BACTERIA IN INFECTIOUS DISEASES. 619 



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. l 



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 rio 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- 

 ply one portion remains perfectly healthy, while another, and usually the 

 most filthy portion, may be decimated by the scourge. 



The experimental evidence recorded, and the facts just stated, seem to 

 justify the recommendation that the dejecta of yellow-fever patients should 

 be regarded as infectious material, and that such material should never be 

 thrown into privy vaults or upon the soil until it has been completely disin- 

 fected. 



This rule thoroughly enforced, together with an efficient quarantine ser- 

 vice and proper attention to the sanitary police of our exposed seaport cities, 

 would, I believe, effectually prevent this pestilential disease from again ob- 

 taining a foothold within the limits of the United States. 



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. 



