318 



THE ANATOMY OF THE HORSE. 



SM 



Directions. — A few feet of the jejunum and about the same length of 

 the ileum should be taken and slit up along the line of attachment of 

 the mesentery. After the pieces have been gently washed, they should 

 be spread on a flat surface with the peritoneal coat downwards. 



4. The Mucous Membrane forms an inner lining to the intestine. It is 

 a soft, velvety-looking membrane which, when healthy and fresh, has a 



pinkish-yellow colour. When a piece of 

 intestine is floated in water the mucous 

 membrane is seen to be studded with short, 

 thread-like projections, to which the velvety 

 appearance of the membrane is due. These 

 are the intestinal villi. Each of them may 

 be regarded as an upheaval of the mucous 

 membrane, containing in its interior micro- 

 scopic blood and lymph vessels, some non- 

 striped muscular fibres, and a framework 

 of lymphoid tissue. The villi are important 

 agents in the absorption of nutrient particles 

 from the contents of the bowel. They are 

 found throughout the whole of the small 

 intestine, but are more numerous in the 

 jejunum than in the ileum. The free 

 surface of the mucous membrane, including 

 the villi, is formed by a single layer of 

 columnar epithelium with goblet cells inter- 

 spersed. Contained within the substance 

 of the membrane are numerous microscopic 

 tubular glands — the glands of Lieberkiihn — 

 whose mouths open on the free surface. 

 The solitary glands are small spherical 

 bodies about the size of a mustard seed. 

 They are covered by the epithelium, and 

 occur throughout the whole intestine, but 

 are more numerous in the ileum than in the 

 jejunum. They are composed of lymphoid 

 tissue. The glands of Peyer, or, as they are commonly called, Peyer's 

 Patches, are circular or oval patches formed by the aggregation of soli- 

 tary glands. They are more numerous in the ileum than in the jejunum, 

 their total number being about one hundred. They are distributed 

 along the convex or free border of the intestine, and hence it was 

 directed that the bowel should be opened along the attachment of the 

 mesentery, so as to leave the patches intact. 



Directions. — The caecum, with the first few inches of the double colon 

 and a like length at the end of the small intestine, should be separated 



Fig. 41. 



Vertical Section through the 

 Wall of the Duodenum, 

 showing the Glands of 

 Brcnnf.r. {Turner). 



V. Intestinal villi ; L. Layer of 

 glands of Lieberkiihn ; B. A 

 Brunner's gland, d. its excretory 

 duct; S.M. Submucous coat; M. 

 Muscular coat. 



