264 BACTERIOLOGY. 



Perhaps still a third group might be added, 

 comprising the critical diseases like intermit- 

 tent fever, relapsing fever and pneumonia. 

 Many observers suppose, in accord with Henle, 

 that the germs of these diseases in man have 

 a course of development sharply defined by 

 hours or days, and that therefore the life-cycle 

 of the germ determines the cycle of the disease. 

 So far, however, as we know anything about 

 these germs, we never find such remarkable 

 cycles occurring outside of the human body. 

 The pneumonia germs cause crises only in man, 

 while in rabbits they bring about simple blood- 

 poisoning without any cycle. In cultures they 

 show no regular cyclical character at all. For 

 these reasons I am inclined to seek the basis 

 of such cyclical manifestations in peculiarities 

 of the human organization, and the more so 

 that even in man pneumonia may sometimes 

 occur without crisis and show a resemblance 

 to forms of blood-poisoning. I have already 

 mentioned the conflicting views of Golgi and 

 Laveran respecting malarial fever. 



Upon sifting all the available material, I can- 

 not find a fact which is in real harmony with 

 Koch's conception of " specific" disease-germs. 

 I must protest also against the view held by 

 Billroth and Naegeli, which is extreme and 

 one-sided, and I expressly acknowledge that we 



