1 86 



NORMAL HISTOLOGY. 



FIG. 231. 



lumen of the acinus, containing numbers of highly refracting par- 

 ticles, while the peripheral outer half of the cells contains the nucleus 

 and is comparatively free from the granules. The relations, how- 

 ever, between the clear and granular zone of the pancreatic cells are 

 not constant, but vary with the condition of functional activity. 

 During the earliest stages of digestion, when the cells are filled 

 with secretion, the clear zone occupies almost the entire cell, the 

 granules being confined to a narrow belt immediately around the 

 lumen ; towards the close of a period of functional activity, on the 

 contrary, the granules occupy the greater part of the cell, while 

 the clear zone is reduced to a narrow peripheral area ; during fasting 

 the clear and the granular zone about equally divide the cells. 



On examining sections of pancreas under low amplification, certain 

 round or oval areas appear lighter and less dense than the ordinary 



tissue of the organ. These peculiar 

 areas, or bodies of Langerhans, 

 under high magnification prove to 

 be composed of groups of small, 

 imperfectly-developed acini, among 

 and about which ramify rich capil- 

 lary net-works, whose frequently 

 tortuous course and lobulated ar- 

 rangement recall somewhat the 

 glomeruli of the kidney. These 

 areas probably represent groups of 

 imperfectly-developed acini ; they 

 are well seen in the pancreas of man 



Section of human pancreas, exhibiting one and ITlOSt mammals. 



of the areas (a) of immature gland-cells ; b, The blood-VCSSClS of the pan- 



the usual acini. . . ., , 



creas are distributed very similarly 



to those of the salivary glands. The larger arterial branches run 

 within the interlobular connective tissue, sending off vessels which 

 pass between the lobules and supply the glandular parenchyma with 

 twigs. These latter enter the lobules and form net-works which en- 

 close the individual acini within the capillary reticulum. The capil- 

 laries lie beneath the basement-membrane in close relation with the 

 glandular epithelium. The veins accompany the arterial trunks within 

 the connective tissue. 



The lymphatic vessels also accompany the arteries, lying be- 

 tween the lobules and receiving as tributaries the lymph-radicles 

 originating within the lobule between the acini. The larger nerve- 

 trunks are confined to the connective tissue between the divisions 

 of the gland, in which situation many accompanying microscopic 

 ganglia also are found. The ultimate termination of the nerve-fibres, 



