DERIVATION OF ANIMAL POWER. 397 



of man. The change of position in the elements of these 

 complex bodies, attendant on their rearrangement into new 

 and simpler compounds, necessarily gives rise to motion ; and 

 the molecular movement of the particles in a state of change 

 is transferred to the muscular mass. Chemical action is thus 

 evidently the source of mechanical power in bodies. 



The elements of the food of men and animals which give 

 rise to power and heat, are produced in living plants only by 

 the action of sunlight. The rays of the sun become latent, 

 so to speak, in them in the same way as the current of elec- 

 tricity becomes latent in the hydrogen by decomposition of 

 water. 



Man, by food, not only maintains the perfect structure of 

 his body, but he daily lays in a store of power and heat, de- 

 rived in the first instance from the sun. This power and 

 heat, latent for a time, reappears and again becomes active 

 when the living structures are resolved by the vital processes 

 into their original elements. 



The rays of the sun add daily to the store of indestructi- 

 ble forces of our terrestrial body, maintaining life and motion. 

 Thus, from beyond the limits of our earth, the body, the more 

 earthly vessel, derives all that may be called good in it, and 

 of this not a single particle is ever lost. 



