THE INTESTINES. 91 



The lacteals pierce the muscularis mucosae, and in the submS^cosa 

 are in connection with a plexus of lymphatic tubes and spaces. 

 eventually unite with efferent lymph tubes (J), and pass by means ol 

 the mesentery to the receptaculum chyli. 



Connected with the plexus of lymphatics in the submucosa are 

 minute nodules of lymphoid structure (adenoid tissue), which have 

 unfortunately been called lymphatic glands. They are in no sense 

 glands. , 



Slit up a portion of intestine along the attached border, and care- 

 fully examine the inner surface: it will present a velvety appearance, 

 due to the minute villi. You will also find little nodules, perhaps 

 one-sixteenth of an inch in diameter, scattered here and there in the 

 mucous coat. These are the lymphatic nodules alluded to above 

 the so-called solitary glands. One of the nodules is indicated in the 

 diagram at I, with its point projecting into the crypt F. 



Continuing your examination of the gut, you will discover, espe- 

 cially in the ileum, roughened patches perhaps two inches long by 

 half an inch broad. These are collections of the lymphatic nodules 

 described in the last paragraph, and are termed agminate glands or 

 patches of Peyer. They have no secretive power, being simply in con- 

 nection with, and a part of, the chain of lymphatics in the walls 

 of the intestine. They consist of adenoid tissue, which will be de- 

 scribed with the lymphatics. 



To recapitulate, the small intestine presents the following: 



1. The villi, each containing a plexus of blood capillaries and the 

 lymphatic or absorbent vessel. 



2. Crypts or follicles of Lieberkuhn, which are simply depressions 

 between the villi. 



3. Brunner's glands, the only true glands of the gut, unless the 

 crypts are so classified. 



4. Solitary lymphatic nodules, the so-called solitary glands. 



5. Agminate lymphatic nodes, agminate glands or patches of Peyer, 

 consisting of aggregations of solitary lymphatic nodules. 



The muscular part of the intestine is arranged not unlike that por- 

 tion of the stomach, i. e., with an inner circular and an outer longi- 

 tudinal layer. Between the two is located Auerbach's plexus of non- 

 medullated nerves. A similar plexus, Meissner's, is found in the sub- 

 mucosa. These we shall not attempt to demonstrate. 



A small quantity of areolar tissue connects the external longitudi- 

 nal muscular layer with the peritoneal investment. 



