256 IMMUNO-CATALYSIS 



fest any effect on fibrinogen. On the other hand, some of the venoms 

 which manifested a high degree of proteolytic activity rendered the 

 fibrinogen non-clotting even by thrombin. These facts were interpreted 

 by Eagle as substantiating the hypothesis that the clotting, like the 

 digestion, is caused by one of the proteolytic enzymes in the venom 

 (see, however, the section on the mechanism of fibrin clot formation, 

 p. 278). 



f. Proteolytic Activity of the Toxin of CI. Welchii. As stated 

 above, Maschmann found that the toxin fraction of the culture filtrate 

 of CI. welchii hydrolyzed gelatin and was not inhibited by the "trypsin- 

 inhibitor" present in normal sera. Taking advantage of this fact he 

 demonstrated that antitoxic horse serum strongly inhibited the pro- 

 teolytic activity of a toxin preparation. Since he did not claim that the 

 toxin he experimented with was a homogeneous substance, the ques- 

 tion as to whether the proteolytic activity of the preparation is a 

 property of the toxin molecule or not must be left open for the present. 



Since /8, 8, 6 and e-toxins were found by MacFarlane, et at. to pro- 

 duce no opalescence in human serum or lecitho-vitellin, the proteolytic 

 activity of the toxin preparation appeared to be associated with the 

 a-toxin. The toxin was a dry preparation prepared from dialyzed culture 



Table XII 



"■Per cent difference between the activity of ovemeutralized toxin and that in 

 normal serum. 



