64 SCIENCE “PROGRESS 
1. Calcium salts. 
2. A zymogen, or pro-ferment. 
3. A substance which may originate from the corpuscles or 
from other tissues known as zymoplastic substance. 
The pro-ferment which arises from the plasma is plasmozym; 
the substance originating from cells is termed cytozym. The 
interaction of these two and calcium ions yields a true thrombin 
or holozym. ‘The subsequent destiny of this, when it is present 
in serum after the process of coagulation, is to pass into 
metazym, which is to be considered as a zymogen capable of 
passing into a ferment stage known as neozym, when it is 
activated by an alkali. The evidence for this conception, which 
may be expressed in the following scheme, can be better 
discussed with the help of later work, particularly that of 
Morawitz. 
The formation and fate of thrombin would be indicated as 
follows (Fuld): 
Plasma Cells 
Plasmozym Cytozym 
Calcium 
Sewras origin of thrombin 
Holozym or 
a-Thrombin 
Metazym ; : 
| by alkali possible modifications of thrombin. 
Neozym or 
8-Thrombin 
The cytozym of Fuld corresponds to the coagulating sub- 
stance in tissue-extract; and since fowls succumbed in a few 
seconds to an intra-venous injection of cytozym, it was con- 
cluded that the formation of thrombin occurred in a circulating 
fluid which already contained calcium and plasmozym. The 
results of Arthus! obtained with fluoride-plasma are only in 
partial agreement with Fuld’s observations. Non-coagulating 
fluoride-plasma is an excellent medium for ascertaining the 
existence of thrombin. Both blood-serum and Schmidt’s throm- 
bin produce coagulation in fluoride-plasma. This, however, 
remains non-coagulable when cytozym alone or calcium alone 
is added. It is a fair conclusion that tissue-extract therefore 
| Journal de Physiologie, p. 887, 1901. 
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