288 PHYSIOLOGY AND HEALTH. 



mained several years an invalid, incapable of any business, 

 or of engaging in any more study. That firm and inflexible 

 constitution, which had held out seven years against the vio- 

 lation of the physical law, was equally inflexible with regard 

 to recovery, and required more than seven years to be so far 

 restored as to allow him again to engage in any pursuit. 



663. The same quantity of exercise is not necessary for 

 the health of all men and women, nor are all able to endure 

 the same amount of labor. It must be measured out accord- 

 ing to the constitution, the strength, and the habits of various 

 persons. What is necessary for one may exhaust another. 

 The quantity of action should be determined, not by any 

 previously established theory, but by its results in each case 

 by its effects upon each individual. 



664. If the exercise is too violent or too long continued, 

 the body is rather exhausted than invigorated; the process 

 of waste is carried on beyond the power of nutrition, and 

 then the muscles grow thin and lank, rather than full and 

 strong, and the individual suffers from languor, and is ill 

 fitted for any other labor. But if, on the other hand, after 

 the exertion, we are only a little fatigued, but not languid, 

 if we are ready then for any other occupation, for reading, 

 writing, or conversation, we may be assured that the in- 

 creased waste is counterbalanced by the increased nutrition, 

 and the labor has strengthened rather than weakened the 

 body. The exercise should never go beyond a slight fa- 

 tigue, never to exhaustion, nor produce that uneasy rest- 

 lessness which unfits one for any other immediate duty, and 

 which rather wears uoon than adds to the general health. 



665. Although tne muscles have a power of contraction, 

 they have not a permanence of this power. The muscle 

 needs alternate relaxation with its labor. One can strike with 

 more force than he can pull, and lift a much heavier weight 

 than he can continue to hold up, for even a few minutes. It is 

 one of the severest and most painful punishments to compel a 

 boy in school to hold out the arm in a horizontal position, 

 even without a weight in his hand, for any length of time. 



