SPIRILLUM CHOLERA ASIATICS. 469 



disposition of the soil, is either that y so prepares man 

 that he becomes susceptible for x, or that x is altered 

 under the influence of the y properties of the soil, and 

 is only then capable of producing infection in man. 

 Pettenkofer looks on the latter alternative as the 

 most probable, and he is also of opinion that # is a 

 species of bacterium, the development or distribution 

 of which is much influenced by these y properties of 

 the soil. 



Pettenkofer holds that Koch's comma bacillus is not Pettenkofer '* 

 the proper x, because its characters show that it cannot the comma t0 

 be favourably influenced by the y properties of the soil ; 

 the comma bacillus dies as the result of drying, while a 

 relatively dry soil furnishes the best seasonal predis- 

 position for cholera. The comma bacillus further rapidly 

 dies in putrefying substrata, while a soil contaminated 

 with dejecta is one of the predisposing factors in favour 

 of cholera. Neither of these objections are, however, 

 valid. Where the moisture of the soil diminishes the 

 degree of dryness is almost never such that the comma 

 bacilli which reach the soil must at once die. On the 

 contrary, the conditions for the spread of the infection 

 are, as was shown on p. 457, more favourable under these 

 circumstances. In like manner the rapid destruction 

 of comma bacilli in putrefying substrata has reference 

 to their behaviour in fluids where there is active multi- 

 plication of saprophytes, but does not apply to the soil 

 in which the multiplication and hurtful influence of the 

 saprophytes are practically of no moment. It is, there- 

 fore, evident that Pettenkofer 's opposition to the comma 

 bacillus is in reality not at all justified ; while the fact 

 of the constant and exclusive occurrence of the comma 

 bacilli in cholera has led him to the assumption, which 

 certainly does not seem by any means probable, that the 

 virus of cholera is an organism as yet unknown, that 

 this virus becomes altered in an as yet unknown 

 manner under the influence of a porous, impure, and 

 somewhat moist soil, and can then cause the infection, 

 and that after the occurrence of infection the vibriones, 

 which are present in small numbers in the intestine, 



