ANTI-ENZYME IMMUNITY 299 



they arrived at, however, appear to be open to question. They reported 

 that coagulase by itself is inert as far as the conversion of fibrinogen 

 to fibrin is concerned. It is, however, presumed to be the precursor of 

 a thrombin-hke substance which can convert the fibrinogen of all 

 species, so-far tested, into fibrin clot. The formation of thrombin-like 

 substance requires the participation of an activator; this is present in 

 adequate quantity in some plasmas. The reaction is therefore con- 

 sidered to be analogous to normal thrombin formation from prothrom- 

 bin by the agency of thrombokinase, with the important diff^erence that 

 calcium is not required. The experimental data reported by them and 

 other investigators do not support these conclusions and pattern of 

 thought. The data as discussed below, may permit, however, the formu- 

 lation of a different mechanism which could account for the experi- 

 mental facts. 



e. "Activation" of the Staphylococcal Clotting Factor. Smith and 

 Hale (1944) observed that a testicular aqueous extract is a rich source 

 of the activator substance which added to non-clotting plasma of cer- 

 tain species produces fibrin clot promptly. Human and rabbit plasma 

 respond to clotting (without the added activator), and guinea pig 

 plasma fails to clot under the same conditions. They reported that 

 guinea pig plasma clots at 20°C. but not at 37°C., though clotting at 

 the higher temperature was slow. On the other hand, mouse and fowl 

 plasmas failed to clot at any temperature. The addition of either human 

 or rabbit testis extract to guinea pig, mouse or fowl plasmas was found 

 to render them as fully susceptible to the effect of staphylococcal factor 

 as were human and rabbit plasmas. Human and rabbit sera were also 

 found to serve as sources of activator substance. The failure of occa- 

 sional samples of human plasma to clot with staphylococcal strains 

 known to produce clotting factor was attributed by experimental 

 verification to a deficiency of activator substance. The addition of testis 

 aqueous extract caused atypical plasma to behave like the normal in 

 every respect. 



They reported that clotting factor alone is entirely without effect 

 on purified fibrinogen-prothrombin because of the removal of all 

 activator substance. This fibrinogen readily clotted on the addition of 

 clotting factor and testis extract. The combination of clotting factor 

 and testis extract was considered to serve as thrombokinase (thrombo- 

 plastin). The clotting of this fibrinogen by activated clotting factor was 



