DIPHTHERIA 121 



is lost by exposure to sunlight for a few hours or 

 by boiling for five minutes. 



Animals inoculated with diphtheria toxin show all 

 of the conditions of typical diphtheria, except the 

 false membrane, which is conclusive evidence that 

 the chief injury arising from diphtheria infection is 

 due to the toxins secreted by the bacilli. 



The Antitoxin of Diphtheria. — In 1890 Behring 

 and Kitasato found that the blood-serum of an animal 

 which had been immunized against diphtheria 

 would neutraUze the effects of a diphtheria infection 

 in another animal; in other words, the blood-serum 

 of an immunized animal contained an antitoxin 

 which is now known as the antitoxin of diphtheria. 

 By a long series of wonderful experiments it was 

 found practical to manufacture the antitoxin of 

 diphtheria for both protective and curative purposes. 

 Horses are used for this purpose on account of their 

 size and their endurance. For two or three months 

 gradually increasing doses of diphtheria toxin are 

 injected subcutaneously into the horse at intervals 

 of five or six days. When the blood has reached the 

 desired potency, it is drawn from the jugular vein into 

 sterile glasses and allowed to clot, when the serum is 

 drawn off under aseptic conditions, filtered, tested, 

 bottled, and kept in the dark at a l6w temperature. 



