iv.] YEAST. 91 



If any of them possess the same powers as yeast (and 

 the same capacity for Jiving without light is exhibited 

 by some other fungi) there would seem to be no difficulty 

 about the matter. 



Of the pathological bearings of the study of yeast, and 

 other such organisms, I have spoken elsewhere. It is 

 certain that, in some animals, devastating epidemics are 

 caused by fungi of low order similar to those of which 

 Torula is a sort of offshoot. It is certain that such 

 diseases are propagated by contagion and infection, in 

 just the same way as ordinary contagious and infectious 

 diseases are propagated. Of course, it does not follow 

 from this, that all contagious and infectious diseases are 

 caused by organisms of as definite and independent a 

 character as the Torula ; but, I think, it does follow that 

 it is prudent and wise to satisfy oneself in each parti- 

 cular case, that the " germ theory " cannot and will not 

 explain the facts, before having recourse to hypotheses 

 which have no equal support from analogy. 



