272 



THE TISSUES AND MECHANISMS OF DIGESTION. 



carmine or with certain other dyes. The discharged cell in similar prepara- 

 tions (Fig. 86, 6) differs from the loaded cell in the amount of transparent 



FIG. 86. 



Alveoli of Dog's Submaxillary Gland Hardened in Alcohol and Stained with Carmine. (Lang- 

 ley.) The network is diagrammatic, a, from a loaded gland. 6, from a discharged gland ; the 

 chorda tympani having been stimulated at short intervals during five hours. 



non-staining material being much less and chiefly confined to the inner part 

 of the cell, while the protoplasmic cell-substance around the now large and 

 well-formed nucleus is not only, both relatively and absolutely, greater in 

 amount, but stains still more deeply than in the loaded cell. 



It would appear, therefore, that in the mucous cell, as in the pancreatic 

 cell, the cell-substance forms and deposits in itself certain material in the 

 form of granules. During secretion these granules disappear and presum- 

 ably form part of the secretion. 



206. The " central " or "chief" cells of the gastric gland also ex- 

 hibit similar changes. In such an animal as the newt these cells may, though 

 with difficulty, be examined in the living state. They are then found to be 

 studded with granules when the stomach is at rest. During digestion these 

 granules become much less numerous and are chiefly gathered near the 

 lumen, leaving in each cell a clear outer zone. And in many mammals 

 the same abundance of granules in the loaded cell, the same paucity of 

 granules for the most part restricted to an inner zone in the discharged cell, 

 may be demonstrated by the use of osmic acid (Fig. 87). 



When the stomach is hardened by alcohol these changes, like the similar 

 changes in an albuminous cell, are obscured by the shrinking of the 

 " granules," or by their swelling up and becoming diffused through the rest 

 of the cell-substance ; so that, though in sections so prepared very striking 

 differences are seen between loaded and discharged cells, these are unlike 

 those seen in living glands. In specimens taken from an animal which has 

 not been fed for some time, the central cells of the gastric glands are pale, 

 finely granular, and do not stain readily with carmine and other dyes. 

 During the early stages of gastric digestion, the same cells are found some- 

 what swollen, but turbid and more coarsely granular ; they stain much more 

 readily. At a later stage they become smaller and shrunken, but are even 

 more turbid and granular than before, and stain still more deeply. This is 

 true not only of the central cells in the cardiac glands, but also of the cells 

 of which the pyloric glands are built up. In a loaded cell very little 

 staining takes place, because the amount of living staining cell-substance 

 is small relatively to the amount of material with which it is loaded and 



