258 STUDIES IN ADVANCED PHYSIOLOGY. 



the gland. It has a digestive action which might lead it to 

 attack the gland itself in which it is stored. Both of these 

 difficulties are avoided by forming the trypsinogen granules. 

 These are, in the first place, solid and can easily be stored. 

 In the second place they do not have the active digestive 

 properties of the trypsin and so exert no digestive action at 

 all. When, then, finally the trypsin is needed all this stored 

 trypsinogen may by slight changes be at once transformed 

 into trypsin and so poured out in large quantities into the 

 intestines. Trypsin is a digestive fluid of rather complex 

 composition and it would be practically impossible for the 

 pancreas to secrete large quantities of this at sudden notice, 

 but by devoting all of its resting period to the production 

 of these trypsinogen granules, storing these up in the outer 

 part of each cell, and then just at the moment when the 

 trypsin is needed changing these trypsinogen granules into 

 the soluble trypsin, sudden and large quantities of trypsin 

 are at once available. 



What has been said with reference to the pancreas applies 

 to the mucous glands. Here during rest are produced gran- 

 ules which at the proper occasion are changed into mucus 

 and poured out. These stored granules are called mucino- 

 gen granules. While it has been impossible to actually 

 demonstrate a similar condition of things in the gastric 

 gland, there is every reason to believe that here, also, dur- 

 ing the resting period of the stomach the peptic cells are 

 storing up granules of pepsinogen. Such granules not being 

 easily dialyzable could be stored in the cell, and not having 

 the active digestive property of regular pepsin, would exert 

 no chemical effect on the glands themselves. Then, at the 

 moment food enters the stomach, these pepsinogen granules 

 are, by slight additional changes, transformed into the pep- 

 sin and so poured on the food. Possibly a similar antece- 

 dent substance is present in the salivary glands from which 

 the specific element ptyalin is derived, a kind of ptyalino- 

 gen. It is well, however, to keep in mind that the actual 

 presence of granules of the nature just described can be 



