CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 343 



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 pan- 

 creas. For, the demarcation of an inner and outer zone is not 

 a necessary feature of a secreting cell at rest. What is essential 



FIG. 78. 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. 



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 inwards towards 

 the lumen, the whole cell becoming smaller and as it were 

 shrunken. 



In the cells of the parotid gland and other albuminous cells 

 the granules seen in the living or fresh cell differ from the 

 granules seen in the pancreatic cell, inasmuch as they are easily 

 dissolved or broken up by the action of alcohol, chromic acid, and 

 the other usual hardening reagents, and hence in hardened speci- 

 mens have disappeared. In consequence, in sections of hardened 

 and prepared albuminous glands the differences between resting 

 or loaded and active or discharged cells are not so conspicuous as 

 in the pancreas. The difference however even in hardened speci- 

 mens between the parotid of the rabbit at rest, and that excited 

 by stimulation of the sympathetic is well marked. During rest, 

 the cells (Fig. 79 A) are pale, transparent, staining with difficulty, 

 and the nuclei possess irregular outlines as if shrunken by the 

 reagents employed. After stimulation of the sympathetic, the 

 cell-substance becomes turbid (Fig. 79 B\ and stains much more 

 readily, while the nuclei are no longer irregular in outline but 

 round and large, with conspicuous nucleoli, the whole cell at the 



