42 INTERNAL SECRETION 



(except a community of embryonic origin) with the secreting 

 tubules of the pancreas. 



Some among the first group of writers even consider there 

 may be no difference in function between the two structures. 

 Thus Harris and Gow thought that the islets might take part 

 in the external secretion, probably forming one of the ferments. 

 Some authors look upon the islets as exhausted secreting 

 cavities, and believe that after a period of repose they may 

 again take on their secretory function. Others, on the con- 

 trary, look upon the islets as exhausted acini which are unable 

 to return to their former state. 



In most vertebrates there are no lumina in the islets of 

 Langerhans, but such have been described occasionally in 

 amphibians and reptiles. 



Laguesse refuses to admit that the islets are simply exhausted 

 masses of acini, or that they are in their nature simply secreting 

 tubes modified by inanition, and he urges against either of these 

 theories the abundance of the granules of secretion in the islets, 

 the permanent juxtasplenic islet of the Ophidians, and the fact 

 that islets are found in every functional state of the pancreas. 

 The presence of lumina in the islets of reptiles is a strong indi- 

 cation that their origin is from alveoli. The same author, in 

 his numerous contributions on the subject, has laid stress on 

 the anatomical details above referred to, and inclines strongly 

 to the view that the islets of Langerhans are portions of the 

 secreting tubules temporarily modified for the purpose of 

 supplying an internal secretion. 



Dale employed a new method for investigation of the sub- 

 ject, using secretin to exhaust the gland. He concluded that 

 the islets of Langerhans are not independent structures, but 

 are formed by certain changes in the cells of the secreting tissue 

 of the pancreas. The change from the secreting to the " islet " 

 condition may be accelerated by the administration of secretin 

 and as a result of inanition. 



The authors belonging to the second chief group all believe 

 in the internal-secretion theory of the islets, and, indeed, so 

 convinced are many of them that this is the correct theory, that 

 they do not accept the statements of the first group, who 

 i be changes in the islet in exhaustion and inanition, and 

 the t mi i -it inn tmins from one kind of tissue to the other. 

 According to Diaman -. tin- i>l< -ts are "epithelial bodies" in 



