GLANDS. 487 



In the mesentery, the lacteals become variously coiled and 

 knotted, these aggregations of coils, together with fibrous 

 tissue and blood-vessels, forming the mesenteric glands ; the 

 lymphatic glands have a similar structure and origin, being 

 placed in certain determinate regions of the human body. 



The lymphatics which enter a gland, or the afferent lym- 

 phatics, vary in number from two to six ; they divide at a 

 short distance from the gland into several smaller vessels, 

 and enter it by one of the flattened surfaces: while those which 

 leave it, or the efferent lymphatics, escape from the gland on 

 the opposite, but not unfrequently on the same surface ; they 

 also consist, at their junction with the gland, of several small 

 vessels, which unite after a course of a few lines and form 

 from one to three trunks, often twice as large as the afferent 

 lymphatics. 



The afferent lacteals and lymphatics, as they enter the 

 gland, become somewhat dilated ; and the epithelium, in place 

 of forming a single layer of flattened cells firmly adherent to 

 the walls of the tubes, consists of several layers of rounded 

 and glandular cells, which are very readily displaced. 



These cells are doubtless more or less concerned in the 

 elaboration of the fibrin of the chyle ; and there is much 

 reason to believe that from time to time the more mature 

 cells become detached from the walls of the lacteals, and are 

 conveyed along with the chyle into the blood, where they 

 become the white or granular corpuscles of that fluid. 



Such is a very brief outline of the minute anatomy of the 

 mesenteric and lymphatic glands. 



This is probably the most fit place to introduce a few re- 

 marks on the structure of the villi themselves, the chief agents 

 in the absorption of the chyme, and the parts in which the 

 lacteals themselves take their origin. 



The Villi of the Intestines. 



The villi exist in the whole extent of the small intestines, 

 but it is in the lower part of the duodenum and the whole 



