APPLICATION OF METHOD IX INFECTIOUS DISEASES 



Ehrlich. At the same time, a careful analysis of the 

 processes effected by the ferments gives us the chance 

 of determining, with more certainty than has hitherto 

 been the case, what is the nature of the injuries set 

 up by the presence of cells that are out of harmony 

 with the body. Sometimes the parasite takes an 

 active part, sometimes only a passive one, while at 

 other times its influence is extremely varied. 



j 



The proof, that ferments play an important part in 

 the means of defence of animal cells against dishar- 

 monious substances, opens up new paths for ex- 

 perimental research. It may be long before the true 

 nature of ferments is elucidated ; nevertheless, we 

 shall always be getting nearer to the possibility of 

 excluding the second unknown the substrate. The 

 more we extend our knowledge of the composition and 

 structure of the food material, and of the components 

 of the cells, the more do we find ourselves in a 

 position to make use of substrates of a known 

 structure, which enable us to investigate the ferments 

 in a much surer manner, and to determine exactly how 

 they decompose a particular product. We shall be 

 able to get hold of individual decomposites, and study 

 their properties, so as gradually to penetrate into the 

 mysteries of the effects of infectious diseases, as well 

 as into the principles of immunity. 



There is scarcely, in the whole domain of biology, 

 a more stimulating task than that of finding 



