320 THE ANATOMY OF THE HORSE. 



the bowel between them into alternate ridges and furrows. The 

 number of these bands is different at different points. The caecum has 

 four. The colon in its 1st part has also four. Three of these disappear 

 on the 2nd part, so that at the pelvic flexure there is only a single 

 band, on the concave side of the flexure. The single band is continued 

 along the 3rd part, and near the diaphragmatic flexure other two bands 

 originate. The 4th part has three bands. The single colon has two 

 bands, one on each curvature, and these are continued on the first half 

 of the rectum, but are lost on its terminal half, as will be seen on the 

 dissection of the pelvis. The inner layer of circular fibres is uniformly 

 distributed. 



3. The Submucous Coat is a layer of loose areolar tissue uniting the 

 muscular and mucous coats. 



4. The Mucous Coat lines the cavity of the bowel. Its surface is 

 covered by a single layer of columnar epithelium, and in its deeper part 

 it contains solitary glands and glands of LieberJcuhn^ similar to those of 

 the small intestine. No Peyer's patches are found in it, and it is with- 

 out villi. The foldings of the wall of the bowel produced by the longi- 

 tudinal muscular bands involve all the coats, and the interior therefore 

 shows the alternately ridged and furrowed appearance already seen on 

 the exterior. 



Orifices of the Crook. — These are the apertures of communication with 

 the ileum and w T ith the large colon. At its termination the ileum pro- 

 jects slightly into the interior of the csecum, and beneath the mucous 

 membrane surrounding the orifice there is developed a ring of mus- 

 cular fibres. This fold of mucous membrane with its included muscular 

 fibres constitutes the ileo-ccecal valve. The opening of communication 

 with the colon is considerably larger than the preceding, above which 

 it is placed. 



Directions. — The student must now return to the parts left within the 

 abdominal cavity, where, without further dissection, he will be able to 

 examine the stomach, spleen, pancreas, and liver. Should the stomach 

 be nearly empty, the ligature should be untied from the cut end of the 

 duodenum, and by means of bellows that intestine and the stomach 

 should be moderately inflated. To permit this it will not be necessary 

 to ligature the oesophagus. At the present stage the above-mentioned 

 organs may be studied as regards their form, situation, and relations, 

 their structure being postponed for future consideration. 



The Stomach (Plates 43 and 44) is the most dilated segment of the 

 alimentary tube. When moderately distended, it will be seen to have 

 the following configuration. It possesses an anterior and a posterior 

 surface, both being smoothly rounded. It has a concave or lesser cur- 

 vature, which is turned upwards and to the right; and a convex or 

 greater curvature, which is directed downwards and to the left. The 



