64 THE GROWTH OF THE BRAIN. 



The mystery of this running down of the animal 

 machine awaits explanation, though of course the 

 mechanical hindrances to nutrition following increase in 

 bulk, and the greater exertion necessary to obtain food 

 after separation from the mother, have long been 

 recognised. There is, however, something beyond 

 mechanics in the problem. Indeed there is some 

 ground for considering each animal as possessed of a 

 certain limited store of potential energy with which to 

 go through its life, but the complexity of the manner 

 in which this energy may be expended is so great, and 

 the combinations of its expression so manifold, that as 

 yet it is possible only in the most general way to guess 

 at the capacity of a given individual. We admit that 

 disease is fundamentally exhausting, that excessive 

 exertion and privation leave an indelible mark on the 

 bodily organism, and yet there is so much art in the 

 manner of putting forth exertion, that at present we aie 

 quite without means to adequately record its expendi- 

 ture, or to explain how structural deficiencies may be 

 masked, for the measure of the whole man is neither the 

 number of pounds that he can lift, nor facts that he can 

 discover, nor the influence that he can exert upon his 

 fellows, nor yet the age to which he can attain, but 

 something of all these and what they stand for, taken 

 together. 



