192 



DIGESTION. 



[CHAP. xxiv. 



Over the whole surface of the membrane as seen on laying open the 

 organ, and stretching it so as to obliterate the larger folds, there are 

 visible, even with the naked eye, but still better with a lens, a mul- 

 titude of cavities of very irregular shape, and about ^^th of an inch 

 in diameter, more or less (fig. 154, A). These cells are not the re- 

 sult of creasings of the membrane, and they do not disappear when 



it is stretched. They are usually 

 filled with mucus, which requires 

 to be removed. Over the greater 

 part of the stomach they extend 

 in depth only about th or -^th 

 of the thickness of the membrane, 

 but they are larger and deeper 

 near the pylorus. In the ridges 

 between them runs a plexus of 

 vessels larger than ordinary ca- 

 pillaries (fig. 155 A,d), and which 

 often retains its blood after death, 

 so as to map out the cells in a 

 beautiful manner. This plexus is 

 supplied by vessels sent up from 

 below, and may be very easily 

 injected artificially. 



The epithelium which lines 

 these stomach cells and covers the 

 ridges between them is of the 

 columnar variety (fig. 154 B) ; the 

 particles are shorter than in some 

 other parts : one end is free, 

 while the other is directed to- 

 ward the basement membrane; 

 and they contain each a clear 



A. Inner surface of the stomach, shewing the 

 cells after the mucus has been washed out. Mag- 

 nified 25 diameters. 



B. Columnar epithelium of the inner surface and 

 cells of the stomach: a. Free ends of the epithe- 

 lial particles, seen on looking down upon the 

 membrane. 6. Nuclei visible at a deeper level. 



c. The free ends seen obliquely, d. Deep or at- ,, . -. 

 tached ends of the same. The oval nuclei are pellUCld nUClCUS near tneir deeper 

 seen near the deeper ends. T mi v j 



From the dog. Magnified 300 diameters. end. 1 hey Seem to lie in a QOU- 



ble series, the deeper being in course of development while the 

 more superficial is in course of decay. It has appeared to us 

 that each particle when arrived at maturity has, besides the nu- 

 cleus, granular contents enclosed, and that at a subsequent period 

 the granular contents escape at the free extremity by a dehi- 

 scence or opening of the wall at that part, leaving the transparent 

 husk with its nucleus subsisting for some time longer. The clear 

 structureless mucus which is almost always found occupying the cells 



