192 LOUIS PASTEUR. 



tory, where a temperature absolutely constant reigned, 

 a circumstance which permits of the deposit of all 

 the parasitic filaments at the bottom of the tubes. 

 Inoculating afterwards both with the clear upper 

 liquid and with the deposit at the bottom, he found 

 that the latter alone produced disease and death. It 

 is, then, the bacteria which cause splenic fever. The 

 proof was given and no further doubt remained. 



I. 



Yes, splenic fever is no doubt produced by bacteria 

 just as itch is produced by acaries and trichinosis 

 by trichinae. The only difference is that the para- 

 site of splenic fever can only be seen by means of a 

 rather powerful microscope. Here, then, is a disease 

 in the highest degree virulent, due in its first cause to 

 the infinitely little. Pasteur laid hold of and isolated 

 this terrible virus. It was in a microscopic parasite, 

 and in it alone, that the virulence of splenic fever re- 

 sided. A great scientific fact had been gained. A 

 virus might consist not of amorphous matter, but of 

 microscopic beings. The virulence was due to their 

 life. 



Liebig, and all the chemists and doctors who had 

 Accepted and maintained his doctrine, totally repudi- 

 ated all vital action in fermentation as well as in con- 

 tagious and infectious diseases. Dominated by their 



