THE BACTERIA 



213 



198. Preparation of antitoxin. It has been found possible 

 to secure from horses and mules an antitoxin that will coun- 

 teract diphtheria toxins in the human body. These animals 

 are naturally immune to diphtheria, but by injecting into their 

 bodies toxins produced in beef broth by diphtheria bacteria, 

 this natural immunity is greatly increased. First into the ani- 

 mal's body there is injected a small amount of toxin. This 

 process is repeated, with an increasing amount, at intervals of 

 a week or a little less, for a period of two or three months. 

 The animal finally withstands, with no ill consequences, an 

 amount of toxin that would have proved fatal if used at first. 

 At this time some of the blood is drawn off and allowed to 

 clot, and the antitoxic serum is sterilized. This antitoxic 

 serum is usually concentrated, in order to make it possible to 

 inject the desired strength of antitoxin without an unneces- 

 sarily large amount of liquid. After its relative strength is 

 determined, it is sealed in small bottles and is ready for dis- 

 tribution. A human being who has diphtheria may then be 

 given the proper amount of antitoxin. If it is properly given, 

 and given early enough, the attack is defeated. 1 



AVERAGE ANNUAL DEATH RATE FROM DIPHTHERIA 

 PER 10,000 POPULATION 2 



1 A few inexcusable cases have occurred where impure antitoxin was used. 



2 Jordan, E. 0., General Bacteriology, 1911. 



8 The use of antitoxin was begun in 1895-1896 ; the death rate dropped 

 from 12.01 in 1895 to 7.62 in 1896. 



