256. The SPLEEN, (milt,) so called because the ancients supposed it to be the seat of melancholy, is an oblong, flattened organ, situated in the left side, in contact with the diaphragm, stomach, and the pancreas. It is of a dark, bluish color, and is abundantly supplied with blood, but has no duct which serves as an outlet for any secretion. Its use is not well determined. [Illustration: Fig. 64. The pancreas with its duct, through which the pancreatic secretion passes into the duodenum.] 257. The OMENTUM (caul) consists of four layers of the serous membrane, which descends from the stomach and transverse colon. A quantity of adipose matter is deposited around its vessels, which ramify through its structure. Its function is twofold in the animal economy. 1st. It protects the intestines from cold. 2d. It facilitates the movements of the intestines upon each other during their vermicular, or worm-like action. 258. Every part of the digestive apparatus is supplied with arteries, veins, lymphatics, and nervous filaments, from the ganglionic system of nerves. -=-=-=-=-=-=-=-=-=-=-=-= 256. Why is the spleen so called? What is peculiar to this organ? 257. Of what is the omentum composed? What is its use? 258. With what is every part of the digestive apparatus supplied? -=-=-=-=-=-=-=-=-=-=-=-= CHAPTER XIV. PHYSIOLOGY OF THE DIGESTIVE ORGANS. 259. Substances received into the stomach as food, must necessarily undergo many changes before they are fitted to form part of the animal body. The solid portions are reduced to a fluid state, and those parts that will nourish the body are separated from the waste material. 260. The first preparation of food for admission into the system, consists in its proper mastication. The lips in front, the cheeks upon the side, the soft palate, by closing down upon the base of the tongue, retain the food in the mouth, while it is subjected to the; process of _mas-ti-ca´tion_, (chewing.) The tongue rolls the mass around, and keeps it between the teeth, while they divide the food to a fineness suitable for the stomach. 261. While the food is in process of mastication, there is incorporated with it a considerable amount of _sa-li´va_, (spittle.) This fluid is furnished by the salivary glands, situated in the vicinity of the mouth. The saliva moistens and softens the food, so that, when carried into the pharynx. it is passed, with ease, through the oesophagus into the stomach. 262. When the food has been properly masticated, (and in rapid eaters when it is not,) the soft palate is raised from the base of the tongue backward, so as to close the posterior opening through the nostrils. By a movement of the muscles of the tongue, cheeks, and floor of the mouth, simultaneous with that of the soft palate, the food is pressed into the upper part of the pharynx. -=-=-=-=-=-=-=-=-=-=-=-=