DIPHTHERIA TOXINS 333 



substance is a protein body, which they designated a 

 " tox -albumin." It is destroyed by a temperature of 

 60 C. but not by one of 50 C., even in the presence of an 

 excess of hydrochloric acid, and hence is probably not an 

 enzyme. The tox-albumin is non-dialysable, is precipi- 

 tated by saturation with ammonium sulphate but not 

 with magnesium sulphate, and hence is neither a peptone 

 nor a globulin, contains a large amount of sulphur, and 

 gives the biuret and Millon's tests. Brieger and Boer 

 prepared the diphtheria tox-albumin by precipitating 

 a broth culture with a 1 per cent, solution of zinc sulphate 

 or chloride. The precipitate of the zinc double salt is 

 washed with slightly alkaline water and decomposed 

 with a stream of carbonic acid gas. The purified tox- 

 albumin gives the xanthoproteic, biuret, and Adam- 

 kiewicz's reactions, and the red coloration on heating 

 with Millon's reagent. 



According to Ehrlich the toxin broth is a complex 

 mixture of toxic and non-toxic constituents (see p. 192), 

 but this is denied by Madsen and Arrhenius (see p. 194). 

 Its toxicity gradually diminishes on keeping, and is 

 destroyed by boiling in five minutes, at lower temperatures 

 more slowly, and also by light. 



Diphtheria antitoxin. By the injection of sub -lethal 

 and increasing doses of the toxin into an animal an anti- 

 toxin is generated. For the preparation of a potent 

 antitoxin for therapeutic use the first essential is a highly 

 toxic toxin, and for obtaining this a diphtheria bacillus of 

 high virulence is required, and few strains possess the 

 necessary virulence. The medium used is an alkaline 

 meat broth (rendered alkaline to the extent of about 

 6-7 c.c. of normal caustic soda solution per litre beyond 

 the neutral point to litmus) in Erlenmeyer flasks contain- 

 ing half to one litre. These are seeded with several 

 strains of virulent diphtheria bacilli and grown for seven 



