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rabies vaccine.* It may be interesting to describe the last, 

 viz., the preparation of the rabies vaccine in full, as not only 

 man but cattle also are subject to rabies. 



1.329. Preparation of Rabies Vaccine. It has been 

 already stated that successive generations of rabies virus 

 passing through rabbits increase in virulence. The rabbit 

 inoculated (in the brain) with the virus taken directly from a 

 mad dog dies in about 18 days. A second rabbit inoculated 

 with the virus taken from the first rabbit so dying dies in a 

 shorter time. The rapidity with which death follows con- 

 tinues to increase at each successive generation until the 3oth. 

 The 3ist rabbit inoculated with the virus from the 3oth dies 

 like the 3oth in six days, and so the 32nd, the 33rd, and so on. 

 The maximum of the virulence of the rabies virus is thus 

 attained in the 3oth generation of its passage in the bodies 

 of rabbits. This is the standard virulent virus used by Pasteur 

 in his preparation of the vaccine, as the strength of the virul- 

 ence is from this stage onwards constant. 



1.330. In the case of the human subject (bitten by a mad 

 dog), ten graduated inoculations are made, beginning with the 

 weakest or the most attenuated forms, which do not kill rab- 

 bits, and ending with stronger vaccines which are sufficient to 

 kill rabbits. 



1.331. The vaccine, like the virulent virus of rabies pass- 

 ing through successive generations in the bodies of rabbits, 

 also increases in virulence. 



1.332. To keep a perpetual supply of vaccine a rabbit is 

 inoculated every Saturday in Pasteur's laboratory with the 

 standard virus of maximum strength, the standard attained 

 after the death of the 3oth rabbit. Rabbits are used instead of 

 monkeys in the preparation of this as well as other vaccines, 

 as the former are inoffensive animals. It is risky having 

 to do constantly with mad dogs and monkeys. Although the 

 first rabbit is inoculated with virus taken from a mad dog, it 

 is quite unnecessary to have anything else to do with mad 



