On the Relations between the „Islets of Langerhans" etc. 65 



The width of the islet cohimn is on an average 17— 25t< against 

 25 — 50 i-i in the zymogenous tissue. 



As pointed out by Opie^) and Dale-) the islets are larger and 

 more numerous at the splenic end than at the free end of the pancreas. 



It is frequently impossible under the high power of the microscope 

 to assign definite limits to the islets. Many of the solid cell columns 

 are in diiect tissue continuity with the zymogenous tubules (PJ. IV, fig. 1, 

 trans, c), or in other words, the structure may be in one part secre- 

 ting tubule, in another part solid column of islet, and there may be no 

 sudden change from zymogenous cell of acinus to hyaline or finely 

 granular cell of islet. At any rate, such change is not definitely 

 marked in all islets, nor in the whole periphery of any one islet 

 (PI. IV, fig. 1). Very frequently the zymogenous tissue shades away 

 gradually into the clearer tissue of the islet. There are all transitions 

 to be found between the most strongly granulated of alveolar cells and 

 the clearest of the islet cells (PI. IV, fig. 1 and PI. IV, fig. 2, trans, c). 



Frequently one sees small islands of zymogenous tissue surrounded 

 by „islet". These islands appear to be undei-going transformation into 

 islet tissue, or to represent stages in the reconstruction of zymo- 

 genous tissue. 



Of course one of the characteristic anatomical features of islet as 

 opposed to zymogenous tubule, is the absence of a lumen in the formei-, 

 and this would appear a priori a practical method of marking the 

 limits of the islets. But the lumina are not always easily visible in 

 the zymogenous tissue, and injection of the ducts of the pancreas is 

 notoriously a very difficult process. We have attempted this, however, 

 and also the method of Golgi without reaching any satisfactory con- 

 clusions. This point will be referred to again in connection with the 

 islets of lower vertebrates. 



As pointed out by Dale, the islet cells are sometimes similar to 

 the epithelium cells lining the ducts, but so far we have not observed 

 an islet apparently continuous with the epithelium of a ductule. 



M Bull. Johns Hopkins Hospital. Vol. II, p. 205. 1900; Journ. of Exper. 

 medicine, p. 397, V. 527. New York 1901. 

 -) Loc. cit. 

 Internationale Monatsschrift f. Anat. u. Phys. XXIV. 5 



