240 PASTEUR: THE HISTORY OF A MIND 



No solids pass through the filter. The serum passes 

 through and it is not infectious. The cause of the mal- 

 ady is, therefore, not soluble in the serum. It remains 

 on the surface of the filter where there are only red 

 corpuscles, white corpuscles and bacteridia. Choose 

 the cause among these three, but choose!" 



Davaine was not only ambitious to demonstrate that 

 the bacteridium was the cause and the only cause of 

 the development of anthrax: he wished also to explain 

 by its aid the etiology of the disease, that is to say, the 

 different conditions governing its natural appearance 

 and its endemic or epidemic character. In this direc- 

 tion he was less successful. He had observed, as we 

 have just said, that putrefaction rendered the blood 

 incapable of transmitting anthrax. He was obliged, 

 therefore, to give up seeing in the blood and tissues of 

 an animal buried as a victim of anthrax the cause of the 

 revival of the disease from one year to another, in the 

 same region or pasture. He observed, nevertheless, that 

 blood rapidly dried preserved its virulence for a 

 long time. Now, said he, this rapid desiccation must 

 often occur in countries where anthrax is prevalent; 

 when animals are slaughtered for the sake of the skins, 

 pools or drops of blood remain on the ground, on the litter, 

 on the walls, and these dry rapidly and preserve their 

 germs. As for the infection of other animals, Davaine at- 

 tributed it to flies some of which by sucking, and others 

 simply by means of their feet, are the agents of infection 

 among animals in stables or the open field, and he sup- 

 ported all these opinions by well carried out experiments. 



There were grave objections to this etiology. If 

 it is the fly which disseminates the virus, it was said, 

 why does it sometimes respect so carefully the bound- 

 aries of a field or an estate? There are in Beauce and 

 in Auvergne dangerous fields or meadows; the adjoining 



