THE INTESTINES. 105 



with in immense quantities in the small intestine and 

 stomach, in catarrhal affections of the alimentary tract, may 

 very probably be entirely or partially pathological, since the 

 occurrence of such follicles has been demonstrated in other 

 organs also (in the liver, according to Virchow). The solitary 

 follicles have the same position as the elements of the patches, 

 only they occur also in the mesenteric border and support villi 

 upon their intestinal surface, which is usually somewhat 

 convex. 



[I consider it as quite certain, that the follicles of Peyer's 

 patches have no apertures, but 1 may here adduce the follow- 

 ing facts. 1. In animals examined while fresh, the cap- 

 sules are invariably closed, as may be very readily seen in the 

 well developed patches of the Pig, Sheep, Cat, Dog, &c, 

 which I particularly recommend for the examination of these 

 organs, because the patches in the human subject have so 

 frequently undergone alteration. 2. The appearance of an 

 aperture may proceed from the depression of the mucous 

 membrane over the single follicles, especially when the pro- 

 jecting portion of the wall of the follicles is not very tense. 

 3. In man, the closed follicles of the intestine are subject to 

 very many morbid changes ; they are frequently ruptured and 

 so altered, that in place of the patches nothing remains but a 

 reticulated, indistinctly pitted surface. As Virchow was the 

 first to show (Med. Reform. 1848, No. 10, p. 64), they may 

 also burst after death, if they are allowed to stand in water or 

 in a warm place ; whence, perhaps, many of those apertures 

 which are met with in the dead subject should be regarded as 

 the result of putrefactive change. 



It is easy to understand, that little can be said concern- 

 ing the physiology of Peyer's follicles so long as their relations 

 to the lymphatics are not understood. They, and the follicles 

 of the intestine in general, appear to me to be closed glandular 

 organs, analogous to the splenic follicles, the tonsils, and the 

 lymphatic glands, which contain peculiar elements and a 

 vascular network. In these a constant development of cells 

 takes place and at the same time, substances are elaborated 

 from the plasma, supplied by the blood-vessels and perhaps also 

 from matters not of a fatty nature, absorbed from the intestine, 



