208 STANDING, WALKING. 



strength, or if you should fall asleep, or forget 

 yourself, the same thing would follow. 



Standing is, therefore, an action of the voluntary 

 muscles ; you wish to stand, and that enables you 

 to do it. This is done by what we may call a 

 balance of action between the two great orders of 

 muscles, the flexors, and the extensors. ^ These 

 extensors, by acting on the bones, keep the limbs 

 and trunk erect, whilst the flexors yield and make 

 no efforts to contract. 



By these means, we are enabled to retain an 

 upright posture. But we are soon fatigued by it. 

 This is owing to there being no change of action, 

 one set of muscles only being employed. Hence 

 when we are obliged to stand for a long time, we 

 are continually changing our posture, now resting 

 on one leg, and then on the other. This is done 

 in order to relieve the muscles from their state of 

 continued action, by calling others for a moment 

 into play. 



Walking is easier to us than standing quite 

 still, for this reason, that both sets of muscles, 

 namely, the flexors and extensors, act now one and 

 now the other, and thus are constantly relieving 

 each other. 



When we walk, one leg is lifted and carried for- 

 wards ; at the same time, the body is made to rest 

 on the leg that is planted on the ground. The leg 

 which has been carried forwards is now fixed on 

 the ground, and the body is shifted upon it, by the 

 strong muscles of the trunk and thigh bone. Thus 



