38 Swale Vinceiii and F. D. Thompson. 



VI. Discussion of certain Views as to the Morphology and 

 Physiology of the Islets of Langerhans. 



The earlier observers for the most part considered that the islets 

 of Langerhans were masses of lymphoid cells. This view need not be 

 discussed. 



More modern writers may be divided into two chief groups accor- 

 ding to their views as to the morphological significance of the islets. 

 The first of these believe that the islets are essentially of the same 

 embryological and morphological nature as the zymogenous tubules and 

 are not in any sense to be looked upon as organs sui generis. The 

 second group of observers regard the structures in question as definite 

 and distinct organs, analogous to the cortex of the suprarenal, the 

 epithelial part of the pituitary body, and the parathyroids, and consider 

 that they have no connection (except perhaps a community of embryonic 

 origin) with the secreting tubules of the pancreas. 



The most recent contributions on the subject are in support of 

 the view that the islets are organs sui generis and this notwithstanding 

 that in our view the evidence is overwhelmingly against this hypo- 

 thesis. In the handbooks, too, the islets are usually considered as a 

 separate kind of tissue^). 



Kohn") also classifies the islets of Langerhans as one of his „ürüsen 

 ohne Ausführungsgang — ohne Drüsenlumen" („corpora glanduliformia") 

 along with the parathyroids, epithelial part of the pituitary, and the 

 cortex of the suprarenals '*). 



') ThiLS V. V. Ebner in Köllilcers „Gewebelehre". 8. Bd., Ü. AuH.. 1902 says: 

 „Durch die sorgfältigen Untersiichungen von Laguessc über die histogenotischo 

 Entwicklung der Bauchspeiclieldriise des Schafes ist nachgewiesen, dass die Langer- 

 hansschen /ellcnhaufen aus dersel))en entodennalen Anlage hervorgehen, wie die 

 seccrhierenden Schläuche. Doch kann man nach dem histologischen Befunde an 

 den au.sgcbildeten Zellenhaufen dieselben nicht zu dem eigentlich secernierenden 

 Paren(diym rechnen, da Sekretwege, trotz gegciiiciliger Angaben von J/ewaschew, 

 in (h-nscllicii niclit nachzuweisen sind. Die I>ang(Mhaiisschcn /ellcnhaufen scheinen 

 mir vielmelir einige Ähidiciikcit mit gewissen Blutgefässdriisen, wie die Nebenniere, 

 <ler vorden; l,ait[)en der Hypojìhyse usw. zu hal)cn. 



■^) Ergebnisse der Anat. u. Entwickl. IX. Bd. 18<.»'.). S. 2-\h. 



') It has been shown, however, tliat tlic parathyroid is very iniimalely related, 

 physiologically and histologically with (lie (h\roid (Vincent & .lolly, Journ. of Fliysiol. 

 Vol. ;^2, l'JÜ4j. 



