128 APPLIED BACTERIOLOGY 



probably that of a proteid, possibly a globulin. Hankin 

 isolated a proteid body from the blood serum of a naturally 

 immune rat, which possessed the property of destroying the 

 pathogenic power of anthrax bacilli. Furthermore, the in- 

 jection of this proteid, together with anthrax spores, into 

 mice prevented the development of the disease. Hankin 

 has suggested the term defensive proteids, and Buchner the 

 term alexins (from aXefm, I defend), to denote these anti- 

 bodies. They are destroyed by a temperature of 60° C, 

 and are precipitated by alcohol and ammonium sulphate, 

 and correspond generally in character with the enzymes or 

 unorganised ferments. 



Preparation of Diphtheric Antitoxin. — The steps in the 

 preparation are as follows: First, the preparation of a 

 powerful toxin ; second, the estimation of the power of 

 the toxin ; third, the gradual immunisation of a suitable 

 animal by the inoculation of gradual and increasing doses 

 of toxin; fourth, the testing and standardisation of the 

 resulting blood serum. 



Preparation of the Toxin. — The diphtheria toxin is 

 prepared by growing a pure virulent culture of the Klebs- 

 Loffler bacillus in slightly alkaline beef broth at 37° C, in 

 flat-bottomed flasks, supplied with a regulated current of 

 sterile air. Some observers state that the current of air is 

 quite unnecessary. Liquid blood serum may be used instead 

 of the broth for the preparation of the toxin. The 

 growth first causes the liquid to become cloudy, and a 

 sediment eventually develops at the bottom of the flasks, 

 the liquid becoming clear again. The growth gradu- 

 ally slackens, and the operation is usually complete at 

 the end of three weeks. The culture is then filtered 

 through a Pasteur -Chamberl and filter, to separate the 

 organisms from their toxic products. The toxic strength 

 of the filtrate is next ascertained experimentally by finding 



