THE LABORATORY OF THE ECOLE NORMALE. 289 



' "When the virus is inoculated from rabbit to 

 rabbit, the microbe acclimatises itself to the rabbit. 

 All the animals die, and death comes in a very few days. 

 The cultures of the blood of these rabbits in sterilised 

 media become progressively easy and more abun- 

 dant. The microbe itself changes its aspect somewhat, 

 grows rather larger than in the pig, and appears in 

 the form of an 8, without the filiform lengthening out 

 characteristic of certain other cultures. 



' When pigs are inoculated with the blood of the 

 last rabbits, and the results compared with those 

 obtained from the first of the series, it is found 

 that the virulence has been progressively diminishing 

 from the first rabbit to the following ones. Very soon 

 the blood of the rabbits ceases to cause death in the 

 pigs, though it renders them ill. On recovery they 

 are proof against the deadly swine fever.' 



III. 



But in the midst of these investigations undertaken 

 by Pasteur, there is one which is paramount over all 

 the others, one on which for three years all his 

 efforts, as well as those of his pupils, have been con- 

 centrated, and this is Hydrophobia. Mysterious in its 

 incubation, alarming in its symptoms, Pasteur's 

 attention had for a long time been drawn to it, when 

 in 1880 he finally attacked it. Besides the attraction 



