On the Relations between the „Islets of Langerhans '' etc. 91 



According to Diamare the islets are „Epithelial bodies" in 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 have no 

 relation to the surrounding tissue except that of contiguity, and they 

 have no lumina even in reptiles. He denies also the continuity of the 

 islets with the exocrine gland and all forms of physiological variation. 

 Rennie, in his work upon teleostean fishes, describes the fairly con- 

 stant occurrence of an encapsuled islet („principal islet") of large size, 

 whose relation to the pancreatic tissue is frequently extremely slight. 

 He considers the islets as „blood-glands which have entered into a 

 secondary' relation to the pancreas". This author finds no sign of any 

 transitional forms, 



Helly also believes that the islets are organs sui generis and 

 denies the existence of any form of transition. 



Pensa ^) finds a very abundant vascular and nervous supply to 

 the islets of Langerhans and the latter present certain peculiarities. 

 He does not believe that the islets are rudimentary organs or even 

 modified portions of the zymogenous tissue. 



As may be gathered from the preceding pages, we are opposed 

 to the views of these latter authors and consider that the embryological 

 work of Laguesse and the experimental researches of Dale are con- 

 firmed in all essential points by our own investigations. Diamare, in 

 his most recent communication-^) still holds to his original view. He 

 only refers to Dale's work in a footnote, and neither he nor any other 

 observer has (previously to our own work) so far as we are aware 

 repeated Dale's experiments upon the mammalian pancreas. Diamare, 

 has, it is true, done some experiments upon fishes, but with negative 

 results. It is of course remotely possible that in fishes the islets are 

 constant structures, while in other vertebrates they are variable, but 

 we should certainly hesitate at present to adopt this view. It is to 

 us remarkable that Diamare has been unable to see the various tran- 



1) Arch. ital. de Biol. t. XLIV, fase. 1, 1905; Boll della Soc. med. Chir di 

 Pavia 1904. 



2) Internat. Monatsschr. f. Anat. u. Physiol. Bd. XXII. 1905. 



