DIPHTHERIA. 297 



conditions their vitality, when dried on paper, silk, etc., 

 continues for a few days. In air that is moist the dura- 

 tion of vitality is prolonged to about a week. In sand 

 exposed to a dry atmosphere they 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 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. 



From time to time reference has been made to the 

 toxin elaborated by the diphtheria bacillus. Roux and 

 Yersin first demonstrated the existence of this substance 

 in cultures passed through a Pasteur porcelain filter. 

 The toxin is intensely poisonous; it is not an albumin- 

 ous substance, and can be elaborated by the bacilli 

 when grown in non-albuminous urine, or, as suggested 

 by Uschinsky, in non-albuminous solutions whose prin- 

 cipal ingredient is asparagin. The toxic value of the 

 cultures is greatest in the second or third week. 



In addition to the toxin, a toxalbumin has been isolated 

 by Brieger and Frankel. 



Bearing discovered that the blood of animals rendered 

 immune to diphtheria by inoculation, first with attenu- 

 ated and then with virulent organisms, contained a neu- 

 tralizing substance which was capable of annulling the 

 effects of the bacilli or the toxin when simultaneously or 

 subsequently inoculated into non-protected animals. This 

 substance, in solution in the blood-serum of the immu- 

 nized animals, is the diphtheria antitoxin. 



The preparation of the antitoxin for therapeutic pur- 

 poses received a further elaboration in the hands of Roux. 

 The subject is one of great interest, but must be consid- 

 ered briefly in a work of this kind. 



The antitoxin is manufactured commercially at present, 

 the method being the immunization of large animals to 

 great quantities of the toxin, and the withdrawal of their 

 antitoxic blood when the proper degree of immunity has 

 been attained. The details are as follows : 



