THE MANUFACTURE OF ANTISERA. 481 



given culture should not be relied upon until tests have been made of 

 the final product. 



To produce the diphtheria toxin with which the antitoxin horses are 

 treated, the diphtheria organisms in pure culture are transferred to beef 

 broth, contained in large flasks, and incubated at a temperature of 37. 

 A rapid growth soon takes place, during which the specific toxin is elab- 

 orated by the organisms and thrown off into the bouillon. After a period 

 of incubation of about two weeks, the bouillon culture is removed from 

 the incubator, examined microscopically in order to make sure that con- 

 tamination is not present, a preservative is added usually, carbolic acid 

 or trikresol, and the organisms are removed from the culture by pass- 

 ing the liquid through a Berkefeld filter. The filtrate (diphtheria toxin) 

 is then placed in the refrigerator until used. 



The horses which are used in the manufacture of antidiphtheritic 

 serum, as well as for the preparation of other antitoxins, must be sub- 

 mitted to rigid inspection before being placed on the treatment. These 

 animals, when purchased, are placed in a detention stable for several 

 weeks. During this time they are subjected to a thorough physical 

 examination and to the mallein test for glanders by a qualified veterinarian. 

 Finally, only those animals which are pronounced normal in every way 

 are admitted to the antitoxin stables. The stables which are designed 

 for the antitoxin horses, and the operating rooms, with their appointments, 

 should be constructed with a view to perfect sanitation and cleanliness. 

 Concrete floors, simply constructed, sanitary stalls, mangers, stocks and 

 apparatus, absence of lofts, 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 treatment. 

 The intervals of time between injections and the rate of increase of suc- 

 ceeding doses at any given time depend upon the condition of the animal. 

 During this treatment a constant process of antitoxin formation is taking 

 place in the body of the horse. In order to produce a potent serum, the 

 injection of the toxin should be continued throughout the course of treat- 

 ment as rapidly as the resulting reactions, following each injection of the 

 animal, will allow. 



After the completion of the toxin treatment, which usually occupies 

 31 



