320 A MANUAL OF PHYSIOLOGY 



the lumen. In the uniformly clouded parotid cell a similar 

 change takes place ; a transparent outer zone arises ; and, 

 after prolonged secretion, only a thin edging of granules 

 may remain at the inner portion of the cell. In both glands 

 the outlines of the cells become more clearly indicated, and 

 a distinct lumen can be now recognised. The cells are 

 smaller than they are during rest, and in the pancreas they 

 stain more readily with carmine and other protoplasmic 

 dyes, the outer zone always staining more deeply than the 

 inner, as is the case with the same zone even m the resting 

 pancreatic cell (Plate II., 2). 



When the glands are hardened with alcohol, or most of the 

 ordinary hardening reagents, the appearances in the serous salivary 

 cells differ from those described, for the granules, unlike those ot 

 the pancreatic cells, are altered by the treatment, and the two zones 

 in the discharged gland are not distinguishable by any difference in 

 the depth of the carmine stain. But in the rabbit's parotid after the 

 scanty secretion caused by prolonged stimulation of the sympathetic 

 the whole cell stains more deeply than the loaded cell. Its protoplasm 

 is turbid with fine and uniformly diffused granules ; its nucleus is 

 large and spherical, and contains well-marked nucleoli, in contrast 

 to the pale and transparent protoplasm and the small shrivelled 

 nucleus of the resting cell, in which nucleoli are indistinct or invisible. 

 Now, carmine being a protoplasmic dye, it is fair to conclude that 

 depth of stain is propoitional to amount of protoplasm present. The 

 deeper stain of the outer rim of the pancreatic cell during rest indicates 

 that here the protoplasm predominates over the dead and unstained 

 products of its activity, which are accumulated in the remainder 

 of the cell. The increase of the deeply-staining zone during secretion 

 shows that these produces are being moved towards the lumen of the 

 alveolus, and that the relative amount of protoplasm in the outer 

 zone is being increased, although the absolute size of the cell may be 

 diminished. The deeper stain of the parotid cell after sympathetic 

 stimulation, as well as the changes in the nucleus, indicate regenera- 

 tion of protoplasm as much as elimination of non-protoplasmic 

 elements. For in the dog changes similar to those in the rabbit are 

 caused, although the amount of secretion on stimulation of the 

 sympathetic is very small, and generally only sufficient to block the 

 ducts without appearing externally. The disappearance of granules 

 from without inwards during activity suggests that these are manu- 

 factured products eliminated in the secretion. 



Changes in the Glands of the Stomach during Secretion. The 

 mucous membrane of the stomach is covered with a single layer of 

 columnar epithelium, largely consisting of mucigenous goblet-cells. 

 It is studded with minute pits, into which open the ducts of the 

 peptic and pyloric glands, the ducts being lined with cells just like 



