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TEXT-BOOK OF PHYSIOLOGY 



to the functional activity of the glancU During the intervals of digestion 

 the granular layer is very deep and occupies almost the entire cell; after 

 active digestion the granular layer is very narrow, while the clear zone is 

 Jargely increased in depth (Fig. 79). The blood-vessels of the pancreas 



are arranged around the acini 

 in a manner similar to that ob- 

 served in the salivary glands. 

 The ultimate terminations of 

 the nerves in the epithelium 

 are probably by means of the 

 usual end-tufts. 



The Islands ofLangerhans. 

 Throughout the body of the 

 pancreas and especially in the 

 outer extremity there are found 

 between and among the acini 

 collections of globular cells ar- 

 ranged in the form of rods or 



FIG. 78. FIG. 79. 



ONE SACCULE OF THE PANCREAS'OF THE RABBIT 

 IN DIFFERENT STATES OF ACTIVITY. Fig. 78. 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. Fig. 79. After the gland has poured 

 out its secretion, when the cell outlines (d) are clearer, 



columns, separated from the 

 acini and from one another 



uubiiaawicuuU) wneu LUC v-cn vj u uuiica \i*j u.ic uicuici, 'Li c *.* j. 



the granular zone (a) is smaller, and the clear outer b Y layers Ot connective tissue 

 zone is wider. (Kuhne and Lea.) in which ramify large tortuous 



capillary blood-vessels. These 



columnar bodies, seen in cross-section in Fig. 81, have been named, after 

 their discoverer, the islands of Langerhans. 



Embryologic investigations have shown that these cells are outgrowths 

 from the primitive acini, to which they remain attached for some time by 



FIG. 80. SECTION OF HUMAN 

 PANCREAS, INCLUDING SEVERAL ACINI 

 AND Two DUCTS. THE CELLS PRE- 

 SENT A CENTRAL GRANULAR AND A 

 PERIPHERAL CLEAR ZONE. (Piersol.) 



FIG. 81. SECTION OF HUMAN PAN- 

 CREAS SHOWING a, a, ISLAND OF LAN- 

 GERHANS, AND b, THE USUAL ACINI. 

 (Piersol.) 



means of a foot-stalk. This subsequently becomes constricted by the 

 connective tissue and the cells become completely detached. The cells 

 then assume the columnar arrangement, after which vascularization takes 

 place. 



From the fact that complete extirpation of the pancreas as well as its 

 various diseases is followed by serious disturbances of the carbohydrate 



