88 BACTERIOLOGY. 



cially in sprouting- seeds. Malt, or sprouting- barley, is 

 rich in diastase. Similar ferments are elaborated by 

 bacteria. 



The proteolytic enzymes act on albuminous substances 

 and convert these into albumose and the latter into pepton. 

 The pepsin of the gastric juice and the trypsin of the pan- 

 creatic secretion will serve as types of this class of ferments. 

 As indicated above, similar enzymes are met with in the 

 higher as well as in the lower forms of plant-life. The 

 liquefaction or the peptonizing of gelatin is due to similar 

 ferments. 



The fat-splitting ferment breaks up neutral fats into 

 glycerin and fatty acids. A ferment cf this kind is pres- 

 ent in the pancreatic secretion. Many bacteria possess a 

 similar action which may be carried on in the intestines, or 

 otherwise. The rancidity of fats, especially butter-fat, is 

 frequently due to such organisms. 



Inverting ferments change cane-sugar into glucose. 

 They are elaborated by plants as well as by animals. 



Rennet, as is well known, coagulates or curdles milk. 

 The gastric secretion of all vertebrate animals contains a 

 rennet ferment. The mucous membrane of the calf's stom- 

 ach, is utilized for this reason in the preparation of curd 

 or cheese. A rennet-like action is exhibited by many 

 bacteria. 



Ptomains. These are organic, basic products resulting 

 from the action of bacteria on albuminous matter. They all 

 contain C, H, and N, and some contain O. They are alka- 

 line substances which, when neutralized by acids, yield crys- 

 tallizable salts. Most of the ptomains are not poisonous, 

 or but very feebly so. Only a few can be said to be very 

 toxic. 



The discovery of, more or less, poisonous basic substan- 

 ces among the bacterial products led to the belief that bac- 

 teria produced disease by giving rise to ptomains. This 



