742 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



several weeks. During this time they are subjected by a qualified 

 veterinarian to a thorough physical examination and to the mallein 

 test for glanders. Finally, only those animals which are pronounced 

 normal in every way are admitted to the antitoxin stables. The stables 

 and the operating rooms with their appointments, which are designed 

 for the antitoxin horses, should be constructed with a view to perfect 

 sanitation and cleanliness. Concrete floors, sanitary stalls, mangers, 

 stocks and apparatus, good water, free ventilation and plenty of light 

 should characterize the quarters. 



The antitoxin horses are injected subcutaneously with the diphtheria 

 toxin. The initial dose of toxin usually consists of only a fraction of a 

 cubic centimeter, then increasingly larger doses are administered until 

 the animals are finally able to receive 300 c.c. or more at a single treat- 

 ment. The intervals between injections and the rate of increase of 

 succeeding doses at any given time depend upon the condition of the 

 animal. During this treatment a constant process of antitoxin forma- 

 tion is taking place in the body of the horse. In order to produce a po- 

 tent serum, the injection of the toxin should be continued throughout 

 the course of treatment as rapidly as the resulting reactions, following 

 each injection of the animal, will allow. 



After the completion of the initial toxin treatment, which occupies 

 a period of from six weeks to three months, the horse is allowed a 

 rest of about two weeks, during which time all the toxin which has been 

 injected should be absorbed. During the remainder of the antitoxin- 

 producing period of the animal's life (approximately two years), treat- 

 ment with diphtheria toxin is continued at regular intervals. When 

 desired, a small sample of blood serum may be secured from the horse for 

 preliminary potency tests. Finally, the animal is bled from the 

 jugular vein, under aseptic conditions. As much blood is secured as 

 the horse can conveniently yield, varying in quantity from 10 to 15 1. 

 The blood may be drawn through a sterile canula and rubber tube into 

 tall, sterile glass cylinders. After the blood has clotted the serum 

 separates and at the end of twenty-four to forty-eight hours, the clear, 

 amber-colored fluid is poured from the cylinders into large, sterile glass 

 containers, a preservative is added and the material is transferred to 

 the laboratory. The serum is then passed through a Berkefeld filter. 



Each lot of antidiphtheritic serum is submitted to rigid tests 

 relative to potency, safety and microbial contamination. In deter- 



