INTRODUCTION. 15 



butyricum or Bacillus amylobacter plays an important part 

 in determining the butyric acid fermentation of the vegetable 

 acids, and that it plays an active part in the ripening of 

 cheese. Because of its action on cellulose, and then of its 

 further action on dextrine and glucose, it also has much to 

 do with the decomposition and destruction of the cellulose 

 of fleshy and juicy plant tissues, and its aid is requisitioned 

 in the separation of these parts from the tougher fibre of 

 hemp, flax, and similar materials, as in the process of macera- 

 tion the enzyme converts the cellulose into butyric acid. 



Van Tieghem holds that much the same processes go on 

 in the stomachs of ruminant animals, and that the Bacillus 

 amylobacter, which is usually found there, thus does a very 

 large part of the work which, otherwise, would have to be 

 performed by the epithelial cells of the stomach itself. This 

 bacillus, however, acts not only upon cellulose and starch 

 paste, but it also exerts a most important action on nitro- 

 genous substances. Fitz and Hueppe have both pointed out 

 that the casein of milk is first coagulated in the presence of this 

 organism, is then peptonized and liquefied by the action of its 

 enzyme, and that the products thus formed are afterwards 

 converted into certain lower compounds, such as leucine, 

 tyrosine, and even ammonia, all of which are constantly met 

 with during the processes of both digestion and decomposition. 

 Duclaux also showed by experiment that an organism, which 

 resembles the bacterium amylobacter very closely in many 

 respects, sets up a series of similar changes in the casein of 

 milk, and in casein that has been converted into cheese ; 

 and he showed that the process of u ripening " brought 

 about in the presence of the Tyrothrix bacillus, is due to 

 the peptonization and liquefaction of some of the substances 

 of which unripe cheese is composed ; certain secondary or 

 ultimate products similar to those above mentioned being 

 found during the ripening process. 



That bacteria are general scavengers is now generally 

 acknowledged, and almost innumerable observations have 

 been made with the object of proving that the presence of 

 certain definite organisms is essential for the perfect breaking 

 down of dead or effete animal and vegetable matter. It has 

 already been mentioned that some species have the power 

 of breaking up cellulose and of converting it into much 

 simpler substances, both externally and in the alimentary canal. 



