ASIATIC CHOLERA. 191 



household. The cholera-bacillus has never been demon- 

 strated in the air or in the soil, which likewise might be 

 considered as sources of such explosive outbreaks of cholera. 

 The bacillus has been found during recent epidemics in 

 river-water and in conduits. 



Epidemics of cholera do not always conform strictly to 

 one or the other of the two types described by Koch ; one 

 may be combined with, or pass over into, the other, etc. 

 Individual predisposition, the quantity and quality of food, 

 the density of population, individual and civic cleanliness, 

 distinctly influence the distribution of the disease. 



The foregoing theories, representing essentially Koch's 

 views, are, in fact, capable of explaining almost all of the 

 manifestations of recent cholera-epidemics. One point only, 

 however, is obscure : namely, the question why in some in- 

 stances an epidemic does not occur. Thus, Paris escaped 

 in 1892, although the bacilli were present in the sewers; 

 and only a few cases occurred in Berlin in the year 1893, 

 although the waterways were known to be infected. It is 

 possible that the energetic intervention on the part of the 

 authorities, the filtration of the water, as well as the careful 

 observance of all hygienic regulations, prevented the irrup- 

 tion of an epidemic. The thought, however, can not be en- 

 tirely put aside that possibly the " local predisposition " 

 was wanting. According to Pettenkofer, for the occurrence 

 of an epidemic a local and a temporal predisposition are 

 necessary. " The cholera-germ (x) forms upon the basis 

 of the local and the temporal predisposition of the soil (j/) 

 the cholera-poison (V)." According to this view, the dis- 

 ease can never be transmitted from one human being to an- 

 other, but the germ must first mature in the earth, and then 

 the poison is taken up by the lungs. In view of the facts 

 mentioned this theory of Pettenkofer's can scarcely be main- 

 tained any longer as against the bacillus of Koch. A 

 number of epidemiologic facts, however, indicate that, in 

 addition to the comma-bacillus, some other not yet suffi- 

 ciently determined influences are necessary for the occur- 

 rence of an epidemic. 



Experiments upon Animals and Human Beings. Even 

 though some uncertainty exists with regard to the last 

 point, there can, however, be no further doubt with regard 

 to the etiologic significance of the comma-bacillus as the 

 exciting agent of cholera. The final evidence for this was 



