404 INFECTION AND IMMUNITY. 



The duration of active immunity to diphtheria 

 varies greatly. Usually an individual has diph- 

 theria but once, yet not infrequently those are en- 

 countered who suffer from repeated attacks. In 

 some instances the susceptibility continues into 

 adult life. 



Prophylaxis. The advent of serotherapy justifies no relaxa- 

 tion in the customary prophylactic measures, such 

 as isolation of the diseased, quarantine and disin- 

 fection. A patient should not be considered harm- 

 less until his mouth, pharynx and nose are free 

 from bacilli, a condition which may be brought 

 about by antiseptic applications, and for the de- 

 termination of which repeated bacteriologic exam- 

 inations are necessary. The danger that others 

 who have been in contact with the patient may 

 carry the infection should be met by appropriate 

 treatment. It is not to be forgotten that anti- 

 toxin does not destroy the organisms. The injec- 

 tion of antitoxin is our most effective measure for 

 individual prophylaxis. 



serotherapy. Experimentally, it is possible to vaccinate 

 against diphtheria by the inoculation of dead diph- 

 theria bacilli, or extracts of agar cultures (Lip- 

 stein, also Bandi and Gagnoni), but the conditions 

 hardly warrant the use of this method for pro- 

 tecting man. Extracts of the organisms may be 

 mixed with antitoxin and injected for protection. 

 This is the so-called serovaccination. 



The efficacy of diphtheria antitoxin is so well 

 known that little comment is needed. It has 

 caused a reduction of more than 50 per cent, in 

 the mortality of the disease; from 41 per cent, to 

 8 or 9 per cent., according to Baginsky. 



