ANIMAL MECHANICS. 



55 



be calculated also from a totally different set of observations 

 made by the Messrs. Weber.* 



When the body is at rest, in the standing posture, the 

 line drawn from the centre of gravity of the trunk to the 

 centre of the horizontal line joining the centres of the acetabula 

 of the pelvis must be vertical ; and when, in walking or run- 

 ning, the body is carried horizontally with a velocity v, this 

 line must incline forwards, with an inclination such that it shall 

 be in the direction of the resultant of the momentum of the 

 horizontal velocity and the weight of the body. 



Thus, if 0 B be 

 the horizontal space 

 through which the 

 trunk (balanced, like 

 a jugglers' pole, on the 

 pelvis) is carried in 



sistance caused by 

 setting the forward 

 foot upon the ground, 

 or by the air; the 



a given time, and OA 

 bethe vertical space, 

 which on the same 

 scale represents the 

 weight of the body ; 

 if there were no re- 



body would be 

 obliged to lean for- 

 ward through an an- 

 gle 0 AB, such that 



tan i « tan U A B - — = 



mg 32.2 



* Mechanik der menschliehen Gewerkzeuge, pp. 233, 4. 



(■3) 



