196 THE PHENOMENA OF MOTION 



recognizable, not by abstraction, but only by com- 

 parative observations. 



If the vital phenomena be considered as mani- 

 festations of a peculiar force, then the effects of 

 this force must be regulated by certain laws, which 

 laws may be investigated ; and these laws must be 

 in harmony with the universal laws of resistance 

 and motion, which preserve in their courses the 

 worlds of our own and other systems, and which 

 also determine changes of form and structure in 

 material bodies; altogether independently of the 

 matter in which vital activity appears to reside, or 

 of the form in Avhich vitality is manifested. 



The vital force in a living animal tissue appears 

 as a cause of growth in the mass, and of resistance 

 to those external agencies which tend to alter the 

 form, structure, and composition of the substance of 

 the tissue in which the vital energy resides. 



This force further manifests itself as a cause of 

 motion and of change in the form and structure of 

 material substances, by the disturbance and abolition 

 of the state of rest in which those chemical forces 

 exist, by which the elements of the compounds 

 conveyed to the living tissues, in the form of food, 

 are held together. 



The vital force causes a decomposition of the 

 constituents of food, and destroys the force of at- 

 traction which is continually exerted between their 

 molecules ; it alters the direction of the chemical 

 forces in such wise, that the elements of the con- 



