SERUM THERAPY 91 



for the well-established fact that to be of much value 

 tetanus antitoxin must be administered before the ad- 

 vent of convulsions which mark the attack of the poison 

 upon the nervous tissue. 



Diphtheria Antitoxin. Preparation. The method of 

 preparing antitoxin followed by the firm of H. K. Mul- 

 ford Company may be taken as fairly representative of 

 the process followed by all manufacturers of antitoxin, 

 and is, therefore, described herewith. 



Preparation of the Toxin. A virulent culture of diph- 

 theria germs is grown in pure culture on specially pre- 

 pared media in incubators and under the most favorable 

 conditions for the production of toxin. After five to 

 seven days' growth trikresol is added to kill the germs, 

 which are then removed by filtration through a Berke- 

 feld filter. The toxin is then tested for strength by 

 determining the minimum fatal dose for a guinea-pig 

 of certain weight in a definite length of time. 



Injecting the Horse. The toxin having been obtained, 

 a small amount is injected into a horse, and the sub- 

 sequent reaction, temperature, and pulse carefully 

 noted. With the subsidence of the reaction, another 

 and larger dose of the toxin is administered, and this is 

 repeated, gradually increasing the dosage until the 

 horse ceases to react to large doses of toxin or until, in 

 other words, he is immune to the toxin, when his blood 

 will be found to be charged with antitoxin. 



It will be noted that the horse is not infected with 



