_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. _First_, it mixes the food and makes it pass down the tube. _Second_, two sets of cells behind the stomach make two liquids and pour them into the intestine. One set of cells is the _sweetbread_, or _pancreas_, and its liquid is the _pancreatic juice_. The other is the _liver_ and its fluid is the _bile_. _Third_, the pancreatic juice makes three changes in food. _First_, like the mouth, it changes starch to sugar. _Second_, like the stomach, it makes albumin a liquid. _Third_, it divides fat into fine drops. These drops then mix with water and do not float on its top. =20. Bile.=--The bile is yellow and bitter. It helps the pancreatic juice do its work. It also helps to keep the inside of the intestine clean. =21. Digestion of water and minerals.=--Water and the mineral parts of food do not need to be changed at all, but can become part of the blood just as they are. Seeds and husks and tough strings of flesh all pass the length of the intestine and are not changed. =22. How food gets into the blood.=--By the time food is half way down the intestine it is mostly liquid and ready to become part of the blood. This liquid soaks through the sides of the intestine and into the blood tubes. At last the food reaches the end of the intestine. Most of its liquid has then soaked into the blood tubes and only some solid waste is left. =23. Work of the liver.=--The food is now in the blood, but has not become a part of it. It is carried to the liver. There the liver changes the food to good blood, and then the blood hurries on and feeds the cells of the body. Spoiled food may be swallowed and taken into the blood with the good food. The liver takes out the poisons and sends them back again with the bile. The liver keeps us from getting poisoned. =24. Bad food.=--Sometimes the stomach and intestine cannot digest the food. They cannot digest green apples, but they try hard to do so. They stir the apples faster and faster until there is a great pain. Sometimes the stomach throws up the food and then the pain and sickness stop. Spoiled food makes us sick in the same way.