14 PHYSIOLOGY. 



of the muscle is further shown by the fact that when a 

 bone is broken, as in the upper arm or thigh, the ends 

 of the bones slip by each other, and the limb has to be 

 strongly stretched to bring the ends back together. Mus- 

 cles act better when slightly stretched, and probably need 

 a slight resistant action of the opponent muscle. 



Symmetrical Development of the Muscles. The mus- 

 cles of the two sides of the body are the same in number 

 and arrangement. At birth they are probably about equal 

 in size, weight, and strength. Most persons early become 

 right-handed, and the greater use of the right hand and 

 shoulder makes the muscles of this side larger and heavier. 

 The muscles pulling on the bones slightly modify them 

 in shape. The whole body may become noticeably un- 

 symmetrical. Most persons step harder on one foot than 

 the other, as shown by the sound of the footstep, and as 

 shown by the constant wearing of one shoe sole or heel 

 faster than the other. In many persons one shoulder is 

 habitually carried higher than the other. Symmetrical 

 development should be carefully sought, and any tendency 

 to a one-sided development should, so far as possible, be 

 avoided. We should use the left hand more. There are 

 many advantages in being able to use either hand. In 

 carving, in shaving, in bandaging, in administering medicine, 

 it may be necessary to use the left hand skillfully. The 

 pianist and the harpist use the two hands about equally, 

 while the violinist puts much more skill into his left hand. 

 Trainers of athletes often begin by developing the left 

 side of the body till it equals the right in size and strength. 



Muscles the Source of Strength. Our strength de- 

 pends on our muscles. It is a fine thing to have strong, 

 well-developed muscles, not only because they give beauty 



