LOUIS PASTEUR 305 



It was there seen, once again, that when all is ready for the final 

 triumph of truth, the united conscience of a great assembly feels it 

 instinctively and recognises it. 



All clear-sighted minds had already foreseen that the theory of the 

 spontaneity of diseases received its death-blow on the day when it 

 became possible reasonably to consider the spontaneous generation of 

 microscopic organisms as a myth, and when, on the other hand, the 

 life-activity of those same beings was shown to be the main cause of 

 organic decomposition and of all fermentation. 



From the London Congress, also, dates the recognition of another 

 very hopeful progress ; we refer to the attenuation of different viruses, 

 to the production of varying degrees of virulence for each virus, and 

 their preservation by suitable methods of cultivation ; to the practical 

 application, finally, of those new facts in animal medicine. 



New microbic prophylactic viruses have been added to those of 

 fowl-cholera and of splenic fever. The animals saved from death by 

 contagious diseases are now counted by hundreds of thousands, and 

 the sharp opposition which those scientific novelties met with at the 

 beginning was soon swept away by the rapidity of their onward 

 progress. 



Will the circle of practical applications of those new notions be 

 limited in future to the prophylaxis of animal distempers ? We must 

 never think little of a new discovery, nor despair of its fecundity ; but 

 more than that, in the present instance, it may be asserted that the 

 question is already solved in principle. Thus, splenic fever is com- 

 mon to animals and man, and we make bold to declare that, were it 

 necessary to do so, nothing could be easier than to render man also 

 proof against that affection. The process which is employed for 

 animals might, almost without a change, be applied to him also. It 

 would simply become advisable to act with an amount of prudence 

 which the value of the life of an ox or a sheep does not call for. 

 Thus, we should use three or four vaccine-viruses instead of two, 

 of progressive intensity of virulence, and choose the first ones so 

 weak that the patient should never be exposed to the slightest morbid 

 complication, however susceptible to the disease he might be by his 

 constitution. 



The difficulty, then, in the case of human diseases, does not lie in 

 the application of the new method of prophylaxis, but rather in the 



