THE GASTRO-INTESTINAL CANAL, 1 51 



The excretory ducts are also lined with cylindrical 

 epithelium, and open on the surface of the mucous 

 membrane. 



Smooth muscle-cells pass up from the muscularis 

 mucosae into the villi. The central portion of the 

 villi is occupied by one or more usually blind 

 canals the chyle-vessels which pass outward to 

 the bases of the villi, where they usually unite to 

 form a net-work around the orifices of the tubular 

 glands of Lieberkuhn and the lymph-nodules pres- 

 ently to be described ; they then pass into the 

 submucosa, where they form larger anastomosing 

 channels ; from thence trunks pass through the 

 musculosa, receiving vessels from its two layers, and 

 from a well-developed net-work between them. 

 The distribution of the nerves is essentially similar 

 to that in the stomach. 



Closely connected with the lymphatic vessels, and 

 apparently forming a part of the lymphatic appa- 

 ratus of the intestines, are found certain structures 

 called lymphatic nodules, and of these it is custom- 

 ary to distinguish two kinds: i. Solitary nodules ; 

 and 2. Agminated nodules, or Peyers patches. 



i. Solitary Nodules. These are irregularly scat- 

 tered through the mucous membrane of both small 

 and large intestines, in the form of small grayish 

 nodules. They lie chiefly in the mucosa, often 

 piercing the muscularis mucosce and descending into 

 the submucosa ; they are usually spheroidal or pear* 



