ACTION OF ANTITOXINS ON TOXINS. 277 



of combination, is necessary. We may, however, note that certain 

 well-known hitherto enigmatic facts become easily explicable on 

 the hypothesis of union in variable proportions. One or two exam- 

 ples may be given : 



It has been noted (particularly with tetanus) that a toxin-anti- 

 toxin mixture that is harmless for an animal of species A shows 

 evident toxicity for an animal of species B. Instances of this 

 sort have been mentioned, particularly by Buchner and by Roux 

 and Vaillard. Such apparently peculiar results are an almost 

 necessary corollary to our hypothesis. A mixture of toxin with 

 even a weak dose of antitoxin contains no primitive toxin, but in 

 its place an attenuated toxin, a new complex endowed with in- 

 dividual characteristics, and it will not necessarily act in the same 

 manner on different animals. It is reasonable to anticipate that 

 its toxic power will be so attenuated as to produce no trouble with 

 certain animals, but distinct effect on others; why, indeed, should 

 they all react alike to this new compound? It is even theoretically 

 conceivable that completely saturated toxin should poison certain 

 species or certain individuals. According to our conception there 

 is no sharp, radical difference between attenuation and neutraliza- 

 tion of a toxin, or, in other words, there is no absolute neutraliza- 

 tion. There is simply a greater or less degree of attenuation in 

 accordance with the more or less complete saturation of the toxin 

 by antitoxin. This saturation is often practically equivalent to 

 a neutralization. The expression "neutralization" implies that 

 the toxin has become irrevocably inactive for very sensitive animals 

 owing to a radical abolition of the substance that renders it toxic. 

 With such complete neutralization the degree of a given animal's 

 susceptibility is not a significant factor in the result. When, 

 however, an apparent neutralization is, in reality, only a very marked 

 attenuation, the degree of susceptibility must be taken into account, 

 as the attenuation may be very marked as far as animal A is con- 

 cerned, but very little for animal B. The conception of variation 

 in attenuation, then, must constantly take into account the relation 

 between the sensitivity of the animal body and the harmful nature 

 of the substance under consideration. 



It is quite comprehensible, then, how a mixture that is rich in 

 antitoxin (i.e., with the toxin well saturated) and inoffensive for 



