148 



NO n MA L JILSTOL Y. 



mucosa. The muscular fibres in the villi probably aid iu the pro- 

 pulsion of the chyle in these lymphatics (Fig. 127). 



Fig. 127 



■ K 





y — 



- - - - g» . — e 



Axial section of villus of the dog. (Kultschitzky.) a, epithelial covering with cuticle ; b, 

 goblet-cell ; c.'space between tapering ends of the epithelial cells ; d, cell of the base- 

 ment-membrane ; e, smooth muscular fibres; /, reticulum of the tunica propria (the 

 lymphoid cells have been, for the most part, removed); g, lumen of the central lymphatic 

 The bloodvessels are not represented. 



The submucous coat of the intestine is composed of areolar fibrous 

 tissue. Outside of this coat is the muscular coat, divisible into two 

 layers, which is covered throughout the whole circumference of the 

 intestine, except at the line of mesenteric attachment, with a serous 

 investment of the peritoneum. 



In the duodenum the submucous coat contains compound tubular 

 glands, the glands of Brunner, the ducts from which penetrate the 

 miiscularis mucosae and open upon the surface of the mucous mem- 

 brane, between the crypts of Lieberkiihn. Here and there, in the 

 duodenum, are little collections <>f lymphadenoid tissue, occupying' 

 an enlarged villus and often extending through the muscularis 

 mucosae into the submucous areolar tissue (Fig. 128). These 

 lymph-follicles may be regarded as the result of an increase in the 

 amount of reticular tissue of the villus, which has replaced the 

 other structures usually present. In the lower portions of the 



