17. The stomach.—When food is swallowed it goes to the stomach. The stomach is a thin bag. In a man it holds about three pints. Like the mouth, it does three things to the food.
Gastric glands in the stomach
(×200).
The cells a and b, form the juice.
The fibers c, bind the tubes in place.
First, the stomach gently stirs and mixes the food.
Second, it pours a fluid over the food. This fluid is called the gastric juice. The gastric juice is sour and bitter.
Third, the gastric juice changes some of the albumin of food to a liquid form.
If the mouth has done its work well, the stomach does its work easily and we do not know it. But if the mouth has eaten food too fast and has not chewed it well, then the stomach must do the work of the mouth too. In that case it gets tired and aches.
18. The intestine.—The food stays in the stomach only a little while. All the time a little keeps trickling into a long coil of tube. This tube is called the intestine or the bowels. Three or four hours after a hearty meal the stomach is empty. Some of the food has been changed to a liquid, but most of it has only been ground to smaller pieces, and mixed with a great deal of water. Now it all must be changed to a liquid.
19. What the intestine does.—Like the mouth and stomach, the intestine does three things.