290 



THE ORGANS 



wedged in between the latter. They extend from the lumen to the 

 basement membrane and are probably siistentacular . 



Passing from the lumen of the terminal tubule, sometimes between 

 the centro-tubular cells, directly into the cytoplasm of the secreting 

 cells are minute intracellular secretory tubules. These are demonstra- 

 ble only by special methods (Golgi) (Fig. 191). 



The pancreas also contains peculiar groups of cells, the cell-islands 

 of Lajigerhans, having a diameter from 200 to 300/^ (Figs. 188, 192, 

 and 193). The "island" cells differ quite markedly both in arrange- 

 ment and structure from those which line the terminal tubules (Fig. 



a 





.1 



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?5' 



Fig. 192. — Island of Langerhans and few surrounding Pancreatic Tubules. (Bohm and 



von Davidofif.) a, Capillary; b, tubule. 



192). They contain no zymogen granules. They are arranged in 

 anastomosing cords or strands which are separated from one another 

 by capillaries. There are no ducts and the method of Golgi shows no 

 inter- or intra-cellular secretory tubules. Their protoplasm is un- 

 stained by basic dyes, but stains homogeneously with acid dyes. 

 Their nuclei vary greatly in size, some, especially where the cells are 

 closely packed, being small, others being large and vesicular. Some 

 of the islands are quite sharply outlined by delicate fibrils of connec- 

 tive tissue containing a few elastic fibres (Fig. 192). Others blend 

 with the surrounding tissues. 



