Chap. 11 FOODS AND NUTRITION 185 



them (Figs. 11.15, 11.16). While food is in the stomach it is stirred and 

 pressed by the contractions of the walls, and digestion of protein and some 

 fats is begun by the gastric juice. Nerves from the taste organs in the tongue 

 are associated with the vagus nerve, branches of which spread through the 

 stomach wall and carry impulses that start the secretion of the gastric juice 

 while food is still in the mouth. 



Glands in the wall of the stomach produce the gastric juice containing 

 mucin, hydrochloric acid, and three digestive enzymes or ferments, pepsin, 

 rennin, and gastric lipase, of which pepsin is the most important. The esti- 

 mated 35,000,000 gastric glands formed by inpocketings of the stomach lining 



Fig. 11.15. An x-ray photograph of the waves of contraction of the human 

 stomach. Such contractions work upon food and in the early stages of an empty 

 stomach cause hunger pangs. The stomach is here made visible by barium salts 

 recently swallowed in milk. Bits of intestine are similarly visible in the lower 

 part of the illustration. (Courtesy, Gerard: The Body Functions. New York, John 

 Wiley and Sons, 1941.) 



