214 INTESTINAL DIGESTION 



patches of Peyer are wanting. They usually are in less number than 

 the first variety. 



The villi are large and prominent on the mucous membrane cover- 

 ing the first variety of Peyer's patches, especially at the summit of the 

 folds. In the second variety the villi are the same as over other parts 

 of the mucous membrane, except that they are placed more irregularly 

 and are not so abundant. 



The follicles of the patches of Peyer are closed and are somewhat 

 pear-shaped, with their pointed projections directed toward the lumen 

 of the intestine. Just above the follicle, there usually is a small open- 

 ing in the mucous membrane, surrounded with a ring of intestinal 

 tubules, and leading to a cavity, the base of which is convex and is 

 formed by the conical projection of the follicle. The diameter of the 

 follicles is Y V to 2T or tV ^ an ^ nc ^ (-34 to I or 2 millimeters). The 

 small follicles usually are covered by mucous membrane and have no 

 opening leading to them. Each follicle consists of a rather strong 

 capsule composed of an almost homogeneous or slightly fibrous mem- 

 brane, enclosing a semifluid, grayish substance, cells, bloodvessels and 

 possibly lymphatics. The semifluid matter is of an albuminous charac- 

 ter. The cells are small, rounded and interspersed with small free 

 nuclei. The bloodvessels have rather a peculiar arrangement. In the 

 first place they are distributed between the follicles, so as to form a 

 rich network surrounding each one. Capillary branches are sent from 

 these vessels into the interior of the follicle, returning in the form of 

 loops. Lymphatic vessels have not been distinctly shown within the 

 investing membrane. They have been demonstrated surrounding the 

 follicles, but it is still doubtful whether they exist in their interior. All 

 that is known is that, during digestion, the number of lacteals coming 

 from the Peyerian patches is greater than in other parts of the mucous 

 membrane; but vessels containing a milky liquid are not seen within the 

 follicles. 



The description of the follicles of the patches of Peyer answers, in 

 general terms, for the solitary glands, except that the latter exist in both 

 the small and large intestines. They are sometimes called lymph-nodes 

 a name given to the lymphatic glands from their close resemblance 

 to these bodies in their general structure (see Plate V, Fig. 5). 



INTESTINAL JUICE 



Nearly all observers agree that the intestinal juice which they have 

 been able to collect is yellow, thin and strongly alkaline; but some 

 have found it thin and opalescent, while others state that it is viscid 



