STUDIES ON THE PANCREAS OF THE GUINEA PIG 333 



answer this question positively because Dale does not describe 

 the characters of his cells except to say that they are islet cells. 

 But they cannot be islet cells because they do not contain islet 

 granules. They differ from other acinus cells, as one can see from 

 Dale's figure, in not staining in the basic dye. I have found in 

 my preparations of the pancreases of secretin toads, acinus cells 

 of two sorts which do not stain with basic dyes. Whether either 

 of these corresponds to those obtained by Dale or not I am un- 

 able to state, because Dale does not give any description of his 

 clear cells except to say that they are islet cells. One type of 

 acinus cell which I have found sometimes present in large numbers 

 in my preparations made by the method recommended by Dale, 

 owes its failure to stain with toluidene blue to post mortem 

 changes. These cells show, instead of the usual deeply stained 

 basal zone, a pale stained protoplasm in which no zymogen is visible 

 and which has a coarse alveolar structure. Examination of these 

 cells by methods suitable for the demonstration of mitochondria 

 shows that the granules of this type also have disappeared or are 

 disappearing. The nucleus shows also a certain degree of chro- 

 matolysis. The change which these cells have undergone can be 

 produced in any desired degree by simply keeping the pancreas 

 in normal salt solution and it may be observed going on gradually 

 under the microscope if fresh preparations mounted in salt solu- 

 tion are observed continuously for one-half to one hour. It does 

 not affect all cells of the acinus at the same time. Sometimes a 

 single cell will show the change, and at other times only a single 

 cell retains the normal structure. Sometimes large areas of the 

 section may show this change. 



The other type of clear cell owes its lack of staining power to 

 a true exhaustion of the chromophile substance of the pancreas. 

 In these cells the nucleus shows no degenerative changes, the 

 mitochondria are well preserved, but the cell differs from the nor- 

 mal resting cell in the absence of zymogen granules and in the 

 great reduction of the basophile material of the base of the cell. 

 These cells, however, are in no sense islet cells, because they do 

 not contain the characteristic granules of the islet cells and they 

 differ from the islet cells in their nuclear characters and in the 

 nature of their mitochondrial apparatus. 



