THE SMALL INTESTINE. 



167 



glands, but occupy chiefly the submucosa (Fig. 209). The upper part of 

 the duodenum possesses, therefore, a double layer of true glands the 



Submucosa Villi 





Mucosa 



Sub- 

 mucosa 



Longi- 

 tudinal 

 muscle 



FIG. 207. Longitudinal section of duodenum ; plicae circulares are cut across, showing relation of these 



folds to the villi. X n. 



crypts of Lieberkuhn within the mucous coat, beneath which, in the sub- 

 mucosa, lie the glands of Brunner. The individual duodenal glands, tubo- 



Duct of Brunner's gland Villus 



Gland of Lieberkuhn 



Lymph- 

 nodule 



Brunner's v 

 glands 



Circular ,' 

 muscle 



Longitudinal 



muscle '^'-~M 

 Serous coat 



FIG. 208. Longitudinal section of duodenum, showing Brunner's and Lieberkuhn's glands, villi and 



lymph-nodule. X 68. 



alveolar mucous in type, form somewhat flattened spherical or polygonal 

 masses (.5-2 mm.), consisting of richly branched tubules ending in dila- 

 tations. Their excretory ducts pierce the muscularis mucosae and, after 



