690 



E. V. COWDRY 



has confirmed Opie's (&) observation that this condition obtains in man. 

 In guinea pigs the average, as found by Bensley, is 22.28 islands per cubic 

 millimeter. The entire gland contains in the guinea pig about 25,000 

 islands. These seem to be rather more abundant in young animals. There 

 is considerable variation, even in animals of the same litter. The islands 



Fig. 1. Islands of Langerhans in the pancreas of the guinea pig stained by inject- 

 ing neutral red into the blood vessels, after Bensley. 



are usually larger and more abundant in the deeper parts of the lobule. 

 Obviously, therefore, ordinary microscopic preparations cannot be relied 

 upon to give us any idea of normal or abnormal variations in the number 

 of the islands in the human pancreas. 



Bensley has discovered in the guinea pig, and Clark has confirmed 

 his observation in man, that the islands of Langerhans are connected with 

 the ducts of the pancreas by a very delicate and intricate system of chan- 

 nels, which may be specifically counterstained by the addition of a little 

 pyronin to the neutral red solution, These connections are shown in 

 Fig. 2. 



