52 ANAPHYLAXIS AND ANTI-ANAPHYLAXIS 



that the animal was for practical purposes vaccinated 

 against anaphylaxis as early as the day after the 

 inoculation, we became convinced that we — together 

 with Rosenau, Anderson, and Otto — had gone astray. 

 From that time it was clear that the hypothesis of 

 toxin in serum must be rejected, and that the pro- 

 cedure of immunisation such as Rosenau and Ander- 

 son had employed, and such as we ourselves employed 

 at the beginning of our researches, could not be 

 upheld. We were forced to make a clean sweep of 

 all we knew about vaccination, and to pursue an 

 altogether different line. One fact had been acquired, 

 however, namely, that in vaccinating guinea-pigs 

 against anaphylaxis in the way one vaccinates against 

 a toxin — that is to say, repeating the injections at 

 given intervals — Rosenau, Anderson, and Otto had 

 made use of a technique which in no wise responded 

 to the end which they had in view. We would even 

 go further-, and say that this technique of vaccination 

 was in direct opposition to the end in view, because, 

 in multiplying the injections of serum, not only was 

 the appearance of the anaphylactic state temporarily 

 deferred, but there was no immunisation. We there- 

 fore found ourselves in the presence of an extremely 

 ■curious and quite inexplicable phenomenon ; a guinea- 

 pig rendered anaphylactic with horse serum, after 

 having received a non-lethal dose of this serum sub- 

 cutaneously, was thereafter in a position to tolerate, 

 some hours after, one or even two lethal doses of 

 serum. From the point of view of prevailing concep- 

 tions on immunity, it is a fact which has not its 

 parallel in biology. Reduced to its simplest terms, 

 it may be summed up thus: a toxin — granted, pend- 

 ing further information, that there is one in the serum 

 — injected in a dose which is not lethal protects the 

 animal against the lethal dose of this same toxin 

 when the latter is injected one to two hours after. 



