INTESTINE (Lat. intestinurn, neut. sing. of intestinns, internal. from intim. within, from in, in). The part. of the digestive tract between the stomach and the anus. The small intestine in cludes the duodenum. the jejunum. and the ileum, and averages 22 feet 6 inches in the male, 23 feet 4 inches in the female. With the exception e the duodenum, the small intestine lies in gen. oral in the central part of the abdominal cavity, bounded by the largo intestine on either side and above. The jejunum and ileum are connected to the posterior abdominal mall by•a rellexion of the peritoneum, called the mesentery. The duodenum is about 10 inches long, to 2 inches in diam eter, and curved like a horseshoe. The heal of the pancreas is received into the curve. It is the part of the intestine vvhieli is continuous Willi the stomach at its pyloric extremity. The jeju num is described under its title. The jejunum and ileum vary much in the arrangement of coils, and there is little regularity in their posi tion beyond that already stated. The term ileum is applied to the last three-tifths of the small gut.. It ends at the ileo-eweal valve, through which the contents of the small intestine eseape into the head of the colon. The small intestine has four coats: Serous or peritoneal, nmseular, areolar or submucous, and mucous. The last is covered with minute prolongations called and lined with columnar cpithelimn. There are few na va/a' ronn i ren I es, or folds of mucous membrane, in the ileum. Solitary glands alone or in aggre gations (called l'eyer's pat('hes) are found in the lower part of the ileum. These are largely obliterated in typhoid fever.
The large intestine is divided into the crecum: the ascending. transverse. and descending colon: the sigmoid flexure: and the 'whim. It is so placed as to encircle the small intestine. The e•ecnin lies in the hollow of the right iliac region. From this point the colon rises to the liver. then crosses the abdominal cavity to the opposite side, passing below the stomach to the spleen: then. making a sharp turn, it. descends to the left iliac fossa, where it forms a loop termed the sigmoid flexure (from its resembling the old (:reek letter sigma) : and finally. now termed the rectum, curves hack to the head of the sacrum, thence follows the concavity of the sacrum, and thence curve, backward to the anus. Attaehed to the c:ecum. generally back of it, is a small. short, blind tube, alamt 3 to 4 inches lone'. opening into the gut, and termed the vermiform appendix (q.v.). The subdivisionp, of the large intestine are treated under their own titles. The constant motion of the intestine (peristalsis). by which its contents are conveyed along, is due to the con tractions of the muscular fibres of the gut. See DicEsmoN.
n ISTOLOGY.
The wall of the intestine is composed of four distimt coats, which from without inward are known as: (1) The serous coat. (2) the muscular coat, (3) the sulinmeous coat, and (4) the mucous coat or mucous membrane. These coats present certain differences in structure in the two main divisions of the intestine, the small in testine and the large intestine.