[Sidenote: 33. The presence of food in the intestines? Bile?] 33. INTESTINAL DIGESTION.--As soon as the food passes the pylorus and begins to accumulate in the upper {95} part of the intestines, it excites the flow of a new digestive fluid, which enters through a small tube, or _duct_, about three inches below the stomach. It is formed by the union of two distinct fluids--the _bile_ and the _pancreatic_ juice. The bile is secreted by the liver, which is the largest gland of the body, and is situated on the right side and upper part of the abdomen (Fig. 22). The bile is constantly formed, but it flows most rapidly during digestion. During the intervals of digestion it is stored in the _gall-bladder_, a small membranous bag attached to the under side of the liver. This fluid is of a greenish-yellow color, having a peculiar smell, and a very bitter taste. [Sidenote: 34. The pancreatic juice? The joint action of these fluids?] 34. The pancreatic juice is the product of a gland called the _pancreas_, situated behind the stomach. This fluid is colorless, viscid, and without odor. Like the digestive juices previously described, it owes its solvent power to its peculiar ferment principle, called _pancreatin_. By the joint action of these fluids, the fatty parts of the food are prepared for absorption. By previous steps of digestion the fats are merely separated from the other components of the food; but here, within the intestines, they are reduced to a state of minute division, or _emulsion_, resembling the condition of butter in milk, before it has been churned. There results from this action a white and milky fluid, termed the _chyle_, which holds in solution the digestible portions of the food, and is spread over the extensive absorbent surface of the small intestines. [Sidenote: 35. The mucous membrane? Experiments on inferior animals?] 35. The mucous membrane of the intestines, also, secretes or produces, a digestive fluid by means of numerous "follicles," or minute glands; this is called the intestinal juice. From experiments on the inferior animals, it has been ascertained that this fluid exerts a solvent influence over each of the three organic food principles, and in this way may supplement and complete the action of the {96} fluids previously mentioned, viz.:--of the saliva in converting starch into sugar, of the gastric juice in digesting the albuminoids, and of the pancreatic juice and bile in emulsifying the fats. [Sidenote: 36, 37. How much thus far has been done with the food? The next process? Give the first way.]