PREFACE. 



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L HE investigation of the subject of the fol- 

 lowing Treatise Was suggested to the author by acci- 

 dentally observing the spontaneous recovery of an 

 animal in whom all the appearances of life had been 

 suspended by drowning. Reflecting on this part of 

 the pathology of respiration, and on the theories 

 which have been proposed to explain it, he was led 

 to consider with particular attention the physiology 

 of that function. The result of his inquiry termi- 

 nated in a conviction, that although many great 

 and important steps had been made, yet much hy- 

 pothetical conjecture was blended with established 

 fact, and many suppositions were admitted into our 

 theories which but ill accorded with the structure 

 and economy of the animal system. 



