METABOLISM. 



353 



secretory granules, but can be stained by neutral gentian. Further, 

 the islets do not communicate with the secretory ducts, and are clearly 

 not concerned with the formation of pancreatic juice. 



That the islets probably take some part in carbohydrate metabolism is 

 shown by two observations. In the first place, ligature of the pancreatic 

 duct leads, eventually, to atrophy of the secreting tissue, but the islets 



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crag 



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zymogen granules. 



FIG. 130. Islet of Langerhans in pancreas. (From Romans, Proc. Roy. Soc.) 



are unaffected and glycosuria does not occur. Secondly, it might be 

 expected that, if the islets produce an internal secretion essential for 

 normal carbohydrate metabolism, the removal of the greater part of the 

 pancreas would lead to over-activity of the islets still remaining in the 

 body, which might be demonstrated by histological or other methods ; 

 and this has recently been found to be the case. When the pancreas is 

 almost completely removed, only a small fragment being left intact, the 

 animal remains well for a time, but eventually developes diabetes of a 



23 



