crops of 1878 and 1879, and were regarded as
+ in a great measure responsible for the severe famine which
+ followed.[CH] A writer in Chambers’s Journal stated that the Dutch
+ abandoned the Isle of France (Mauritius) in 1610 because of the great
+ abundance of rats.[CI]
+
+Footnote CH:
+
+ Brit. Med. Journ., p. 623, September 15, 1905.
+
+Footnote CI:
+
+ Chambers’s Journal, vol. 21, p. 244, 1854.
+
+
+ AMOUNT OF LOSSES CAUSED BY RATS.
+
+ The damage done by a single rat varies greatly with the circumstances.
+ We have already stated that the cost of feeding a rat on grain varies
+ from 60 cents to $2 a year. Assuming that much of the rat’s food is
+ waste, each rat on a farm will cause a loss of over 50 cents a year.
+ In cities the damage by a single rat probably averages more than in
+ the country. Hotel managers and restaurant keepers state that $5 a
+ year is a low estimate of the loss inflicted by a rat. In making an
+ estimate it should be remembered that the rat is to be charged not
+ only with the food it actually consumes but also with what it destroys
+ or pollutes and renders unfit for use.
+
+ If an accurate census of the rats in the United States were possible,
+ and if the minimum average loss caused by a rat were known, an
+ estimate of the total annual losses from their depredations could be
+ made. It was on such a minimum basis that the Incorporated Society for
+ the Destruction of Vermin arrived at their total estimate of
+ £15,000,000 ($73,000,000) as the yearly losses from rats in Great
+ Britain and Ireland. Three propositions were assumed: first, that in
+ cities and villages the number of rats equals the population; second,
+ that in the country there is at least one rat for every acre of
+ cultivated land; third, that each rat in the kingdom inflicts a damage
+ of at least a farthing per day. Circulars asking whether these
+ assumptions are excessive were distributed throughout the country.
+ From 90 to 99 per cent of the replies fully indorsed each of the
+ assumptions.
+
+ It can readily be seen that the English basis of estimate would not
+ apply to farm conditions in the United States, where the area in the
+ twelve leading crops alone is over 250,000,000 acres. On a basis of a
+ rat per acre and damage of a farthing per day the annual loss on this
+ area would be $450,000,000, a sum much too great for serious
+ consideration. However, in the more thickly populated parts of the
+ country an estimate of one rat per acre would not be excessive; and it
+ is probable that in most of our cities there are quite as many rats as
+ people. Yet it would be unsafe, owing to our vast territory and
+ varying conditions, to make these assumptions the basis for
+ conclusions.
+
+ Over a year ago the writer made an attempt to investigate actual
+ conditions, and thus arrive at an estimate of the total damage by rats
+ in the cities of Washington and Baltimore. From the data obtained the
+ direct annual damage in the two cities was calculated at $400,000 and
+ $700,000, respectively. The Census Bureau in 1906 estimated the
+ population of these cities at 308,000 and 554,000, respectively. If
+ the estimates of damage were correct, the average loss for each person
+ is $1.27 a year; and, on the same basis, the 28,000,000 of urban
+ population in the United States (census of 1900) sustains an annual
+ direct injury of $35,000,000 from rats. This is considerably lower
+ than on the English assumption, which would make the losses in our
+ cities over $50,000,000.
+
+ Denmark (population 2,500,000) has an estimated rat bill of about
+ $3,000,000 a year, or $1.20 a person. Germany (population 56,000,000)
+ is said to sustain a loss from rats of 200,000,000 marks ($47,640,000)
+ a year, or about 85 cents for each person. The per capita estimate for
+ the United Kingdom is about double that made for Germany. In France
+ the loss from rats and mice for a single year (1904) was placed at
+ $38,500,000, or a little over a dollar for each of its 38,000,000
+ inhabitants. These estimates are supposed to include only direct
+ losses, but they vary enough to show that no common basis can be
+ assumed for all countries. With present information, therefore, any
+ attempt to state the amount of loss from rats in the United States
+ would be largely guesswork. Considering the population and wealth of
+ the country, however, and the vast area over which rats are abundant,
+ it is not unreasonable to conclude that in the United States the
+ losses from rats amount to much more than in any of the other
+ countries named.
+
+
+ INDIRECT LOSSES.
+
+ To the direct losses caused by rats must be added the cost of fighting
+ the animals and of protecting property from them. In our larger cities
+ a number of so-called expert rat catchers are to be found, who operate
+ with dogs, ferrets, traps, poisons, or other means, and who have an
+ extensive clientage among merchants, hotel managers, and others. These
+ pay the rat catcher a yearly or monthly stipend to keep their premises
+ free of rats and mice. Some of the large establishments pay $200 to
+ $600 yearly for such service. While the agreements are seldom kept in
+ full, the clients are usually satisfied that results warrant the
+ expense. Even when no contractor is employed, merchants are at expense
+ for traps, poisons, the keep of cats or dogs, and other means of
+ fighting rats. The same is true in less degree of nearly every
+ householder.
+
+ The cost of protecting property from rats is no small item. It
+ increases the expense of nearly all building, but it greatly reduces
+ direct losses from the animals. The economy of rat-proof construction
+ is everywhere manifest, in city or country, and the necessity for it
+ can not be too strongly emphasized.
+
+ Depreciation of property and loss of rents and custom are items not
+ generally thought of in connection with rat damage. A few years ago
+ the writer knew of almost an entire block of city houses that remained
+ untenanted for several months, because infested by rats. As the houses
+ were otherwise desirable, the loss of rent to the owners was probably
+ nearly $2,000. The presence of rats in markets, hotels, and
+ restaurants inevitably results in loss of custom, besides the direct
+ damage by the rodents.
+
+ From every point of view the keeping of rats is exceedingly expensive,
+ and the sooner our population can be made to realize the enormous
+ drain upon our resources caused by these rodents the sooner can
+ concerted measures for their destruction be made effective.
+
+
+
+
+ THE RAT IN RELATION TO INTERNATIONAL SANITATION.
+
+ By Asst. Surg.-Gen., JOHN W. KERR,
+
+ _Public Health and Marine-Hospital Service_.
+
+
+ Rats, like man, had their origin in Asia, from which continent they
+ have finally become disseminated throughout the world. They, too, like
+ man, are great travelers, and therefore prey on the commerce of the
+ ships in which they are carried. For this reason, and on account of
+ the fact that they are subject to plague and may transmit the disease
+ from one country to another, these animals have an influence on
+ international policy, and their control aboard ships is an
+ international problem.
+
+ It has been estimated that there are as many rats as there are human
+ beings, and that each rat causes each day a loss by the destruction of
+ material of at least half a cent.
+
+ Assuming that the rat population aboard ships is as great as the human
+ population—and my experience gained during the fumigation of ships to
+ kill rats convinces me that on the whole it is greater—some idea may
+ be had of the enormous migrations of rats and the toll they exact for
+ food from international commerce. Some idea can also be had of the
+ danger of rats in transmitting plague when it is remembered that 51
+ countries have been infected with the disease since the present
+ pandemic began in Canton, China, in 1894, and when it is known that at
+ least 146 ships have had plague infection on board during that time.
+
+ During the International Sanitary Conference of Paris in 1903 the
+ influence of the rat in transmitting plague was borne in mind, and the
+ international sanitary agreement, which was signed ad referendum
+ December 3, 1903, requires the destruction of rats aboard
+ plague-infected ships, recommends it on ships suspected of being
+ plague infected, and permits it on ships indemne from plague. The ship
+ is considered indemne from plague which, although coming from an
+ infected port, has had neither death nor case on board either before
+ departure, during the voyage, or at the moment of arrival.
+
+ The International Sanitary Convention signed at Washington, October
+ 14, 1905, follows the text of the Paris convention, with respect to
+ plague, consequently embodying similar requirements and
+ recommendations as follows:
+
+
+ ART. XX. _Classification of ships._—A ship is considered as infected
+ which has plague, cholera, or yellow fever on board, or which has
+ presented one or more cases of plague or cholera within seven days,
+ or a case of yellow fever at any time during the voyage.
+
+ A ship is considered as suspected on board of which there have been
+ a case or cases of plague or cholera at the time of departure or
+ during the voyage, but no new case within seven days; also such
+ ships as have lain in such proximity to the infected shore as to
+ render them liable to the access of mosquitoes.
+
+ The ship is considered indemne which, although coming from an
+ infected port, has had neither death nor case of plague, cholera, or
+ yellow fever on board, either before departure, during the voyage,
+ or at the time of arrival, and which in the case of yellow fever has
+ not lain in such proximity to the shore as to render it liable, in
+ the opinion of the sanitary authorities, to the access of
+ mosquitoes.
+
+ ART. XXI. Ships infected with plague are to be subjected to the
+ following regulations:
+
+ 1. Medical visit (inspection).
+
+ 2. The sick are to be immediately disembarked and isolated.
+
+ 3. Other persons should also be disembarked, if possible, and
+ subjected to an observation,[CJ] which should not exceed five days,
+ dating from the day of arrival.
+
+Footnote CJ:
+
+ The word “observation” signifies isolation of passengers, either
+ on board ship or at a sanitary station, before being given free
+ pratique.
+
+ 4. Soiled linen, personal effects in use, the belongings of crew[CK]
+ and passengers which, in the opinion of the sanitary authorities are
+ considered as infected, should be disinfected.
+
+Footnote CK:
+
+ The term “crew” is applied to persons who may make, or who have
+ made, a part of the personnel of the vessel and of the
+ administration thereof, including stewards, waiters, “cafedji,”
+ etc. The word is to be construed in this sense wherever employed
+ in the present convention.
+
+ 5. The parts of the ship which have been inhabited by those stricken
+ with plague, and such others as, in the opinion of the sanitary
+ authorities, are considered as infected, should be disinfected.
+
+ 6. The destruction of rats on shipboard should be effected before or
+ after the discharge of cargo, as rapidly as possible, and in all
+ cases with a maximum delay of forty-eight hours, care being taken to
+ avoid damage of merchandise, the vessel, and its machinery.
+
+ For ships in ballast, this operation should be performed immediately
+ before taking on cargo.
+
+ ART. XXII. Ships suspected of plague are to be subjected to the
+ measures which are indicated in Nos. 1, 4, and 5 of Article XXI.
+
+ Further, the crew and passengers may be subjected to observation,
+ which should not exceed five days, dating from the arrival of the
+ ship. During the same time the disembarkment of the crew may be
+ forbidden, except for reasons of duty.
+
+ The destruction of rats on shipboard is recommended. This
+ destruction is to be effected before or after the discharge of
+ cargo, as quickly as possible, and in all cases with a maximum delay
+ of forty-eight hours, taking care to avoid damage to merchandise,
+ ships, and their machinery.
+
+ For ships in ballast this operation should be done, if done at all,
+ as early as possible, and in all cases before taking on cargo.
+
+ ART. XXIII. Ships indemne from plague are to be admitted to free
+ pratique immediately, whatever may be the nature of their bill of
+ health.
+
+ The only regulation which the sanitary authorities at a port of
+ arrival may prescribe for them consists of the following measures:
+
+ 1. Medical visit (inspection).
+
+ 2. Disinfection of soiled linen, articles of wearing apparel, and
+ the other personal effects of the crew and passengers, but only in
+ exceptional cases when the sanitary authorities have special reason
+ to believe them infected.
+
+ 3. Without demanding it as a general rule, the sanitary authorities
+ may subject ships coming from an infected port to a process for the
+ destruction of the rats on board before or after the discharge of
+ cargo. This operation should be done as soon as possible, and in all
+ cases should not last more than twenty-four hours, care being taken
+ to avoid damaging merchandise, ships, and their machinery, and
+ without interfering with the passing of passengers and crew between
+ the ship and the shore. For ships in ballast this procedure, if
+ practiced, should be put in operation as soon as possible, and in
+ all cases before taking on cargo.
+
+ When a ship coming from an infected port has been subjected to a
+ process for the destruction of rats, this process should only be
+ repeated if the ship has touched meanwhile at an infected port, and
+ has been alongside a quay in such port, or if the presence of sick
+ or dead rats on board is proven.
+
+ The crew and passengers may be subjected to a surveillance, which
+ should not exceed five days, to be computed from the date when the
+ ship sailed from the infected port. The landing of the crew may
+ also, during the same time, be forbidden except for reasons of duty.
+
+ Competent authority at the port of arrival may always demand, under
+ oath, a certificate of the ship’s physician, or in default of a
+ physician, of the captain, setting forth that there has not been a
+ case of plague on board since departure, and that no marked
+ mortality among the rats has been observed.
+
+ ART. XXIV. When upon an indemne ship rats have been recognized as
+ pest stricken as a result of bacteriological examination, or when a
+ marked mortality has been established among these rodents, the
+ following measures should be applied:
+
+ 1. Ships with plague-stricken rats:
+
+ (_a_) Medical visit (inspection).
+
+ (_b_) Rats should be destroyed before or after the discharge of
+ cargo, as rapidly as possible, and in all cases with a delay not to
+ exceed forty-eight hours; the deterioration of merchandise, vessels,
+ and machinery to be avoided. Upon ships in ballast, this operation
+ should be performed as soon as possible, and in all cases before
+ taking on cargo.
+
+ (_c_) Such parts of the ship and such articles as the local sanitary
+ authority regards as infected, shall be disinfected.
+
+ (_d_) Passengers and crew may be submitted to observation, the
+ duration of which should not exceed five days, dating from the day
+ of arrival, except in special cases, where the sanitary authority
+ may prolong the observation to a maximum of ten days.
+
+ 2. Ships where a marked mortality among rats is observed:
+
+ (_a_) Medical visit (inspection).
+
+ (_b_) An examination of rats, with a view to determining the
+ existence of plague, should be made as quickly as possible.
+
+ (_c_) If the destruction of rats is judged necessary, it shall be
+ accomplished under the conditions indicated above in the case of
+ ships with plague-stricken rats.
+
+ (_d_) Until all suspicion may be eliminated, the passengers and crew
+ may be submitted to observation, the duration of which should not
+ exceed five days, counting from the date of arrival, except in
+ special cases, when the sanitary authority may prolong the
+ observation to a maximum of ten days.
+
+ ART. XXV. The sanitary authorities of the port must deliver to the
+ captain, the owner, or his agent, whenever a demand for it is made,
+ a certificate setting forth that the measures for the destruction of
+ rats have been efficacious and indicating the reasons why these
+ measures have been applied.
+
+
+ To be in conformity with these agreements regarding the destruction of
+ rats, quarantine authorities may demand the fumigation of infected and
+ suspected ships; suspected ships within the meaning of the treaties
+ being those on board of which there have been a case or cases of
+ plague at the time of departure or during the voyage, but no new case
+ within seven days. In the case of indemne ships, on the other hand,
+ without demanding it as a general rule, the sanitary authorities may
+ subject them to fumigation to kill rats. When upon such ships rats
+ have been recognized as pest stricken, as a result of bacteriological
+ examination, or when a marked mortality has been established among
+ these rodents, fumigation is prescribed.
+
+ While the classification of ships and the limitations placed on
+ quarantine procedures in relation thereto, as contained in existing
+ international sanitary agreements, is more apparent than real, there
+ appears to be a lack of exactness with respect to the destruction of
+ rats necessary for the prevention of the importation of plague from
+ one country to another.
+
+ Since the adoption of the international sanitary agreement of Paris in
+ 1903, some of the unproven convictions of that time regarding the rôle
+ of rats and fleas in the transmission of plague have been proven to be
+ positive facts. Many epidemiological observations and exact scientific
+ experiments have demonstrated particularly the importance of the rat
+ in the propagation of plague and the rôle of the flea as the carrier
+ of infection from rat to rat and from rats to man.
+
+ At the same time there has been a growing conviction that other
+ agencies, such as passengers, baggage, and merchandise play a very
+ minor rôle in the dissemination of plague. It is of interest,
+ therefore, to review the efforts being made at the more important
+ seaports to exterminate rats, as well as the methods being employed to
+ that end.
+
+
+ INQUIRY INTO THE CRUSADE AGAINST RATS THROUGHOUT THE WORLD.
+
+ The first law in modern times aiming at the destruction of rats
+ appears to have been enacted in Barbados in 1745.[CL] According to
+ Boelter this act was incorporated into a new act which was passed in
+ 1748. The same author states that the next legislative body to enact a
+ law against rats was in Antigua in 1880. In the same article he refers
+ to the rat ordinance of Hongkong, adopted in 1902.
+
+Footnote CL:
+
+ W. R. Boelter, “On Rat Laws,” Journal of Incorporated Society for
+ the Destruction of Vermin, October, 1908.
+
+ Private measures against rats have undoubtedly been practiced from
+ time immemorial. The action of Denmark, however, in passing a law for
+ the systematic destruction of rats and providing the organization for
+ that purpose is perhaps the most notable advance taken on this
+ subject. A copy of the Danish law appears elsewhere in this
+ publication.
+
+ That the citizens of other countries are equally alive to the
+ importance of rat extermination is shown by the fact that in England
+ there exists an incorporated society for the destruction of vermin,
+ which society in October, 1908, began the publication of a journal
+ which would supply trustworthy information upon the subject.
+
+ It is recognized that a detailed review of past efforts against
+ rodents would be unprofitable, but on account of the enormous trade
+ relations between important seaports it is thought that a review of
+ the measures taken therein against rodents would be of value.
+
+
+ RAT EXTERMINATION IN UNITED STATES PORTS.
+
+ Prior to the adoption of the International Sanitary Conventions of
+ Paris and Washington, the Federal Government had made provision in its
+ quarantine regulations for the prevention of the spread of plague on
+ ships through rodents.
+
+ The articles contained in the United States Quarantine Regulations,
+ issued April 1, 1903, and bearing on the subject, are as follows:
+
+
+ 14. At ports or places where plague prevails every precaution must
+ be taken to prevent the vessel becoming infected through the agency
+ of rats, ants, flies, fleas, or other animals. At such ports or
+ places the vessel should not lie at a dock, or tie to the shore, or
+ anchor near any place where such animals may gain access to the
+ vessel. In case cables are led to the shore they should be freshly
+ tarred and provided with inverted cones or such other devices as may
+ prevent rats and other animals passing to the ship. The introduction
+ of vermin on board the vessel from lighters and all other sources
+ should be guarded against. In such ports sulphur fumigation should
+ be resorted to in the holds when empty and from time to time during
+ loading in order to destroy vermin.
+
+ 45 (b) Free ventilation and rigorous cleanliness should be
+ maintained in all portions of the ship during the voyage and
+ measures taken to destroy rats, mice, fleas, flies, roaches,
+ mosquitoes, and other vermin.
+
+ 45 (h) In the case of plague, special measures must be taken to
+ destroy rats, mice, fleas, flies, ants, and other vermin on board.
+
+ 128. Vessels infected with plague, or suspected of such infection,
+ should be anchored at a sufficient distance from the shore or other
+ vessels to prevent the escape of rats by swimming.
+
+ 133. Special precautions must be taken against rats, mice, ants,
+ flies, fleas, and other animals, on account of the danger of the
+ infection of the disease being spread through their agency.
+
+ 134. As soon as practicable there shall be a preliminary
+ disinfection with sulphur dioxide for the purpose of killing rats
+ and vermin before further disinfecting processes are applied to the
+ vessel and her cargo. The killing of any escaping rats shall be
+ provided for by a water guard in small boats, and no person with
+ abrasions or open sores should be employed in the handling of the
+ vessel or her cargo.
+
+ 135. The vessel shall be submitted to a simultaneous disinfection in
+ all parts with sulphur dioxide to insure the destruction of rats and
+ vermin. The rats shall be subsequently gathered and burned, due
+ precautions being taken not to touch them with the bare hands, and
+ the places where found disinfected with a germicidal solution; and
+ the quarantine officer shall assure himself that the vessel is free
+ of rats and vermin before granting free pratique.
+
+
+ Additional regulations prescribe the method of disinfection of vessels
+ for plague, and elsewhere in this publication is given a detailed
+ description of the measures taken aboard ships at Angel Island, one of
+ the national quarantine stations.
+
+ Elsewhere is also given an account of the measures taken to eradicate
+ plague from certain cities on the Pacific coast, among the measures
+ being the systematic destruction of rodents and practical rat
+ proofing.
+
+ In a letter dated November 21, 1908, requests were made to the
+ Department of State for reports from certain of the more important
+ foreign seaports as to systematic measures being practiced for the
+ destruction of rats. As a result much valuable information has been
+ received, and acknowledgments are due and here made to the consular
+ officers furnishing it. The data received was abstracted and
+ classified according to countries as follows:
+
+
+ RAT EXTERMINATION IN CHINESE CITIES.
+
+ Although the present pandemic of plague had its origin in Canton,
+ China, in 1894, and the disease has been endemic there practically
+ ever since, Consul-General Bergholz states that the provincial
+ government of Kwangtung has made no efforts to exterminate rats.
+
+ In Amoy the local authorities have never taken measures to encourage
+ the extermination of rats, and in the absence of assistance from the
+ local authorities but little can be done toward effective eradication.
+
+ An outbreak of plague in Shanghai in December, 1908, was attributed to
+ the introduction of rats by ships from plague-infected ports.[CM] A
+ plan of campaign for such an emergency had previously been formulated
+ and was put in operation. It included collection and laboratory
+ examinations of rats and organization of rat parties to destroy rats
+ and render houses rat proof.
+
+Footnote CM:
+
+ The Municipal Gazette, Shanghai, January 7, 1909, Health Officer’s
+ report for December, 1908.
+
+ In Tientsin official efforts made to exterminate rats are on lines to
+ suit the convenience of the particular health official. The consulate
+ at that port states that generally on the appearance of plague, the
+ officials pay about one-half cent for each rat brought, and as the
+ epidemic becomes severe, as much as 2½ cents gold.
+
+ In Hongkong, the question of rats in relation to plague has been of
+ perennial interest. While on duty in the American consulate at that
+ port, my attention was forcibly called to the influence of rodents in
+ the transmission of plague. In 1900 it had been the practice to
+ encourage the destruction of rats in the city, and a reward of 2 cents
+ Mexican money was offered for each rat brought to the health
+ department. A certain number of these rats were examined from day to
+ day from different districts.
+
+ In August, 1901, arrangements were made by which the health department
+ collected and examined a specified number of rats each day to try to
+ determine in some degree the relative prevalence of plague among these
+ animals. This practice was continued for several months, with the
+ result that the mortality among rodents from the disease was shown to
+ have rapidly decreased until in November practically no
+ plague-infected rats were found.
+
+ In a discussion of the subject, furnished February 2, 1909, by Dr. W.
+ W. Pierce, medical officer of health, through Consul-General A. P.
+ Wilder, it is stated that in 1902 the fee for rats was raised to 5
+ cents, and a special staff of coolies was engaged to destroy rats. The
+ abuses on account of these bounties were so great, however, that it
+ was found necessary to discontinue it in 1903, but the method of
+ trapping rats was continued.
+
+ While the total number of rats taken in 1903 was 101,047, Doctor
+ Pierce stated in effect that on account of the prejudice against
+ disinfection, it was practically impossible to secure the addresses
+ where the infected rats were found. The services of the staff were
+ continued, however, until 1908, when they were abolished because it
+ was thought, as stated by Doctor Pierce, that results were not
+ commensurate with the cost, and many complaints were heard. The plan
+ of furnishing traps to all persons who applied was then introduced,
+ and in addition, structural methods which had gone on for years were
+ continued.
+
+ The traps were distributed through district committees consisting of
+ the more educated natives, who were informed that with their
+ assistance it would be possible to avoid abuses which had been
+ practiced by the official rat-catching staff.
+
+ Doctor Pierce stated that it had been impossible under other systems
+ to secure the addresses where infected rats were found, and in order
+ to overcome this prejudice, several hundred receptacles were placed in
+ different parts of the city whereby the rats could be collected. These
+ tins were visited from day to day, and by this means it was possible
+ to locate infected districts.
+
+ Doctor Pierce stated that the use of ordinary disinfectants in
+ plague-infected houses had been discontinued, and that a 2 per cent
+ mixture in water of a kerosene emulsion made by stirring warm tank
+ oil, 85 parts added gradually to 15 parts of hot, strong solution of
+ “sunlight” soap, was used. This solution was found to instantly kill
+ fleas and bugs, and it has been used systematically.
+
+ For ordinary cleansing a 1 per cent solution is used, but Doctor
+ Pierce stated that on the recurrence of plague special gangs would be
+ employed to apply a 2 per cent solution in infected localities.
+
+ Beginning with January 1, 1909, Doctor Pierce stated that a rat poison
+ known as “Punjaub rat exterminator” had been laid down, and that the
+ intensive destruction of rats by this means was under consideration.
+
+ In summarizing the measures taken against rats, the American
+ consul-general stated that four methods were in use, namely, rat
+ proofing, trapping, poisoning, and use of cats. The use of bacterial
+ viruses as poisons has thus far been unsatisfactory, and the use of
+ chemical poisons, such as phosphorus, prepared, and known as “Punjaub
+ rat exterminator,” has only given moderate results.
+
+ The keeping of cats is encouraged, and the consul states that some
+ hundreds of these animals have been imported from Macao and Canton by
+ the colony and distributed.
+
+ Finally, the consul states that the use of “rat funnels” has long been
+ compelled whenever large vessels lie at the wharves.
+
+ In Sinyang the work of exterminating rats is in charge of a physician
+ who has 12 assistants, which number, however, may be increased in case
+ of emergency. The means employed are trapping, offering rewards, and
+ catching by means of cats. In his report, the consul states that the
+ best results have been secured by trapping. For ridding houses of
+ rats, some use is made of fumigation. It is stated that there is not
+ much danger of rats invading cargo boats, but that in the country rats
+ are present in enormous numbers, and that the problem of their
+ destruction has thus far baffled all attempts at solution. Bounties at
+ the rate of 15 cents per hundred are paid, and in one year the
+ Government expended for this purpose $32,500.
+
+
+ RAT EXTERMINATION IN MADRAS, BOMBAY, AND CALCUTTA, INDIA.
+
+ In Madras, Consul N. B. Stewart states there is no legal enactment in
+ effect requiring the destruction of rats, but the Government has done
+ everything in its power to make the public understand the value of
+ such a measure as a preventive against plague. In 1907 a reward of
+ one-half anna, equal to 1 cent, was offered by the city for each large
+ rat killed, and one-fourth anna for each small one. Bounties of
+ one-fourth anna and one-twelfth anna each for the respective varieties
+ of rats were still being continued at the time report was made.
+
+ In Bombay, where plague has been endemic since 1896, destruction of
+ rats and examination of all dead rats and evacuation of rat-infected
+ areas are included among the measures taken by the health department
+ in connection with plague operations. In his report Consul E. H.
+ Dennison states that the present antirat campaign in Bombay includes
+ the distribution of poisons, the trapping of rats, and the reward of 1
+ cent for each live rat, and a half cent for each dead rat, delivered
+ to the health department. He also states that there are no by-laws or
+ acts under which the destruction of rats can be enforced in private
+ houses.
+
+ On account of religious opposition, and to teach the people,
+ educational posters signed by the health officer were displayed,
+ containing advice what to do to prevent plague, which in part reads as
+ follows:
+
+
+ 1. Beware of rats in your dwelling houses.
+
+ 2. To harbor rats is to court plague.
+
+ 3. Rat infection and consequent rat mortality are the indications of
+ the impending plague visitation among human beings.
+
+ 4. Allow the health department staff to place rat traps in and about
+ your houses to catch rats and take them back.
+
+ 5. Freedom from plague is in the removal of rats.
+
+ 6. Inform the health department when dead rats are found in or near
+ your houses.
+
+ 7. Clear your houses of all materials likely to harbor rats.
+
+
+ The same placard also contains information regarding disinfection to
+ kill fleas, evacuation of infected areas, and inoculations to produce
+ immunity.
+
+ In a special report dated January 23 the consul described a new
+ experiment in rat destruction; that is, an intensive effort in the
+ Kamatipura district. The district was divided into divisions and
+ subdivisions in which simultaneously there were distributed for use on
+ a certain day 19,642 poison baits and 2,670 traps. It was stated that
+ as a result hundreds of rats were collected the following morning.
+
+ No reference is made to measures taken for the destruction of rats
+ aboard ships in the harbor.
+
+ In Calcutta, it is reported by Consul-General W. H. Michael that
+ various methods are resorted to for the extermination of plague, rats,
+ the use of poison being the most general. Rewards have been offered
+ for live and dead rats, and about 11,135 dead rats were produced, but
+ it was found that a considerable portion of these was picked up by
+ conservancy coolies, and the reward for dead rats was therefore
+ discontinued. Of live rats, only 9,447 were produced. After December
+ 1, 1908, the reward was raised to 4 cents, with the result that 49,396
+ live rats were captured. It is stated, however, that this did not seem
+ to have any appreciable effect upon the rat population.
+
+
+ RAT EXTERMINATION IN YOKOHAMA AND NAGASAKI, JAPAN.
+
+ In the Kanagawa Ken, in which Yokohama is located, the following
+ ordinances relating to the extermination of rats have been enacted:
+
+
+ _Kanagawa Ken Ordinance No. 64 of 1902 (issued October 8)._
+
+ Finders of dead rats within the prefecture shall immediately report
+ and deliver same to the nearest police, village, or other
+ authorities in charge. Upon receipt thereof, the police or other
+ authorities shall without delay transmit the same to the police
+ headquarters (Yokohama).
+
+ _Kanagawa Ken Ordinance No. 45 of 1903 (issued June 26)._
+
+ Finders of a dead rat or capturers of a live rat shall report and
+ deliver the same within twelve hours to the police, mayor, medical
+ inspector or officer, antiplague committee, or officer in charge of
+ the Hygiene Guild.
+
+ Violation of the foregoing shall be punishable either by a fine or
+ detention in jail.
+
+ _Kanagawa Ken Ordinance No. 63 of 1907 (issued June 8)._
+
+ Persons who plan or are engaged in the importation of rats from
+ without into the city of Yokohama, or persons who plan to breed rats
+ in the said city, shall be punished by detention in jail or by a
+ fine.
+
+ _Extract from Kanagawa Ken Ordinance No. 14 of 1907, relating to
+ supervision over storage and warehouses (issued March 6)._
+
+ ARTICLE 1. The term “storage and warehouses,” hereinafter mentioned,
+ shall mean and include any godown, storage or storehouses, or
+ warehouses, used by storage or warehouse companies, individuals,
+ forwarding agents or express companies, wholesale dealers, works and
+ factories, wherein cotton, cereals, or grains, flour, peanuts,
+ beancake, and other pressed oil cakes, cocoons, feathers, leather,
+ old or waste cotton, old straw, bags, etc., are stored and kept.
+
+ ART. 8, sec. 1. Owners of a storage or warehouse shall exercise at
+ least four times a year a rigid and thorough method of house
+ cleaning and rat destruction in the storage or warehouse. The date
+ and time of cleaning shall be reported to the police, to whose
+ satisfaction and approval the cleaning must be carried out.
+
+ ART. 8, sec. 2. Owners of a storage or warehouse shall furnish and
+ always keep at each doorway a suitable rat trap, and shall always
+ endeavor to exterminate rats or pursue such method of extermination
+ as may be directed by the police.
+
+
+ In forwarding the above ordinances, Vice-Consul Babbit stated that
+ vessels engaged in foreign trade, when deemed advisable by the harbor
+ authorities, are required to endeavor to exterminate the rats on board
+ by sulphur fumigation or other effective methods, as are also
+ coastwise vessels.
+
+ To encourage the extermination of rats, the mayor of Yokohama was
+ authorized by the city council to pay bounties, the rate being 3 sen
+ (1½ cents) each. The vice-consul states that in addition to this
+ purchase price a ticket is given for a lottery, and for each 60,000
+ rats 156 prizes, amounting to a total of 1,000 yens are given by the
+ city.
+
+ In a table giving the number of rats purchased and sent to the hygiene
+ bureau for bacteriological examination, it is seen that for the year
+ ending December 31, 1908, 447,981 were received.
+
+ In Nagasaki the municipal council passed an ordinance January 6, 1906,
+ as follows:
+
+
+ 1. Rats to be purchased are of two kinds—house and field rats—and
+ they must be either caught or found dead within this city.
+
+ 2. A bounty of 3 sen (1½ cents) shall be paid for each rat with a
+ ticket, to be cashed on presentation.
+
+ 3. Such tickets, to be cashed, must be presented at the city office
+ within thirty days from the date of issue.
+
+ 4. Rats shall be purchased at the city office, police stations,
+ branch police stations, police boxes, or by city officials, who go
+ around for such purpose, by giving a ticket to be cashed upon
+ presentation, provided that distinction must be made between a rat
+ caught and one found dead.
+
+
+ In transmitting a copy of this ordinance Consul G. H. Scidmore stated
+ that it was issued in accordance with the infectious diseases law of
+ Japan, No. 36, of March, 1897, which provides that cities, towns, and
+ villages shall make all necessary arrangements relating to the
+ extermination of rats as may be ordered by the prefectural governors.
+
+ He also stated that when the above ordinance was decreed the mayor of
+ Nagasaki issued detailed instructions regarding its enforcement. The
+ ordinance was enforced from the time of its enactment until July 7,
+ 1908, when the city ceased paying bounties; from January 13, 1908, to
+ July 7, 1908, 980.33 yen ($488.20) having been expended, and 30,767
+ rats having been destroyed.
+
+
+ RAT EXTERMINATION IN LOURENÇO MARQUEZ, EAST AFRICA, AND MADAGASCAR.
+
+ In Lourenço Marquez, Consul W. S. Hollis states that a disinfecting
+ barge is maintained, and requisitioned from time to time by vessels,
+ by which means considerable numbers of rats are destroyed.
+
+ He also states that the last efforts to destroy rats on shore were
+ made during the plague outbreak in November and December, 1907.
+
+ In a circular accompanying Provincial Decree No. 754 of the
+ governor-general, the following relates to the destruction of rats:
+
+
+ 1. For the destruction of rats we advise the public to make use of
+ poison paste.
+
+ 2. These may be obtained by requisition on the municipal chamber and
+ from police stations.
+
+ 3. The paste furnished shall be divided into portions and
+ distributed in different parts of the dwellings.
+
+
+ In Provincial Decree No. 737, issued December 11, 1907, by the
+ governor-general, it is required that grain and forage warehouses and
+ stables be provided with cement floors, and that ventilators be
+ provided with wire screens sufficiently fine to prevent the access of
+ rats, and that interior doors and salient angles be provided with
+ metallic points to prevent the climbing and entrance of rats.[CN]
+
+Footnote CN:
+
+ Cases of pest in Lourenço Marquez, official report.
+
+ In Provincial Decree No. 48, issued by the governor-general January
+ 30, 1908, it is proposed among other things to establish a permanent
+ service for the capture and bacteriological examination of rodents in
+ the city and its suburbs.
+
+ In transmitting the publication containing copies of these decrees the
+ consul stated that by the end of February, 1908, the campaign against
+ rats was relaxed, and since then nothing had been done to continue the
+ work of extermination.
+
+ In Tamatave, Madagascar, and other ports of that island no efforts
+ were being made to exterminate rats, and the American consul reported
+ that there were no municipal or colonial laws or regulations directing
+ such action.
+
+
+ RAT EXTERMINATION IN CAPE TOWN, SOUTH AFRICA.
+
+ In a report dated January 20, 1909, Dr. A. J. Gregory, medical officer
+ of health for the colony, states that at present no persons are solely
+ employed on rat catching, but the sanitary staff is required to take
+ all possible measures to reduce the rodent population. By the use of
+ bird lime a very large number of rats have from time to time been
+ destroyed. Doctor Gregory also refers to experiments made to determine
+ the value of tar and funnels placed on ropes to prevent the access of
+ rats to ships. The experiments were made to simulate actual conditions
+ that would prevail at ships lying at docks. It was found that thickly
+ coating a rope with fresh tar had not the slightest deterrent effect
+ on rats passing along. Funnels of a less diameter than 20 inches were
+ equally unsuccessful, and it was thought the experiments proved the
+ fallacy of trusting to tarred ropes or to disks of a workable diameter
+ being able to prevent rats from migrating in either direction between
+ shipping and shore.
+
+
+ RAT EXTERMINATION IN ALEXANDRIA AND CAIRO, EGYPT.
+
+ In Alexandria, Consul D. R. Burch stated that measures for the
+ extermination of rats were practiced; that the cost of disinfection
+ was defrayed by the municipality, which also supplied rat traps and
+ poison.
+
+ In Cairo rat destruction was being practiced, but it was stated that
+ the results could not be described as encouraging.
+
+
+ EXTERMINATION OF RATS IN THE PORT OF CONSTANTINOPLE.
+
+ Consul-General E. H. Ozmun, at Constantinople, states that while no
+ special measures have been taken to exterminate rats in that city, the
+ sanitary administration of the Ottoman Empire has provided measures
+ for the destruction of rats and mice on all vessels arriving from
+ places contaminated with plague, and he has furnished the following
+ copy of instructions concerning vessels which have or have not
+ undergone disinfection in view of destroying rats and mice on board:
+
+
+ ARTICLE 1. Vessels coming from places contaminated with plague and
+ which have not been disinfected either in the port of departure or
+ in an intermediary port during voyage, for the destruction of rats
+ and mice on board, according to the regulations of the superior
+ council of health, shall undergo their disinfection in the lazaretto
+ while finishing their quarantine.
+
+ ART. 2. Vessels coming from places contaminated with plague provided
+ with a certificate stating that the aforementioned disinfection has
+ been undergone may, after their admission, work in the port but
+ without landing on the quay.
+
+ ART. 3. Vessels proceeding from an uncontaminated Ottoman or foreign
+ port and which are provided with the certificate mentioned in
+ article 2 shall be free to moor at the quay if it is proved that the
+ vessel has been disinfected within a period of forty days; if not,
+ the vessel will operate in the port or at anchor.
+
+ Vessels in a similar case not provided with this certificate but
+ which can prove by the journal of the vessel that they have not
+ sailed within a period of four months to a contaminated port shall
+ be authorized to moor at the quay.
+
+ ART. 4. Vessels mooring at the quay must be at a distance of from 1
+ to 2 meters (39⅓ inches to 78¾ inches) maximum. During night they
+ must draw up the gangways and ladders, and must leave no towline
+ suspended without protecting it with funnels, brush wood, etc.
+
+ The vessels working in the harbor must also protect their towlines
+ in the same manner.
+
+ It is prohibited for lighters and boats to remain attached to these
+ vessels during the night outside of the time for working.
+
+ ART. 5. The above-mentioned vessels, mooring at the quay and on the
+ way to an Ottoman port, shall be required after having finished the
+ loading and discharging of cargo, to pass through the disinfection
+ prescribed by article 1 if their certificate of disinfection
+ mentioned by article 3 is found to be out of date, and also as long
+ as the city of Constantinople shall be considered as contaminated.
+
+ ART. 6. Vessels coming from uncontaminated quarters, although not
+ under any restraint, are free to go to any lazaretto in the Empire
+ and ask to be disinfected according to article 1; the latter will
+ work without delay so as to prevent loss of time as much as
+ possible.
+
+ ART. 7. The expenses of disinfection are to be paid by the vessels
+ disinfected.
+
+ ART. 8. Captains, doctors, or any officers of vessels are expected
+ to furnish the sanitary authorities with all information asked for
+ relating to the presence of rats and mice on board the vessel.
+
+
+ RAT EXTERMINATION IN RUSSIAN PORTS.
+
+ In Vladivostok, according to Consul Lester Maynard, the only efforts
+ to exterminate rats were made by the commissary department of the
+ army. Poisons, which had for their active principle caustic lime, were
+ distributed but were not entirely satisfactory, as the baits were not
+ sufficiently tempting food.
+
+ The keeping of cats had been recommended as the best method of
+ exterminating rodents, and it had been suggested that skunks, weasels,
+ and similar animals should not be killed, as they are the best
+ destroyers of rats and mice.
+
+ In Riga and Libau there were no laws and regulations prescribing a
+ systematic extermination of rats. The consul reported that only in
+ case of plague did the sanitary authorities order a thorough
+ destruction of rats not only on ships but also in warehouses and
+ private dwellings. The steamship companies, however, were said to
+ employ rat poison on their vessels, and, in addition, the ships were
+ thoroughly disinfected by means of sulphur fumes several times a year.
+
+ In Odessa it was reported by Consul J. H. Grout that the public health
+ officers of the port had been fully alive to the importance of
+ exterminating rats in order to prevent plague. In 1901 a systematic
+ extermination of rats on board vessels had been inaugurated, and in
+ 1902 this practice was extended to include all vessels leaving the
+ port. The agent used in this process was the burning of sulphur in
+ specially designed iron containers. In 1902, 2,054 rats were killed in
+ 346 vessels. In 1903, 1,038 rats were killed in 68 vessels. In 1904,
+ 17,074 were killed in 168 vessels. In 1905, 512 rats were killed in
+ 166 vessels. In 1906, 553 rats were killed in 188 vessels. In 1907,
+ 1,887 rats were killed in 135 vessels; and in 1908, 1,138 rats were
+ killed in 97 vessels.
+
+ In St. Petersburg and vicinity no consistent effort, according to the
+ consul, had been made to exterminate rats, but at Cronstadt the port
+ authorities had experimented with ratin.
+
+
+ DESTRUCTION OF RATS IN TRIESTE, AUSTRIA.
+
+ All vessels arriving at Trieste from plague-infected countries on
+ board of which rats appeared in abnormal numbers were disinfected with
+ sulphur in accordance with rules of the Paris convention of 1903.
+ Consul G. M. Hotschick stated that it was a rule, whether rats were
+ numerous or not, to disinfect every vessel every six months so as to
+ exterminate rats on board. An exception was made in the case of the
+ Austrian Lloyd steamships plying between Trieste and the Far East,
+ these vessels being disinfected by the Clayton apparatus. All attempts
+ to destroy rats along the port shore had proven fruitless, according
+ to the consul, but in custom warehouses cats were kept, thus limiting
+ the number of rats.
+
+ The rules applying to Trieste extended to all the ports of Austria.
+
+
+ DESTRUCTION OF RATS IN GENOA, ITALY.
+
+ The methods employed at Genoa for the extermination of rats found on
+ ships were those prescribed by the ministry of the interior at Rome in
+ accordance with the Sanitary Convention of Paris.
+
+ As stated by Consul-General J. A. Smith, the regulations place all
+ ships arriving from plague-infected ports into three categories, as
+ follows: Infected, suspected, and noninfected. On ships coming under
+ the first two headings all rats must be destroyed previous to the ship
+ being allowed to pass quarantine. Noninfected ships were subject to
+ the same regulations only in case of an unusual mortality among rats
+ aboard, or in case of an excessive number of them being found on board
+ on arrival, which, in the opinion of the port medical officer,
+ required their destruction. Sulphur was used as the agent of
+ destruction, the gas being generated in a special apparatus. This
+ apparatus had been installed in the ports of Naples, Genoa, Messina,
+ Brindisi, Venice, and Asinara.
+
+ Further regulations of the ministry provided for the means to be
+ employed in preventing rats from reaching shore.
+
+
+ RAT DESTRUCTION IN BARCELONA, SPAIN.
+
+ In Barcelona Vice-Consul-General Wm. Dawson, Jr., reported that the
+ officials in charge of public health measures attached no really great
+ importance to the destruction of rats as an effective means of
+ preventing the spread of plague. Several attempts, however, had been
+ made to kill rats, which invade Barcelona to an enormous extent. In
+ his report the vice-consul further stated that bacterial cultures
+ known as _Tifus ratoso_, and supposed to have given excellent results
+ in Formosa, had been tried without appreciable results on wild rats.
+ He further stated that wheat boiled in a 5 per cent solution of
+ corrosive sublimate, dried in the air, and spread in sewers and other
+ places, had proved the most effective means of killing a few thousand
+ of them, but this practice had not been carried out to any great
+ extent nor for any length of time.
+
+
+ RAT DESTRUCTION AT FRENCH PORTS.
+
+ In Marseille the following was the practice as reported by the
+ director of the maritime health service at that port and forwarded by
+ Consul-General H. L. Washington:
+
+
+ The obligatory destruction of rats in all French ports is enforced
+ by virtue of a decree dated May 4, 1906. This applies: (1) To all
+ vessels arriving from a port regarded as contaminated by plague or
+ having only touched at such port. (2) To all vessels having received
+ in transshipment—that is to say, from ship to ship—merchandise
+ originating in a country deemed contaminated by plague. The
+ destruction of these animals is carried out exclusively by means of
+ apparatus whose efficacy has been recognized by the Superior Council
+ of Hygiene of France.
+
+ The devices employed at Marseille are:
+
+ (1) The “Marot,” adopted June 19, 1905. This apparatus utilizes
+ liquid sulphurous anhydrite, which is slackened, diluted in the air,
+ and subjected or not to the action of the electric spark. The gas is
+ introduced into the vessel by means of a ventilator at a rate of
+ from 25 to 30 meters per minute (82.02 to 98.42 feet).
+
+ (2) The “Gauthier-Deglos,” adopted February 18, 1907. This method
+ requires the combustion in an oven of a mixture of sulphur and coal
+ dust. A ventilator withdraws air from the vessel and causes it to
+ pass over the mixture in combustion; the gas thus produced is cooled
+ and then introduced into the vessel. A third device, known as the
+ “Clayton,” in use in some of the French ports, also operates from
+ time to time in Marseille on such vessels as are provided with it,
+ but it does not exist in the port itself. The principle of this
+ device is based upon the combustion of sulphur, its transformation
+ into sulphurous sulphuric gas, the cooling of the gases leaving the
+ oven, aspiration of the exterior air or the air in the holds of
+ vessels, and introduction into the holds by means of a powerful
+ ventilator.
+
+ With all three systems, the ships’ holds are opened only after they
+ have been in operation for three hours.
+
+
+ In Bordeaux, according to the consul, contracts had been entered into
+ between the Government and a private individual for the extermination
+ of rats on all ships coming from plague-infected ports, the apparatus
+ employed being that in use at Marseille.
+
+ In Havre the extermination of rats on vessels from plague-infected
+ ports was reported by Consul A. Gaulin as being systematically carried
+ out in accordance with a ministerial decree of May 4, 1906, which is
+ as follows:
+
+
+ ARTICLE 1.—The destruction of rats, or “deratization,” effected
+ exclusively by means of apparatus the efficiency of which has been
+ recognized by the Superior Council of Public Hygiene of France, is
+ obligatory for admission into French ports:
+
+ 1. Of every ship coming from or having called at a port considered
+ as being contaminated with plague.
+
+ 2. Of every vessel having taken in transshipment—that is to say,
+ from one vessel to the other—more than 50 tons of merchandise coming
+ directly from a country considered as being contaminated by the
+ plague.
+
+ The above provisions are applicable to vessels having already
+ discharged a part of their cargo in one or several foreign ports.
+
+ ART. 2.—May be exempt from deratization:
+
+ 1. Vessels which only land passengers in French ports without
+ docking and which sojourn only several hours.
+
+ 2. Vessels making a call of less than twelve hours and discharging
+ less than 500 tons of merchandise, on condition that the
+ surveillance of discharging be accomplished during the day
+ exclusively, the ship being moored away from the quays, and the
+ hawsers provided with rat guards.
+
+ 3. Steamships which shall not have called at any port considered as
+ being contaminated by the plague for sixty days since their
+ departure from the last contaminated port, and on board of which
+ there shall have been observed nothing of a suspicious sanitary
+ nature.
+
+ 4. Vessels which, having called at a port considered as being
+ contaminated by the plague, will prove that they neither berthed
+ alongside the quay or landing stages, nor embarked merchandise.
+
+ 5. Vessels which have undergone the process of deratization in a
+ foreign port subsequent to their departure from the last port
+ considered as being contaminated. It must be proven, in this case,
+ that nothing of a suspicious sanitary nature has taken place on
+ board during the voyage, and that the deratization has been effected
+ with the same apparatus and the same guarantees as in France. The
+ captain of the vessel shall deliver as proof to the sanitary
+ authorities a certificate mentioning the apparatus employed, the
+ conditions under which the operation was effected, the verifications
+ made, etc., and a certificate viséed by a French consular officer.
+
+ 6. Vessels whose status is that indicated in paragraph 2 of article
+ 1, on condition that the merchandise has been transshipped from a
+ vessel which has been deratized under the conditions prescribed in
+ the preceding paragraph, and if such merchandise is accompanied by a
+ certificate of deratization provided for in said paragraph.
+
+ ART. 3.—Shall be considered as merchandise, for the application of
+ the present decree, all products embarked, figuring or not figuring
+ on the manifest, the only exception being coal embarked for the
+ needs of the ship without touching the quay.
+
+ ART. 4.—Deratization may be effected during the voyage by any French
+ ship having a surgeon, and one of the machines prescribed by article
+ 1.
+
+ The sanitary official at the port of arrival shall determine, upon
+ examining the documents presented and the proofs furnished, the
+ conditions under which the operation has been effected, and he may
+ exact a total or partial renewal of the same.
+
+ The same provisions are applicable to foreign vessels, by virtue of
+ reciprocity, on the twofold condition that the sanitary officials of
+ the one (nation) enjoy the same standing as French sanitary
+ officials, and that the apparatus used are the same as those
+ mentioned in article 1.
+
+ ART. 5.—In ports, the deratization is effected before the unloading
+ of the ship.
+
+ The operation comprises the holds, bunkers, storerooms, crew’s
+ quarters, emigrants’ quarters or compartments for third and fourth
+ class passengers, and, in general, all interior compartments of the
+ ship.
+
+ The officers’ cabins, and those of first and second class
+ passengers, as well as the dining rooms, and saloons which are
+ provided for them, are not subjected to deratization except in cases
+ where the sanitary official judges it necessary—notably when the
+ ship is suspected of being or is infected by plague, when it has
+ been observed that the malady exists among the rats on board, or
+ when there has been a death from unusual causes.
+
+ ART. 6.—The apparatus to be employed for the deratization, by virtue
+ of article 1, are placed at the disposal of the owners or agents,
+ according to the conditions approved by the sanitary authority.
+
+ Ports possessing one of these machines are alone open to vessels
+ coming from countries considered as being contaminated by plague.
+
+ The operations are effected under the permanent supervision of the
+ sanitary authority and with the least possible delay.
+
+ ART. 7.—The expenses of deratization are borne by the owners, in
+ conformity with the provisions of article 94 (last paragraph) of the
+ decree of January 4, 1896. No sanitary tax is due, in consequence,
+ for the operation.
+
+ ART. 8.—The expenses considered in article 7 are based on the gross
+ tonnage of the ship, if the deratization comprises all its parts,
+ and on the cubic capacity of the parts deratized, if the operation
+ is partial. The cubic capacity is determined by and from the plans
+ of the ship, without allowing for the space actually occupied by
+ merchandise.
+
+ ART. 9.—A certificate setting forth the conditions under which the
+ operation has been effected is delivered to the captain or owners by
+ the sanitary authority.
+
+ ART. 10.—Ships which are not necessarily subject to the requirements
+ of deratization may, upon their request, be subjected to this
+ operation upon their departure, as on their arrival, either with
+ full or empty holds, and obtain, in consequence, the delivery of the
+ certificate mentioned in article 9. Every facility should be
+ accorded them for this purpose.
+
+ ART. 11.—Violations of the provisions of the present decree are
+ punishable by the penalties set forth in article 14 of the law of
+ March 3, 1822, independently of the measures taken for the isolation
+ or other measures to which ships are subjected by reason of their
+ origin or the sanitary condition on board at the time of arrival.
+
+ ART. 12.—Are annulled, the decree of September 21, 1903, and the
+ provisions of the decree of September 23, 1900, which would be at
+ variance with the second paragraph of article 6 above cited.
+
+ ART. 13.—The minister of the interior is charged with the execution
+ of the present decree, which shall be published in the Official
+ Journal, inserted in the Bulletin of Laws, and posted in the ports.
+
+
+ DESTRUCTION OF RATS IN GERMAN PORTS.
+
+ In Hamburg, according to Consul-General R. P. Skinner, stationed at
+ that port, persistent efforts were being made to exterminate rats not
+ only on board ship but in the city itself, and he reported the
+ following method of procedure:
+
+
+ Upon the arrival of every vessel an inspecting officer employed by
+ the board of health boards the same to inquire whether, during the
+ voyage, rats have died in exceptionally large numbers. While in port
+ the vessel is visited almost daily by inspectors, who search for
+ dead rats, particularly in the holds. On vessels from such ports
+ whence plague-infected rats have been brought to Hamburg repeatedly
+ an officer of the board of health is posted on board constantly to
+ watch the discharging of the cargo. All dead rats found are
+ immediately delivered to the Hygienic Institute; and if the latter’s
+ bacteriological examinations give reason to suspect plague, the
+ discharging is immediately discontinued and communication with the
+ shore interrupted. The vessel’s crew and discharging gangs are
+ placed under medical observation for a period of five days, the
+ cargo compartments are treated with generator gas, so as to
+ exterminate all rats, and, after the quarantine has been
+ discontinued and the cargo discharged, all compartments are
+ carefully disinfected. For the purpose of treating infected ships by
+ means of generator gas the Hamburg government owns a special
+ disinfection ship, called the _Desinfektor_, which will be described
+ later.
+
+ In order to exterminate rats on ships frequenting the port of
+ Hamburg the master of every vessel arriving here receives the
+ following instructions from a representative of the health officer
+ of the port:
+
+ He shall cause rat poison to be laid and fumigate holds by means of
+ sulphur and charcoal as soon as the cargo has been discharged, not
+ less than 10 kilos (22 pounds) of sulphur and 20 kilos (44 pounds)
+ of charcoal to be used for a room of 1,000 cubic meters (1,308 cubic
+ yards). Such rooms must be kept closed at least ten hours. On ships
+ arriving from ports infected with plague, rat poison is laid, free
+ of charge, immediately upon arrival, by an employee of the municipal
+ disinfection establishment, at all places within reach. On all other
+ ships the laying of rat poison is done by private persons whose
+ charges are payable by the vessel’s master or owner.
+
+ The disinfectors employed by the State of Hamburg use principally a
+ rat poison called “Rattengiftspeise,” consisting chiefly of
+ phosphorus and squills. Private rat killers may choose any other
+ material, but from time to time samples of such poisons as are laid
+ out on ships are taken by order of the harbor surgeon, and rats kept
+ in the public laboratories are fed with them, to enable a control as
+ to the effectiveness of the poison.
+
+ Under special circumstances the harbor surgeon is authorized to
+ waive the requirement of fumigation.
+
+ Killed rats are not permitted to be thrown overboard, but must be
+ delivered to the nearest police station, which causes their
+ cremation.
+
+ On river barges rat poison is laid by official disinfectors every
+ three months.
+
+ Finally there is rat poison laid, from time to time, in warehouses,
+ cargo sheds, and trade establishments in the harbor, partly by
+ official disinfectors and partly by private rat killers, which is
+ regularly controlled by the harbor surgeon, a special officer of his
+ department being engaged for such purpose.
+
+ The ship called the _Desinfektor_, owned by the government of
+ Hamburg for the purpose of disinfecting ships arriving from infected
+ ports and for the extermination of plague infected rats, is a
+ steamer equipped with a generator gas apparatus and other
+ disinfecting facilities. The method of using generator gas has been
+ chosen for reasons which are described in a booklet issued some time
+ ago by the local board of health on this subject.
+
+
+ In respect to the extermination of rats in Hamburg, aside from the
+ system adopted for ships and in the harbor, the consul-general states
+ that efforts to this end are being successfully carried out by
+ official disinfectors by order of the board of health, and he refers
+ to the procedures as follows:
+
+
+ If it becomes known to the board of health that in any locality or
+ group of buildings there are rats in large quantities, rat poison is
+ immediately laid. For such purpose the above-mentioned
+ Jungclaussen’s preparation is almost exclusively used. The several
+ local citizens’ associations (Bürgervereine), at the meetings of
+ which all topics of interest are discussed, contribute largely to
+ the bringing to the knowledge of the proper authorities of all
+ matters a remedy of which is, in public interest, considered
+ necessary, among them rat and mice nuisances in the several
+ districts of the city. Of late the board of health has also begun to
+ lay rat poison in houses in the old parts of the city, employing the
+ house-to-house method, and rat poison is laid, from time to time in
+ sewers and other underground canals where rats usually congregate in
+ large numbers.
+
+ As the laying of rat poison at or in the vicinity of places where
+ domestic animals are kept is dangerous to the latter, the Hamburg
+ board of health has only shortly ago caused a small gas generator to
+ be constructed, similar to that on the _Desinfektor_. The apparatus
+ can easily be removed from one place to another, and is chiefly to
+ be used on yards or unimproved lots, public parks, zoölogical
+ gardens, etc., where rats live under the ground. In fumigating such
+ a rat nest, all holes leading out of it are closed with earth,
+ except two. The hose of the gas apparatus is introduced into one of
+ the holes and gas insufflated. The majority of rats in the hole are
+ dead before being able to reach the fresh air. Those succeeding in
+ doing so, by getting out of the one open hole, are so dizzy that
+ they can easily be killed with a club. Only a few experiments have
+ so far been made with this apparatus, but the same promises good
+ success.
+
+
+ In Bremen, according to the consul, all disinfection of vessels and
+ their cargoes was done with sulphur dioxide by means of a Clayton
+ apparatus, and vessels equipped with this apparatus, and those having
+ physicians aboard, had the advantage of being able to start
+ disinfection twenty-four hours before arrival at port, this process
+ having been recognized as sufficient compliance with the quarantine
+ laws of Germany.
+
+
+ MEASURES AGAINST RATS AT THE PORT OF ROTTERDAM.
+
+ In the report from Consul-General S. Listoe it was stated that the
+ extermination of rats had not been officially undertaken by the
+ authorities of Rotterdam, either in the port or aboard incoming ships.
+ The question had been investigated, however, and the harbor master had
+ strongly advised the installation of a fumigating machine, which would
+ be installed on one of the numerous river police boats. Ship owners
+ had, for their own protection, caused their ships to be occasionally
+ fumigated, and two of the well-known lines had fitted out some of
+ their steamers with fumigating apparatus.
+
+
+ DESTRUCTION OF RATS AT ANTWERP, BELGIUM.
+
+ Consul-General H. W. Diedrich stated that no official action had been
+ taken in the port of Antwerp for the extermination of rats, but that
+ every vessel entering the port had to pass the sanitary station at
+ Doel, and there was authority to hold up any suspected vessel and to
+ insist on fumigation for the destruction of rats.
+
+
+ DESTRUCTION OF RATS IN DENMARK.
+
+ As a result of the agitation started in 1898, the following law was
+ passed and signed by the King of Denmark on March 22, 1907:
+
+
+ 1. When an association constituted for the purpose of effecting the
+ systematic destruction of rats has proved to the satisfaction of the
+ minister of the interior that it is in a position to expend on the
+ furtherance of its objects, within a period of three years, a sum of
+ not less than 10,000 kroner per annum, it shall become incumbent
+ upon each local authority to make suitable arrangements at the
+ expense of the local funds, and commencing with a date to be made
+ known hereafter by the minister of the interior, for the reception
+ and the destruction of all rats killed within the district of such
+ authority and delivered up to such authority.
+
+ For each rat delivered up each local authority shall pay a premium,
+ for the payment of which an annual grant shall be made out of the
+ local funds, which shall be not less than three kroner per each
+ hundred inhabitants within the district of each local authority,
+ according to the then last general census.
+
+ The State shall make for a period of three years an annual grant of
+ 30,000 kroner, of which one-third may be expended on scientific
+ experiments with preparations for the extermination of rats, under
+ the control of, and in consultation with, the Royal Veterinary and
+ Agricultural College, while the remainder shall be expended on
+ purchasing preparations for the extermination of rats, which shall
+ be either employed on or in public lands or buildings, or out of
+ which remainder grants may be made to associations toward the
+ purchase of such preparations, in a manner to be defined hereafter
+ by the minister of the interior.
+
+ 2. Each local authority shall fix the amount of the premium (sec. 1)
+ which shall not, however, be more than 10 oere or less than 5 oere.
+
+ Instructions for the collection and destruction of the rats killed
+ will be issued by the minister of the interior.
+
+ 3. The association cited in section 1 shall submit for the sanction
+ by the minister of the interior at the beginning of each year a plan
+ showing the proposed expenditure, and at the end of each year an
+ account of the money expended by it, together with statistics
+ obtained by it showing the expenditure on premiums made by each
+ local authority.
+
+ 4. Where the proprietor or occupier of a messuage has participated
+ in the grant to be made by the State (sec. 1), he shall not deliver
+ up, or cause to be delivered up, for the purpose of obtaining a
+ premium or premiums, rats killed within the said messuage, until the
+ expiration of one month from the employment of such preparation for
+ which such grant has been made. Any person acting in contravention
+ of this section shall be liable to a penalty of 100 to 500 kroner.
+
+ 5. Any person who preserves or breeds rats or imports rats from
+ abroad, in order to obtain premiums or enable another person to
+ obtain them, shall be liable to a penalty of 100 to 500 kroner,
+ unless he is liable to a higher penalty under the common law. A
+ person who shall deliver up rats knowing them to have been
+ preserved, bred, or imported for the purpose of obtaining a premium
+ shall be liable to the same penalties.
+
+ All proceedings under this act shall be taken in a public police
+ court, the fines to go to the special funds provided by this act, or
+ where such fund does not exist, to the public funds of such local
+ authority.
+
+ Any person delivering up rats to any other local authority than to
+ that within the district of which they have been caught shall be
+ liable to a penalty not exceeding 100 kroner.
+
+ This act shall come into operation on a date to be fixed hereafter
+ by the minister of the interior and remain in operation for three
+ years.
+
+ In the session of the Riksdag immediately preceding the expiration
+ of this law a vote shall be taken for the renewal or revision of
+ this law.
+
+ The Government is authorized by royal rescript to make such
+ alterations in the operations of this law within the Faroe Islands
+ as may be considered most suitable, having regard to the special
+ conditions obtaining within those islands.
+
+
+ Following the enactment of this law, there was issued by the ministry
+ of the interior May 1, 1907, a circular to the local authorities on
+ the subject.
+
+
+ CIRCULAR TO THE LOCAL AUTHORITIES.
+
+ Whereas the Association for the Authorized Extermination of Rats has
+ proved to the satisfaction of the ministry of the interior that it
+ is in a position to expend on the furtherance of its objects not
+ less than 10,000 kroner within a period of three years, it is hereby
+ requested, in pursuance of act No. 59, of the 22d March, 1907 (see
+ public notice dated this day), and commencing with the 1st day of
+ July of this year each local authority shall at its own expense take
+ all such measures as may be necessary for the reception and
+ destruction of all rats killed within the district of such authority
+ and delivered up to it. For the purpose of paying a premium for each
+ rat delivered up each local authority shall out of the common funds
+ make an annual grant which shall be not less than 3 kroner for each
+ hundred inhabitants, according to the then last general census,
+ should the amount required for the payment of premiums make such
+ grant necessary. It shall be left to each local authority to decide
+ whether further grants shall be made toward this purpose. The
+ premium to be paid for each rat delivered up shall not be more than
+ 10 oere or less than 5 oere, and shall be fixed by each local
+ authority which shall give due and sufficient notice both of the
+ date fixed for the commencement of the operations of the law and the
+ premium to be paid. As far as possible, a uniform rate of payment by
+ premium shall be fixed by local authorities within the same county.
+ Rats may not be delivered up to any local authority but to that
+ within the district of which they have been caught; any person
+ acting in contravention (par. 5 of the aforementioned law) shall be
+ liable to a penalty not exceeding 100 kroner.
+
+ The chairman of the councils of the various local authorities are
+ hereby requested to take steps for the discussion and carrying out
+ of the provisions of this law.
+
+ If the grant made by any local authority for the purposes of this
+ law should prove insufficient for the payment of premiums on all
+ rats delivered up, such authority may apply to the Association for
+ the Authorized Extermination of Rats, Colbjornsengade 14, Copenhagen
+ B, for a subsidy, this association having undertaken to organize the
+ obtaining of voluntary subscriptions for the carrying out of the
+ purposes of this act.
+
+ The said association is further prepared, at the request of local
+ authorities, to render expert assistance in commencing and carrying
+ through operations under this act.
+
+ For the collection and destruction of rats killed the ministry of
+ the interior issues the following instructions:
+
+ A.—THE LARGER TOWNS.
+
+ _Collecting depots._—The local authorities shall provide a
+ sufficient number of places suitable for collecting depots. Such
+ depots must not be within any place where food or clothing is made
+ or offered for sale. Fire brigade stations are considered most
+ suitable for collecting depots.
+
+ The collecting may suitably be done in the manner that for each
+ depot a number of receptacles are provided, made of galvanized iron
+ and furnished with a tight-fitting lid. Into these receptacles the
+ rats are to be thrown after their tails have been cut off. The tails
+ are to be kept in a separate tin box. All receptacles and boxes are
+ to be collected daily and to be replaced by empty receptacles. The
+ full receptacles are to be taken to the place where the destruction
+ of the rats is effected.
+
+ Further advice on the purchase of such receptacles and the apparatus
+ for cutting off their tails will be given by the Association for the
+ Authorized Extermination of Rats at the request of a local
+ authority.
+
+ The destruction may be effected either by cremating the dead
+ rats—for instance, at the municipal gas works—or by burying the
+ carcasses in the open, at a sufficient distance from the town,
+ unless this course is prohibited by local sanitary considerations.
+ It is recommended that the local authority act in this manner always
+ with the local health committee.
+
+ B.—THE SMALLER TOWNS.
+
+ Instead of opening a fixed depot, it would appear more suitable in
+ the smaller towns to provide a collecting cart. Any horse-drawn
+ vehicle would serve the purpose as long at it is furnished with a
+ fixed apparatus for cutting off the tails and a receptacle of
+ galvanized iron for receiving the carcasses of the rats. The vehicle
+ should also be fitted with a bell, to announce the arrival and
+ presence of the collecting cart.
+
+ The destruction of the carcasses is to be effected in the manner
+ described under A.
+
+ C.—THE VILLAGES.
+
+ The authorities in the villages shall appoint a suitable person to
+ receive the rats delivered up, for which work he shall be paid an
+ adequate remuneration. Such persons must be supplied with an
+ apparatus for cutting off the tails of rats handed in. After the
+ tails have been cut off, the rats may be buried in a suitable place
+ without delay. It is most undesirable that any person engaged in the
+ carrying of milk or other foodstuffs be asked to convey rats to the
+ persons appointed to receive them. Villages in close proximity to
+ towns are advised to make arrangements for the cremation of the rats
+ at the municipal gas works.
+
+ In the case of villages whose buildings approximate those of a town
+ it is recommended that the regulations given for towns are adopted.
+
+ Respecting the payment of the premiums it is recommended that the
+ person in charge of a collecting depot or otherwise appointed to
+ receive rats is supplied with a fixed amount of petty cash, out of
+ which he pays the premium for each rat delivered up. The tails cut
+ from the rats serve as a receipt for the payment made, so that the
+ total amount of tails will be a discharge for the total amount of
+ petty cash received and paid out in premiums.
+
+ In order to prevent abuse it is particularly requested that the
+ local authorities take care that the rat tails are destroyed in an
+ efficient manner as soon as they have served the purpose of control
+ and checking.
+
+ For the purpose of keeping satisfactory accounts the Association for
+ the Authorized Extermination of Rats has on sale specially arranged
+ account books which are recommended by the ministry of the interior.
+
+ As in accordance with paragraph 3 of the law of 22d March, 1907, it
+ is the duty of the Association for the Authorized Extermination of
+ Rats to submit to the ministry of the interior a report on the money
+ expended in the whole of the kingdom on such premiums, the local
+ authorities are hereby desired to make a quarterly return to the
+ aforementioned association on the number of rats killed within the
+ district of each authority in each month of the quarter covered by
+ such return and on the money paid out for premiums. Forms for such
+ returns will be supplied by the association.
+
+ Any associations which in accordance with terms of paragraph 1 of
+ the law of 22d March, 1907, desire to participate in the grant made
+ by the State for the purpose of purchasing preparations for the
+ extermination of rats (ratin, etc.) must send a request to that
+ effect to the minister of the interior, together with a statement
+ showing the approximate cost of the proposed campaign and the amount
+ at the disposal of the association for that purpose. As this law is
+ essentially of an experimental character, the requests of all such
+ associations will be treated as preferential, which show that the
+ proposed extermination may be easily and successfully effected (as,
+ for instance, on small islands).
+
+ A number of copies of this circular will be forwarded to each local
+ authority.
+
+
+ DESTRUCTION OF RATS IN SWEDISH PORTS.
+
+ Consul W. H. Robertson at Gothenburg, Sweden, quoted the city
+ physician to the effect that “upon the appearance of plague in Great
+ Britain the city council decided in April and November, 1901, to make
+ an appropriation of $2,680 for an attempt to reduce the number of rats
+ within the community.” These attempts were continued during the period
+ May, 1901, to September, 1902, 2.68 cents being paid for each rat
+ caught. Any unusual mortality among rats on board a vessel coming from
+ a plague-infected port was being dealt with in accordance with a royal
+ proclamation of June 16, 1905.
+
+ In Malmo, according to the consular agent, the authorities during the
+ past seven years had given a premium for every rat killed during the
+ first five years, 2.68 cents for each rat, but during the past two
+ years only half of that amount.
+
+
+ DESTRUCTION OF RATS IN ENGLISH PORTS.
+
+ The Local Government Board has issued regulations for the prevention
+ of plague and certain other diseases. One of these regulations is as
+ follows:
+
+
+ The master of a ship which by reason of plague is an infected ship,
+ or a suspected ship, or which has come from, or has during the
+ voyage called at, a port infected with plague, or in which there are
+ rats infected with plague, or in which there is or has been during
+ the voyage an unusual mortality among rats, shall, under the
+ direction and to the satisfaction of the medical officer of health,
+ take all such precautions or employ all such means for effectually
+ stopping the access of rats from the ship to the shore as in the
+ opinion of the medical officer of health are measures reasonably
+ necessary for the prevention of danger arising to public health from
+ the ship.
+
+
+ In accordance with this regulation, notice was given in a circular
+ issued by the medical officer of health of the port of London of the
+ precautions necessary for stopping the access of rats from ship to
+ shore in that port. These precautions were outlined as follows:
+
+
+ 1. All ropes and mooring tackle for securing the vessel either to
+ the shore or mooring buoys shall be fitted with metal brushes,
+ funnels, or other effective guards, the portions of such ropes and
+ mooring tackle leading from the vessel to a distance from the
+ vessel’s side of at least 4 feet shall be coated each night with
+ fresh tar. Ropes may, if desired, be protected by a covering of
+ canvas or yarns before tarring.
+
+ 2. When not engaged in discharging cargo, one gangway only shall be
+ permitted to afford means of communication between the ship and the
+ shore.
+
+ 3. The end of the gangway near the ship shall be whitened for a
+ length of 10 feet, and the watchman shall keep the gangway pulled
+ inboard after sunset, or it shall be guarded in some approved
+ manner.
+
+ 4. When alongside the quay, the ports on the side of the vessel
+ nearest the quay shall be kept closed after sunset.
+
+ 5. All empty cases and barrels, especially those from the
+ storerooms, shall be examined before being landed, to insure that no
+ rats are contained therein.
+
+ 6. It is recommended that all possible means be adopted for catching
+ and destroying rats, both on the voyage and during the stay of the
+ vessel in port. Any rats so caught shall be killed, then placed in a
+ bucket of strong disinfecting solution, and afterwards burnt in the
+ ship’s furnace.
+
+ 7. No rats, alive or dead, are to be removed from the ship without
+ my permission in writing.
+
+
+ In London, the practice of destroying rats on the docks had been
+ systematically carried out by the dock companies at their own expense
+ and under the supervision of the port sanitary authority. Vice-consul
+ Richard Westacott reported that the destruction of rats on vessels was
+ provided for by regulation whenever the medical officer of health was
+ satisfied that such precaution against the introduction of the spread
+ of plague was necessary.
+
+ In Liverpool, Consul J. L. Griffiths stated that earnest endeavors
+ were made to capture rats by professional rat catchers. On infected or
+ suspected ships, special precautions were taken to prevent the escape
+ to the shore of rodents. On noninfected or nonsuspected ships the
+ medical officer of health might also require the destruction of rats,
+ and in this case the expense was borne by the sanitary authority. It
+ is evident, therefore, that the precautions taken are in accordance
+ with the provisions of the International Sanitary Convention of Paris.
+
+ It was the practice, at the time the consul sent his dispatch, to
+ maintain strict surveillance over vessels likely to develop plague
+ aboard until after the period of incubation had been passed.
+
+ In Southampton, according to Consul A. W. Swalm, a competent man was
+ employed by the dock authorities whose sole duty was to wage war on
+ rats. In addition, the night watchmen on all vessels were required to
+ perform the additional duty of trapping rats. The usual precautions to
+ prevent the passage of rats from ship to shore were also observed.
+
+
+ MEASURES AGAINST RATS AT AUSTRALIAN PORTS.
+
+ The following are the regulations issued under the quarantine act of
+ 1908 by the commonwealth of Australia relating to the ingress to and
+ egress from vessels of rats and mice; the destruction of rats, mice,
+ and other vermin; and precautions against the introduction of vermin
+ from plague-infested places.
+
+
+ 136. (1) The master or owner of every vessel shall—
+
+ (_a_) Effectively obstruct—against the migration of rats—by means of
+ stout wire netting, all pipes, ports, cabin scuttles, and other
+ openings or holes in the side of the vessel next to the wharf, and
+ also when cargo is being discharged into lighters, in the side next
+ to the lighters, and keep them so obstructed while the vessel is
+ alongside the wharf or lighters;
+
+ (_b_) Prevent any organic refuse, galley scraps and waste from being
+ discharged into the waters or on the wharfs of any port.
+
+ (2) The master or owner of any vessel arriving in any port in
+ Australia from any place proclaimed infected with plague, or as a
+ place from or through which plague may be brought or carried, under
+ section 12 of the quarantine act, 1908, shall—
+
+ (_a_) Produce to the quarantine officer a certificate showing that
+ an efficient fumigation of such vessel while empty had been carried
+ out prior to departure. Such certificate, in the case of an oversea
+ vessel, must (if the port of departure be within the British
+ dominions) be signed by the health officer of the port; or, when
+ such port is a foreign port, by the British consul. In the case of
+ an interstate vessel the certificate must be signed by a quarantine
+ officer. In the absence of such certificate the quarantine officer
+ may require the cargo to be discharged in the stream. Efficient
+ fumigation in this regulation shall mean fumigation as specified in
+ regulation 137 (2) _b_;
+
+ (_b_) Suspend or cause to be suspended over the side of the vessel
+ against the wharf, or against any lighter alongside, electric or
+ other effective lights, distributed so as to afford from sunset to
+ sunrise thorough illumination fore and aft along the whole side of
+ the vessel.
+
+ 137. (1) The owner or master of any vessel shall—
+
+ (_a_) Keep all foodstuffs and food refuse in rat-proof and
+ mouse-proof receptacles;
+
+ (_b_) Thoroughly flush out and afterwards empty the bilges before
+ berthing at any port;
+
+ (_c_) Keep on board the vessel a dog or a cat—or both—efficient for
+ rat and mouse killing, and give it or them constant access to those
+ parts of the vessel where rats or mice may harbor;
+
+ (_d_) Set and keep set in sufficient numbers and in suitable places
+ metal break-back traps or other effective traps for rats and mice;
+ and
+
+ (2) When so ordered by a quarantine officer, shall—
+
+ (_a_) Lay on the vessel poison baits effective for rats and mice;
+
+ (_b_) Submit the holds and other such parts of the vessel as the
+ quarantine officer directs to sulphur fumigation in accordance with
+ this regulation, or to some other method of fumigation approved by
+ the director of quarantine. Sulphur fumigation shall be effected by
+ passing sulphur fumes into the vessel under pressure, and at the
+ same time exhausting the air in the parts of the vessel under
+ fumigation, and shall be continued until all parts of the vessel
+ under fumigation are filled with a gaseous mixture of a strength of
+ not less than 3 per cent of sulphur oxides, and are kept so filled
+ for at least eight hours.
+
+ The fumigation shall, if the quarantine officer so orders, be
+ carried out in the stream or away from a wharf.
+
+ (_c_) Clean, wash, or spray all portions of the vessel likely to
+ harbor or afford shelter to vermin, with an approved insecticidal
+ solution effective for the killing of fleas, lice, bugs, and other
+ vermin; and
+
+ (_d_) Flush, cleanse, disinfect, or empty all lavatories, water
+ tanks, or any closed-in space on board the vessel, and cause to be
+ produced for disinfection any articles desired by the quarantine
+ officer.
+
+
+ In Sydney, it was stated by the president of the department of public
+ health that steady, systematic poisoning and trapping of rats were
+ done all the year round, and that this had been the case for the past
+ eight years. The experience there had been that mineral poisons were
+ found to answer best, and that organic viruses had been found to be
+ not practically successful.
+
+ In Melbourne, rat destruction was carried on by the board of public
+ health of Victoria and by the local health authorities under the
+ Victorian health act of 1890. As stated in the report of Consul J. M.
+ Jewell, the board of public health restricts its operations to
+ shipping wharves, to shores, and banks of the River Yarra upon which
+ Melbourne is situated. Since 1900, the board had had a staff of men
+ continually engaged in distributing poison baits. In order to prevent
+ the passage of rats to and from vessels, certain specific berthing
+ restrictions were in force. In addition, fumigation of vessels was
+ practiced under the supervision of the board’s officers. The board had
+ continually urged the various municipal authorities to maintain the
+ crusade against rats and render dwellings rat proof.
+
+ The consul also stated that the local municipal councils paid a bonus
+ for every rat, and that the fee was then 4 cents.
+
+ In Adelaide, it was stated there were no compulsory regulations for
+ the destruction of rats, but shipping companies had cooperated with
+ the local sanitary authorities to keep down these rodents on the
+ wharves by means of poison and traps, the poison being supplied gratis
+ by the board of health.
+
+ In Fremantle, and other seaports of Western Australia, according to
+ the consul-general, men were engaged in baiting and trapping rats,
+ these precautions being maintained throughout the year.
+
+
+ MEASURES AGAINST RATS IN SOUTH AMERICAN PORTS.
+
+ In Buenos Aires it was stated by the chief of the asistencia publica
+ that a regular staff of 150 men was employed in the destruction of
+ rats and fumigation of houses. A map of the city showing houses that
+ had been found to contain rats was marked. In addition, a pesthouse
+ was maintained in which live rats were watched, and developments of
+ pest noted.
+
+ In Montevideo Consul F. W. Goding stated that there were no organized
+ efforts for the destruction of rats, but that vessels were fumigated
+ at stated intervals under the direction of the sanitary authorities.
+ He also stated that the Government had required portions of the sea
+ wall to be covered with cement in order to prevent rats obtaining a
+ lodging there.
+
+ In Callao, Peru, provision was made for the fumigation of vessels from
+ infected ports, and it is stated by Consul-General S. M. Taylor that
+ the Government had required steamship companies to install fumigating
+ apparatus on board their passenger vessels.
+
+ It is stated by the consul that there was a new municipal law in
+ Callao calling for stone or brick 2 feet below and 2 feet above ground
+ on all walls and foundations for new buildings, and concrete floors in
+ all establishments where provisions are sold.
+
+ In Iquique, Chile, it was reported by the consul that the director of
+ the municipal laboratory disinfected houses infected with plague, and
+ sent a corps of men to poison and trap rats which might be therein.
+
+
+ MEASURES AGAINST RATS IN WEST INDIAN PORTS.
+
+ From Habana it was reported that no action had been taken by the
+ sanitary authorities toward exterminating vermin, except the
+ promulgation of a circular letter calling attention to the presence of
+ the plague in neighboring countries, and requesting citizens to free
+ their premises of rats. The same statement was also said to apply to
+ other Cuban seaports.
+
+ In Kingston, Jamaica, on account of the appearance of the plague in
+ Venezuela, the government took precautionary measures with the view of
+ exterminating rats. These steps, as reported by Vice-Consul W. H.
+ Orritt, were as follows:
+
+ A. Lectures were delivered in various centers of the island showing
+ how rats are the distributers of plague and the necessity of
+ destroying them.
+
+ B. Virus was imported, and live rats were inoculated and set free in
+ every seaport in the island.
+
+ C. Bamboo pots with poison glued to their bottoms were distributed to
+ householders and placed in the haunts of rodents.
+
+ In Santo Domingo bounties for rats were authorized May 19, 1908, by
+ the city council. In addition, rat virus had been used in considerable
+ quantity.
+
+
+ DESTRUCTION OF RATS IN PANAMA.
+
+ In Cristobal, Canal Zone, Colon, and Bocas del Toro, it was stated by
+ Consul J. A. Kellogg that the sanitary department of the Isthmian
+ Canal Commission had for some time been exterminating rats by traps
+ and poisons.
+
+ In La Boca, Canal Zone, Consul-General Arnold Shanklin stated that the
+ sanitary department of the Isthmian Canal Commission and the Public
+ Health and Marine-Hospital Service had in charge and had most
+ effectually carried on the extermination of rats, and that this
+ crusade had also been extended to the old docks and wharves in the
+ city of Panama.
+
+
+ MEASURES AGAINST RATS IN VANCOUVER.
+
+ It was stated by Consul-General George M. West, December 17, 1908,
+ that the city of Vancouver was paying a bounty of 50 cents per hundred
+ for all rats caught. The following regulations for the docking or
+ mooring of vessels arriving from plague-infected ports became
+ effective April 8, 1908:
+
+
+ 1. All vessels arriving at British Columbian ports from ports
+ infected or suspected of being infected with bubonic plague shall
+ conform to the following regulations:
+
+ (_a_) Vessels shall be moored or docked at a distance not less than
+ 6 feet from wharf or land.
+
+ (_b_) Ropes or chains connecting a vessel with wharf or land shall
+ be protected by funnels of size and shape satisfactory to local and
+ provincial boards of health.
+
+ (_c_) All gangways shall be lifted when not in use. Gangways when in
+ use shall be guarded against the exit of rats by a person specially
+ detailed for this purpose.
+
+ (_d_) All vessels changing route to solely British Columbian ports
+ shall give satisfactory evidence of disinfection and extermination
+ of vermin to provincial board of health.
+
+ 2. Every owner, agent, or captain of any vessel, and every other
+ person violating or instructing, authorizing, ordering, permitting,
+ or otherwise suffering any person to violate any of the foregoing
+ regulations, shall be liable, upon summary conviction before any two
+ justices of the peace, for every such offense to a fine not
+ exceeding $100, with or without costs, or to imprisonment, with or
+ without hard labor, for a term not exceeding six months, or to both
+ fine and imprisonment, in the discretion of the convicting
+ magistrates.
+
+ Dated at Victoria, 8th April, 1908.
+
+
+ In addition, the mayor and council of the city enacted a by law
+ November 11, 1907, one provision of which made it unlawful for any
+ boat entering the port of Vancouver to be connected with any wharf in
+ the city by a gangway which was not guarded by some person there for
+ the purpose of preventing rats from leaving such import by such
+ gangway.
+
+
+ NECESSITY OF CONCERTED ACTION OF NATIONS.
+
+ It appears from the foregoing data that a more or less widespread
+ crusade against rats is being carried on in the different ports of the
+ world, and that the extent and persistence of these measures, with few
+ exceptions, depend upon whether the particular port has been directly
+ threatened with an invasion of plague. It is necessary to state here
+ that the above data are not presented as a complete epitome of
+ measures taken throughout the world, but refer to the ports from which
+ consular reports were received.
+
+ The fact that within fifteen years plague has spread to no less than
+ 52 countries indicates that the measures taken against rats have not
+ been wholly efficient.
+
+ It is too much to expect that the rat population can ever be
+ exterminated from any country, but by the adoption of systematic
+ measures, such as are in force in Denmark, the rat population should
+ be markedly reduced, and the occurrence of plague among rodents
+ quickly detected. It is not too much to expect, however, that ocean
+ carriers could be freed from rodents and kept so, and this action
+ would confine plague within continental boundaries.
+
+ When the existing sanitary conventions were adopted several years
+ since, the importance of the subject was just beginning to be
+ recognized, but now that the rat has been proven beyond all doubt to
+ be the greatest factor in the transmission of plague from one country
+ to another it would appear that the conventions in question should be
+ amended, and the Surgeon-General of the Public Health and
+ Marine-Hospital Service, in a communication of February 26, 1909,
+ addressed to the Secretary of State, suggested the advisability of
+ submitting the question of the systematic destruction of rodents
+ aboard ships to an international sanitary conference with the view to
+ the adoption of an international sanitary regulation on the subject.
+
+ It must be apparent that such a regulation would lessen quarantine
+ restrictions, prevent the destruction of cargo by rodents, and in
+ large measure obviate the danger of the further spread of plague.
+
+------------------------------------------------------------------------
+
+
+
+
+ TRANSCRIBER’S NOTES
+
+
+ Page Changed from Changed to
+
+ 57 similar or identical to the similar or identical to the
+ affection in man known as favus affliction in man known as favus
+
+ 57 This specie of Mus is very This species of Mus is very
+ susceptible to a large number of susceptible to a large number of
+ bacterial bacterial
+
+ 59 Rabinowitch, L., ’03. Ueber ein Rabinowitch, L., ’03. Ueber eine
+ Hauterkrankung der Ratten. Cent. Hauterkrankung der Ratten. Cent.
+ f. Bact., f. Bact.,
+
+ 144 Universitat zu St. Petersburg. Universität zu St. Petersburg.
+
+ ● Typos fixed; non-standard spelling and dialect retained.
+ ● Used letters for footnotes and numbers for endnotes. Renumbered all
+ to avoid duplicates.
+ ● Enclosed italics font in _underscores_.
+ ● Subscripts are shown using an underscore (_) with curly braces { },
+ as in H_{2}O.
+
+
+
+*** END OF THE PROJECT GUTENBERG EBOOK 76630 ***
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