78 PHYSIOLOGY OF ALIMENTATION. 



These are chiefly of a putrefactive character, and affect in the 

 main the protein constituents of the food. Certain of the 

 bacterial enzymes belong to the proteinase group, and these 

 split the undigested protein remnants into leucin, ty rosin, and 

 the other products of proteinase digestion. Indol, skatol, 

 and various phenols are produced also, as well as fatty acids 

 (lactic, butyric, caproic, etc.) and gases (hydrogen, hydrogen 

 sulphide, and methane). 



