66 SCIENCE PROGRESS 
Metathrombin, 
a-Prothrombin, Thrombin Metazym, 
Calcium. 
Zymogen B-Prothrombin 
Circulating blood . + + oO fe) 
Oxalated plasma . 5 oO + oO fe) 
Peptone-plasma + fe) fo) fe) 
Fluoride-plasma o = oO fe) 
Serum from blood — fo) a little + 
Serum from any of the 
coagulated plasmata + fo) a little + 
From the thymus, lymphatic glands, or the stromata of red 
corpuscles, a thermolabile substance can be extracted with a 
weak saline solution. This substance is, for the most part, 
thrombo-kinase, which soon becomes unstable in solution, 
though the extract, dried in a vacuum, yields a powder which 
only slowly changes. On fibrinogen solutions, even in the 
presence of lime, this extract produces no change; it is 
therefore not a thrombin such as occurs in serum. Exactly 
the same negative result follows when extracts from mammalian 
tissues are added either to solutions of fibrinogen or to oxalate- 
or fluoride-plasma, and it is immaterial whether the extracts 
are previously treated with calcium chloride or not. 
On the other hand, the clotting of blood is accelerated, and 
the coagulation process in the plasma of birds, in peptone 
plasma, and sometimes in hirudin-plasma, forthwith commences 
on the addition of thrombo-kinase, provided calcium salts are 
present. The ferment-power of serum is also exalted by 
thrombo-kinase. From these facts Morawitz concludes that the 
development of thrombin results from the interaction of kinase 
with a body in coagulable liquids or in serum in the presence 
of calcium salts. This body is the substance recognised by 
Fuld as plasmozym, and may be termed thrombogen. This 
corresponds to a-prothrombin. Since a-prothrombin exists 
in fluoride-plasma as well as in all the non-coagulated but co- 
agulable plasmata hitherto examined, the following conception 
of the coagulation process may be suggested. In the plasma of 
circulating blood a certain amount of fibrinogen, calcium, and 
thrombogen will be found. It does not coagulate, since thrombo- 
kinase is entirely absent, or if present in small amount is 
neutralised by anti-bodies in the blood. Solutions of thrombo- 
kinase or of substances capable of setting this free in the blood 
will forthwith give rise to thrombin, and be followed by intra- 
