The Anatomy, Embryology, Com- 

 parative Anatomy, and Histology 

 of the Islands of Langerhans 



E. V. COWDEY 



NEW YORK '* 



Anatomy 



Morphology, Technical Methods of Investigation, and Relations. 



The islands of Langerhans are epithelial structures of very small or, 

 often, of microscopic size, scattered throughout the pancreas. 



Unfortunately we know comparatively little of their relations in man, 

 though Bensley has devised methods of supravital staining which have 

 greatly extended our knowledge of them in the guinea pig. Up to the 

 present time these methods have not been applied in detail to other labora- 

 tory animals, and, since the dyes must be injected immediately after death 

 into the blood vessels supplying the pancreas, it is doubtful whether they 

 will ever be used extensively in man. Clark alone has attempted to do so 

 and has shown that the condition in man approximates closely to that 

 found by Bensley in the guinea pig. 



In the guinea pig the islands of Langerhans can best be studied in a 

 pancreas which has been supravitally treated by the injection, through the 

 aorta, of a dilute solution of neutral red in physiological saline solution, 

 for in this way they become specifically stained a dark red color. Such a 

 preparation is illustrated in Fig. 1. 



In size they vary from single cells to clusters of three or four, 

 and to masses of several hundred. Sometimes they may be as much 

 as one millimeter in diameter, though they are usually considerably 

 smaller. In shape they exhibit great variability, rounded masses 

 predominating. 



By staining with neutral red, the islands may easily be counted and 

 the errors introduced through the laborious study of serial sections avoided. 

 For convenience of description it is customary to divide the pancreas into 

 three parts, splenic, body, and duodenal portions. Bensley has found that 

 the islands are relatively more numerous in the splenic portion, and Clark 



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