666 A MANUAL OF BACTERIOLOGY 



solution with 1 per cent, carbolic acid is kept at 37 C. 

 for twenty-four hours. At the end of this time an equal 

 volume of physiological salt solution is added and the 

 emulsion bottled aseptically. This vaccine will keep for 

 months. 



Undoubtedly the Pasteur inoculations will protect 

 animals from rabies, the duration of immunity after 

 vaccination in the dog being at least three years. In man 

 the efficacy of the treatment can only be judged by 

 statistics. The mortality after bites by supposed rabid 

 animals is variously stated, the most favourable being 

 about 16 per cent. (Leblanc). At the Pasteur Institute, 

 Paris, from 1888 to 1919, the annual mortality per cent, 

 of persons treated varied between 0-0 and 0-55. In 1919, 

 1,813 cases were treated with three deaths, a mortality 

 of 0-16 per cent. 



The failure of the treatment may be due to two causes : 

 (1) delay in its commencement, and (2) a short incubation 

 period. The efficiency of the treatment probably depends 

 upon the long incubation period of the disease, owing to 

 which it is possible to forestall the disease, and to immunise 

 the body by the inoculations before its onset. If, unfor- 

 tunately, the infective material should be very virulent, 

 and the incubation period thereby reduced to the lower 

 limit, it may be impossible to do this before the onset 

 of the disease, and the same is the case if the commence- 

 ment of the treatment be delayed. Pasteur's system of 

 inoculation is useless when the disease has declared itself. 



By vaccinating animals by the Pasteur method by a 

 long series of injections, and with the most virulent mate- 

 rial, the blood-serum acquires " anti- " properties, and 

 this . " anti-rabic " serum is said to be of service in the 

 treatment of the declared disease. 



Variations from typical rabies have been described both in 

 animals and in man under such names as " chronic rabies," " abor- 



