THE ERECT POSITION. 



263 



be equal. The moments are found by drawing the shortest line fb from 

 / to the direction of the force ac, and the line fd to the direction along 



which gravity acts. Then bf x push = fd x 



weight of body. 



If the push be greater than -j- f x weight of 



the body, which is viewed as a Strictly speaking, the body not being a rigid 

 rigid body resting on the feet, mass, there can be no question of stable or even 



unstable equilibrium. In fact a living subject 



is constantly in motion, even when trying hard to stand " motionless." 

 Vierordt J by a simple recording method obtained tracings of the swaying 

 movements of persons standing upright. Leitersdorffer 2 proved by this 



FIG. 150. Shows the area of underpropping and the plumb of the 

 centre of gravity (g). (1) At attention. (2) In an erect and 

 easy attitude. (3) When resisting a force applied from the 

 left. (4) When resisting a force applied from the front, as in 

 boxing. 



method the influence of the area of underpropping and the difference between 

 trained and untrained subjects. 



1 "Physiol. des Menschen," Tiibingen, 1862, S. 365. 



2 "Das militarische Training," Stuttgart, 1894, S. 42. 



