Artificial immunity against toxins 367 



some other substance, also inefficacious by itself, met with in the 

 organism of the mouse. Here we should have something analogous 

 to what is met with in immunity against micro-organisms where both 

 fixatives and cytases intervene to bring about the destruction of 

 micro-organisms. By making researches in vitro on the action of 

 the fluids on bacteria, we may easily observe certain phenomena 

 which appear to indicate their direct influence. Take the case of 

 the fluid of an oedema from an animal vaccinated against the cholera 

 vibrio which renders this micro-organism motionless and agglutinates 

 it in vitro ; the oedema of an unvaccinated animal produces no 

 such effect. If, however, we were to conclude from this fact that, in 

 the oedema of the living animal or in its subcutaneous tissue, every- 

 thing goes on as in the test tube and that no other phenomenon of 

 reaction against the vibrios is produced, we should fall into a grave 

 error. It is extremely probable that, in the resistance of the living 

 animal against the toxins, the phenomena are more complicated than 

 are those observed in vitro. The example of the blood of the cray- 

 fish which prevents the poisoning of the mouse, without having any 

 influence on that of the crayfish itself, may here serve as a guide to 

 us. It is possible that, as in the struggle against the micro-organisms, 

 we have here a co-operation of two substances, each one of which, 

 by itself, is inactive. One of these substances would be found pre- [386] 

 existent in the blood of the crayfish, the other forming part of the 

 organism of the mouse. Perhaps the action of this blood is even 

 more complicated and only becomes active through the mediation of 

 some constituent of the living cell. 



Our study of immunity against toxins long ago revealed cases in 

 which this resistance cannot be attributed simply to the antitoxic 

 action of the body fluids. Animals vaccinated against living micro- 

 organisms may succumb to infection in spite of the presence of a 

 strong anti-infective power of the body fluids ; similarly animals 

 immunised against toxins may die from intoxication in spite of the 

 antitoxins contained in their fluids. Facts of this order are not rare. 

 Roux and Yaillard 1 on several occasions observed animals which died 

 from tetanus although they had a large supply of antitoxin in their 

 blood. Von Behriug 2 and his collaborators, Knorr, Ransom, and 



1 Ann. de VInst. Pasteur, Paris, 1893, t. vn, p. 98. 



2 Deutsche med, Wchnschr., Leipzig, 1893, S. 1253; "Allgemeine Therapie der 

 Infectionskrankheiten" in Eulenburg u. Samuel's "Lehrb. d. allg. Therapie," Berlin 

 u. Wien, 1899, Bd. in, S. 1051. 



