24 Physiology. 



force, no motion will be produced. Sometimes this is done 

 on purpose, as when, in wrestling " square-hold," one holds 

 the arm rigidly bent at a right angle, to keep his opponent 

 from either pushing or pulling him. In the body are many 

 flexors and extensors " paired off"; they act alternately, 

 like the biceps and triceps in the arm. 



Symmetrical Development of the Muscles. The muscles 

 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 one-sided. 

 Most persons step harder on one foot than on the other, as 

 shown by the sound of the footstep, or by the constant 

 wearing of one shoe sole or heel faster than the other. In 

 many persons one shoulder is carried higher than the 

 other. 



To Overcome One-sidedness. 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 ad- 

 vantages in being able to use either hand. In carving, in 

 shaving, in bandaging, in giving medicine, it may be neces- 

 sary 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 depends 

 ; on our muscles. It is a fine thing to have strong, well- 



