SERUM TREATMENT OF DIPHTHERIA 717 



removed promptly there is some danger of other persons having been 

 infected, and immunization should, therefore, always be promptly prac- 

 tised. When the patient is treated at home, other members of the 

 household, even if immunized, are liable to develop the infection, prob- 

 ably owing to the fact that the patient harbors virulent bacilli for vary- 

 ing periods of time after the passive immunity in other persons has passed 

 away and the quarantine is broken. Certainly in those homes where 

 antitoxin is not used either for therapeutic or for prophylactic purposes, 

 the percentage of secondary infections is so high as to leave no doubt 

 as to the value of antitoxin. 



In this connection I may mention the desirability of using an anti- 

 toxin prepared by immunization of cattle for the general purpose of 

 prophylaxis, and especially for the treatment of those persons who are 

 hypersensitive to horse serum. In these cases horse antitoxin could be 

 used later if a person contracted diphtheria without danger of anaphy- 

 laxis. 



Behring's Method of Immunization against Diphtheria. Owing to 

 the fact that the antibodies produced through the activities of our own 

 body-cells (active immunization) persist for longer periods of time than 

 those that are introduced passively (passive immunization), Behring and 

 his assistants have been working upon a method of active immuniza- 

 tion in diphtheria whereby our own body-cells are to be stimulated to 

 produce our own antitoxin in sufficient amounts to protect us against the 

 disease. It has long been known that more or less balanced mixtures 

 of this kind produce immunity in animals, and in 1907 Theobald Smith 1 

 suggested that it might be possible to employ this method for the pur- 

 pose of producing immunity in man. Subsequently Smith 2 studied the 

 effects of injections of neutral mixtures in guinea-pigs and horses, and 

 again pointed out the applicability of the method to human beings 



Active immunization in diphtheria could probably be accomplished 

 by the administration of minute and increasing doses of toxin, but there 

 would be some danger of producing an acute toxemia or paralysis, and 

 the process may require so much time as to be useless in the presence of 

 epidemics. 



Behring's method, according to his report read before the German 

 Convention on International Medicine in 1913, is based upon the prin- 

 ciple that the union of toxin and antitoxin is not stable, and when a 

 neutral mixture of the two is injected into animals, sufficient toxin be- 



1 Jour. Med. Research, 1907, xvi, 359. 



2 Jour. Exper. Med., 1909, xi, 241; Jour. Med. Research, 1910, xxiii, 433. 



