CH. XXXI.] PROTEOSES AND PEPTONES 487 



There is a still further action that is, the gastric juice is anti- 

 septic ; putrefactive processes do not normally occur in the stomach, 

 and the organisms that produce such processes, many of which are 

 swallowed with the food, are in great measure destroyed, and thus the 

 body is protected from them. 



The formation of peptones is a process of hydrolysis; peptones 

 may be formed by other hydrating agencies like superheated steam 

 and heating with dilute mineral acids. There are certain intermediate 

 steps in this process: the intermediate substances are called pro- 

 peptones or proteoses. The word " proteose " includes the albumoses 

 (from albumin), globuloses (from globulin), vitelloses (from vitellin), 

 etc. Similar substances are also formed from gelatin (gelatinoses) 

 and elastin (elastoses). 



Another intermediate step in gastric digestion is called para- 

 peptone : this is acid albumin or syntonin. The products of digestion 

 of albumin may be classified, according to the order in which they are 

 formed, as follows : 



1. Parapeptone, or acid albumin. 



Proto-album 

 Hetero-albu 



Deutero-albumose 



, 



((a) Proto-albumose ^ The primary albumoses, ,'. 

 2. Propeptone J (6) Hetero-albumose / se whlch are formed 



3. Peptone. 



- t 



V(c) 



It is doubtful whether all the proteid present passes through the 

 acid-albumin stage. 



The primary albumoses are precipitated by saturation with 

 magnesium sulphate or sodium chloride. Deutero-albumose is not; 

 it is, however, precipitated by saturation with ammonium sulphate. 

 Proto- and deutero-albumose are soluble in water ; hetero-albumose is 

 not ; it requires salt to hold it in solution. 



Peptones. They are soluble in water, are not coagulated by heat, 

 and are not precipitated by nitric acid, copper sulphate, ammonium 

 sulphate, and a number of other precipitants of proteids. They are 

 precipitated but not coagulated by alcohol. They are also precipi- 

 tated by tannin, picric acid, potassio-mercuric iodide, phospho- 

 molybdic acid, and phospho-tungstic acid. 



They give the biuret reaction (rose-red solution with a trace of 

 copper sulphate and caustic potash or soda). 



Peptone is readily diffusible through animal membranes. The 

 utility of the formation of diffusible substances during digestion is 

 obvious. 



Proteoses. They are not coagulated by heat; they are precipi- 

 tated but not coagulated by alcohol: like peptone they give the 

 biuret reaction. They are precipitated by nitric acid, the precipitate 

 being soluble on heating, and reappearing when the liquid cools. 



