THE SMALL INTESTINE. 



397 



Brunner^s glands lie in the submucosa, where they form 

 closely crowded tubules, separated by a small amount of con- 

 nective tissue. Smooth muscle-cells, starting from the muscu- 

 laris mucosse, are of ten seen to pass between them. These con- 

 voluted tubules resemble and correspond to the gastric glands, 

 but have here attained a much greater degree of development. 



k 



FIG. 170. Vertical section throuerh a human Peyer's patch, with its lymphatics injected : a. intestinal 

 villi with their lactea's ; 6, Lieberkuhnian glands; c, muscular layer of the mucous membrane; rf, apex 

 of the follicle ; e, middle zone of the follicle ; /, basis portion of the follicle ; g, continuation of the lacteals 

 of the intestinal villi into the mucous membrane proper : A, reticular expansion of the lymphatics in the 

 middle zone ; i, their course at the base of the follicle ; *, continuation into the lymphatics of the submu- 

 cous tissue ; I, follicular tissue in the latter. Frey. 



They also appear to have been pushed down, as it were, from 

 the mucous into the submucous layer. 



An individual gland consists of its long duct lined by col- 

 umnar epithelium, and the branched tubules, which frequently 

 have terminal clusters, resembling true acini. They are, how- 

 ever, only secondary or tertiary diverticula, so that Brunner's 

 glands really conform to the compound tubular type of secret- 

 ing structures (Renaut). Each ultimate diverticulum has an 

 external membrana propria composed of flattened endothelial 

 cells, and a lining of cylindrical, columnar, or prismatic secret- 

 ing epithelia, containing oval nuclei. 



Histologists have described minute capillary channels pro- 

 ceeding from the central lumen of the gland, between the se- j 

 creting-cells, ending just underneath the membrana propria. 

 The author believes these intercellular channels, as they have 



