STANDING. 85 



the nervous system. The influence of the latter is shown 

 by the fall which follows a severe blow on the head, which 

 has fractured no bone and injured no muscle ; " the con- 

 cussion of the brain" stuns the man, and until it has 

 passed off he cannot stand. 



When we stand erect, with the arms close by the sides 

 and the feet together, the centre of gravity of the whole 

 adult body lies at the articulation between the sacrum 

 and the last lumbar vertebra, and a perpendicular 

 drawn from it will reach the ground between the feet. 

 In any position in which this perpendicular falls within 

 the space bounded by a line drawn close around both feet, 

 we can stand. When the feet are together the area enclosed 

 by this line is small, and a slight sway of the trunk 

 would throw a perpendicular dropped from the centre of 

 gravity of the body outside it ; the more one foot is in 

 front of the other the greater the sway back or forward 

 which will be compatible with safety, and the greater the 

 lateral distance between the feet the greater the lateral 

 sway which is possible without falling. Consequently, 

 when a man wants to stand very firmly he advances one 

 foot obliquely, so as to increase his base of support both 

 from before back, and from side to side. 



In consequence of the flexibility of its joints a dead 

 body cannot be balanced on its feet as a statue can. 

 When we stand, the ankle, knee, and hip-joints, if not 

 braced by the muscles, would give way, and the head also 



Illustrate the influence of the nervous system in connection with 

 standing. 



Where is the centre of gravity of the body when we stand erect? 

 Where does a perpendicular from it reach the ground? Why do we 

 separate the feet when we want to stand firmly? 



Why cannot a dead body be balanced on its feet? What prevents 

 our knee, and hip-joints from bending when we stand? 



