INTKODUCTION. XXxix 



were dying. The twenty-five vaccinated sheep, on 

 the contrary, were ' in full health and gaiety.' In the 

 unvaccinated cows intense fever was produced, while 

 the prostration was so great that they were unable 

 to eat. Tumours were also formed at the points of 

 inoculation. In the vaccinated cows no tumours were 

 formed ; they exhibited no fever, nor even an elevation 

 of temperature, while their power of feeding was 

 unimpaired. No wonder that ' breeders of cattle over- 

 whelmed Pasteur with applications for vaccine.' At 

 the end of 1881 close upon 34,000 animals had been 

 vaccinated, while the number rose in 1883 to nearly 

 500,000. 



M. Pasteur is now exactly sixty-two years of 

 age ; but his energy is unabated. At the end of 

 this volume we are informed that he has already 

 taken up and examined with success, as far as his 

 experiments have reached, the terrible and mysterious 

 disease of rabies or hydrophobia. Those who hold all 

 communicable diseases to be of parasitic origin, in- 

 clude, of course, rabies among the number of those 

 produced and propagated by a living contagium. From 

 his first contact with the disease Pasteur showed his 

 accustomed penetration. If we see a man mad, we at 

 once refer his madness to the state of his brain. It is 

 somewhat singular that in the face of this fact the 

 virus of a mad dog should be referred to the animal's 



