THE INTESTINES. 471 



The omasum completes the trituration and attenuation of the food, by pressing it between 

 its leaves. 



The abomasum acts as a true stomach, charged with the secretion of the gastric juice ; in 

 this reservoir occur the essential phenomena of gastric digestion. 



Comparison of the Stomach of Man with that op Animals. 



In its form, the stomach of Man much resembles that of the Caruivora. 



The insertion of tlie oesophagus, however, does not offer so large an infundibulum. The 

 organ is situated in the left hypochondriac, and is nearly horizontal. 



Everywhere the mucous membrane is red and glandular; the muscular fibres are disposed 

 in three planes, as in Solipeds, but the third is found only in the middle portion of the stomach, 

 two alone being present towards the cardia and pylorus; where the stomach is largest the 

 contractile tunic is thinnest. 



The Intestines (Figs. 275 to 283). 



The alimentary canal is continued from the stomach, in the abdominal 

 cavity, by a long tube doubled on itself a great number of times, and which 

 terminates at the posterior opening of the digestive apparatus. This tube is 

 the intestine. Narrow and uniform in diameter in its anterior portion — which 

 is named the small intestine — it is irregularly dilated and sacculated in its 

 posterior part — the large intestine. These two portions of a whole, so markedly 

 defined in all the domesticated Mammals, are but imperfectly distinguished 

 from one another with regard to the digestive phenomena occurring in their 

 interior. We will study them in all the animals which interest us, and conclude 

 by a general and comparative examination of the entire abdominal portion of 

 the digestive canal. 



Preparation. — The study of the intestines does not demand, properly speaking, any special 

 preparation; it being sufficient to incise the inferior wall of the abdomen to expose these 

 viscera. As their mass, however, is heavy and unmanageable, it is advisable to expel their con- 

 tents in a manner similar to that recommended for the preparation of the stomach : a puncture 

 at the point of the caecum allows the escape of the substances accumulated in that reservoir; 

 those which fill the large colon may be removed by an incision made towards the pelvic curva- 

 ture, and those in the floating colon by the rectum. The small intestine mny be evacuated by 

 three or four openings at about equal distances in the length of the viscus. Having done this, 

 inflate the intestines to somewhat of their natural volume ; this preparation then permits the 

 general arrangement of the intestinal mass in the interior of the abdomen to be easily studied. 



It would be well to remove the entire mass altogether from the body, and lay it out on a 

 table, so as to isolate the various parts, study them in succession, and note their form. 



In order to study the structure of a portion of the intestine, it si ould be treated as was the 

 stomach — plunged into boiling water for a few minutes, then the serous and mucous membranes 

 removed. 



1. The Small Intestine (Figs. 282, 283). 



Length — Diameter. — The small intestine is a long tube, which, in a horse of 

 ordinary height, may average about 24 yards in length, and from 1 to If inches 

 in diameter. This diameter is susceptible of variation, according to the state of 

 contraction of the muscular tunic of the viscus. 



Form. — This tube is cylindrical, doubled on itself, and presents two cur- 

 vatures — one convex., perfectly free ; the other concave, named the small 

 curvature, which serves as a point of insertion for the mesentery that sustains 

 the organ. Removed from the abdominal cavity, freed from the serous folds 

 which suspend it, and distended by air or water, this disposition of the small 

 intestine naturallv causes it to twist in a spiral manner. 



