TOXINS AND ANTITOXINS 257 



be produced by immunizing animals with toxin. Behring and 

 others realized that the reason a patient contracts diphtheria is 

 that he lacks circulating antitoxin and that the rational treat- 

 ment consists in the administration of the latter. It also follows 

 from this observation that susceptible individuals may be tem- 

 porarily protected from diphtheria by the administration of anti- 

 toxin. The presence of circulating antitoxin produced by the 

 body is an example of active immunity, while the protection which 

 results when this antitoxin is injected into a susceptible animal 

 is an example of passive immunity. 



Passive Immunity. — In the treatment of diphtheria with anti- 

 toxin, there are a number of important facts that must be con- 

 sidered by the physician. He should remember that the disease 

 is due to the effect of toxin upon the tissue cells and that the anti- 

 toxin he injects acts only as a neutralizer of toxin and cannot undo 

 any injury to tissue cells that toxin has already produced. It is be- 

 lieved that one large dose of antitoxin will neutralize more toxin 

 than the same amount given in several doses with appreciable inter- 

 vals of time intervening. These facts warrant the administration 

 of a large dose of antitoxin as early as possible in a case that is clin- 

 ically diphtheria even before the report on the culture is available 

 and in some cases when the laboratory findings are negative. 



Improved methods of purifying diphtheria antitoxin have been 

 reported by Pappenheimer and Eobinson (1937), Pope (1938) and 

 Northrop (1941). Northrop says the new antitoxin is about 20 

 times as active as the original antiserum. 



Dosage of Antitoxin. — As to what constitutes an adequate ini- 

 tial dose of antitoxin Park and Williams (1933) recommend that 

 for children under fifteen years of age, 3,000 to 5,000 units be 

 given in mild cases, 5,000 to 10,000 in moderate cases, 10,000 to 

 20,000 in severe cases and 15,000 to 30,000 in malignant eases. 

 For older children and adults the dosage is practically doubled 

 for each type of case. 



Method of Administering Antitoxin. — In regard to the method 

 of administering the antitoxin, they recommend that it be given 

 intramuscularly in mild and moderate cases, both intramuscu- 

 larly and intravenously in severe cases and intravenously only 

 in malignant cases. 



