524 SPECIAL HISTOLOGY. 



cles 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 reti- 

 culated, 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, per- 

 haps, 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 concerning the phy- 

 siology 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^ 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 bloodvessels and perhaps also from matters 

 not of a fatty nature, absorbed from the intestine, a part of which, in 

 all probability, is at once taken up by the internal bloodvessels, while 

 the larger proportion is excreted and absorbed by the lymphatics. The 

 period of their greatest activity (when they become distended) coincides 

 with that of the intestinal absorption, either because they absorb from 

 the intestine or because they simply participate in the greater activity 

 of the intestine at this time ; and perhaps the more albuminous matters 

 which they yield may be connected with the development of cells in the 

 chyle. This hypothesis will hold good in its principal outlines, even if 

 in future the direct connection of the lymphatics with the follicles, or the 

 occurrence of lacteals ^Yithin them, should be demonstrated ; at any rate, 

 it will not be blamed for being too wide of the facts. 



§ 156. 3iucous memhrmie of the large intestine. — The structure of 

 the mucous membrane in the large intestine agrees so closely in essen- 

 tials with that of the small intestine, that it may suffice here to draw 

 attention to a few points only. 



The mucous membrane of the large intestine, if we except the rectu7n, 

 has no proper folds, for the transversely fibrous muscular layer also 

 enters into the ^:>ZiC(:f^ sigmoidecv. The villi also are absent, from the 

 edoje of the ileo-ctecal valve, into which the muscular tunic likewise 

 enters, onwards ; and the mucous surface, apart from some occasional, 

 hardly perceptible, small, wart-like elevations, is even and smooth. It 

 is difficult to detect the muscular layer of the mucous membrane in the 

 human colon, though it is unquestionably present ; it is more distinct in 

 the rectum. In animals I find it well developed. According to Brllcke, 

 in the colon (of animals ?) its longitudinally and transversely fibrous 

 layers, which also exist here, are only 0'013 of a line thick, the diminu- 

 tion having taken place at the expense of the external longitudinal 



