USE AND DISUSE, REVERSION, AND HYBRIDISM. 71 



the vital energy of the body, and the exercised 

 ones more. 



It has frequently been remarked that men of 

 great genius often leave no children, or their 

 families soon die out, while in other cases their 

 children show less than average ability. Great 

 physical strength and great intellect rarely co- 

 exist ; and the French have a proverb, " As 

 stupid as a dancing-girl." Notwithstanding oc- 

 casional exceptions, a man who is obliged to 

 work hard at some manual employment, will 

 seldom retain the mental capacity for study. 

 There are even many mental qualities which 

 appear to be somewhat incompatible with each 

 other, and are rarely found united. Thus, it 

 very rarely happens that a poet is also eminent 

 in science. Goethe is perhaps the only remark- 

 able exception ; -but as remarked in the second 

 chapter, all genius of the highest order is 

 sporadic, and consequently exceptional in its 

 nature. 



Some of these illustrations may be susceptible 

 of various interpretations ; but they do not 

 affect the main point, viz. : that qualities which 

 are exercised tend to increase, and those which 

 are not exercised, to diminish. 



