98 JOHNE^S DISEASE 



out, we may say that from the results we were inclined 

 to believe that the essential substance was formed 

 from such substances as glycerine, mannite, and 

 absolute alcohol. 



If such be the case, the next problem was to find out 

 how these substances might be changed by B. phlei 

 in the process of forming the essential substance for 

 its metabolism. We know that in the process of fer- 

 mentation hydration and oxidation take place. Even 

 in the case of alcoholic fermentation, in the late stages 

 of the process, when the yeast is growing as a film on 

 the surface of the fluid, the alcohol may become oxi- 

 dized and almost entirely disappear, and the proba- 

 bility is that either outside the cell or inside the cell 

 some organic acid is one of the final products formed 

 for the benefit of the bacterial or yeast metabolism, and 

 it may be taken as certain that this acid varies in the 

 case of different bacilli. It may be, in fact, that the 

 carboxyl group (COOH) has to be formed in certain 

 compounds before such micro-organisms can obtain 

 their carbon from sugars and alcohols. 



In the case of B. coli^ the large quantity of acid 

 produced in media containing sugars may be the same 

 process, the conditions being such that more acid is 

 produced than is necessary or beneficial, a phenomenon 

 of over-production so often met with in lowly organized 

 life. 



If, as we believe, some acid is necessary, then it 

 is quite clear that B. phlei and allied bacilli must con- 

 tain a special oxidizing enzyme, in order that they 

 may produce from such substances as glycerine the 

 particular acid which is necessary for each bacillus. 



Now, from our experiments we were led to believe 

 that the essential substance might be an organic acid, 

 and that the reason why it is necessary to add this 



