50 DIGESTION. 



What forms of peptones occur? 



(1) Parapeptone, acid albumin, which results from incomplete 

 action of the gastric juice ; (2) antipeptone, a form on which 

 pancreatic digestion has no effect ; (3) hemipeptone, a form in 

 which pancreatic digestion has the effect of producing leucin and 

 ty rosin. 



What conditions favor gastric digestion? 



The temperature of the body is most favorable, and the presence 

 of acid preferably HC1 is essential. Digestive secretion does 

 not continue except during the presence of food. 



What is the milk-curdling ferment? 



Milk is curdled in the stomach by a ferment, aside from pepsin, 

 which is derived from the gastric juice. This action takes place in 

 the absence of hydrochloric acid. Rennet (derived from the fourth 

 stomach of calves) is used for this purpose in the cheese manu- 

 facture. 



How are non-nitrogenous bodies affected by the gastric juice ? 



Starches are unaffected. Sugar is dissolved and cane-sugar (sac- 

 charose) is changed to grape-sugar (glucose) by the aid of the mu- 

 cus present. Fats are unaffected, except that the albuminous cap- 

 sules of fat-cells in adipose tissues are digested and the oil set free 

 in globules. 



What is the time required for the stomach digestion ? 



The time varies, with the kind and amount of food, from one 

 to five or six hours. Digestion is favored by rest of the stomach 

 before eating, by gentle exercise of the mind or body, by an undis- 

 turbed mental condition, and by a healthy condition of the body. 



Does absorption take place from the stomach? 

 No, except in a very slight degree. 



How does the stomach empty itself? 



The stomach is elastic, and is supplied with circular and longi- 

 tudinal muscles in its middle coat. These muscular fibres are 

 capable of producing peristaltic movements of the organ which turn 

 the food over and over during the process of digestion. This elas- 

 tic pouch is closed at each end by strong, sphincter-like circular 

 bands of muscle at the cardiac and pyloric openings, and until the 

 stomach digestion is well advanced none of the contents escapes ; 



