WALKING. 



117 



walking ; all the vertical oscillations of the pubis will be 

 registered. 



But, in order that the experimental lever may receive and 

 transmit faithfully the vertical oscillations which the pubis 

 executes during the act of walking, the drum itself must be 

 protected from these oscillations. For this purpose an instru- 

 ment has been invented, composed of two horizontal arms, 

 which turn on a centre. These arms can move only in a hori- 

 zontal plane, situated at the height of the pubis of the person 

 under experiment ; to one of these arms is fixed the experi- 

 mental lever drum. 



Fig. 22. — ^The upper curves, one in full line, the other dotted, represent 

 the phases of the impact and of the rise of the right and left foot. Reading 

 the figure from left to right, each rise of the curve denotes the commence- 

 ment of pressure: the upper horizontal part corresponds with the dura- 

 tion of the pressure, and the descent with the rise of the foot. The 

 lower horizontal part of the curve indicates that the corresponding foot 

 is in the air. O Pv. Oscillations of the pubis from above downwards, 

 that is vertically, O P^. Oscillations in a lateral direction, or hori- 

 zontally. It is evident that two oscillations in the vertical direction 

 correspond with a single horizontal oscillation. 



The person who walks, follows during this time a circular 

 path, pushing before him the arm of the instrument, to which 

 is fixed the apparatus which is to experiment on the vertical 

 oscillations of the pubis. We get thus the tracing repre- 



