Protective vaccinations 487 



disease. After the discovery made by Yersin, Borrel, and Calmette 1 , 

 who showed that animals susceptible to human plague could be 

 easily vaccinated against the micro-organism which gives rise to it, 

 Haffkine 2 endeavoured to find a practical method for the vaccination 

 of man. He set up a laboratory at Bombay and, after some 

 preliminary experiments on rabbits, he commenced to inject human 

 beings with pure cultures of the plague coccobacillus. From 

 1897 up to the present he was able to vaccinate a very large [510] 

 number of individuals, and the results obtained have encouraged 

 him to continue the application of his method. The principle 

 of this method is that which had guided him in the preparation 

 of anticholera vaccines and which is used for the vaccines against 

 typhoid fever. It consists in the employment of pure cultures 

 of the specific organism killed by heat. The cultures are grown 

 in large flasks containing peptonised broth and sown with a small 

 quantity of the plague coccobacilli. A little sterile butter or 

 cocoanut oil is poured on the surface of the fluid. Under these 

 conditions the organism grows abundantly and produces growths 

 which hang down into the fluid, reminding us of the stalactites in 

 a grotto. This mode of development forms one of the most typical 

 characters of the micro-organism of human plague. The culture 

 flasks are kept at a temperature of about 30 C. for five to six weeks, 

 at the end of which period a large number of the bodies of the micro- 

 organisms have fallen to the bottom of the flask, allowing much of 

 their toxic contents to escape. The fatty layer on the surface favours 

 a surface development ot the coccobacilli, the number of micro-organ- 

 isms in a flask being thus greatly increased. 



After growing for 35 to 42 days under these conditions the 

 cultures are heated at 65 70 C. for from one to three hours with 

 the object of killing all the micro-organisms and so rendering their 

 injection innocuous. To make sure of the effectiveness of this 

 heating care is taken to remove a small portion of the fluid and to 

 sow it in a suitable medium. Should this medium remain sterile the 

 vaccine may be used. Into adult men it is injected in a dose of 3 c.c., 

 whilst women, children, and adolescents receive 2 2*5 c.c., into the 

 subcutaneous tissue. 



Some hours after the injection of the vaccine the temperature 



1 Ann. de VInst. Pasteur, Paris, 1895, t. ix, p. 589. 



2 Brit. Med. Journ., London, 1897, Vol. i, p. 1461 ; Indian Med. Gaz., Calcutta, 

 1897, Vol. xxxii, p. 201. 



