486 INFECTION AND RESISTANCE 



more recent knowledge concerning cholera immunity it seems likely 

 that the importance which Haffkine attached to the virulence of the 

 cholera culture used for injection was exaggerated, and we have 

 reason to believe that simple immunization with killed cultures may 

 produce results fully as efficacious. After all, we could not expect, 

 at least at present, to produce by active artificial immunization an 

 immunity as permanent as that which results from an attack of the 

 disease. Concerning the reasons for the acquisition of such perma- 

 nent immunity we have as yet little knowledge. Even Haffkine's 

 method of inoculation with living virus does not, by his own estima- 

 tion, last longer than possibly two years. It is therefore likely that 

 prophylactic immunization in cholera is efficacious by reason of the 

 appearance in the blood serum of the specific bactericidal and opsonic 

 substances by which the small numbers of cholera organisms entering 

 during spontaneous infection can be disposed of before a foothold in 

 the body is gained. 



Tamancheff later used Haffkine's method, but killed the cultures 

 by the addition of a 0.5 per cent, solution of carbolic acid. 



Kolle 91 later recommended the injection of dead cholera or- 

 ganisms, maintaining that a single injection of about 2 milligrams 

 of a culture killed by exposure to 50 C. for a few minutes, and by 

 the addition of 0.5 per cent, of phenol, is sufficient to immunize suc- 

 cessfully. Good results with Kolle' s method have been reported from 

 Japan. 



Strong, 92 also proceeding from the idea that the immunizing 

 antigen is present, as such, within the cell body of the cholera 

 spirilla, recommends the injection of autolytic products obtained by 

 digesting cholera spirilla in aqueous suspension and filtering. He 

 prepared his a prophylactic" by growing the organisms upon agar, 

 then suspending the growth in sterile water and keeping it at 60 C. 

 for from one to twenty-four hours. The mixture was then exposed 

 to 37 C. for from two to five days and filtered through Reichel 

 filters. One to 5 c. c. of this was used in his experiments upon 

 human beings. 



PKOPHYLACTIC IMMUNIZATION AGAINST PLAGUE 



The first attempts to immunize human beings prophylactically 

 against plague were those of Haffkine. 93 The first vaccinations were 

 carried out with broth cultures killed at 65 C. He tested out his 

 vaccines on a large scale in Bombay, and obtained apparently prom- 

 ising results. In a plague epidemic occurring in a Bombay prison 



91 Kolle. Deutsche med. Woch., 1897, No. 1. 



92 Strong. Journ. Inf. Dis., Vol. 2, 1905. 



98 Haffkine. Bull, de I'Inst. Past., Vol. 4, 1906, No. 20, p. 825. 



