256 



STUDIES IN ADVANCED PHYSIOLOGY. 



portions of the cells next to the basement membrane seem 

 clearer and more protoplasmic. If, now, for comparison 

 with this gland there be examined the pancreas of the sec- 

 ond animal, which was plentifully fed eight or ten hours 

 before being killed, quite a different appearance of the 

 secreting cells is at once evident. The cells seem smaller, 

 and the granular layer is almost wholly absent, the whole 

 cell now from basement membrane to, lumen appearing 

 clear. 



It is not difficult to account for the relative appearances 

 of these two glands. In the working gland which has just 

 been called upon for a copious secretion the granules have 

 been used up; have, in other words, been changed into a 

 part of the secretion of the gland. If, however, a gland 

 which has been copiously secreting, be given opportunity 

 to recuperate, the granules again begin to appear, become 



Fig. 99. PARTS OF GLANDS. (After I^angley.) 



A, at rest, almost filled with zymogen granules; B, after a short period of activity; 

 C, after a prolonged secretion. In A and B, the nuclei are obscured by the granules. 



more and more plentiful, and soon occupy almost half of 

 the space of the cell. The condition of things is then this: 

 In the process of secretion the pancreatic cells (which 

 gland is here used as an illustration of glands in general) 

 change these stored-up granules into the secretion, while 

 during the period of apparent rest the gland seems engaged 

 in manufacturing and storing up these granules ready for 

 the next secretion. It will thus be seen that the process of 

 secretion in cells is essentially a process of growth. The 

 secreting cells take proper nourishment from the blood 

 bathing them, and in that way construct within themselves, 



