Artificial immunity against toxins 383 



latter case the toxin becomes separated from the particles of the [402] 

 cerebral substance that had fixed it. Danysz 1 convinced himself 

 that the mixture of pounded brain with tetanus toxin when it is 

 left in physiological saline solution, in distilled water, or in a 

 10 /o solution of sea salt, allows the tetanus toxin to pass into the 

 macerating fluid. The fixation of the toxin to the cerebral substance 

 is, therefore, more comparable to the mordanting of colouring-matters 

 by the tissues than to a real combination. 



Observers who have repeated the experiments of Wassermann 

 and Takaki have been greatly struck by the difference between the 

 action of the pounded cerebral substance and that of the living brain 

 upon the tetanus toxin. Whereas the former, taken from the guinea- 

 pig, an animal very susceptible to tetanus, prevented intoxication 

 when employed in minimal dose, the living brain of the same species 

 was found to be incapable of neutralising the most minute quantities 

 of toxin. On the other hand, Roux and Borrel 2 have shown that the 

 brain of rabbits, whether untreated or vaccinated against tetanus, 

 was very susceptible to the action of the tetanus toxin. This toxin, 

 injected directly into the brain, set up in both groups of rabbits 

 a special and characteristic cerebral tetanus. On the other hand, 

 when a little of the cerebral substance of the rabbits, mixed in 

 vitro with tetanus toxin, was injected into other susceptible animals, 

 these remained unaffected. 



This great difference between the antitoxic action of the living 

 brain and that of the pounded cerebral matter, on the one hand, 

 and the rigorous localisation of the antitetanic influence of this 

 cerebral substance, on the other, have suggested to several observers 

 the idea that the brain cannot be regarded as the organ of formation 

 of the true antitoxin, such as is found in the fluids of immunised 

 animals. This view has been expressed by Roux and Borrel, Marie 

 and ourselves. Knorr 3 also shares this view, being struck by the 

 fact that rabbits attacked by tetanus remain for weeks with contrac- 

 tions, but are incapable of producing in their nerve-cells sufficient 

 antitoxin to disintoxicate them, although their blood is already 

 loaded with dissolved antitoxin. 



At this period it was generally supposed that, in accordance with 

 Ehrlich's theory, the hypothetical side-chains were capable, under [403] 



1 Ann. de Vlnst. Pasteur, Paris, 1899, t. xni, p. 156. 



2 Ann. de VInst. Pasteur, Paris, 1898, t. XII, p. 225. 



3 Munchen. med. Wchnschr., 1898. 



