IN THE ANIMAL ORGANISM. 251 



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 

 labour, it will be available for involuntary motions. 

 If the motion of the heart, of the fluids, and of the 

 intestines (the circulation of the blood and diges- 

 tion), 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, therefore, can only increase 

 in mass, if the force accumulated during sleep, and 

 available for mechanical purposes, is employed nei- 

 ther for voluntary nor for involuntary motions. 



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 tempe- 

 rature. In a different temperature, and with defi- 

 cient nourishment, 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 occurs, more or less quickly, in consequence of 

 the loss of heat, an accelerated change of matter in 

 the cooled part. 



The resistance of the living tissues to the action 

 of oxygen is weaker at the cooled part than in the 



