322 A MANUAL OF PHYSIOLOGY 



the outer part of the chief cells of the peptic glands, 

 leaving a clear zone, the lumen being bordered by a granular 

 layer. Or, more rarely, there may be a uniform decrease in 

 the number of granules throughout the cell. The ovoid 

 cells swell up, so as to bulge out the membrana propria, but 

 no definite changes in their contents, such as those observed 

 in the other cells, have been made out. 



Changes in Mucous Glands during Secretion. In the mucous 

 salivary and other mucous glands similar, but apparently 

 more complex, changes occur. During rest the cells which 

 line the lumen may be seen in fresh, teased preparations to 

 be rilled with granules or ' spherules.' After active secretion 

 there is a great diminution in the number of the granules. 

 Those that remain are chiefly collected around the lumen, 

 although some may also be seen in the peripheral portion of 

 the cell ; and there is no very distinct differentiation into 

 two zones. That a discharge of material takes place from 

 these cells is shown by their smaller size in the active gland. 

 That the material thus discharged is not protoplasmic is 

 indicated by the behaviour of the cells to protoplasmic stains 

 such as carmine. The resting cells around the lumen stain 

 but feebly, in contrast to the deep stain of the demilunes, 

 while the discharged cells take on the carmine stain much 

 more readily. Further, when a resting gland is treated 

 with various reagents (water, dilute acids, or alkalies), the 

 granules swell up into a transparent substance apparently 

 identical with mucin, which appears to fill the meshes of a 

 fine protoplasmic network (Fig. 105). 



In ordinary alcohol-carmine preparations only the network and 

 nucleus are stained; the nucleus, small and shrivelled, is situated close 

 to the outer border of the cell. When a discharged gland is treated 

 in the same way there is proportionally more ' protoplasm ' and less 

 of the clear material, what remains of the latter being chiefly in the 

 inner portion of the cell, while the nucleus is now large and spherical, 

 and not so near the basement membrane (Plate II., i and 3). 



Everything, therefore, points to the granules in what we 

 may now call the mucin-forming cells as being in some way 

 or other precursors of the fully-formed mucin; manufactured 

 during * rest ' by the protoplasm and partly at its expense, 



