APPLICATION OF METHOD IX INFECTIOUS DISEASES I2~ 



conditions under which certain bacteria can exist, 



mainly on the basis of more exact studies on the 



j 



composition of the medium, then we should undoubt- 

 edly be in a position to employ more objective 

 therapeutic methods. Further, it would be possible 

 to formulate a conception of the injurious activities 

 of certain kinds of bacteria more clearly than we 

 can at present. Unfortunately, it would scarcely be 

 possible to make use of direct methods in this case, 

 unless we were to succeed in cultivating individual 

 micro-organisms on substrates the composition of 

 which we were thoroughly acquainted with. Our 

 ^ progress in the field of the chemistry of the different 

 kinds of cell units, and of their nutritive bases, has 

 brought us nearer to this objective, but a large 

 part of the road lies before us yet, before we shall 

 obtain such an exact knowledge of the composition 

 of certain albuminous substances, such as phospha- 

 tides and nucleoproteids, &c., as to be able to properly 

 appreciate differences of configuration, as well as 

 differences of structure. Once we have advanced so 

 far, we shall be able to replace our present conception 

 of " disposition ' by definite facts. 



The train of thought we have been pursuing is 

 only intended to show that, in considering the ques- 

 tion of the injuries which bacteria may inflict on their 

 host, we must not only consider the bacteria as such, 

 but must realize that their entire metabolism is of 



