THE SMALL INTESTINE. 



1637 



this respect much variation exists, which partially accounts for the differences found 

 at the lower part of the small intestine, where often the valves are absent, while at 

 other times they are well marked. Sernoff ' found in subjects treated with chromic 

 acid injections that the valves were as frequent in one part of the small intestine 

 as another, but less regularly transverse in the lower. He observed places without 

 valves, usually at the convexity of folds, in all parts of the gut, and regards them as 

 largely dependent upon the condition of the muscular coat. It is certain, however, 

 that the valves of the upper part of the intestine are independent of this influence ; 

 those in the lower portion, perhaps, may be produced in such manner. 



Glands. The structures within the alimentary tube to which the term "glands" 

 has been applied include two entirely different groups, the true and the false glands. 



FIG. 1386. 



Stroma of tunica propria 



Lacteal 



Surface epithelium 



Submucous coat 





Gland of Lieberkiihn 





^ffi- ^S s*w3&^ v~^*^;: cj^&S*.. 



g 



*"- , ** "V->-. - '-- _ ">* " ^ ' 



Circular muscle- 



Transverse section of small intestine (jejunum), showing villi cut lengthwise. X 150. 



The former are really secreting organs, the glands of Lieberkuhn and of Brunner ; 

 the latter are more or less extensive accumulations of adenoid tissue, and are appro- 

 priately spoken of as lymphatic nodules or follicles. 



The glands of Lieberkiihn are simple tubular depressions which are found not 

 only throughout the entire small intestine, but in the large as well. They are very 

 closely set, narrow, and extend the thickness of the mucous coat as far as its mus- 

 cular layer. In length they vary from .3 .4 mm. and in diameter from .060 .080 mm. 

 The fundus of the glands is slightly expanded and in exceptional cases divided. The 

 lining of the crypts rests upon a delicate basement membrane, and consists of a single 



1 Internal. Monatsschrift f. Anat. u. Physiol., Bd. xi., 1894. 



