The Frontiers of the Sciences 



was perhaps born in a stable or a slaughter- 

 house. 



The sum of human knowledge has increased 

 gradually, facts have been condensed into more or 

 less general laws, and the whole has been organised 

 from time to time according to the prevailing 

 ideas concerning the interdependence of the 

 various parts; these ideas have changed fre- 

 quently in the course of time. Thus the pro- 

 duction of animal heat, long considered a 

 manifestation of life, was only classified as a 

 chemical phenomenon after Lavoisier's in- 

 vestigations; the solution of sugar in water 

 and of metals in the acids figured for a long 

 time in the same chapter, and even to-day 

 musical intervals are studied as part of 

 acoustics, though they belong to the domain 

 of sensations and have no relation with the 

 object of physics as we understand it to-day. 



Every science becomes constituted and defines 

 the object of its study and the aim of its research 

 little by little, by successive additions and 

 eliminations. Each successive century has 

 modified the classifications which the preceding 



one had framed and considered both logical and 



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