THERAPEUTIC IMMUNIZATION IN MAN 487 



only 2 of 151 vaccinated persons became ill, and neither of these 

 died; whereas, of 177 unvaccinated persons 12 became ill and 6 

 died. In large series of vaccinated people only 1.8 per cent, were 

 infected with plague, with a mortality of 0.4 per cent, for 

 the total, whereas of unvaccinated individuals in the same epidemic 

 7.7 per cent, fell victim to the disease, with a mortality of 4.7 per 

 cent. 



The German Plague Commission, consisting of Gaffky, Pfeiffer, 

 and Dieudonne, recommended a vaccine of killed agar cultures. 

 Kolle and Otto, 94 basing their earlier results upon experiments car- 

 ried out with monkeys, mice, guinea pigs, and rats, have come to the 

 conclusion that vaccination with dead plague cultures is much in- 

 ferior to that obtained when attenuated living cultures are used. 

 The same conclusion has been reached by Kolle and Strong. 95 Kolle 

 and Otto found that the immunization of animals with large doses 

 of killed agar cultures of plague bacilli and with Haffkine's prophy- 

 lactic did not protect them against subsequent inoculation with 

 virulent cultures. 



Strong 96 subsequently made a very careful comparative study of 

 the various methods of plague vaccination, and concluded that the 

 most efficient method is immunization with attenuated living cul- 

 tures. He showed that when carefully done this method can be 

 safely employed in human beings, but admits that his work must be 

 as yet considered as experimental and further studied before it can 

 be universally employed. 



Besredka 9T has advised the use of sensitized dead plague cul- 

 tures, claiming, from animal experimentation, that such vaccines 

 produce an efficient and relatively durable immunity. 



Rowland 98 confirms the immunizing properties of Besredka's 

 vaccines in plague, and believes that the antigenic properties of the 

 plague bacillus are attached to the bacterial nucleoproteins, and can 

 be extracted with these. Rowland prepares a vaccine by the treat- 

 ment of the moist bacteria with enough anhydrous sodium sulphate 

 to combine with all the water present, freezing and thawing the 

 mixtures, then filtering off the bacterial deposits at 37 C., and ex- 

 tracting them with water. The solution so obtained was fatal to 

 rats in small quantities and afforded substantial protection, reducing 

 the mortality on subsequent inoculation of a standard culture from 

 80 to 10 per cent. 



94 Kolle and Otto. Deutsche med. Wocli., 1903, p. 493, and Zeitschr. f. 

 Hyg., Vol. 45, 1903. 



95 Kolle and Strong. Deutsche med. Woch., XXXII, 1906, p. 413. 



96 Strong. Journ. of Med. Res., N. S., 13, 1908. 



97 Besredka. Bull de I'Inst. Past.. Vol. 8, 1910. 



98 Rowland. Journ. of Hyg., VoL 12, 1912, p. 344. 



