STRUCTURE OF THE MAMMALIAN GASTRIC GLANDS. 369 



zymogen. Grlitzner ^ also noted this peculiar staining with 

 osmic acid. 



Some information as to the nature of the substance in 

 question is afforded by the researches of Macallum,- who 

 describes the difference in staining properties exhibited by the 

 resting and exhausting pancreatic cell, and explains the dif- 

 ference as follows : — '' The chromatin of the nucleus gives rise 

 to a substance which we may call prozymogen, sometimes 

 dissolved in the nuclear substance, sometimes collected in 

 masses (plasmosomata), and finally diffused into the cell 

 protoplasm, uniting with a constituent of the latter as 

 zymogen." In a subsequent research into the distribution of 

 assimilated iron compounds in animal and vegetable cells,^ he 

 found, in the outer protoplasmic zone of the pancreatic and 

 many other gland cells, a firm organic compound of iron, 

 which he regards as the prozymogen of his earlier investiga- 

 tion. A similar view is taken by Mouret of the nature of the 

 fibrillar chroraophilous element in the outer zone of the pan- 

 creatic cell, and the term " prezymogen " is applied by this 

 observer to the substance in question. 



I have made a series of experimental studies of the gastric 

 and many other glands, with a view of determining the relation 

 of this substance to the formation of zymogen granules, and 

 also its source in the cell. The results of these studies will be 

 contributed in a separate paper, and I will content myself at 

 present with a recital of the facts that are of importance from 

 the stand-point of determining the morphological relationships 

 of the cells. 



The prozymogen is co-extensive with the protoplasm of the 

 cell, and, even in cells which possess only a small outer zone, 

 usually presents quite definite staining and structural charac- 

 ters, which enable one to decide with ease as to its presence. 

 The most favorable material for studying its characters is offered 



^ ' Pfliiger's Arcbiv,' Bd. xx. 



^ 'Trans. Canadian Institute,' vol. i, part ii, 1891. 



'^ 'Quart. Journ. Micr. Science,' vol. xxxviii, part ii, new series. 



'' ' Journal de I'Anat. et de la Physiol.,' annee xxxi, 1895. 



