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BOOK IV. 



CHAPTER I. 



Life. 



" First then, if any one think that the secrets of nature remain 

 shut up, as it were with the seal of God, and by some divine 

 mandate interdicted to human wisdom, we shall address ourselves 

 to remove this weak and jealous notion ; and, relying on simple 

 truth, shall bring the inquiry to this issue, not only to silence the 

 howl of superstition, but to draw religion herself to our side." 



BACON. 



WHETHER in a theoretical or practical point of 

 view, the animating principle is the most im- 

 portant problem that ever engaged the attention 

 of mankind ; for it connects all that is profound 

 and fascinating in physics, with the science of 

 preserving health and prolonging life. Never 

 can the healing art take its appropriate rank 

 among the exact sciences until the cause of vital 

 force and animal motion is distinguished from 

 the operations which it produces ; but must re- 

 main, as in all the ages that are past, a mere col- 

 lection of empirical rules. If it be true that every 

 deviation from health is immediately connected 

 with some derangement of the vital principle, there 

 cannot be a doubt, that a clear comprehension 



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