470 SPIRILLUM CHOLERJ2 ASIATICS. 



become transformed into the enormously multiplying 

 comma bacilli. 



The peculiarities of the local and seasonal distribu- 

 tion of cholera are undoubtedly facts which we must all 

 recognise. Pettenkofer 's observation that the condition 

 of the superficial layers of the soil frequently plays a 

 causal part in these peculiarities is likewise undoubtedly 

 correct ; but it has been previously shown that this con- 

 dition of the soil can exert an important influence, even 

 though we admit the etiological significance of the 

 comma bacillus. But also to an unbiased mind it is 

 evident that the nature of the soil, to which Pettenkofer 

 gives such prominence, is by no means of itself suffi- 

 cient to explain all the peculiarities in the spread of the 

 epidemics. There is no doubt that Pettenkofer's ex- 

 planation is not applicable in many cases; that, for ex- 

 ample, cholera epidemics in the eastern part of Prussia 

 have occurred on dense clayey soil, and in Bombay on 

 non-porous rock, while, on the other hand, porous soils 

 have been passed over. We must at all events regard 

 Pettenkofer's views only as hypotheses, and must not 

 ascribe to them the value of a firmly established theory, 

 which must be used as a basis on which to test the 

 results of present and future investigations. We must, 

 on the contrary, admit the possibility that numerous 

 other causes come into play in the peculiar mode of 

 spread of the epidemics, and we can only take the 

 proper course if we also take into account the other 

 possible explanations. If we base our investigations on 

 the known biological characters of the comma bacillus, 

 we are at all events on firmer ground, and are more 

 likely to find out the truth than if we stubbornly hold 

 to the view of an unknown x, and a still more un- 

 known y. 



Prophylactic The practical prophylactic measures to be taken 



regulations against cholera differ also in an important manner 



against x 



cholera. according as the localistic or the contagionistic view is 



