STANDING. 



17. The Muscles concerned in Standing. In consequence 

 of the flexibility of the ankle-, knee-, and hip-joints, a 

 dead body cannot be balanced on 

 its feet, as a marble statue may be. 

 When a man stands, the joints would 

 bend, were they not braced and held 

 firm by muscles. When we stand, mus- 

 cles (Fig. 20, i) in front of the ankle- 

 joint, and others (/) behind it, con- 

 tracting at the same time, keep that 

 joint from yielding. In the same way, 

 j _C/J muscles (2) in front of the knee- and 



hip-joints, are opposed by others (//) 

 behind them, and when we stand, both 

 contract and keep those joints rigid. 

 The muscles (///) which run from the 

 pelvis to the back of the head, in like 

 manner pull against others (3 and 4) 

 which run from the pelvis to the lower 

 [ end of the breast-bone, and from the 

 lull I i u ppcr end of the breast-bone to the 

 front part of the skull; their bal- 

 anced contraction keeps the head erect. 

 If one falls asleep while sitting or 

 illustrating the mus- standing, the chin drops, because the 

 muscles holding the head upright have 

 relaxed their vigilance, and its front' 

 b h o e djr ire s c[. igidandthe part is heavier than its back. Since 

 the degree to which each muscle contracts when we 



17. How do the muscles enable us to stand ? Why does the head 

 fall forward if one goes to sleep standing? Why does it take time to 

 learn to stand ? 



FIG. 20. Diagram 



lustrating the mus- 



cles (drawn in thick 



