384 CJiapter XII 



certain conditions, not only of fixing the tetanus toxin, but also of 

 neutralising it. It was said, therefore, that these chains, reproduced 

 in large quantities in the cerebral cells, must exercise their neutral- 

 ising action in the brain itself. Consequently, when it was seen that, 

 in Roux and Borrel's experiments on vaccinated rabbits, this organ 

 was itself affected, it was concluded that the brain must not be 

 regarded as the producer of the antitoxin. 



Later, Ehrlich and his supporters, amongst whom I will name 

 especially Weigert, have developed the theory of side-chains in a 

 much more detailed fashion, leading to a different interpretation of 

 several facts previously established. Ehrlich distinguishes in the 

 toxin molecule a haptophore group which combines with the side- 

 chain or the corresponding receptor of the living elements, and a 

 toxophore group which produces the poisoning of the protoplasm. 

 The side-chains, inactive for the toxophore group, neutralise only 

 the haptophore group. Consequently, when these side-chains are 

 numerous in the nerve elements which produce them, they may be 

 a source of great danger to this living element, by attracting the 

 toxic molecules. In this case, these chains, or receptors, serve to 

 attract the poison, just as the badly adjusted lightning conductor 

 attracts lightning. For this reason rabbits vaccinated against tetanus 

 become tetanic when the toxin is injected directly into the brain. 

 It is only at a distance from the nerve centres that the receptors, 

 excreted into the body fluids, fulfil their r61e of true antitoxins. 

 There they combine with the haptophore group of the toxic molecule, 

 leaving the toxophore group intact; this latter group, however, 

 diverted from the nerve-cells, is incapable of exercising an injurious 

 action. 



From this point of view not only the cerebral tetanus of vaccinated 

 rabbits, but also the hypersusceptibility of immunised animals, upon 

 which von Behring has so strongly insisted, may be explained. The 

 argument, drawn from these facts, against the nervous origin of 

 tetanus antitoxin, loses, therefore, much of its weight. If we confront 

 this hypothesis with the other data collected on the question, the 

 solution of the problem becomes beset with great difficulties. Previous 

 [404] to the discovery made by Wassermann and Takaki, I attempted to 

 solve the problem by removing from fowls portions of the brain and 

 spinal cord, proposing to take advantage of the fact that birds, which 

 are capable of producing antitoxins, withstand these operations fairly 

 well My hopes were not fulfilled ; I could never keep my fowls 



