THE PANCREAS IOI 



in the alveoli are of the serous type aiid-'sxe gr&nular V>\v;ird 

 the central lumen. During activity they undergo- .changes 

 very similar to the salivary cells; Ihe'il6il->&#nuter,'&ite to- 

 ward the basement membrane increasing and extending and 

 the granular zone becoming correspondingly smaller. Here, 

 as in the salivary glands, it is believed that the granules are 

 made from the clear protoplasm, and contain the enzymes or 



a 

 A 



FIG. 42. One sacctile of the pancreas of the rabbit in different states 

 of activity. (From Brubaker after Yeo.) 



A, after a period of rest, in which case the outlines of the cells are indistinct 

 and the inner zone i. e., the part of the cells (a) sext 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 zone is wider. 



their formative materials. The formative material in all 

 these glands is given the name of zymogen, although the zy- 

 mogen in a particular gland may have a particular name, as 

 pepsinogen, the forerunner of pepsin, or trypsinogen, the 

 forerunner of trypsin. 



Properties and Composition of Pancreatic Juice. The 

 pancreatic juice is a colorless liquid, alkaline in reaction, and 

 has -a specific gravity of about 1040 if taken from a recent 

 fistula. It coagulates when heated and is prone to putrefac- 

 tion on exposure. With a specific gravity of about 1040, it 

 contains per thousand about 900 parts of water, the remain- 

 der being different solid food materials in solution. These 

 constituents are a proteid and three very important digestive 



