458 INFECTION AND RESISTANCE 



and has the advantage of introducing less foreign protein into the 

 human body. It retains its potency, according to Park and Throne, 

 as long as does the whole serum. 



ACTIVE IMMUNIZATION IN DIPHTHERIA WITH MIXTURE OF TOXIN 



AND ANTITOXIN 



Recently Behring 28 has advocated the immunization of human 

 beings with mixtures of diphtheria toxin and antitoxin. This 

 method represents essentially active immunization with toxin ren- 

 dered harmless by neutralization with antitoxin. The use of such 

 mixtures had previously been studied with considerable care, in the 

 case of the toxin of symptomatic anthrax, by Schattenfroh and 

 Grassberger, 27 and the procedure had been used in the New York 

 Department of Health for some years in the initial treatment of 

 antitoxin horses. Theoretically considered on the basis of Ehrlich's 

 opinions, one would be inclined to wonder at the fact that relatively 

 neutral mixtures of toxin and antitoxin should possess any antitoxin- 

 inciting properties. Behring explains the immunizing value of such 

 mixtures by the reversible nature of toxin-antitoxin union in the 

 animal body. He calls attention to the fact that our analyses of 

 diphtheria toxin-antitoxin mixtures have been made entirely with 

 guinea pigs as indicators. In studying such mixtures in other ani- 

 mals Behring has come to the conclusion that complete detoxication 

 of the poison in vitro does not occur. He found, for instance, that a 

 toxin-antitoxin mixture that was entirely innocuous for guinea pigs 

 produced an active febrile reaction in an ass. In monkeys (Maca- 

 cus rhesus) he finally found an animal in which he obtained evidence 

 satisfactory to him that toxin may be powerfully active in the animal 

 body, even if it has been previously mixed with antitoxin. If, for 

 instance, he gave a monkey a mixture in which as much as 20 to 40 

 antitoxin units were mixed with one toxin unit, and repeated the 

 injection two or three times, the animal died of subacute diphtheria 

 toxin poisoning. The mixture ceased to be poisonous for monkeys 

 only when the relation of antitoxin to toxin became one of 80 to 100 

 antitoxin units to one toxin unit. This final detoxication when suffi- 

 cient amounts of antitoxin were used, it seems to us, may be taken 

 as sufficient evidence that Behring's monkeys did not die of ana- 

 phylaxis. 



We gather from Behring' s writings that he attributes these dif- 

 ferences in susceptibility to toxin-antitoxin mixtures in various ani- 

 mals to differences in the reversibility of the toxin-antitoxin com- 

 plex in the bodies of the individual species. 



26 Behring. Deutsche med. Woch., Vol. 39, No. 19, 1913. 



27 Schattenfroh and Grassberger. Deuticke, Wien, 1904; see also Schat- 

 tenfroh, Wien. kl. Woch., No. 39, Sept., 1913. 



