J28 SMALL INTESTINE STRUCTURE OF VILLI. [SECT. 153. 



Meissner discovered (l.i.c.) in the submucous layer, a great number 

 of microscopic ganglia. Similar ganglia also occur in the stomach 

 and the large intestine. 



§ 153. The epithelium of the villi and of the surface of the 

 mucous membrane, although, during life, very intimately con- 

 nected with the subjacent parts, and falling off only through 

 accident or disease, is readily detached in the dead body, and is 

 perceptible only upon perfectly fresh portions of the intestine. It 

 everywhere consists of a simple layer of cylindrical cells, slightly 

 narrowed at the lower end, o'oi"' to o - oi2'" in length, 0003'" to 

 CT004-'" in breadth, which have a clear, vesicular, oval, single or 

 double, nucleolated nucleus, but generally contain nothing else 

 except fine granules. These cells, which agree in all their che- 

 mical characters with the deeper cells of the epithelium of the 

 oral cavity, are so intimately connected together, that even after 

 death their contours, when viewed in a longitudinal section, are at 

 first not at all or only indistinctly recognisable ; whilst they appear 

 as a beautiful mosaic structure, when viewed from the surface. 

 Properly speaking, the cylindrical cells become first quite distinct 

 when they are detached from the subjacent surface, which gene- 

 rally takes place in such a manner that they come off in patches, 

 or even all the cells of a villus together, like the calyptra of a 

 moss. 



I have recently shown (Wilrzburg Transactions, vi., 1855) that 

 the membranes of these cells are thickened and very finely striated 

 at their free surface, and that these thickened parts represent, as it 

 were, in their totality, a special membrane covering the cells, 

 similar to the cuticula of plants. By the influence of water, the 

 cells are dilated into long, pyriform, clear vesicles, or burst at the 

 free extremity, and allow their contained mueus to pass as a clear 

 globule, which frequently carries the nucleus along with it. The 

 mucus, which covers the surface of the intestine in the dead body, 

 is, in great part, nothing but the transuded contents of the epi- 

 thelial cells. By the absorption of water, it swells up in form 

 of a thick crust, and always contains numerous ruptured and 

 empty cell-envelopes. 



The normal secretion of the mucus in the small intestine is 

 effected exactly as in the stomach, except that the cells never 

 fall off, and appear usually to discharge their mucus without 

 bursting. 



