LETTERS TO BROTHER JOHN. 93 



And thus we observe in the aged, in whom the 

 process of renewal goes on but feebly, and in whom 

 the laws of fermentation and putrefaction are gra- 

 dually gaining the ascendancy over the laws of life 

 the laws of that contrivance which was instituted 

 in order to remove living beings, for a time, from 

 the influence of fermentation and putrefaction we 

 observe, I say, in the aged that contractility i& 

 greatly diminished it has waned, it has faded 

 their strength is greatly reduced they are no 

 longer a fit residence for active contractility ; since 

 this property can only reside, in its perfection, in 

 very recently-organized matter; whereas, in the 

 old, organization goes on very slowly and imper- 

 fectly. On the contrary, in children, contractility 

 exists in a very high degree ; because, in them, the 

 process of organization goes on with great rapidity. 

 A child will romp about on its legs for a whole day, 

 without feeling fatigue; and can endure exertion 

 far longer than a man, when we take into consi- 

 deration the comparatively small size of the child's 

 muscles. 



It is a law, then, of contractility, that in order to 

 its perfection, it is necessary that the molecules of 

 the parts in which it resides should be rapidly re- 

 organized in a word, that they should always have 



