EEVIBW — TROPICAL MEDICINE, ETC. 161 



M. demimanus, it is noted, harbours twice as many iieas as M. rattus. Plague— 



A study of the epidemic and its relation to the epizootic showed : — 



With regard to the incidence of plague ou different classes of the population, we may note that little 

 difference, if any, exists in the liability to infection of males and femalea ; that there is a varying incidence on 

 persons of different age-periods, the greatest incidence being on persons between 11-20 years of age; and that of 

 the different races in Bombay, Hindus and Mahomedans suffer most severely from the disease. 



We may summarise our conclusions regarding the inter-relations of the epidemic and the epizootics 

 as follows:— 



1. The time-relation of the epidemic and the raltus epizootic is explicable on the view that the rat flea is the 

 transmitting agent of the infection from M. rattus to man. 



2. From the point of view of place-infection, there is an intimate relation between the epidemic and the 

 rattus epizootic. 



3. There is a definite quantitative relation between the incidence of human and of rat plague. 



4. The epidemic is directly attributable to the rattus epizootic, and since this epizootic is in its turn 

 directly attributable to the dccumanus epizootic, the epidemic is indirectly attributable to the latter epizootic. 



While the last conclusion expresses the broad relations of the epidemic and the epizootic, it must be added 

 that : — 



5. Infection is occasionally transferred directly from M. dccumanus to man, i.e. without the intervention of 

 M. rattus. 



Another important list of conclusions is as follow ; — 



1. The question of the alleged spread of infection by direct contact with a suffering case has been discussed. 

 Our observations in a plague hospital, and with material obtained from this hospital, lead us to conclude that 

 such a mode of spread does not exist. Support is given to this view by a consideration of the influence of 

 imported cases on the spread of the epidemic and by an investigation of the relative frequency of single and 

 multiple cases in houses and buildings. We have, further, referred to our experience that a rat epizootic is 

 alone sufficient to account for a widespread dissemination of infection throughout a locality. A review of the 

 whole of the evidence on this point brings us to the conclusion that contact plays no part in the spread of the 

 epidemic. 



2. In discussing this question, the question of the infectivity of houses, evidence has been brought forward 

 which points to the rat flea being the transmitting agent of infection from rat to man. Further, reasons have 

 been given for the view that plague does not persist in a locality apart from infection amongst the rats. 



3. From the arguments brought forward in the discussion of the two previous questions we conclude that the 

 epidemic is wholly dependent upon the epizootics. 



4. It has been shown that infection may be transported to a distance by means of rat fleas in clothing or 

 merchandise, and that such infection, when imported into a hitherto uninfected locality, may give rise to an 

 epizootic in the rats. 



5. Our observations lead us to conclude, that plague in domestic animals in Bombay either does not occur 

 or occurs so seldom that it cannot be said to possess any significance from an epidemiological standpoint. 



A study of the insanitary conditions prevailing in Bombay led to the conclusion that 

 these exert no direct influence on the spread of epidemic plague, although ill-constructed 

 buildings, by affording shelter to rats, undoubtedly indirectly facilitate its diffusion. 



Hunter,' of Hong Kong, in a paper written some time ago, but none the less interesting, 

 drew attention to the prevalence of gastro-intestinal lesions in plague, and to the fact that 

 diarrhoea and vomiting often constitute the earliest symptoms. 



It is suggested that the alimentary tract is the avenue by which the plague bacillus 

 enters the human body. It must be confessed that the evidence put forward is very 

 suggestive, though later work has not confirmed this view. The presence of skin eruptions in 

 plague is noted ; papules, vesicles and pustules being frequently seen. Hunter's work tended 

 rather to discredit the flea theory and to support the view that insects, such as cockroaches, 

 and possibly bugs and spiders, may carry the bacilli to food, which thus becomes the vehicle 

 of infection, and which, of course, may also become infected in other ways. This theory 

 seems to have been somewhat lost sight of, and the enquiries of the Indian Conmiissiou 

 serve, in some measure, to discredit it, but the last word has not been said on plague. 

 Should it revive, one would like to suggest that ants be added to the list of insects likely to 

 be harmful. In the Sudan at least, of all the insects one has studied, these seem by far the 

 most likely to bring about infection of food and drink as mentioned under the heading 

 " Cholera " (jiage 30). It is hoped to carry out some investigations on this point. 



' Hunter, W. (January 2nd, 1905), "A Besearch into Epidemic and Epizootic Plague." Journal of Tropical 



Medicine and Ri/i/iene, Vol. VIII. 



