ENVIRONMENT AMONG MEN 339 



It is well known that exercise has considerable effect upon the 

 development of the muscles. It is also well known that there is 

 a clearly defined point for each individual beyond which exercise 

 will produce no further effect. Though exercise has a considerable 

 effect upon other organs, especially certain internal organs, it is 

 probable, not only that it has more effect upon the muscles than 

 upon any other system of organs, but that the effect upon the 

 muscles is relatively at least as great as, if not greater than, the 

 effect upon any organ of any other factor that we shall consider 

 except disease. Owing to differences in the amount of exercise 

 the bodily development of man in a modern community varies 

 very considerably ; owing to such modifications clerical workers 

 differ from blacksmiths, whether or not there are also germinal 

 differences. So too owing to differences in habits men of one 

 race differ from men of another race. Darwin, for instance, refers 

 to the thin legs and thick arms of the Payagua Indians who spend 

 a large part of their lives in canoes.^ It is certain that all such 

 physical differences are not due to germinal differences and that 

 environment in the shape of use is in part the cause. The position 

 is similar with regard to certain peculiarities observable among 

 races that have adopted unusual modes of squatting. 



Little is known as to the effects of use upon mental characters. 

 To some degree no doubt the intellect is developed by use, though, 

 perhaps, the degree to which this is so is apt to be exaggerated in 

 popular estimation owing to the fact that modes of thinking 

 acquired through education add to the effi-^iency of the faculty, 

 which result is mistaken for the effects of use. That the effects of 

 exercise are not great is shown by the experience of the Workers' 

 Education Association. This institution gives advanced courses 

 to men often of middle age who have received but little intellectual 

 training in early life. It does not appear that the strength of 

 their intellects is much less than it would have been had they 

 received a university training. It seems at any rate certain 

 that the differences in the amount of use now obtaining between 

 the various professions and classes in England have less effect 

 generally upon mental than upon physical characters. Given, 

 for example, two men of equal intellect, one of whom received 

 the best educational training of the day, and the other of whom 

 [received the training given to the working classes, it does not 



! ' Darwin, Descent of Mem, p. S'.i. 



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