{VINCENT & THOMPSON] THE ISLETS OF LANGERHANS PTT 
T'estudo tabulata. 
All our material from this species was fixed in Flemming’s fluid 
and stained either in safranin or by the iron-hæmatoxylin method. 
This procedure does not as a rule render the islets and ductules readily 
visible either in reptiles or in the elasmobranchs, and it is curious that 
so far we have been unable to detect with certainty any islets of Langer- 
hans. In some of the ductules there are two rows of cells and in some 
cases the ducts are surrounded by adenoid tissue. In these respects 
there is a resemblance to what is found in the Elasmobranchii. 
(b) Lacertilia. 
Our examination of these animals has been confined to one specimen 
of Lacerta viridis, and we have found a few islets near the splenic end. 
These are very small, consisting in most cases of a few cells only. They 
are lightly stained and stand out in marked contrast to the surrounding 
zymogenous tissue. Transition forms between islet and alveoli are 
fairly common. ‘The islets are so small that they are not arranged in 
definite cell columns but consist, in our preparations, of clumps of not 
more than six cells. They are frequently in contiguity to the ducts, 
Teminding one of the arrangement in the elasmobranchs. 
(c) Ophidia. 
Our description applies equally well to Tropidonotus natrix and 
Coluber longissimus. There are large and numerous islets, especially 
at the splenic end. In material prepared with corrosive sublimate and 
stained with hematoxylin the islets are stained more lightly than the 
surrounding tissue. After Fiemming’s fluid and iron-hæmatoxylin they 
are, however, distinctly darker, as first pointed out by Laguesse.1 On 
careful examination they often reveal fine granules, as also was noted 
by Laguesse. The large irregular islets are a striking feature at the 
splenic end of the pancreas of these animals. In hæmatoxylin and eosin 
preparations it may be seen that the granules have an eosinophile 
Teaction. 
THE ISLETS or LANGERHANS IN ELASMOBRANCHII. 
In 1899 Diamare ? came to the conclusion that there are no islets 
of Langerhans in elasmobranchs, but that certain structures which at 
first sight appeared to represent them were in reality tortuous ducts 

Jour. de l’Anat. et de la Physiol., xxxiie Année, 1896, Nr. 3, Mai-Juin, 
Archives de l’Anat. micr., t. iv, fasc. ii et iii, Nos., 1901; ibid, t. v., 1902. 
2Internat. Monatsschr. f. Anat. u. Physiol., 1899, Bd. xvi, Heft 7/8. 
