286 PHYSIOLOGY AND HEALTH. 



CHAPTER X. 



Muscular Action strengthens the whole System, and aids the Brain 

 and Mind. Neglect of Exercise debilitates the whole Powers 

 Various Persons need different Quantities of Exercise. Too vio- 

 lent Exercise exhausts. 



659. IT will be easy now to understand how a muscle 

 that is used grows and becomes hard and strong. The 

 active contraction promotes the flow of blood and increases 

 nutrition by the deposit of new particles of flesh. After the 

 labor has ceased, there is less waste of particles by the absorp- 

 tion of the old. But the rapid motion of the heart does not 

 cease with the exercise ; the increased flow of blood is thus 

 continued, and with it the increased deposit of new particles 

 in the muscles; and thus it gains in size and strength by 

 labor. 



660. Thus we see that muscular action promotes diges- 

 tion, respiration, circulation, and nutrition, and it assists the 

 preparation and maintenance of animal heat. Finally, as the 

 health and functions of the nervous system are connected 

 with the condition of the other systems, we may safely add, 

 that muscular exercise aids the brain also in its work, and 

 that no mind can be the clearest and the most vigorous for 

 study and reflection, unless the body is accustomed to action. 



661. A sagacious physician, whose domestic economy 

 was worthy of all imitation, when any one of his daughters 

 complained of a headache, was accustomed to inquire, first, 

 whether she had taken her usual exercise abroad ; and, 

 if this had been insufficient for the purpose, he frequently 

 advised, not. medicine, but another walk. Some judicious 

 schoolmasters, when they find their boys and girls heavy and 

 indisposed to study, send them out to play awhile. After 

 exercise out of doors, they return to their studies with new 

 alacrity. If older students, when they find it difficult to fix 

 their minds upon the subjects before them, when the reason- 

 ing powers are clouded and the imagination is dull, would 



