IN THE ANIMAL ORGANISM. 217 



the period at which the cause of waste ceases to oper- 

 ate, can the capacity of growth be manifested. 



Now, since, in different individuals, according to the 

 amount of force consumed in producing voluntary me- 

 chanical effects, unequal quantities of living tissue are 

 wasted, there must occur, in every individual, unless 

 the phenomena of motion are to cease entirely, a con- 

 dition in which all voluntary motions are completely 

 checked, in which, therefore, these occasion no waste. 

 This condition is called sleep. 



The growth of one part, which is not deprived of 

 its vital force, cannot be in the slightest degree affected 

 by the consumption of the vital force of another part 

 in producing motion. The one may increase in vol- 

 ume, while the other diminishes , and the waste in 

 one can neither increase nor diminish the supply in the 

 other. 



Now, since the consumption of force for the in- 

 voluntary motions continues in sleep, it is plain, that 

 a waste of matter also continues in that state ; and 

 if the original equilibrium is to be restored, we must 

 suppose that, during sleep, an amount of force is accu- 

 mulated in the form of living tissue, exactly equal to 

 that which was consumed in voluntary and involuntary 

 motion during the preceding waking period. 



If the equilibrium between waste and supply of mat- 

 ter be in the least degree disturbed, this is instantly seen, 

 in the different amount of force available for mechanical 

 purposes. 



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