HISTORIC DEVELOPMENT OF IMMUNOLOGY 67 



Production of Toxin The first step in the 

 process of the production of Diphtheria Anti- 

 toxin is the preparation of the solution of diph- 

 theria toxin, which is accomplished by growing 

 a culture of the diphtheria bacillus on a suit- 

 able fluid nutrient medium. The strain of or- 

 ganism that is selected is noted for its capacity 

 for producing powerful toxin. Most of the 

 diphtheria toxin produced in the laboratories 

 of the world for some years past has been ob- 

 tained from the same highly toxogenic strain 

 of the bacillus isolated many years ago by Dr. 

 William H. Park of the New York City Health 

 Department. The nutrient medium most gen- 

 erally employed is beef or veal bouillon, with 

 peptone added. This culture medium after be- 

 ing placed in flasks is sterilized by heating, 

 after which it is inoculated with a pure culture 

 of the diphtheria bacillus and kept for a week 

 or ten days at a temperature of 35 C. At the 

 end of that time, the bacteria are killed by tri- 

 kresol and removed from the toxin solution by 

 filtration. The toxin is then stored and pro- 

 tected from the action of light and heat until 

 required for use. Its strength is determined 

 by finding the least quantity that will kill a 



