252 LOUIS PASTEUR. 



you will reduce in proportion the losses caused by the 

 excess of the ultra-nutritious substances with which 

 you supersaturate your cattle.' 



' Such is the very logical conclusion to which Dela- 

 fond was led,' adds M. Bouley, ridiculing these obser- 

 vations, based on a method of reasoning, instead of on 

 the experimental method. * And as a fresh proof of his 

 theory he mentions the fact that the disease decreases 

 as you descend the country towards the Loire. On 

 the right bank of that river in Sologne, for instance, 

 which is a low, sandy, damp district blood disease is 

 unknown. In the arrondissements of Gien and Mont- 

 argis and in parts of those of Orleans and Pithiviers 

 it prevails but little. There, Delafond imperturbably 

 remarks, the soil is sandy and the herbage not nearly 

 so rich as in the Beauce plateau ; and there the blood 

 disease is consequently less common.' 



When we consider that such opinions could be 

 written unchallenged only forty years ago, that they 

 could even borrow a scientific character from the in- 

 spiration that gave them birth, we can see the pro- 

 gress that has since been made, and can realise how 

 great were the obscurity and uncertainty which have 

 been dispelled by the experimental method. 



The presence of a parasite having been brought to 

 public notice in the blood of animals suffering from 

 splenic fever, at the very time when Pasteur had 

 shaken the belief in spontaneous generation, people 



