Page:Structure and functions of the body; a hand-book of anatomy and physiology for nurses and others desiring a practical knowledge of the subject (IA structurefunctio00fiskrich).pdf/151

 capillaries, an active part being taken by the cells. By the time they reach the liver the peptones have been changed back into proteins. In fact, peptones seem to have some poisonous effect upon the blood if they get into it as such.

The Large Intestine.—The large intestine differs from the small in size and in fixity of position, lying curved in horseshoe shape above and around the small intestine. It is five or six feet long, large in caliber, and is thrown into crosswise folds. It has the same four coats as the small intestine, but the mucous coat is pale and smooth, without villi. Its glands are the crypts of Lieberkühn and the solitary glands. The arteries are branches of the superior and inferior mesenteric and the nerves come from sympathetic plexuses.

The blind sac lying in the right iliac fossa, with which the large intestine begins, is called the cecum, and into this the ileum opens, the ileo-cecal valve preventing regurgitation. Just below the ileo-cecal opening is the vermiform appendix, a narrow, worm-like tube with a blind end, varying in length from one to nine inches, but generally about four and one-half inches long, which, so far as is known, is functionless as well as dangerous. People have been born without an appendix and it has in rare instances grown again after operation. Its base is located in the living by McBurney's point, a point two inches from the anterior superior spine of the ilium on a line drawn from the spine to the umbilicus.

From the cecum the intestine ascends in what is known as the ascending colon along the abdominal wall at the right to the under surface of the liver, where it turns in the hepatic flexure abruptly across the body to the left, passing below the liver, stomach, and spleen in the transverse colon. In the splenic flexure it turns down the left abdominal wall, the descending colon passing to the crest of the ilium, where there is another curve, the sigmoid flexure, leading to the rectum, which passes for six or eight inches down along the vertebræ, a little