Page:The American Cyclopædia (1879) Volume I.djvu/342

 318 ALIMENTARY CANAL ALIMENTUS the tortuous windings of its internal cavity. Its mucous membrane is provided, first, with a great number of glandular follicles which secrete the intestinal juice, one of the active agents in digestion; and secondly, with mi- nute filamentous vascular prominences or villi, Abdominal Portion of the Alimentary Canal. A, oesophagus; B, diaphragm; C, stomach; D, cardiac ex- tremity of the stomach; E, peat pouch; F, pylorus; G, duodenum, IL right lobe of liver ; I, left lobe of liver ; K, gall bladder; L. bile duct; M, small Intestine; K, entrance of email intestine into the large Intestine ; O, caecum ; P, appendix vermiformis; Q, ascending colon; K 8 T, trans- verse colon; U, stgmoid flexure; V, rectum; W, urinary bladder; -X. pancreas; Y, spleen. the heart), because it is situated near the heart ; that by which it communicates with the intes- tine is called the pylorfls (Gr. n-vAwpdf, a gate- keeper). Both are provided with a special circular bundle of muscular fibres by which the food, once in the stomach, is retained there for a time, to allow of the secretion and operation of the gastric juice. The gastric juice is se- creted by the mucous membrane of the stomach, which is soft, glandular, and vascular in texture, and, when stimulated by the contact of the food, pours out the gastric juice in considerable abun- dance, as the perspiration is exuded by the skin. Next the stomach follows the small in- testine. This is a tubular canal about 25 feet in length and between one and two inches in diameter. It is thrown into numberless folds and convolutions, by which, notwithstanding its great length, it occupies a comparatively moderate space in the abdomen. It is attached to the abdominal portion civile spinal column by a thin, flexible membranci sheet termed the mesentery, which, while retaining it in its proper position, allows of the necessary movement of its different convolutions upon each other. Its muscular layers are well developed and active, and by their contractions continuously urge the semi-fluid ingredients of the food through Two Vllll of the Small Intestines. A, substance of the villus; B, its epithelium, of which some cells are seen detached at B 1 ; CD, the artery and vein, with then- connecting capillary network, which envelopes and hides the lacteal radicle,, which occupies the centre of the villas and opens into a network of lacteal vessels at its base. which are so abundant and thickly set as to give its internal surface a velvety texture, and which by their absorbent action take up from the intestine the nutritious elements of the digested food. Into the upper part of the small intestine, a few inches below the stomach, there are also discharged two accessory secre- tions, namely, the bile from the liver, and the pancreatic juice from the pancreas. The small intestine terminates, in the lower part of the abdomen on the right side, by a junction at right angles with the large intestine. The large intestine, so called from its greater capa- city as indicated by a transverse measurement, is about five feet long, and from 1 to 2-fr inches in diameter. It extends from its commence- ment in the right iliac region (see ABDOMEN) upward on the right side of the abdomen, then transversely across to the left side, then down- ward upon the left side, then through an S-like convolution to the top of the pelvis, and finally through the cavity of the pelvis to the anus. At the point of junction of the small with the large intestine there are two parallel folds of mucous membrane, with their edges turned toward the cavity of the large intestine, which act as a double valve (called the ileo-caecal valve), allowing the passage of materials in this direction, but preventing their regurgita- tion from the large into the small intestine. The mucous membrane of the large intestine has no villi, but is provided with simple glan- dular follicles, which secrete various excremen- titious materials. This portion of the aliiiuen' tary canal contains also the refuse portions of the food, which, together with the excremen- titious matters supplied by its lining membrane, assume a faecal consistency and appearance from the situation of the ileo-csecal valve down- ward, and are finally discharged from the lower extremity of the large intestine. I. PI i:TI s. Lndns Cineins, a Roman historian and jurist, praetor in Sicily 209 B. C. He was