7 6 THE POPULAR SCIENCE MONTHLY. 



receive that training which brings them under the complete con- 

 trol of the will ; that the perceptive organs be habituated to con- 

 vey clear and accurate impressions to the brain. 



To the wholesome use of the mind it is essential that the im- 

 pressions coming thereto be perceived in their exact relation, so 

 that nerve and muscle may be directed to most efficient result ; 

 its development means the more extended and the more complex 

 correlation of an increasing number and variety of impressions. 



The highest moral development is attained through the in- 

 creasing and constantly more refined perception of that conduct 

 which contributes to the highest good of one's self and others, and 

 action in accordance therewith. 



Here arises the fact that the physical and mental structures 

 of different individuals are of greatly varying capacities. An 

 amount of physical exertion that serves only as wholesome exer- 

 cise to one man might ruin another of less sturdy structure. 

 The amount of mental exertion upon which one brain thrives and 

 develops would cause another pain, and would be utterly impos- 

 sible for yet another. Different impressions coming under differ- 

 ent conditions, through bodies of different fiber, to brains of dif- 

 ferent caliber, have, together with the mold given by differing in- 

 fluences of heredity, produced that difference of characteristics in 

 different individuals that is so incalculable that it is accepted as 

 a truism that no two persons are exactly alike. It is obvious, 

 therefore, that no one can contribute to the totality of effort in 

 greater degree or in kind other than his physical and mental 

 structure and characteristics will permit. The laborer on the 

 embankment has the muscle wherewith to use the pick and 

 shovel, but ordinarily is incapable of that co-ordination of hand 

 and brain which would enable him to use tools of a higher class. 

 The blacksmith has that adjustment of brain and muscle which 

 enables him to bend and shape the bars of iron. Through the 

 ascending ranks of artisans this adjustment of brain and muscle 

 becomes more delicate, reaching a rare degree of precision in, for 

 example, the optician who grinds and shapes the glasses for spec- 

 tacles, microscope, and telescope. The clerk who keeps journal 

 and ledger, or who prepares deeds and mortgages, has that con- 

 trol of the hand and that mental development which suffice for 

 this work. Neither laborer, blacksmith, optician, nor clerk could 

 perform the work accomplished by the other; but each, by giv- 

 ing to others the benefit of effort of which he is physically and 

 mentally capable, receives that which enables him to obtain the 

 food, shelter, and clothing necessary to his maintenance. 



And it is through work of body and brain that yet higher re- 

 sult is achieved. The blacksmith's son, compelled to contribute 

 early in life to the support of himself, his brothers and sisters, be- 



