THE USE OF MUSCLES IN THE BODY 131 



The great muscles of the " brawny " arm of the blacksmith or 

 wrestler illustrate the reverse fact, the growth of the muscles by 

 exercise. We may note, incidentally, that in this growth from 

 exercise there is no increase in the number of muscle-fibers. The 

 greater size is due to growth of the individual fibers. Exercise, to 

 be effective, must be judicious; repeated frequently to the point of 

 exhaustion it does harm; the period of repair is not sufficient to 

 counteract the injurious effects of fatigue, and the muscles thus 

 waste under too violent exercise as with too little. Rest should 

 alternate with work, and that regularly, if benefit is to be obtained. 

 Moreover, violent exercise should never be suddenly undertaken 

 by one unused to it, not only lest the muscles suffer, but because 

 muscular effort greatly increases the work of the heart. No gen- 

 eral rule can be laid down as to the amount of exercise to be taken ; 

 for a healthy man in business the minimum would perhaps be 

 represented by a daily walk of five miles. 



Varieties of Exercise. In walking and running the muscles 

 chiefly employed are those of the lower limbs and trunk. This is 

 in part true of rowing, which when good is performed much more 

 by the legs than the arms; especially when sliding seats are 

 used. Hence any of these exercises alone is apt to leave 

 the muscles of the chest and arms imperfectly exercised. Indeed, 

 no one exercise employs equally or proportionately all the muscles : 

 therefore gymnasia in which various feats of agility are practiced, 

 so as to call different parts into play, have very great utility. It 

 should be borne in mind, however, that the legs especially need 

 strength; while the upper limbs, in which delicacy of movement, 

 as a rule, is more desirable than power, do not require so much 

 exercise; and the fact that gymnastic exercises are commonly 

 carried on indoors is a great drawback to their value. When the 

 weather permits, out-of-door exercise is far better than that 

 carried on in even the best ventilated and lighted gymnasium. 

 For those who are so fortunate as to possess a garden there is no 

 better exercise, at suitable seasons, than an hour's daily digging 

 in it; since this calls into play nearly all the muscles of the Body; 

 while of games, lawn-tennis is perhaps the best from a hygienic 

 view that has ever been invented, since it not only demands 

 great muscular agility in every part of the Body, but trains the 

 hand to work with the eye in a way that walking, running, row- 



