STUDIES ON THE PANCREAS OF THE GUINEA PIG 377 



a hasty assumption based on the fact that these cells sometimes 

 occur on the surface of the islet and sometimes are interposed 

 between the acinus cells and the islet cells. Laguesse ('06-'08) 

 in his summary of the literature supports this idea of the A cells 

 but in his latest paper appears to have abandoned it, because he 

 describes there a different sort of transitional element, and at- 

 tempts to realize the logical necessities of the transition as I have 

 indicated them above. 



Mankowski studying preparations of the pancreas of the guinea 

 pig fixed in Flemming's fluid found cells which he regarded as 

 transitions. These require careful consideration, for Mankow- 

 ski ('01) demonstrated the granules in the islet cell, and found 

 similar granules in certain acini which were alongside of the islet. 

 Laguesse ('08) also described similar granules in the base of the 

 acinus cell of the human pancreas, which he regarded as evidence 

 of the assumption, by the acinus cell, of a new internal secretory 

 function. 



These acinus cells containing small granules I have studied 

 with great care, because if the granules were really similar to islet 

 granules, then it might be claimed with justice that the first of 

 the criteria of real transitions which I have laid down, had been 

 established and that these cells were in reality transitions. As a 

 result of this study I have found that these granules are not islet 

 granules at all but that they result from a degeneration of the baso- 

 phile material of the acinus cells. In some guinea pigs this gran- 

 ular condition of the acinus cells is so abundant that practically 

 every cell in the pancreas may show some trace of it. In such 

 pancreases, it is very easy to study the process of formation of the 

 granules. The process begins by the appearance of a few of the 

 granules in the base of the cell. As they increase in number the 

 basophile material diminishes. Later the zymogen granules 

 disappear, but there is an intermediate stage where the cell con- 

 tains a few zymogen granules but all of the basophile material of 

 the base of the cell is replaced by minute granules (fig. 15). As- 

 sociated with the disappearance of the basophile material there 

 is a profound modification of the mitochondrial filaments When 

 the base of the cell is well filled with the tiny granules but some 



