IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 225 
the other; and so intimate did these relations appear that I 
was led to apply the term prozymogen to the chromatin. I 
have found, as a result of experiments on the active pancreas 
of Amblystoma, that the zymogen granules under certain 
conditions give an iron reaction. When the organ, hardened 
in alcohol, is put in a quantity of Bunge’s fluid, and the pre- 
paration kept at the temperature of the room (20° C.) for a 
week, or when it is kept for two days in a quantity of sulphuric 
acid alcohol, teased-out portions, after the removal of the acid 
and on the addition of ammonium hydrogen sulphide, give pre- 
parations of which that represented in fig. 38 is an illustration. 
The zymogen granules give a greenish reaction, the colour 
making them more prominent than the other elements in the 
cells. The cytoplasm of the “ outer zone” gives but a feeble 
iron reaction, and this appears only to a minor extent in the 
nuclear elements, both results being caused by the lessened 
action and feeble extractive capacity of the acid alcohols when 
used on the tissue in mass. When the reagents are used for 
longer periods than those specified the iron disappears from the 
zymogen granules, while it becomes more strongly marked in 
the nuclear elements and in the cytoplasm of the “ outer zone.” 
Owing to the effect that ammonium hydrogen sulphide exer- 
cises on the granules, causing them to dissolve or disintegrate, 
an effect already referred to above, it is not possible to control 
the results obtained with the acid alcohols by experiments with 
this reagent, and one may, therefore, not regard the presence 
of iron in the zymogen granules as conclusively demonstrated, 
since it may be urged that the iron reaction which they gave 
was due to the iron which diffused into them from that liber- 
ated in the other cellular elements. When one remembers, 
however, the fact that the zymogen is elaborated in a cyto- 
plasm which is iron-holding and at its expense, the occurrence 
of a faint reaction for iron in the granules after the use of 
acid alcohols is best explained by the view that the zymogen 
of the pancreas contains iron, and that its antecedent, the 
prozymogen, is the iron-holding constituent in the cytoplasm 
of the “ outer zone.” 
