66 Swale Vincent and F. D. Thompson, 



There are some darkly-staining cells in the zymogenous tissue 

 (PL IV, fig-. 1, PI IV, fig. 2, Ijath. c). 



The islets of Langerhans in the cat. 



There is apparently no ftmdamental difference between the islets 

 in the cat and those in the dog. We have devoted our attention 

 here, as in the dog, principally to the splenic end, because the islets 

 in most animals are more abundant at this end, and it is essential in 

 all cases to compare corresponding regions in different glands and in 

 different species. 



As regards the zymogenous structure in the two animals, it is 

 obvious at once that there is more connective tissue separating the 

 acini in the cat than in the dog, and therefore a less compact structure 

 of the whole gland. 



The alveoli, too, are smaller and nairower than in the dog. The 

 width of the zymogenous tubules averages 27 (.i, that of the islet 

 columns 24 (.i. The capillaries in the islets average 12 // in diameter. 

 The nuclei in the islets are about 6,5 i-i across, those in the seci'eting 

 tubules 6 //. The alveolai- dutline in the islets is frequently very dis- 

 tinctly seen, and continuity between islet cords and acini is about as 

 common as in the case of the dog. Transitions, as indicated by varying 

 amounts of zymogenous granules in the different cells, are frequent. 



The islets of Langerhans in the badger. 



The specimen of pancreas was taken from a badger which was 

 killed some few weeks after thyroidectomy, but had shown no symptoms. 

 The islets are particularly numerous and of large dimensions. Many 

 of the larger islets show a distinct alveolar arrangement and in many 

 places the zymogenous tissue is seen to merge gradually into „islet". 



Small gi'oups of darkly staining cells and individual elements of 

 the same character aie found distributed throughout the zymogenous 

 tissue. These are more numerous than in the dog. 



The islets of Laju/erhans in. Uir o.i:. 



Although at first sight the islets in the ox present a very différent 

 ;i|)|)('niaìi(<' lìoiii thos(^ in tln^ dog and other carnivora, yet as regards 

 the type of islet so lai' dealt, with there is no veiy fundamental dis- 

 limtidii hctweeii I lie 1 Wo niammaliaii gi'onps. Many of the islets in 



