64 SCIENCE PROGRESS 



i. 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 



Cak' 



- origin of thrombin 



Holozym or 

 a-Thrombin 



Metazym 



I by alkali \ possible modifications of thrombin. 

 Neozym or 

 /3-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 1 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 



1 Journal de Physiologie, p. 887, 1901. 



