110 



HUMAN PHYSIOLOGY. 



fats. Its most distinctive action is the inversion of cane-sugar, 

 maltose, and lactose into dextrose, thus preparing them for absorp- 

 tion. This change is dependent on the presence of a ferment body 

 known as invertin. 



The pancreatic juice is secreted by the pancreas, a flattened gland, 

 about six inches long, running transversely across the posterior wall 

 of the abdomen behind the stomach ; its duct opens into the duo- 

 denum. 



The pancreas is similar in structure to the salivary glands, and 

 consists of a system of ducts terminating in acini. The acini are 

 tubular or flask-shaped, and consist of a basement membrane lined 

 by a layer of cylindric, conic cells, which encroach upon the lumen 

 of the acini. The cells exhibit a difference in their structure (Fig. 

 14), and may be said to consist of two zones viz., an outer parietal 



FIG. 14. ONE SACCULE OF THE PANCREAS OF THE RABBIT IN DIFFERENT 

 STATES OF ACTIVITY. (Yeo's "Text-book of Physiology," after Kuhne 

 and Lea.) 



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) next the lumen (c) is 

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

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

 smaller, and the clear outer zone is wider. 



zone, which is transparent and apparently homogeneous, staining 

 rapidly with carmin ; an inner zone, which borders the lumen, and 

 is distinctly granular and stains but slightly with carmin. These cells 

 undergo changes similar to those exhibited by the cells of the salivary 

 glands during and after active secretion. As soon as the secretory 

 activity of the pancreas is established, the granules disappear, and the 

 inner granular layer becomes reduced to a very narrow border, 



