282 MICROBES AND TOXINS 



of advantage to the Algerian breeders, and helps in the 

 suppression of the disease. 



Cattle plague or rinderpest is an epizootic disease which 

 has caused incalculable losses throughout Europe, especially 

 by attacking the herds of pure blood. The mortality always 

 exceeds 50 per cent. The microbe is unknown, but it is 

 known that the virus can pass through filter bougies, even 

 the finest : it is therefore an ultramicroscopic organism. An 

 animal which survives possesses an immunity which seems 

 quite invincible : as soon as the illness is over any quantity 

 of virulent blood may be injected into it without killing it. 

 But it is not possible to immunize by a method similar to 

 that in sheep-pox, for inoculation produces an attack as severe 

 as the naturally acquired disease. 



The animals may be made to acquire an immunity lasting 

 for four to six months by injecting the bile of animals dead of 

 the plague, but the method is not practical. 



A good serum can be obtained by " charging " with virus an 

 animal which has recovered. The sero-vaccination of Kolle 

 and Turner consists in injecting simultaneously this serum and 

 virulent blood : they must be injected at different spots. 



It is always risky to employ a virus in therapeutics : there is 

 always the danger of spreading it or introducing it into a 

 country where it does not hitherto exist. The serum alone 

 suffices for prophylaxis, for treatment, and for the prophylaxis 

 of the healthy animals. The prophylactic dose is one of 

 50 c.c. Capable veterinary surgeons have succeeded by using 

 the serum alone in reducing the mortality to 12 per cent. 

 (Nicolle). The same principles are at work in the treatment of 

 the horse-sickness of the Transvaal and the plague of pigs, hog- 

 cholera, which are also septicaemic diseases due to an ultra- 

 microscopic virus. 



Sensitized Vaccines. 



The vaccines employed against typhoid fever, cholera and 

 plague may be rendered less painful, more prompt, more 

 powerful and more durable by impregnating the bacteria of 



