248 THE MUSCLES. 



the greater the necessity. This is founded on the organic 

 law that muscular action must be alternated by rest. Any one may 

 notice that the small children in a school room, after sitting a short 

 time, become restless. A change of position, for a short time, will 

 enable their imperfectly developed muscles to regain their strength 

 when they will again support the spinal column without pain. 



Exhaustion This is the constant and necessary effect of con- 

 tinuous muscular contraction. No difference how seemingly light 

 and easy the exertion, its continuance becomes, after a time, intol- 

 erably wearisome. The mere motion of a finger, if long continued, 

 exhausts the whole frame. Change of employment brings a new 

 set of muscles into play, and is often equivalent to rest. 



The Utmost Muscular Capacity This is to be attained 

 not by prolonged exertion, but by taking sufficient time for rest. Of 

 two men of equal strength, the judicious and understanding one, 

 who never hurries and who rests at regular intervals when the mus- 

 cles require relaxation, will accomplish far more labor, in a pro- 

 tracted time, than the nervous, over-strained and long-continued 

 exertions of his competitor. This principle may be profitably 

 applied to the labor of domestic animals, as to all other kinds of 

 employment. Convalescing invalids frequently suffer relapses from 

 inattention to this law. 



A Common Experience Neither growing youth nor habitu- 

 ally hard-working men can endure the severe muscular strain which 

 can easily be borne by those who are at once mature and unexhaust- 

 ed. Napoleon I. complained that his boy-conscripts could not bear 

 the severe marches of his campaigns and in our own war between 

 the States, the young men from the towns and cities were found 

 capable of sustaining vastly more hardships than the young men 

 from the country. This was owing, in the first instance, to imma- 

 turity, and in the second, to the habitual exhaustion of the farm- 

 laborer. 



Graduation of Exertion After rest, the first motions 

 should be slow, and the increase to strong or violent exertion, very 

 gradual. Of a task requiring several hours for its completion, con- 

 siderably less than half should be performed in the first half of the 

 allotted time. On this plan, we snould conduct the labor of domes- 

 tic animals. The reason for this is that the muscles require more 

 blood and nervous fluid when in action, than when at rest; and as 

 the circulation of these fluids can only be increased gradually, it 

 follows that sudden and violent muscular exertions have an effect 

 similar to that of working machinery unoiled; that is, the friction 

 of the parts consumes the very substance of the machinery. 



Gradual Rest This is also important. If one has been mak- 

 ing violent or long-continued exertions, it is better to substitute 

 some other or gentler exercise than to turn immediately to rest.' 

 Thus time is allowed for the reflux of the blood and nervous fluids 

 into their ordinary and more diffused channels, instead of allowing 



