CHANGES IN PANCREATIC CELLS. 159 



It will be seen immediately that one of the most important 

 functions of the pancreatic juice is the formation of peptone from 

 proteid, which operation is carried out by a special ferment called 

 trypsin. It has been found that this ferment can only be obtained 

 from the active pancreas, and that the wider the inner granular 

 zone of the cells is, the richer in ferment is the glycerin extract 

 made from the gland. But it has been found that if a glycerin 

 extract be rapidly made from an actively secreting absolutely 

 fresh gland, i.e., removed from the dead animal while still warm, 

 the extract is found to be quite inert towards proteids, while an 

 extract made from a portion of the same pancreas which has been 

 kept some hours after death is very active ; and a portion of the 

 fresh pancreas pounded in a mortar with a little weak acid so as 

 to develop the trypsiu in it, acts in an alkaline solution and forms 

 peptone energetically. 



We must therefore conclude that the special proteolytic fer- 

 ment of the pancreas does not exist prior to the period at which 

 the secretion is poured out from the gland cells. 



Although a definite relation seems to exist between the amount 

 of granules in the active cells and the degree of efficacy of the 

 secretion, the ferment does not appear in full force for some time 

 after that the height of the gland activity has been established, 

 and it is likely that the presence of an acid helps in the birth of 

 the ferment. 



It has therefore been assumed that the granules of the gland 

 cells give rise, not to the proteolytic ferment, but to a ferment- 

 producing substance which is called Zymogen. 



So that if we trace the history of the pancreatic proteolytic fer- 

 ment, we shall find that, so far as this trypsin is concerned, there 

 can be no question as to whether it pre-exists in the blood and is 

 removed thence by the gland or not, because by studying the process 

 we find that the final elaboration of the secretion takes place after 

 it has got into the ducts or the intestinal cavity. Thus the blood 

 gives to the protoplasm of the gland-cells nutriment. The proto- 

 plasm of the cells, by its intrinsic chemical processes, manufac- 

 tures peculiar granules. These granules give rise, among other 



