64 IMMUNITY 



ficially supplied to the animal unite with the haptophorous chains in 

 the toxin molecule, and neutralize, or bind, the toxophorous or pois- 

 onous chains in the molecule, and prevent toxophore from attacking 

 important vital cells belonging to the animal. But if the an ti- toxin 

 and toxin, after being mixed in a test-tube, are injected into a sus- 

 ceptible animal, no harm results, if they are in proper proportions, 

 since the same thing has happened in vitro that happened in the 

 animal, the receptors and haptophores have united; the toxophores 

 are bound, and the animal is unharmed. 



The manner of making the diphtheria anti-toxin can be taken as a 

 type. 



Diphtheria bacilli are grown for several days in dextrose bouil- 

 lon at 37 C.; as the bacilli grow they elaborate a very powerful 

 poison or toxin, which is highly complex in compositon. It is 

 easily decomposed by heat, light and oxygen, and should be used 

 soon after it is prepared. After the cultures have grown for several 

 days, the bouillon is filtered through a porcelain or Berkefeld 

 filter, and is then stored in sterile bottles in an ice chest. Horses are 

 generally immunized, since they are susceptible to the action to the 

 toxin, and are easily managed. Before being used they are care- 

 fully tested with tuberculin for tuberculosis and with mallein for 

 glanders. Being very susceptible to infection with tetanus while 

 undergoing treatment, a prophylactic injection of tetanus anti-toxin is 

 given each animal. McFarland found that the death rate from 

 tetanus, in a large stable, was greatly reduced after using tetanus 

 anti-toxin as a prophylactic measure. 



To make an ti- toxin, a very virulent toxin is employed.- A horse, 

 previously examined for health, is injected with from .1 to i. c.c. of 

 toxin. This is followed by a rise of temperature, local reaction, and 

 systemic disturbance. After waiting for all reactions to disappear 

 a second injection is given, which is followed by others larger in size, 

 until, after a few weeks or months, 1,000 c.c. of toxin are injected 

 at one time (enough to have killed a dozen horses that had not re- 

 ceived the smaller doses previously). The injection of the toxin is 



