CHAP, i.] DIGESTION. 267 



refractive granules. These however are crowded towards the 

 inner side of the cell abutting on the lumen of the alveolus, 

 leaving the outer part of the cell next to the basement membrane 



B. 



FlG. 50. A PORTION OF THE PANCREAS OF THE EABBIT (E.CHNE AND SHERIDAN LEA), 



A at rest, B in a state of activity. 



a the inner granular zone, which in A is larger, and more closely studded with 

 fine granules, than in B, in which the granules are fewer and coarser. 



b the outer transparent zone, small in A t larger in B, and in the latter marked 

 with faint striae. 



c the lumen, very obvious in B, but indistinct in A. 



d an indentation at the junction of two cells, seen in B, but not occurring in A. 



clear and hyaline. We can in fact distinguish in each cell two 

 zones, a smaller outer zone, free from granules, and a larger or 

 broader inner zone thickly studded with granules. At the same 

 time it may be remarked that the lumen of the alveolus* is 

 narrow and very obscure ; the blood-supply moreover is scanty, 

 the small arteries being constricted and the capillaries imperfectly 

 filled with corpuscles. 



If, however, the same pancreas be examined while it is in a 

 state of activity, either from the presence of food in the stomach, 

 or from the injection of some stimulating drug such as pilocarpin, 

 a very different state of things is seen. The individual cells 

 (Fig. 50 B) have become smaller and much more distinct in outline 

 and the lumen of the alveolus is now wider and more conspicuous. 

 In each cell the granules have become much fewer in number and 

 as it were have retreated to the inner margin, so that the inner 

 granular zone is much narrower and the outer transparent zone 

 much broader than before ; the latter too is frequently marked at 

 its inner part by delicate striae running into the inner zone. At 

 the same time the blood-vessels are largely dilated and the stream 

 of blood through the capillaries is full and rapid. 



These things, the disappearance of granules during activity 

 leading to a diminution of the inner granular zone and a widening 

 of the outer transparent zone, and the appearance of new granules 

 during rest leading to a restoration of the inner zone and its 

 consequent encroachment on the outer zone, may be witnessed in 

 the living pancreas of the rabbit, and the changes from the one 



