STRUCTURE OF THE SMALL INTESTINE. 



225 



which the particles of fat take when they are undergoing the 

 process of absorption (p. 261) i. e., from the lumen of the in- 

 testine (1) through the interstitial or cement-substance of the 

 columnar epithelium ; (2) through the same substance in the 

 basement-membrane ; (3) through the reticulum of the matrix ; 

 (4) through the interstitial substance of the lacteals into the inte- 

 rior of this structure. 



The lacteals are the lymphatic vessels of the small intestine, 



Epithe- 

 lium of 

 villus. 



Central 



chyle-vessel 

 of villus. 



-Mucosa. 

 Muscularis 

 mucosse. 



Submucosa. 



S; Plexus of 

 5?"" lymph-ves- 



sels. 



^_ Circular mus- 

 -"" cular layer. 

 !- Plexus of 



__ _ _ _ ^ _ a ___ ^ __ ^_ = ^^_ 



&%%>;^y^^^ 



layer with 

 Vein. serous coat. 



FIG. 120. Schematic transverse section of the human small intestine (after F. P. 



Mall). 



which, on leaving the villi, form a plexus in the mucous and sub- 

 mucous tissue, and discharge into larger lymphatic vessels, and 

 theii. contents finally pass into the thoracic duct. 



Brunner's Glands (Fig. 121). In the submucous coat of the 

 upper part of the duodenum, and to a less extent in that of the 

 lower part, and in the beginning of the jejunum, are certain glands 

 known as the glands of Brunner, or the duodenal glands. These 

 are tubulo-racemose glands, similar to the lobules of a salivary 

 gland. They discharge through ducts which open upon the sur- 



15 



