174 HITCHCOCK'S ANATOMY 



properties, or the power of preventing decay or putrefaction 

 for a long time. These three properties, the acid, fermenta- 

 tive, and antiseptic, are of service in the following manner. 

 The acid assists in the solution of the different materials in 

 the stomach. The Pepsin, which constitutes two thirds of 

 the solid materials of the gastric juice, does its office by es- 

 tablishing the lactic fermentation, such as is seen in the 

 changes through which milk passes in hot weather. The 

 antiseptic properties are important in order to prevent putre- 

 faction, which would be so liable to be set up among organic 

 substances in such a condition, and at such an elevated tem- 

 perature as the stomach usually possesses. 



315. Digestion partly dependent on Chemical Action. — 

 Thus we see that this part of digestion is mainly a chemical 

 affair, although not entirely so : since by experiments care- 

 fully conducted in a vial outside of the body, maintaining the 

 same* temperature and all the essential conditions of digestion, 

 the process goes on very slowly and quite imperfectly. It 

 was found, however, that a piece of meat did digest in a vial 

 in nine hours and a half, while that in the stomach under 

 precisely similar circumstances, was digested in one hour and 

 a half. 



316. Digestion partly a vital Process, — Consequently to 

 say exactly what stomach digestion is, must at present be im- 

 possible. We can only say that it is a chemico- vital process, 

 essentially a chemical action depending upon vital power. 



317. Movements of the Stomach in Digestion. -In order 

 to bring the food in contact with the largest amount of Gastric 

 Fluid, the stomach, by an instinctive movement, carries its 

 contents over the greater curve in it, from the right to the 

 left, and returns it in a reverse direction, occupying about 



What constituent is it that is primarily essential in this process? 315. How much of 

 the process thus far described is mainly a chemical one? What experiment proves it? 

 816. What definition can he given of Digestion ? 317. What instinctive movements does 

 the stomach seem to possess? 



