=The Food Tube.=--The food canal is about thirty feet long. Its first part, the _mouth_, opens back of the tongue into the throat, named the _pharynx_. This leads into a tube, the gullet, passing down through the back part of the chest into the _stomach_ below the diaphragm. The stomach is a bent sac opening into a tube over twenty-five feet long called the _bowels_ or _intestines_. This tube is folded into a bunch which fills a large part of the cavity of the abdomen. [Illustration: FIG. 23.--The plan of a gland. _a_ carries blood to the gland and _v_ takes it away after the gland has taken out what it needs. On the right side the top of the gland has been cut off.] =The Glands or Juice Makers.=--A gland is a little tube closed at one end, or a bunch of such tubes, which can take something out of the blood and make it into a juice. A gland under each ear and four others near the tongue make the juice called _saliva_ which flows into the mouth through tubes. A long, flat, pink gland back of the stomach is called the _sweetbread_ or _pancreas_. This and a large brown gland, the _liver_, empty their juices into the intestines. The whole inner surface of the stomach and intestines is lined with tiny tubes, the glands. The juice of these with that of the other glands softens the food and makes it into a liquid. =The Work of the Mouth.=--The mouth has three things to do: It should break the lumps of food into fine bits so it can be well wet with the slippery fluid called _saliva_ and also easily swallowed. It must roll the food about so that it gets soaked with saliva. It must hold the food long enough to get much taste from it because this starts the juices to flowing into the stomach. Food gives out its taste only after it is changed to a liquid. It should not be washed down with water, as this weakens the juices in the stomach. [Illustration: FIG. 24.--The three glands which make the saliva for acting on the food in the mouth.] No food should be swallowed until it is broken into bits nearly as small as the head of a pin. Some foods, such as cheese, bananas, and nuts, should be made even finer than this. There is nothing in the stomach to crush to pieces large lumps of food. The juices of the stomach can do their full work only when the food is well chewed in the mouth. [Illustration: FIG. 25.--Photograph of a chestnut chewed a half minute by a boy who had poor teeth because he had not taken care of them. The lumps are so large that the juices of the stomach could not dissolve them.]