158 MANUAL OF PHYSIOLOGY. 



again encroached oil the outer, owing to the accumulation of gran- 

 ules which, rapidly increasing, fill the greater part of the cells, 

 and cause them to bulge inwards and occlude the lumen of the 

 gland. When digestion commences, the cells undergo a slight 

 change in form, so that each individual cell is more distinctly 

 seen, and its angles are retracted, giving a notched appearance to 

 the margin of the acinus. The blood supply during this period 

 is much increased, red arterial blood flowing from the veinlets of 

 the gland. At the same time the granules are diminished in uum- 



FIG. 70. 



A. B. 



One Saccule of the Pancreas of the Rabbit in different states of activity. 

 A. After a period of rest, in which case the outlines of the cells are indis- 

 tinct, and the inner zone, i.e., the part of the cells (a) next the lumen (c), 

 is broad and filled with fine granules. B. After the gland has poured out its 

 secretion, when the cell outlines (d) are clearer, the granular zone (a) is 

 smaller, and the clear outer /one is wider. (Kiihne and Lea.) 



ber, escaping at the free central margin of the cells into the lumen 

 towards which they appear to crowd, leaving the outer zone once 

 more clear and free from granules, while the lumen of thesaccule 

 and of the ducts are filled with secretion. 



Let us then examine a single cell ; during the period of rest 

 with a comparatively poor supply of blood, the cell receives its 

 normal nutrition, which is accompanied by an accumulation of 

 granules in the protoplasm next the free side of the cell. During 

 secretion these granules are pushed out of the cell, and seem in 

 some way to form the secretion. 



