34 



HUMAN PHYSIOLOGY. 



This stage of digestion is probably the most complex and important ; here 

 the different alimentary principles are further elaborated and prepared for 

 absorption into the blood by being acted upon by the intestinal juice, pan- 

 creatic juice and bile. 



Throughout the mucous coat are imbedded the intestinal follicles, the 

 glands of Brunner and Lieberkiihn. They secrete the true intestinal juice , 

 which is an alkaline, viscid fluid, composed of water, organic matter and 

 salts. \\s> function is to convert starch into glucose, and assist in the diges- 

 tion of the albuminoids. 



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 duodenum. 



FIG. 4. 



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 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 out- 

 lines (d) are clearer, the granular zone (a) is smaller, and the clear outer zone is wider. 

 From Yto's Text-Book of Physiology, after Kiihne and Lea. 



The pancreas is similar in structure to the salivary glands, consisting ot 

 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 cylindrical, 

 conical cells, which encroach upon the lumen of the acini. The cells 

 exhibit a difference in their structure (Fig. 4), and may be said to consist 

 of two zones, viz., an oziter parietal zone, which is transparent and appar- 

 ently homogeneous, staining Vapidly with carmine; an inner zone, which 

 borders the lumen, and is distinctly granular and stains but slightly with 

 carmine. These cells undergo changes similar to those exhibited by the 

 cells of the salivary glands during and after active secretion. As soon as 



