BONES, MUSCLES, EXERCISE, AND REST. 279 



One man is very powerful, another is very weak ; one is strong 

 in the arms and weak in the legs, while another is strong in 

 the legs and weak in the arms. 



644. This great and almost infinitely varied muscular 

 power is given to men and animals for action. It was no 

 intention of the benevolent Creator that this should remain 

 dormant. Some of the involuntary muscles work inces- 

 santly; day and night, asleep or awake, from birth to 

 extreme old age, the heart beats, and the chest moves, and 

 the digestive organs carry on their operations and find no 

 rest ; nor yet are the muscles which perform these labors 

 exhausted or even weary. It is the design of our being that 

 we use the muscles that are put under our control, and, by 

 their action, both procure our subsistence and sustain our 

 health. These two ends are attainable b*y the same means, 

 and are made to correspond with each other. 



645. Exercise of tJie muscles increases the waste of their 

 dead particles , ( 252, p. 115,) and consequently the demand 

 for nutrition. The arteries then act more vigorously, carry 

 more blood, and deposit more new particles. The active 

 muscle, being better nourished, is composed of fresher 

 atoms, and has more strength. When this exercise is ju- 

 diciously taken, neither too little nor too much, the nutrition 

 exceeds the absorption, more new atoms are brought .than 

 old carried away ; then the muscle grows larger, and more 

 dense and powerful. We find proof and examples of this 

 too frequently to escape notice. The muscles of the inac- 

 tive, those who neither labor nor exercise, are small, soft, 

 and flabby, and hang loosely on the bones ; consequently, 

 they are weak. But the muscles of the active and laborious 

 are large and firm ; they are full and very strong, and en- 

 dowed with great energy of action. 



646. The robust and healthy laborer exercises his limbs 

 and his trunk, and consequently has strong muscles. He 

 can take his scythe and mow from morning till night, and 

 follow this from Monday till Saturday; he can lay stone 

 wall or cut wood with the same perseverance; and he does 



