BONES, MUSCLES, EXERCISE AND REST. 299 



extent, the body grows strong with labor, and every exertion 

 adds new particles and power to the muscular fibre. The 

 man who walked to Niagara Falls ( 668, p. 281) was stronger 

 the second day than he was the first, and stronger the third 

 than the second. He began with a power to walk three 

 miles, and ended in six weeks with a power to walk forty 

 miles. Whether he could have added still more to this 

 power, or how much stronger he could have grown, is not 

 known, for the experiment was not tried any further. In the 

 same manner, any one unaccustomed to labor, if he has a 

 good constitution and health, and if he proceeds gradually, 

 and cautiously increases from small beginnings, can, in time, 

 become sufficiently strong to do the ordinary agricultural 

 labor. 



691. In this process of invigoration there may be fatigue, 

 but there must be no languor nor exhaustion. But if either 

 of these happens, if the working man finds himself exhausted 

 after his toil, if he is uneasy, and restless, and unable to sleep, 

 and awakes the next morning unrefreshed and unprepared 

 for new exertion, he may be sure that he has overworked his 

 frame, and reduced rather than increased his strength. 



But by faithful and prudent use of the power already 

 gained, by never over-working on any one day, by always 

 stopping short of exhaustion, additions are made to the 

 strength day by day, for a certain period and to a definite 

 extent. The laborer may increase his exertion as long as 

 he feels this increase of power. But there must be, and is, 

 a limit to this. No man grows infinitely strong, and sooner 

 or later he must reach the end of his growth of power; then 

 he possesses his fullest measure of strength. 



692. Having arrived at this fulness of strength, he can 

 maintain it if he uses it discreetly and temperately, and if he 

 exercises daily, but never expends in any one day more than 

 its due portion of power. By this self-management, a man 

 can keep himself in the highest working order, and he will 

 be able to accomplish the most labor, not in any one day, nor 

 in a single year merely, but in the whole course of life, and 



