TO BE DUE TO SPECIFIC MICROORGANISMS. 531 



low-fever cases contain a great variety of bacilli, and not a nearly pure cul- 

 ture of a single species, as is the case in recent and typical cases of cholera. 



Comparatively few liquefying bacilli are found in the faeces discharged 

 during life, or in the intestinal contents collected soon after death from yel- 

 low-fever cadavers. On the other hand, non-liquefying bacilli are very 

 abundant. 



The one most constantly and abundantly present is the Bacterium coli 

 commune of Escherich. 



This is associated with various other bacilli, some of which are strict 

 anaerobics and some facultative anaerobics. 



Among the facultative anaerobics is one my Bacillus X which has been 

 isolated by the culture method in a considerable number of cases and may 

 have been present in all. This bacillus has not been encountered in the 

 comparative experiments made. It is very pathogenic for rabbits when in- 

 jected into the cavity of the abdomen. 



It is possible that this bacillus is concerned in the etiology of yellow fever, 

 but no satisfactory evidence that this is the case has been obtained by experi- 

 ments on the lower animals, and it has not been found in such numbers as 

 to warrant the inference that it is the veritable infectious agent. 



All other microorganisms obtained in pure cultures from yellow-fever 

 cadavers appear to be excluded, either by having been identified with known 

 species, or by having been found in comparative researches made outside of 

 the area of yellow-fever prevalence, or by the fact that they have only been 

 found in small numbers and in a limited number of cases. ' 



Finally we remark that many facts relating to the origin and extension 

 of yellow-fever epidemics give support to the inference that the specific in- 

 fectious agent is present in the dejecta of those suffering from the disease, 

 and that accumulations of faecal matter, and of other organic material of ani- 

 mal origin, furnish a suitable nidus for the development of the "germ" 

 when climatic conditions are favorable for its growth. 



It may be that such a nidus is essential, and that the culture media 

 usually employed by bacteriologists do not afford a suitable soil for this par- 

 ticular microbe. 



It is also possible that its development depends upon the presence of other 

 microorganisms found in faecal matter, which give rise to chemical products 

 required for the development of this one. 



Some of the microorganisms present in the dejecta of yellow-fever pa- 

 tients, as shown by stained smear preparations, have not developed in the 

 cultures made, either aerobic or anaerobic. One extremely slender filiform 

 bacillus, which can only be seen with high powers and which is quite abun- 

 dant in some of my preparations, has never been obtained in the cultures 

 made, and no doubt there are others in the same category. 



That the yellow-fever germ is a strict anaerobic, or that it will only grow 

 in a special nidus, may be inferred from certain facts relating to the exten- 

 sion of epidemics. 



There is no evidence that yellow fever is propagated by contamination of 

 the supply of drinking water, as frequently, and probably usually, occurs in 

 the case of typhoid fever and cholera. Moreover, epidemics extend in a 

 more deliberate manner and are restricted within a more definite area than 

 is the case with cholera and typhoid fever. It is usually at least ten days or 

 two weeks after the arrival of an infected vessel or of a person sick with the 

 disease before cases of local origin occur; and these cases occur in the imme- 

 diate vicinity of the imported case or infected vessel. When the disease has 

 effected a lodgment the area of infection extends slowly and usually has 

 well-defined boundaries. In towns and cities having a common water sup- 



1 The possibility, of course, remains that the specific infectious agent in yellow 

 fever may belong to an entirely different class of microorganisms from the bacteria, 

 or that it may be ultra-microscopic or not capable of demonstration in the tissues 

 by the staining methods usually employed by bacteriologists. 



