392 Chapter XII 



by subcutaneous injection, is minimal or nil, from which it may be 

 argued that in this very susceptible animal there is no destruction 

 of toxin outside the nerve centres and that the whole of the poison 

 introduced makes its way without hindrance as far as these organs. 

 Ehrlich, in his report to the International Congress of Medicine in 

 Paris (August, 1900), accepted these results, as seen from his tenth 

 [412] and eleventh propositions : " The receptors exist, sometimes in certain 

 tissues only, sometimes in the majority of the organs (action of 

 tetanus poison in the guinea-pig and in the rabbit)," " ...the presence 

 of numerous receptors in the organs of less vital importance may 

 bring about thanks to a kind of diversion of the toxin molecules a 

 diminution in the susceptibility of the animal to this toxin 1 ." We must 

 here recall the differences between the susceptibility of the guinea- 

 pig and that of the rabbit to small doses of tetanus toxin frequently 

 repeated as in Knorr's experiments already referred to. The guinea- 

 pig, subjected to these injections, dies in a tetanic condition long 

 before it has received the minimal lethal dose for this species when 

 injected in a single dose. The rabbit, on the other hand, is very 

 tolerant of repeated doses and even rapidly acquires an immunity 

 against five minimal lethal doses for the rabbit (injected at once). 

 Knorr explained this difference as due to the hypersusceptibility 

 of the nerve centres in the guinea-pig and to their acquired in- 

 susceptibility in the rabbit. The experiments of Roux and Borrel 

 on the cerebral tetanus of rabbits vaccinated against tetanus, have 

 demonstrated that this insusceptibility is not produced in these 

 animals. We must, therefore, seek some other explanation. In 

 rabbits subjected to small repeated doses, the poison is more and 

 more prevented by certain living elements from reaching the nerve 

 centres. Further, it is neutralised by the antitoxin which is rapidly 

 produced. We find from Knorr's 2 researches that in rabbits anti- 

 toxin appears in the blood in cases where, affected with a transitory 

 tetanus, their limbs remain contracted for weeks. In guinea-pigs, 

 affected with the same form of tetanus, antitoxin in appreciable 

 quantity is never found, even after complete recovery. All these 

 facts accord with the hypothesis that there exist, outside the nervous 

 system, certain living cells which absorb the tetanus toxin and pro- 

 duce antitoxin. Rabbits and fowls possess this property in a much 



1 Compt. rend. Congres intemat. de Medicine de Paris, Section de bacteriologie 

 et de parasitologie, Paris, 1891, p. 30. 



2 Munchen. med. Wchnschr., 1898, S. 321. 



