IN THE ANIMAL ORGANISM. 239 



the next 24 hours. If this be not done, the mass of 

 the body decreases, and the state characteristic of old 

 age more or less decidedly supervenes. 



With every hour of sleep the sum of available force 

 increases in the old man, or approaches the state of 

 equilibrium between waste and supply which exists in 

 the adult. 



It is further evident, that if a part of the force which 

 is available for mechanical purposes, without disturbing 

 the equilibrium, should not be consumed in moving the 

 limbs, in raising weights, or in other labor, it will be 

 available for involuntary motions. If the motion of the 

 heart, of the fluids, and of the intestines, (the circula- 

 tion of the blood and digestion,) are accelerated in 

 proportion to the amount of force not consumed in 

 voluntary motions, the weight of the body will neither 

 increase nor diminish in 24 hours. The body, there- 

 fore, can only increase in mass, if the force accumulated 

 during sleep, and available for mechanical purposes, is 

 employed neither for voluntary nor for involuntary mo- 

 tions. 



The numerical values above given for the expen- 

 diture of force in the human body refer, as has been 

 expressly stated, only to a given, uniform temperature. 

 In a different temperature, and with deficient nourish- 

 ment, all these proportions must be changed. 



If we surround a part of the body with ice or snow, 

 while other parts are left in the natural state, there oc- 

 curs, more or less quickly, in consequence of the loss 



