6 VITALITY INDEPENDENT 



ance. Except in regard to this, all the vital chemical 

 processes go on precisely in the same way in man and 

 in the lower animals. 



The efforts of philosophers, constantly renewed, to 

 penetrate the relations of the soul to animal life, have 

 all along retarded the progress of physiology. In this 

 attempt men left the province of philosophical research 

 for that of fancy ; physiologists, carried away by ima- 

 gination, were far from being acquainted with the laws 

 of purely animal life. None of them had a clear con- 

 ception of the process of development and nutrition, or 

 of the true cause of death. They professed to explain 

 the most obscure psychological phenomena, and yet 

 they were unable to say what fever is, and in what way 

 quinine acts in curing it. 



For the purpose of investigating the laws of vital 

 motion in the animal body, only one condition, namely, 

 the knowledge of the apparatus which serves for its 

 production, was ascertained ; but the substance of the 

 organs, the changes which food undergoes in the living 

 body, its transformation into portions of organs, and its 

 re-conversion into lifeless compounds, the share which 

 the atmosphere takes in the processes of vitality ; all 

 these foundations for future conclusions were still 

 wanting. 



What has the soul, what have consciousness and 

 intellect, to do with the development of the human 

 foetus, or the foetus in a fowl's egg ? not more, surely, 

 than with the development of the seeds of a plant. 

 Let us first endeavor to refer to their ultimate causes 



