THERAPEUTIC IMMUNIZATION IN MAN 481 



However, these results apparently were not accepted by all observers 

 as proving the efficiency of the serum, since the number - of cases 

 observed were few, and the irregularity in the gravity of the disease 

 in different individuals makes statistical evidence unreliable unless 

 large material can be studied. Kolle and Martini 76 announce that 

 Dr. Choksy reported very poor success with the Yersin serum, and 

 cite a number of later writers whose results with this serum were 

 also unsatisfactory when used on human beings. That the serum 

 unquestionably contains antibodies against the plague bacillus is 

 testified to, not only by the French observers themselves, but also by 

 the German Plague Commission of 1899, and by Kolle and Mar- 

 tini 7T themselves. The Commission experimented with this serum 

 upon monkeys, and showed that it possessed unquestionable protec- 

 tive powers in rodents and in monkeys when given 24 hours before 

 the plague infection, and in monkeys possessed fair curative prop- 

 erties when injected 24 hours later than inoculation with the plague 

 bacilli. Because of the doubtful success in the treatment of human 

 beings with this serum Yersin and Roux at the Pasteur Institute 

 later altered their methods of serum production by injecting, not 

 only dead and living plague cultures, but considerable quantities of 

 culture filtrates after the horses had attained a high degree of im- 

 munity. Later observations on the Yersin 78 serum have been pub- 

 lished by the British. Plague Commission in 1908 and 1911. In this 

 investigation the cases were controlled as to their severity by blood 

 culture, since it had been claimed by a number of earlier investi- 

 gators that the Yersin serum was efficient in mild cases, but failed 

 entirely in the severe ones. It seems from the report of this Commis- 

 sion that ordinarily 70 per cent, of cases of plague without bacilli in 

 the blood survive while three-quarters of those with mild septicemia 

 die, and all of those with a marked septicemia succumb. In the 

 summary given of 146 cases treated with Yersin's serum by the 

 British Commission 65.1 per cent, died, whereas of 146 untreated 

 controls 71.90 per cent. died. These figures, together with an 

 analysis of the percentages, classified according to the severity of the 

 infections, do not show a very marked curative action on the part 

 of the serum. 



Markl, 79 who claims that the plague bacillus produces a soluble 

 toxin, has produced a plague serum by immunization of animals by 

 filtrates of broth cultures. He claims that 0.1 c. c. of his serum, as 

 produced at Vienna, will protect various animals against lethal doses 

 of plague bacilli if given at the same time. H attributes much of 



76 Kolle and Martini. Deutsche med. WocU., 1902, p. 29. 



77 German Plague Commission. Arb. a. d. kais. Amt., Vol. 16, 1899. 



78 British Plague Commission. Journ. of Hyg., Vol. 12, Sup., 1912, p. 326. 



79 Markl. Centralbl. f. Bakt., 24, 1898; Zeitschr. f. Hyg., 37, 1901; 

 Zeitsclir. /. Hyg., 42, 1903. 



