5io HYDROPHOBIA. 



nervous system, the saliva, etc., which yield what we have 

 called the hydrophobic virus, for by no mere toxine could 

 the disease be transmitted through a series of animals, as 

 we shall presently see can be done. The resistance of the 

 virus to external agents varies. Thus a nervous system 

 containing it is virulent till destroyed by putrefaction ; it 

 can resist the prolonged application of a temperature of 

 from - 10 to - 20 C. but, on the other hand it is rendered 

 non-virulent by one hour's exposure at 50 C. Again, its 

 potency probably varies in nature according to the source. 

 Thus, while the death rate among persons bitten by mad 

 dogs is about 16 per cent, the corresponding death rate 

 after the bites of wolves is 80 per cent. Here, however, it 

 must be kept in view that, as the wolf is naturally the more 

 savage animal, the number and extent of the bites, i.e., the 

 number of channels of entrance of the virus into the body, 

 and the total dose, are greater than in the case of persons 

 bitten by dogs. As we shall see, alterations in the potency 

 of the virus can certainly be effected by artificial means. 



The Prophylactic Treatment of Hydrophobia. Until 

 the publication of Pasteur's researches in 1885, the only 

 means adopted to prevent the development of hydrophobia 

 in a person bitten by a rabid animal, had consisted in the 

 cauterisation of the wound. Such a procedure was un- 

 doubtedly not without effect. It has been shown that 

 cauterisation within five minutes of the infliction of a rabic 

 wound prevents the disease from developing, and that if 

 done within half an hour, it saves a proportion of the cases. 

 After this time, cauterisation only lengthens the period of 

 incubation ; but, as we shall see presently, this is an 

 extremely important effect. 



The work of Pasteur has, however, revolutionised the 

 whole treatment of wounds inflicted by hydrophobic animals. 

 Pasteur started with the idea that, since the period of 

 incubation in the case of animals infected subdurally from 

 the nervous systems of mad dogs, is constant in the dog, 

 the virus has been from time immemorial of constant 

 strength. Such a virus, of what might be called natural 



