DIGESTION. 



107 



min into a new form of proteid termed peptone. In this transforma- 

 tion it is possible to isolate intermediate bodies by the addition of 

 ammonium and magnesium sulphates, to which the term albumoses 

 or proteases has been given. Because of the order in which they are 

 obtained they have been divided into primary and secondary. The 

 primary proteoses are in turn separated into proto- and hetero- 

 albumose ; the secondary proteoses are termed deutero-albumose. 

 This supposed change is represented by the following scheme : 



Albumin. 



I 

 Acid-albumin. 



C Primary 

 Albumoses 



(proto and hetero). 



Secondary 

 Proteoses. 



I (deutero). 



Peptone. 



Peptones. Peptones are the final products of the digestion of 

 proteid bodies, and differ from the bodies from which they are de- 

 rived in the following particulars : 



1. They are diffusible, i. e., capable of passing readily through ani- 

 mal membranes, a condition essential for their absorption. 



2. They are soluble in water and in saline solution. 



3. They are non-coagulable by heat and nitric or acetic acids. They 

 can be readily precipitated, however, by tannic acid, by bile 

 acids, and by mercuric chlorid. 



4. They are absorbable and assimilable, soon becoming transformed 

 into serum-albumin. 



The duration of gastric digestion will depend largely upon the 

 quantity and quality of the food. The digestion of the average meal 

 occupies from three to five hours. 



Movements of the Stomach. During the period of gastric diges- 

 tion the walls of the stomach become the seat of a series of move- 

 ments, somewhat peristaltic in character, which serve not only to 

 incorporate the gastric juice with the food, but also serve to eject 

 the liquefied portions of the food into the intestine. 



After the entrance of the food both the cardiac and pyloric 

 orifices are closed by the contraction of their sphincters. Within 

 five minutes (in the cat) annular constrictions begin in the pyloric 



