400 THE DIGESTIVE APPARATUS IN MAMMALIA. 



The rumen is a sac where the aliment taken during feeding-time is kept in reserve, 

 and whence it is again carried into the mouth during rumination, after having been 

 more or less softened. 



The reticulum participates in the functions of the rumen, to which it is only a kind 

 of diverticulum. But it is particularly with regard to liquids that it plays the part of a 

 reservoir ; the solid substances contained in it being always diluted by a larger quantity 

 of water. 



The (zsophageal groove carries into the omasum the substances swallowed a second 

 time after rumination, or even those which the animal ingests in very small quantity for 

 the first time. 



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

 between its leaves. 



The abomasum acts as a true stomacli charged with the secretion of the gastric juice ; 

 in this reservoir occur the essential phenomena of gastric digestion. 



COMPARISON OP THE STOMACH OP MAN WITH THAT OF ANIMALS. 



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



The insertion of the 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 superficial and deep are particularly 

 directed towards the left sac. 



THE INTESTINES. (FigS. 204, 205, 206.) 



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 ante- 

 rior portion, which is named the small intestine, it is irregularly dilated 

 and sacculated in its posterior part, the large intestine. These two por- 

 tions, so markedly defined in all the domesticated mammals, are but im- 

 perfectly distinguished from one another with regard to the digestive 

 phenomena occurring in their anterior. 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 contents 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 toward the pelvic curvature, and those in the floating colon 

 by the rectum. The small intestine may 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 gen- 

 eral 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. 



1. The Small Intestine. (Figs. 204, 205, 206.) 



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, presenting two cur- 

 vatures : one convex, perfectly free ; the other concave, called the small cur- 

 vature, which serves as a point of insertion to the mesentery that sustains 



