Diphtheria Antitoxin 437 



demonstrated that in absolutely dry air diphtheria bacilli 

 die in a few hours. Under ordinary conditions their vitality, 

 when dried on paper, silk, etc., continues for but a few days, 

 though sometimes they can live for several weeks. In sand 

 exposed to a dry atmosphere the bacilli die in five days 

 in the light; in sixteen to eighteen days in the dark. When 

 the sand is exposed to a moist atmosphere, the duration 

 of their vitality is doubled. In fine earth they remained 

 alive seventy-five to one hundred and five days in dry air, 

 and one hundred and twenty days in moist air. 



Diphtheria Antitoxin. Behring * discovered that the 

 blood of animals rendered immune against diphtheria by 

 inoculation, first with attenuated and then with virulent 

 organisms, contained a neutralizing substance (Anti-korper) 

 capable of annulling the effects of the bacilli or the toxin when 

 simultaneously or subsequently inoculated into susceptible 

 animals. This substance, held in solution in the blood- 

 serum of the immunized animals, is the diphtheria antitoxin. 



The antitoxin is commercially manufactured at present 

 by immunizing horses against increasing quantities of diph- 

 theria toxin until the proper degree of immunity has been 

 attained, then withdrawing the antitoxic blood. The details 

 are as follows: 



I. The Preparation of the Toxin. The toxic metabolic products 

 of the Bacillus diphtherias are for the most part freely soluble, and 

 are therefore best prepared in cultures grown in fluid media. The 

 medium best adapted to the purpose is that recommended by Theobald 

 Smith.t 



To make it, the usual meat infusion receives the addition of a 

 culture of Bacillus coli, and is stood in a warm place overnight. The 

 colon bacilli ferment and remove the muscle and other sugars. The 

 infusion is then made into bouillon, titrated so that the reaction 

 equals + 1.1 when tested with phenolphthalein. It then receives an 

 addition of 0.2 per cent, of dextrose, and is sterilized in the autoclave. 

 To secure the best toxic product, the bacilli at hand must be carefully 

 studied and that naturally possessing the strongest toxicogenic power 

 employed for the cultures. The greatest toxicity seems to develop 

 between the fifth and seventh days. If the culture is permitted to 

 remain in the incubating oven beyond this period, the toxin gradually 

 is transformed to toxoid and its activity declines. The fatal dose for 

 a 250-300 gram guinea-pig should be about 0.001 c.c. given hypo- 

 dermically. 



II. The Immunization of the Animals. All commercial manu- 

 facturers of diphtheria antitoxic serums now use horses, as recom- 

 mended by Roux, instead of the sheep, dogs, and goats with which 

 the earlier investigators worked. The horse is readily immunized, 



*" Deutsche med. Wochenschrift," 1890, Nos. 49 and 50; "Zeit- 

 schrift fur Hygiene," xn, 1, 1892. 



t "Journal of Experimental Medicine," May and July, 1899, p. 373. 



