186 THE PHENOMENA OF MOTION 



essence of natural phenomena are recognisable, not by 

 abstraction, but only by comparative observations. 



If the vital phenomena be considered as manifesta- 

 tions 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 pre- 

 serve in their courses the worlds of our own and other 

 systems, and which also determine changes of form and 

 structure in material bodies ; altogether independent 

 of the matter in which vital activity appears to reside, 

 or of the form in which 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, struc- 

 ture, and composition of the substance of the tissue in 

 which the vital energy resides. 



This force further manifests itself as a cause of mo- 

 tion 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 con- 

 stituents of food, and destroys the force of attraction 

 which is continually exerted between their molecules ; 

 it alters the direction of the chemical forces in such 

 wise, that the elements of the constituents of food ar- 

 range themselves in another form, and combine to pro- 

 duce new compounds, either identical in composition 



