THE BACILLUS OF BUBONIC PLAGUE. 317 



Wyssokowitz and Zabolotny ' call attention to the 

 fact that the blood of patients convalescing from plague 

 has an agglutinating action upon fluid cultures of the 

 plague bacillus analogous to that observed when the 

 blood-serum of typhoid or of cholera patients is mixed 

 with similar cultures of the typhoid or the cholera 

 bacillus. 



Yersin, Calmette, and Borrel ^ have demonstrated that 

 the general principles underlying the establishment of 

 artificial immunity apply as well to this disease as to 

 a number of others. They have shown that by the use 

 of dead cultures (destroyed by heat) of the plague 

 bacillus animals may be rendered immune from infec- 

 tion by the virulent living organism. They have also 

 shown that the serum of the blood of these animals is 

 not only capable of conferring immunity upon other ani- 

 mals into which it is injected, but it has curative proper- 

 ties as well, providing it be employed at an early stage of 

 the disease. In 1896 Yersin^ used the serum of arti- 

 ficially immunized horses in the treatment of plague 

 in human beings. Of 26 persons (3 in Canton and 23 

 in Amoy, China) who received injections of the serum 

 during the early stages of the disease, in no case later 

 than the fifth day, only 2 died. Comparing this mor- 

 tality of 7.6 per cent, with the mortality of 80 per cent, 

 among persons in this epidemic who were treated in 

 other ways, he feels justified in regarding the method as 

 worthy of consideration. 



haustively reviewed by Plexner in the Bulletin of the Johns Hopkins 

 Hospital, 1894, vol. v. p. 96, and 1896, vol. vii. p. 180. I am indebted 

 to these reviews for much that is here presented on this subject. 



1 Annales de I'lnstitut Pasteur, 1897, p. 663. 



2 Ibid., 1895, p. 589. 



3 Ibid., 1897, p. 81. 



