596 



THE DIGESTIVE TRACT. 



the epithelia themselves, which obtain their material from the 

 alkaline blood. It should be borne in mind that gastric juice is 

 a product of living matter, and as such is beyond the reach of 

 chemical analysis. Chemists have tried in vain, so far, to 

 explain the production of gastric juice by complicated formulae 

 and ingenious calculations. The large number of Greek names 

 given to the artificial products in the chemist's retorts sufficiently 

 proves their want of knowledge in this matter. The solution of 



the puzzle, why the acid gastric 

 juice does not digest the wall of 

 the stomach itself, has also oc- 

 cupied speculative minds to a 

 considerable extent, but no sat- 

 isfactory answer has as yet been 

 obtained. 



The delicate fibrous connec- 

 tive tissue between the tubular 

 glands forms a basement layer, 

 which furnishes support for the 

 epithelia, and carries the blood- 

 vessels, which are very numer- 

 ous in the mucosa of the stom- 

 ach. The vascular plexus woven 

 around the tubules is extremely 

 dense, and near the surface of 

 the mucosa composed of wide 

 ^capillaries. (See Fig. 253.) 



In transverse sections of the 

 pepsine glands, in which the 

 central calibers of the tubules 

 are best marked, the vascular 

 plexus is seen surrounding the 

 tubules, and, if injected with 

 colored gelatine, many of the 

 capillaries appear to be almost 

 in contact with the base of the 

 epithelial wreath. In such sections the relation between the 

 empty and the laden epithelia is also marked ; in the portion 

 nearest the central caliber the latter are partly overlapped by 

 the former. (See Fig. 254.) 



The tubular formations toward the pylorus have been de- 

 scribed as being mucous glands, without any decided anatomical 



FIG. 253. MUCOSA OF THE STOMACH 

 OF A BABBIT. VERTICAL SECTION. 



The delicate connective tissue between the 

 tubular glands containing injected blood- 

 vessels; A, artery: FF, veins; M, smooth 

 muscle-layer of the mucosa. Magnified 300 

 diameters. 



