CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 431 



matters including water, as we shall see, making up the whole 

 secretion ; and the cell would be proportionately reduced in size 

 were it not that the act of the discharge seems to stimulate the cell- 

 substance to a new activity of growth, so that new cell-substance 

 is formed; this however is in turn soon in part consumed in 

 order to form new granules. And what is thus seen with 

 considerable distinctness and ease in the pancreas, is seen with 

 more or less distinctness in other glands. 



234. When we study an albuminous gland, the parotid gland 

 for instance, in a living state, we find that the changes which take 

 place during activity are quite comparable to those of the pan- 

 creas. During rest (Fig. 64 A), the cells are large, their outlines 

 very indistinct, in fact almost invisible, and the cell-substance 

 is studded with granules. During activity (Fig. 64 B), the cells 

 become smaller, their outlines more distinct, and the granules 

 disappear, especially from the outer portions of each cell. After 

 prolonged activity, as in Fig. 64 C, the cells are still smaller with 



FIG. 64. CHANGES IN THE PAROTID DURING SECRETION. (Langley.) 



The figure, which is somewhat diagrammatic, represents the microscopic changes 

 which may be observed in the living gland. A. During rest. The obscure outlines 

 of the cells are introduced to shew the relative size of the cells, they could not be 

 readily seen in the specimen itself. B. After moderate stimulation. C. After 

 prolonged stimulation. The nuclei are diagrammatic, and introduced to shew their 

 appearance and position. 



their outlines still more distinct, and the granules have disappeared 

 almost entirely, a few only being left at the extreme inner margin 

 of each cell, abutting upon the conspicuous, almost gaping lumen 

 of the alveolus. And upon special examination it is found that 

 the nuclei are large and round. In fact we might almost take 

 the parotid, as thus studied, to be more truly typical of secretory 

 changes than even the pancreas. For, the demarcation of an 

 inner and outer zone is not a necessary feature of a secreting cell 

 at rest. What is essential is that the cell -substance manufactures 

 material, which for a while, that is during rest, is deposited in 

 the cell, generally in the form of granules but not necessarily so, 

 and that during activity this material is used up, the disappearance 

 of the granules, when these are visible, being naturally earliest and 

 most marked at the outer portions of each cell, and progressing 



