24 PHYSIOLOGY AND HEALTH. 



CHAPTER IV. 



Gastric Juice secreted in the Stomach when Food is swallowed 

 This Quantity of Juice is the Measure of the Food to be eaten. 

 Hunger. Gastric Juice combines with Food when swallowed, 

 if eaten slowly. 



37. BUT even these careful observers do not explain the 

 mysteries of digestive power and action. They could only 

 discover the steps by which nature accomplishes this won- 

 derful transformation of dead food into the nutriment of the 

 living blood. The food is masticated and swallowed. It 

 then is carried to the left or larger end of the stomach, and 

 there lodged in a great pouch. As soon as the food is 

 swallowed, some gastric juice, sufficient to moisten it, is 

 poured out from the lining membrane, and mingles with and 

 softens it. The more completely the food has been masti- 

 cated, and the more minutely it has been divided in the 

 mouth, the more readily does this gastric juice enter into 

 and combine with it. First it mixes only with the surface 

 of each broken portion, and, as fast as the minute particles 

 are softened by this fluid, they are separated by the continual 

 motion of the stomach, and then the fluid has opportunity to 

 mingle with other particles ; and, these being removed, still 

 other particles are exposed and moistened ; and thus the 

 work goes on, until all the food is wet and softened by this 

 dissolving fluid. 



38. The stomach is not always full of gastric juice. 

 Usually there is none of this fluid in it, except when some 

 food or other matter is there to excite the lining membrane 

 to secrete it and pou r it out. When we put a morsel into 

 the mouth and begin to move the jaws, the salivary glands 

 are stimulated to pour out saliva sufficient to moisten it. In a 

 Bome.what similar manner, the same morsel, when it reaches 



