Artificial immunity against toodns 391 



groups in the toxic molecule, it is to the side-chain, which fixes the 

 first group, that Ehrlich attributes prime importance. " The forma- 

 tion of antitoxins " — he says^ in the opening address at his Institute 

 at Frankfort — " would, therefore, be absolutely independent of the 

 action of the toxophore elements." In other words, for a cell to be 

 capable of producing antitoxin, it is not at all necessary that it should 

 be susceptible to the toxic influence of the poison ; it is only necessary 

 that it should possess receptors, or side-chains, capable of combining 

 with the haptophore group of the toxin. Thus it is possible, as we 

 have described above, to produce antitoxins, with modified toxins [41 1] 

 whose toxic action is nil or almost so, but which have retained their 

 power of combining with antitoxic substances. According to Ehrlich, 

 these modified toxins are toxoidSj in which the toxophore group is 

 completely destroyed; "whilst the haptophore group, the producer of 

 immunising substances, is retained in its integrity.'* It is evident 

 then that, under such conditions, the tetanus antitoxin might be 

 developed elsewhere than in the nerve centres. For that it would be 

 sufficient that outside the nerve cells there should be other living 

 elements capable of fixing the tetanus toxin, or, to use Ehrlich 's 

 phraseology, elements, possessing side-chains, having an affinity for 

 the haptophore group of the tetanus poison. 



Dbnitz^ has already expressed the view that in the rabbit the 

 tetanus toxin may be fixed not only by the nerve elements but also 

 by the various other cells. 



The existence of such cells, outside the nervous system, is not 

 merely hypothetical. It is shown very clearly in Roux and Borrel's 

 experiments on cerebral tetanus. In order to produce this disease in 

 the rabbit, it is sufficient to introduce a very small dose of toxin 

 directly into the brain. When inoculated subcutaneously with much 

 larger quantities of the same tetanus poison, the rabbit remains in 

 good health or exhibits merely a slight and transient tetanus. " The 

 resistance of the rabbit against the tetanus toxin, injected under the 

 usual conditions" — conclude Roux and BorreP — "is not due, then, 

 to a relative insusceptibility of the nerve centres, but to the fact 

 that much of the poison introduced does not reach the nerve cells 

 and is destroyed in some part of the animal." In the guinea-pig, 

 as shown by the same investigators, the diflcrence of the dose of 

 tetanus poison, necessary to produce fatal tetanus by inti-acerebral or 



1 Semaine med.. Paris, 1899, p. 411. 

 2 Deutsche med. TVchnschr., Leipzig, 1897, S. 428. ^ (c, p. 229. 



