Fig. 3. Islet of Langerhans of a human pan- 

 creas fixed in Zenker'a fluid and stained with 

 hematoxylin and eosin, illustrating apparent 

 similarity of "Islet cells (magnification 800). 





Fig. 4. Islet of Langerlians of a guinea pig's pan- 

 creas fixed in chrome-sublimate and stained with 

 neutral gentian, after Bensley, revealing the true 

 polymorphism of the cells: A cells (a), B cells (b), 

 and indifferent cells (i) (magnification 800). 

 693 



