ANTITOXIN. g 



its blood becomes charged with antitoxin of gradually 

 increasing potency (Behring, Roux), so that the true anti- 

 toxic condition of the blood of such an animal can only be 

 due to the action of that toxin ; but an animal is also 

 furnished with resistance by repeated injections of living 

 bacilli in gradually increasing amounts and virulence ; in this 

 process antitoxin is formed indirectly by the multiplying and 

 toxin -producing bacilli, but in addition, when the bacilli 

 cease to multiply and become degenerated, immunising 

 substance derived from the bacterial bodies becomes 

 available. The total amount of these latter would determine 

 the amount of immunising substance, and would of course 

 depend on the total amount of bacteria that had been 

 injected in the various operations, just as the amount of 

 antitoxin depends on the amount and degree of potency of 

 the stimulating toxin injected. 



Considerations like these have led me to immunise 

 horses against diphtheria by injecting them repeatedly with 

 large doses of living bacilli of increasing virulence, and 

 thereby blood serum has been obtained which when tested 

 on the guinea-pig has a powerful immunising (protective and 

 curative) action on otherwise fatal doses of living bacilli. 

 The serum of such horses possesses, in addition to antitoxin, 

 substances which act powerfully on the living bacilli. True, 

 the antitoxin is not of such potency as can be got by long- 

 continued injection of large doses of pure toxin, as in the 

 animals prepared by Behring and Roux ; the immunising 

 action of the serum obtained bv the former methods is the 

 conspicuous part, but there is also antitoxin present, since the 

 living bacilli at each injection cause by their multiplication 

 toxin : rise of temperature and tumour. That the presence 

 of immunising substances is important in protective inocula- 

 tions has been already mentioned ; it now only remains to 

 draw attention to the part they play in the curative pro- 

 ceeding, for it must be obvious that the introduction of 

 sufficient amounts of immunising substances — which have 

 been shown to act specifically against the living bacilli — 

 into the system of an animal and man subject to diphtheria, 

 i.e., in which the living bacilli are still multiplying and 

 producing toxin, must materially accelerate the time in 

 which the life of the bacilli is brought to a standstill, and the 

 production of toxin arrested ; that is to say, the disease is 



cut short. T , T . 



h. Klein. 



