THE MUSCLES. 247 



and false delicacy in this particular. Teachers should be especially 

 careful, in this respect, with regard to their younger pupils. 



THE MUSCLES. 



The Law That whenever a muscle is called into use, its 

 fibres increase in'thickness, and that it correspondingly diminishes 

 with disease, is the law of the muscular system. The force of action 

 of a muscle is proportioned to this thickness. In other words, the 

 action and power of any organ measure each other. In order, then, 

 that the muscular system may be prepared to meet the demands of 

 nature and occasion, it must be exercised. 



Limits of the Law These are full growth, or the matur- 

 ity of life and power. Whenever the muscles act, the flow of blood 

 is increased in the arteries and veins. This increased flow causes a 

 more rapid deposit of the matter of which the muscles are composed. 

 The deposit of new material will be in excess of that removed, and 

 the size and energy of the vessels increased, if the exercise is equal 

 to the power of the system, feo the muscles become strong by use, 

 or labor. 



Excess Exercise, either for pleasure or profit, should never 

 be carried to the point of exhaustion though this should be distin- 

 tinguished from fatigue if one wishes to secure their utmost 

 capacity. The hard labor frequently diminishes the weight, by 

 several pounds, within a few weeks. This is also illustrated by the 

 attenuated frames of overtasked domestic animals. The loss, in 

 these instances, exceeds the new deposits of material. In a word, 

 the muscles are lessened in size and diminished in power, whenever 

 the exercise is continued so long as to produce a feeling of exhaus- 

 tion. 



The Practical Inference The strength should be the 

 measure of exertion. Any other rule will fail to invigorate the 

 system. Exercise and labor must therefore be adapted to the 

 strength of the individual. If a mile of riding or walking cause 

 slight fatigue, this may be beneficial, while the exhaustion occas- 

 ioned by doubling the distance may prove highly injurious. It is 

 therefore plain that the same amount of exercise will not do for dif- 

 ferent people. 



Rest The long strain on a muscle enfeebles its action and 

 impairs its contractibility. One can hold the arm extended but a 

 short time, whatever effort he makes. This holding out of the arm, 

 with a- book in the hand, is sometimes inflicted as a penalty in 

 schools and it is a severe one. Most boys would prefer a sound 

 whipping. The law of health is that relaxation must soon follow 

 contraction; or in other words, that rest must follow labor. 



School Frequent, though short, recesses are necessary for 

 small and feeble children ; the younger and feebler the children, 



