ETIOLOGY OF SPLENIC FEVER. 257 



these two years the same surface earths produced 

 splenic fever, while, away from the graves, the earth 

 exhibited nothing of the kind. Finally, Pasteur and 

 his assistants proved that on the surface of the earth 

 which covered the buried animals, the germs were again 

 found, after all the operations of ploughing, sowing, 

 and reaping. 



But how, it will be asked, can the earth, which is 

 so powerful a filter, allow the germs of microscopic 

 organisms to rise again to its surface ? Is one not 

 tempted here to quote Pasteur against himself, since, 

 in his joint researches with M. Joubert, Pasteur had 

 proved that the waters of springs issuing from the 

 earth, even at a shallow depth, are entirely free from 

 germs ? Such waters, nevertheless, being supplied 

 from the earth's surface, which is constantly washed 

 by rain, the effect must be to carry down the finest 

 particles to the springs. But these latter, notwith- 

 standing conditions so conducive to their pollution, 

 remain perfectly pure. Can there be a better proof 

 that earth of a certain thickness will arrest all solid par- 

 ticles, even the most minute ? Nevertheless, in these 

 experiments on splenic fever, we hear of microscopic 

 germs, starting from the depths and coming up to the 

 surface that is to say, in a direction contrary to the 

 flow of the rain. This is an enigma. 



The explanation will cause surprise. The earth- 

 worms transport the germs, and bring up, from the 



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