212 BACTERIOLOGY. 



and a quotidian parasite), each one of which 

 produces different forms of the fever in accord- 

 ance with the peculiarities of its development. 

 Marchiafava would add to these yet a fourth, 

 the malignant tertian parasite. This belief in 

 the existence of several parasites corresponds 

 to the usage of physicians and has therefore 

 found wide acceptance. But it must still be 

 considered as an open question whether the 

 evidence for the existence of these varieties is 

 altogether conclusive. Such progress as has 

 been made in bacteriology should incline us to 

 use great caution about accepting any attempt 

 at schematic division. Laveran in fact still 

 maintains the other view ; according to him 

 there is only one pleomorphic parasite and the 

 different kinds of fever are due riot to different 

 varieties or species of the parasite but to the 

 varying dispositions of men. This view has 

 the great merit of being more in harmony with 

 the progress of micro-parasitology. 



Since it has been shown that the so-called 

 tubercle bacilli are parasitic growth-forms 

 of a mould, I may, in conclusion, add some 

 remarks upon the diseases of men and animals 

 due to moulds. The true moulds are aerobic 

 and capable of forming spores only with ac- 

 cess of air, while the mycelium and the 

 torula forms are able to develop when air 



