THE PANCREAS 



43 





Kohn's sense. They are constant and invariable, and are a 

 form of " epithelial body " derived from the pancreas (for he 

 admits, of course, the common embryonic origin of pancreas 

 and islets). The adult islets, in his view, have no relation to 

 the surrounding tissue, except that of contiguity, and he denies 

 that the islets ever possess lumina, even in reptiles. He denies 

 the continuity of the islets with the exocrine gland and all 



bid. c. 



c.c.a. 

 zym. 



FIG. 9. Islet of Langerhans, from the splenic end of the pancreas of a 

 normal dog, showing the alveolar form of the islet tissue. The tissue of 

 the islet is seen to consist of solid branching columns of cells, for the most 

 part two deep, separated by wide capillary bloodvessels (Vincent and 

 Thompson). (Drawn by Mrs. F. D. Thompson.) 



Lettering common to Figs. 10, 11, and 12. bld.c., red blood-corpuscles; 

 c.a.c., centro-acinar cells ; cap., blood-capillaries ; i., islet of Langerhans ; 

 ., lumen ; trans. c., transitional cells ; zym., zymogenous tissue. 



forms of physiological variation. Rennie, in his work' on the 

 teleostean fishes, describes the fairly constant occurrence of an 

 encapsuled islet (" principal islet ") of large size, whose relation 

 to the pancreatic tissue is frequently extremely slight'. He 

 considers the islets to be " blood-glands " which have entered 

 into a secondary relation to the pancreas. This author finds 

 no sign of any transitional forms. 



