DISSECTION OF THE ABDOMEN, 



309 



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\ patches, are circular or oval patches 



formed by the aggregation of solitary 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 from the rest of the intestinal 

 mass. After the serous and muscular coats 

 have been observed on the inflated csecumj 

 the bowel should be slit open on the convex 

 side of its crook, the incision being extended 

 to its point. The mucous surfiice is to be 

 gently washed; and in connection with its 

 study, the student is to examine the two 

 orifices found on the concave side of the 

 crook. 



Structure of the Large Intestine. 

 Throughout nearly the whole of its length, 

 the wall of the large bowel is made up of 

 four coats, similar to those of the small 

 intestine. 



1. The Serous Coat is derived from the 

 peritoneum, but it forms here a less com- 

 plete investment than in the case of the 



small intestine, considerable areas of the wall being without this cover- 

 ing. Thus, it is absent where the caecum and double colon adhere to 

 the pancreas and abdominal parietes in the sublumbar region; it is also 

 absent where these two intestines adhere to each other, and where the 

 parallel portions of the double colon come into contact; and lastlv, as 

 will be seen in the dissection of the pelvis, the terminal part of the 

 rectum is without a peritoneal covering. 



2. The Muscular Coat consists of two distinct layers — an external longi- 

 tudinal and an internal circular. Throughout nearly the whole extent 

 of the large intestine, the longitudinal fibres are not uniformly distri- 



'^M 



Fig. 36. 



Vertical Section through the 

 Wall of the Duodenum, show- 

 ing THE Glands of Brunner 

 {Tamer). 



v. Intestinal villi ; L. Layer of 

 glands of Lieberkuhn ; B. A Brun- 

 ner's gland, d. its excretory duct; 

 S.M. Submucous coat ; M. Muscular 

 coat. 



