IMMUNITY. 443 



Amoy, and, more recently, Bombay. The earlier reports 

 of the results obtained were of a distinctly favourable 

 character, the later less so, although no doubt there has 

 been much difficulty in obtaining in India a serum of the 

 requisite strength. 



The system of preventive inoculation against plague 

 devised by Hafifkine has been carried out on a pretty 

 extensive scale in India. In this method the vaccine used 

 is a bouillon culture of the plague bacillus killed by exposure 

 to 70 C. for an hour. To obtain a very abundant growth 

 clarified butter (" ghee ") is added to the bouillon and, 

 after inoculation, from the drops of fat floating on the 

 surface growth takes place in the stalactite form. When 

 this has occurred the " stalactites " are broken by shaking 

 and fall to the bottom, and then fresh growth occurs from 

 above downwards. In this manner six crops may be 

 obtained in about four weeks, the final result being a very 

 abundant deposit with clear supernatant fluid. The former 

 when injected into an animal causes a local inflammatory 

 swelling, the latter a rise in temperature. A mixture of the 

 clear fluid and deposit is used for inoculation against plague, 

 about 3 c.c. in the sterile condition being injected into the 

 flank. The method has been systematically tested by inocu- 

 lating a certain proportion of the inhabitants of districts 

 exposed to infection, leaving others uninoculated, and then 

 observing the proportion of cases of the disease and of fatal 

 results amongst the two classes. The results have been dis- 

 tinctly satisfactory, there being a distinct diminution in the 

 number of cases among the inoculated, and a still greater di- 

 minution in the mortality. In the most favourable series 

 reported by Haffkine and Bannerman the mortality amongst 

 the inoculated was diminished by over 80 per cent. Further 

 observations, which will no doubt be shortly forthcoming, 

 will supply definite results as to the exact value of the 

 method. 



