132 LIFE IN NATURE. 



Having formed part of the animal structure for a 

 time, this living matter decomposes yet again, and 

 again gives off its force. But now, instead of effect- 

 ing, as in the previous cases, a vitalizing action, the 

 force produces a mechanical action in the muscles, or 

 a nervous action in the brain, or, in short, the function 

 of whatever organ the matter we are tracing may 

 have been incorporated with ; the function being 

 but another mode of operation of the same force 

 which caused the nutrition. 



And thus, supposing the action to have been a 

 muscular exertion, say the lifting of a weight, we 

 shall have traced the force, which came from the 

 inorganic world at first, in the form of the sun's rays, 

 and was embodied in the substance of the plant, back 

 again into the inorganic world in the form of motion. 



Let us observe another thing. In previous chapters 

 the function and the nutrition of the body have been 

 distinguished from each other, and even contrasted.* 



* To guard against misapprehension, it is as well to say that by 

 the term nutrition are not intended any of the actions connected 

 with the taking of food, but only those minute internal changes by 

 which the growth and repair of the body are effected. 



