VITAL FORCE. 9 



condition of life, and must be again renewed. Phy- 

 siology has sufficiently decisive grounds for the 

 opinion, that every motion, every manifestation of 

 force, is the result of a transformation of the struc- 

 ture or of its substance ; that every conception, 

 every mental affection, is followed by changes in the 

 chemical nature of the secreted fluids ; that every 

 thought, every sensation, is accompanied by a change 

 in the composition of the substance of the brain. 



In order to keep up the phenomena of life in 

 animals, certain matters are required, parts of organ- 

 isms, which we call nourishment. In consequence 

 of a series of alterations, they serve either for the 

 increase of the mass (nutrition}, or for the supply of 

 the matter consumed (reproduction), or, finally, for 

 the production of force. 



II. If the first condition of animal life be the 

 assimilation of what is commonly called nourish- 

 ment, the second is a continual absorption of oxygen 

 from the atmosphere. 



Viewed as an object of scientific research, animal 

 life exhibits itself in a series of phenomena, the 

 connection and recurrence of which are determined 

 by the changes which the food and the oxygen 

 absorbed from the atmosphere undergo in the organ- 

 ism under the influence of the vital force. 



All vital activity arises from the mutual action 

 of the oxygen of the atmosphere and the elements 

 of the food. 



