LYMPHOID GLANDS. 131 



membrane. It contains numerous lymphoid cells and diffuse 

 lymphoid tissue, and is richly supplied with lymphatics and 

 blood-capillaries. The muscularis mucosce consists of two thin 

 layers of involuntary muscle, the inner circular, the outer 

 longitudinal. It lies just below or outside of the extremities 

 of Lieberkiihn's glands, and separates the mucosa from the 

 submucosa. It sends fibres up into the villi. 



The submucosa of the small intestine is a loose areolar 

 layer, permitting some play between the mucous and muscular 

 coats. It contains the larger blood and lymphatic channels, 

 which send capillaries into the mucosa, and a nerve-plexus, the 

 plexus of Meissner. 



The, duodenal glands, or glands of Brunner, are rounded 

 compound racemose or perhaps tubular glands, of the s&&wT 

 type, located in the submucosa of the duodenum. Each 

 empties by a long outlet-duct which pierces the muscularis 

 mucosa? and traverses the mucosa to the surface, parallel to the 

 glands of Lieberkiihn. Their cells are similar to those of the 

 intestinal glands. 



The lymphoid glands of the small intestine are definite and 

 dense masses of lymphoid tissue, which occur in addition to 

 the diffuse adenoid tissue of the mucosa ; they are of two 

 kinds, solitary and agminate. The solitary glands are spherical 

 nodules or follicles of lymphoid tissue, occurring singly, and 

 circumscribed by a condensation of the surrounding connective 

 tissue. They are situated in the submucosa, or may extend 

 into the mucosa and even to the epithelial covering. They 

 occur throughout the small and large intestines, but are more 

 numerous toward the lower part of the ileum and the begin- 

 ning of the colon. 



The agminate glands, or Pgz^ris patches, are aggregations 

 of a number of solitary lymph-follicles placed in juxtaposi- 

 tion, and sometimes surrounded by looser adenoid tissue. 

 They occupy the submucosa, some of the follicles in places 

 also piercing the muscularis mucosaB and extending into the 

 mucosa and to the surface-epithelium. They form longitudi- 

 nal patches two to eight centimetres long opposite the 

 mesenteric attachment of the intestine, and are most abundant 

 in the lower portion of the ileum. 



The muscular coat of the small intestine comprises two 



