3o6 CLASSICS OF MODERN SCIENCE 

 knowledge of the physiological properties of their viruses. All our 

 experiments must tend to discover the proper degree of attenuation for 

 each virus. But experimentation, if allowable on animals, is criminal 

 on man. Such is the principal cause of the complication of researches 

 bearing on diseases exclusively human. Let us keep in mind, never- 

 theless, that the studies of which we are speaking were born yesterday 

 only, that they have already yielded valuable results, and that new 

 ones may be fairly expected when we shall have gone deeper into the 

 knowledge of animal maladies, and of those in particular which af- 

 fect animals in common with man. 



The desire to penetrate farther forward in that double study led 

 me to choose rabies as the subject of my researches, in spite of the 

 darkness in which it was veiled. 



The study of rabies was begun in my laboratory four years ago, 

 and pursued since then without other interruption than what was 

 inherent to the nature of the researches themselves, which present cer- 

 tain unfavourable conditions. The incubation of the disease is always 

 protracted, the space disposed of is never sufficient, and it thus be- 

 comes impossible at a given moment to multiply the experiments as 

 one would like. Notwithstanding those material obstacles, lessened 

 by the interest taken by the French Government in all questions of 

 great scientific interest, we now no longer count the experiments 

 which we have made, my fellow workers and myself. I shall limit 

 myself to-day to an exposition of our latest acquisitions. 



The name alone of a disease, and of rabies above all others, at once 

 suggests to the mind the notion of a remedy. 



But it will, in the majority of cases, be labour lost to aim in the 

 first instance at discovering a mode of cure. It is, in a manner, 

 leaving all progress to chance. Far better to endeavour to acquaint 

 oneself, first of all, with the nature, the cause, and the evolution of 

 the disease, with a glimmering hope, perhaps, of finally arriving at 

 its prophylaxis. 



To this last method we are indebted for the result that rabies is no 

 longer to-day to be considered as an insoluble riddle. 



We have found that the virus of rabies develops itself invariably in 

 the nervous system, brain, and spinal cord, in the nerves, and in the 

 salivary glands ; but it is not present at the same moment in every one 

 of those parts. It may, for example, develop itself at the lower ex- 



