816 THE INTESTIIs'ES. 



merable small glands, whicli secrete a mucous fluid to lubricate the passages 

 and defend it from irritating or acrimonious substances ; and it is said to 

 be villous, from its soft velvet-like feeling. This coat is crowded with in- 

 numerable minute orifices that are the commencement of vessels called 

 ladeals, from the milky appearance of their contents, by which the nutri- 

 tive part of the food is taken up ; and these vessels, uniting and passing 

 over the mesentery, carry this nutritive matter to a proper receptacle 

 for it, whence it is conveyed into the cu'culation, and distributed to 

 every part. 



The intestines are chiefly retained in their relative positions by the 

 mesentery, c (middle of the intestines), which is a doubling of the peri- 

 toneum, including each intestine in its folds, and also enclosing in its 

 duplicatures the arteries, the veins, the nerves, and the vessels which 

 convey the nutrunent from the intestines to the circiilation. 



The first of the small intestines, and commencing from the right ex- 

 tremity of the stomach, is the duodenum, a, a very improper name for it 

 in the horse, for in that animal it is nearly two feet in length. It is the 

 largest and shortest of all the small intestines. It receives the food con- 

 verted into chyme by the digestive power of the stomach, and here it 

 undergoes another and very important change. It is mixed with the 

 bile, and the secretion from the pancreas, which enter this intestine about 

 five inches from its commencement. The bile seems to be the principal 

 agent in the change now effected, for no sooner does it mingle ^vith the 

 chyme than that fluid begins to be separated into two distinct ingredients 

 — a white thick liquid termed chyle, containing the nutritive part of the 

 food, and a yellow pulpy substance, the innutritive or excrementitious 

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

 the rectum. 



The process of digestion being thus to a certain extent completed, the 

 food passes through the other small intestines, and during that passage 

 the chyle, or nutritious portion, is absorbed by the lacteals, so called from 

 the milky appearance of their contents, to be conveyed into the cii'culation, 

 and converted into blood, while the non-nutritious portion passes on to the 

 larger intestines. 



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 colour 

 than the duodenum. It is more loosely confined in the abdomen — floating 

 comparatively unattached 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 Ileum. There is no point at which the jejunum can be said to 

 terminate and the ileum commence. 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 is evidently less vascular than the jejunum, and gi-adually 

 diminishes in size as it approaches 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, their movements and 

 their relative positions being regulated only by the size or fulness of the 

 stomach, and the stage of the digestive process. 



The small intestines derive their blood from the anterior mesenteric 

 artery, which divide into innumerable minute branches that ramify 

 between their muscular and villous coats. Their veins, which are destitute 

 of valves, return the blood into the vena portae. 



The larjje intestines are three in number : — the ccecwn, the colon, and 



