394 THE SOLIDS. 



of the action of the gastric juice to such an extent as to dis- 

 solve the follicles entirely. 



The follicles dip into the thickness of the mucous mem- 

 brane to a variable extent in the small and large intestines ; 

 their extremities reach nearly to the submucous cellular tissue, 

 and in the lower part of the rectum they are much elongated, 

 and continued for some distance into the submucous fibrous 

 tissue between the mucous and muscular coats ; the follicles 

 usually terminate in rounded and sometimes even in dilated 

 and bifurcated extremities. (Plate L. fig. 7.) 



The object attained by these innumerable follicular inver- 

 sions of the mucous membrane of the stomach and intestines 

 is obvious, viz. a greatly extended surface for secretion. 



The mucus with which the intestinal canal is so abun- 

 dantly provided, is chiefly secreted by the epithelium con- 

 tained in these follicles. 



Todd and Bowman thus describe the epithelium of the 

 stomach cells in the Physiological Anatomy : " They (the 

 epithelial particles) seem to . lie in a double series, the 

 deeper being in course of development, while the more su- 

 perficial is in course of decay. It has appeared to us that 

 each particle when arrived at maturity has, besides the 

 nucleus, granular contents enclosed, and that at a subsequent 

 period the granular contents escape at the free extremity by 

 a debiscence or opening of the wall, at that part, having the 

 transparent husk with its nucleus subsisting for some time 

 longer. The clear structureless mucus which is almost always 

 found occupying the cells and covering the surface of the 

 membrane seems to be the altered contents of these particles 

 after their escape, for the uniform existence of a minute 

 cavity in the centre of it, when it fills the cells, shows that it 

 has oozed out from every part of their wall so as gradually 

 to fill them up." 



The ridges or spaces between the follicles of the stomach 

 and large intestines in the human subject are occupied with 

 a plexus of vessels larger than capillaries (see Plate \j\..Jig. 

 1.); these are situated on the deep surface of the basement 

 membrane, while the epithelial scales are upon its superficial 



