932 



THE EXTERNAL SECRETIONS 



erepsin. Its importance lies rather in the fact that it gives lodgment 

 to a substance, known as enter okinase,^ which possesses the power of 

 greatly augmenting the action of the pancreatic juice on proteins. In 

 the absence of this secretion, following, for example, the resection 

 of extensive segments of the duodenum, serious digestive disturbances 

 result; in fact, it is commonly stated that this operation is fatal for 

 reasons not fully understood. It is supposed, however, that it converts 

 the inactive trypsinogen into the powerful proteolytic agent- trypsin 

 A similar activating enzyme has been abstracted from the spleen 

 (Mendel), but it has not been proved that this organ exerts this par- 

 ticular function under normal conditions. 



The Pancreas. — This gland is tubulo-racemose in its character, 

 the individual acini being separated from one another by a loose net- 



FiG. 495. — Diagram to Show the Position of the Ducts of the Pancreas. 

 D, Duodenum; P, pancreas; DC, ductus choledochus; DW, ductus Wirsungianus; 

 DS, ductus Santorini. 



work of connective tissue in which are imbedded small groups of 

 spindle-shaped cells forming the so-called islets of Langerhans. It 

 will be brought out later on that these cells furnish an internal secre- 

 tion which has to do with the metabolism of the carbohydrates. For 

 the present we are concerned solely with the true secretory ^cells of this 

 organ, forming the typical tubular acini and producing the *' external '* 

 secretion known as the pancreatic juice. These cells are polyhedral 

 in shape and exhibit two zones, namely, a clear outer and a granular 

 inner. Their strongly basophile nuclei occupy a central position 

 within their cytoplasm. 



It will be remembered that this organ forms a narrow band of tissue, the central 

 portion of which partially envelops the duodenum, while its caput and cauda extend 

 for some distance into the mesentery. Its principal excretory channel is the pan- 

 creatic duct or duct of Wirsung, which opens into the duodenum about 10 to 12 cm. 

 below the sphincter of the pylorus. A smaller duct may also be present, which is 

 known as the duct of Santorini and drains the head-region of this organ, entering 



^ Chepowalnikow, Dissertation, St. Petersburgh, 1899. 



