66 MODERN BIOLOGIC THERAPEUSIS 



immune sera, the toxin or the culture is in- 

 jected into a horse in repeated and gradually 

 increasing doses. This process is carried on 

 until the antibodies in the horse's blood have 

 reached a point of maximum concentration. A 

 certain quantity of blood is then withdrawn 

 from the horse and the serum which contains 

 the antibodies is separated from the other con- 

 stituents. 



Care of Horses Various animals have been 

 used for serum production but the horse is gen- 

 erally considered to be the most convenient, 

 most easily managed and, because of its size, 

 yields the greatest amount of blood-serum. All 

 horses must be healthy and vigorous when in- 

 oculated and must be kept so by being well fed, 

 well housed and carefully exercised. Horses 

 selected for serum production are subjected to 

 a thorough physical examination by a compe- 

 tent veterinarian and are kept under observa- 

 tion for several days in a quarantine stable. 

 During this period the mallein test is applied 

 to insure freedom from glanders. All healthy 

 horses are then immunized against tetanus by 

 receiving a prophylactic injection of Tetanus, 

 Antitoxin. 



