CHAPTER XIII.

THE DIGESTIVE ORGANS.

233. FROM the earliest existence of the human system to the last ray of life, change is impressed upon it by the Giver of this curious fabric. New atoms of matter are deposited, while the old and now useless particles are constantly removed. The material necessary to sustain the growth of the body in early life, and also to repair the waste that is unceasing to animal existence, is the food we eat.

234. Food, animal or vegetable, contains most of the elements of the different tissues of the system, yet it must undergo certain essential alterations before it can become a part of the body. The first change is effected by the action of the Digestive Organs.

ANATOMY OF THE DIGESTIVE ORGANS.

235. The DIGESTIVE ORGANS are the Mouth, Teeth,* Sal'iva-ry Glands, Pharynx, E-soph'a-gus, (gullet,) Stomach, In-tes'tines, (bowels,) Lac'te-als, (milk, or chyle vessels,) Tho-racic Duct, Liv'er, and the Pan'cre-as, (sweetbread.)

236. The MOUTH is an irregular cavity, which contains the instruments of mastication and the organs of tasie. It is

* See Chapter XII.

233. What is impressed upon the human system from its earliest existence? What maintains this change? 234. Has animal or vegetable food any resemblance to the different tissues of which it finally forms a part? By what organs is the first change in the food effected? 235-258. Give the anatomy of the digestive organs. 235. Name them. 236. Describe the mouth.

bounded in front by the lips; on each side by the internal surface of the cheeks; above, by the hard palate (roof of the mouth) and teeth of the upper jaw; below, by the tongue and teeth of the lower jaw; behind, it is continuous with the pharynx, but is separated from it by a kind of movable curtain, called the soft palate. This may be elevated or depressed, so as to close the passage or leave it free.

237. The SALIVARY GLANDS are six in number; three on each side of the jaw. They are called the pa-rot'id, the sub-max il-la-ru and the sub-lin'gual.

Fig. 58.

Fig. 58. A view of the salivary glands in their proper situations. 1, The parotid gland. 2, Its duct. 3, The submaxillary gland. 4, Its duct. 5, The sublingual giand, brought to view by the removal of a section of the lower jaw.

238. The PAROTID GLAND, the largest, is situated in front of the external ear, and behind the angle of the jaw. A duct (Steno's) from this gland opens into the mouth, opposite the second molar tooth of the upper jaw.

Give their names. What

237, How many glands about the mouth? does fig. 58 represent? 238. Describe the parotid gland.

239. The SUBMAXILLARY GLAND is situated within the lower jaw, anterior to its angle. Its excretory duct (Wharton's) opens into the mouth by the side of the fra'num lingua, (bridle of the tongue.)

240. The SUBLINGUAL GLAND is elongated and flattened, and situated beneath the mucous membrane of the floor of he mouth, on each side of the frænum linguæ. It has seven or eight small ducts, which open into the mouth by the side of the bridle of the tongue.

Observation. In the "mumps," the parotid gland is diseased. The swelling under the tongue called the "frog" is a disease of the sublingual gland.

Fig. 59.

A side view of the face, oesophagus, and trachea. 1, The trachea (windpipe.) 2, The larynx. 3, The esophagus. 4, 4, 4, The muscles of the upper portion of the œsophagus, forming the pharynx. 5, The muscle of the cheek. 6, The muscle that surrounds the mouth. 7, The muscle that forms the floor of the mouth.

239. The submaxillary. 240. The sublingual. What observation respecting these glands? What does fig. 59 represent ?

upper portion of the spinal column. It extends from the base of the skull to the top of the tra'che-a, (windpipe,) and is continuous with the esophagus. From the pharynx are four passages; one opens upward and forward to the nose, the second leads forward to the mouth, the third downward to the trachea and lungs, the fourth downward and backward to the stomach.

242. The ESOPHAGUS is a large membranous tube that extends behind the trachea, the heart, and lungs, pierces the diaphragm, and terminates in the stomach. It is composed of two membranes—an internal, or mucous, and a muscular coat. The latter is composed of two sets of fibres; one extends lengthwise, the other is arranged in circular bands.

243. The STOMACH is situated in the left side of the abdomen, immediately below and in contact with the diaphragm. It has two openings; one connected with the œsophagus, 'called the car'di-ac orifice; the other connected with the upper portion of the small intestine, called the py-lor'ic orifice. It is composed of three coats, or membranes. The exterior or serous coat is very tough and strong, and invests every part of this important organ. The middle, or muscular coat is composed of two layers of muscular fibres, one set of which is arranged longitudinally, the other circularly. The interior coat is called the mucous, and is arranged in ru'ga, (folds.) The stomach is provided with a multitude of small glands, in which is secreted the gastric fluid.

Illustration. The three coats of the stomach anatomically resemble tripe, which is a preparation of the largest stomach of the cow or ox. The outer coat is smooth and highly polished. The middle coat is composed of minute threads, which are

241. Describe the pharynx and the passages leading from it. 242. Give the structure of the œsophagus. 243. Where is the stomach situated? How many coats has it? Describe them. What article prepared for

food does the stomach resemble?

arranged in two layers. The fibres of these layers cross each other. The inner coat is soft, and presents many folds, usually called "the honey-comb."

Fig. 60. The inner surface of the stomach and duodenum. 1, The lower portion of the esophagus. 2, The opening through which the food is passed into the stomach. 8, The stomach. 9, The opening through which the food passes out of the stomach into the duodenum, or upper portion of the sinall intestine. 10, 11, 14, The duodenum. 12, 13, Ducts through which the bile and pancreatic fluid pass into it. a, b, c, The three coats of the stomach.

244. The INTESTINES, or alimentary canal, are divided into two parts the small and large. The small intestine is about twenty-five feet in length, and is divided into three portions, namely, the Du-o-de'num, the Je-ju'num, and the Il'e-um. The large intestine is about five feet in length, and is divided into three parts, namely, the Ca'cum, the Co'lon, and the Rec'tum. (Appendix D.)

245. The DUODENUM is somewhat larger than the rest of the small intestine, and has received its name from being in

244. Explain fig. 60. What is the length of the small intestine, and how is it divided? What is the length of the large intestine? Give its divisions. 245. Describe the duodenum.