THE INTESTINES. 211 



The inte&tines are chiefly retained in their relative positions 

 by the mesentery, c, (middle of the intestines), which is a 

 doubling of" the peritoneum, including each intestine in its folds, 

 and also inclosing in its duplicatures the arteries, the veins, the 

 nerves, and the vessels which convey the nutriment from the 

 intestines to the circulation. 



The first of the small intestines, and commencing from the 

 right extremity of the stomach, is the duodenum, a. It is the 

 largest and shortest of all the small intestines. It receives the 

 food partially converted into chyme by the digestive power of 

 the stomach, and in which it undergoes another and very im 

 portant change ; a portion of it being converted into chyle. It 

 is here mixed with the bile and the secretion from the pancreas 

 which enter this intestine about five inches from its commence- 

 ment. The bile seems to be the principal agent in this change, 

 for no sooner does it mingle with the chyme than that fluid 

 begins to be separated into two distinct ingredients — a white, 

 thick liquid termed chyle, and containing the nutr-tivj part of 

 the food, and a yellow, pulpy substance, the imiutritive portion, 

 which, when the chyle is all pressed from it, is evacuated through 

 the rectum. 



The next portion of the small intestines is the Jejunum, so 

 called because it is generally found to be empty. It is smaller 

 in bulk and paler in color than the duodenum. It is more 

 loosely confined in the abdomen — floating comparatively unat- 

 tached in the cavity of the abdomen, and the passage of the 

 food being comparatively rapid through it. 



There is no separation or distinction between it and the next 

 intestine — the Hewn. Together they form that portion of the 

 intestinal tube which floats in the umbilical region : the latter, 

 however, is said to occupy three-fifths, and the former two-fifths, 

 of this portion of the intestines, and the five would contain about 

 eleven gallons of fluid. The ileum diminishes in size as it ap- 

 proaches the larger intestines. 



These two intestines are attached to the spine by a loose 

 doubling of the peritoneum, and float freely in the abdominal 

 cavity. 



The large intestines are three in number : — the ccccum, the 

 colon, and the rectum. The first of them is the ccECum (blind 

 o-ut), e, — it has but one opening into it, and consequently every- 

 thing that passes into it, having reached the blind or closed end. 

 must return, in order to escape. It is not a continuation of the 

 ileum, but the ileum pierces the head of it, as it were, at right 

 angles, {d) and projects some way into it, and has a valve — the 

 valvula coli — at its extremity, so that what has traversed trie 

 ileum and entered the head of the colon, cannot return into the 



