TETANUS TOXIN NEUTRALIZED BY BRAIN SUBSTANCE. 363 



All of these experiments show that the mice which received only 

 toxin and brain died, whereas additions of antitoxin as did not by 

 themselves suffice to neutralize the dose of poison were able to save 

 the animals which received the doses of brain emulsion. Hence 

 the action of the brain doses (which by themselves do not protect) 

 adds itself to that of non-protecting doses of antitoxin and so forms 

 a protective dose. 



Resume. 



1. The neutralizing effect possessed by guinea-pig brain on tetanus 

 toxin is supplemented by that of antitoxin when these are allowed to 

 act on the poison in vitro. 



2. From this one can conclude that this neutralizing effect of guinea- 

 pig brain on tetanus toxin and that of the antitoxin can be regarded 

 as equivalent properties. 



