218 



DIGESTION. 



FIG. 71. 



inch in length, and ^ O th in diameter, packed closely together, 

 with their long axis at right angles to the surface of the 

 mucous membrane on which they open, their blind ends rest- 

 ing on the subrnucous tissue. (See Fig. 69.) They are all 

 composed of basement-membrane, and lined by epithelial cells, 

 but they are not all of exactly similar shape ; for while some 

 are simple straight tubes, open at one end and closed at the 

 other (Fig. 69), others present at their deeper extremities 

 a varicose, pouched, or in some cases, even a branched ap- 

 pearance (Fig. 70, b and c). The epithelium lining them is 

 not the same throughout. In the upper third or fourth of their 

 length it is cylindrical, and continuous with that which covers 

 the free mucous surface of the rest of the stomach. In their 

 lower part, on the other hand, it is of the variety called glan- 

 dular or spheroidal, the cells being oval or somewhat angular, 

 and about j^^th of an inch in diameter. The cells, however 

 do not completely fill up the cavity of the gland w r hich they 



line, but leave a slight, central, 

 thread-like space, the immediate 

 lining of which is a layer of 

 small angular cells, continuous 

 with the cylindrical epithelium 

 in the upper portion of the tube. 

 This description will become 

 plain on reference to Fig. 71, 

 which represents on a larger 

 scale a longitudinal section of 

 one of the glands depicted in 

 Fig. 69. In the greater number 

 of the glands which are branched 

 at their deeper extremities, the 

 spheroidal epithelium exists in 

 the divisions, while the main 

 duct and the upper part of the 

 branches are lined by the cylin- 

 drical variety (Fig. 70, c). In 

 the human stomach, according 

 to Dr. Brinton, the simple un- 

 divided tubes are the rule, and 

 the branched the exception. 



The varieties in the epithelial 

 cells lining the different parts of 

 the tubes, correspond probably 

 with differences in the fluid se- 

 creted by their agency the cyl- 

 inder-epithelium, like that on the free surface of the stomach, 



Part of one of the gastric glands 

 highly magnified, to show the ar- 

 rangement of the epithelium in its 

 interior ; a, columnar cells lining the 

 upper part of the tube ; b, small an- 

 gular cells, into which these merge 

 below to form a central or axial 

 layer within ; c, the proper gastric 

 or glandular cells (after Brinton). 



