II 



MECHANICS OF LOCOMOTOE APPARATUS 115 



In order to swing forward without hitting the ground the 

 passive lirub must shorten slightly. But according to the Webers' 

 theory this is not due to contraction of the flexors of the thigh 

 or knee, for the lower limb may be regarded as a compound 

 pendulum which in oscillating becomes slightly flexed at its 

 articulations. Eecent investigation has, however, modified much 

 in this theory. 



It is not correct to say that the limb lifted from the ground 

 and swinging forwards is totally passive. Duchenne, by his 

 clinical observations, demonstrated the 

 necessity in regular walking of the 

 active intervention of the flexors of the 

 thigh, the tensor fasciae, the psoas-iliac 

 and the sartorius muscles to shorten 

 the limb and avoid contact with the 

 ground during the swing. Marey, too, 

 showed that the swing of this limb 

 could not be regarded as passive, since 

 it consists in a progressively acceler- 

 ated movement, and must therefore be 

 associated with, and partly dependent 

 on, muscular force. 



In order to obtain a more exact idea 

 of the complex movements of walking, 

 the way the feet are lifted and set 

 down, and the position assumed by 

 the limbs at their principal articula- 

 tions in each phase of the step, graphic 

 and chronophotographic methods must 



hp rp^nrrprl in FIG. 74. Pedestrian in exploring si s 



which record the pressure applied 

 to the ground upon a portable 



Marey and Carlet were the first who apparatus. (Marey.) 

 applied the graphic method to the study 



of the complex movements of walking and running. Of the different 

 instruments which Marey invented, the most important are the shoes, which 

 register the pressure applied to the ground by the individual who walks or 

 runs. The sole of these shoes contains an air-chamber communicating by a 

 tube with a recording tambour, which writes upon a portable revolving 

 cylinder, held in the hand of the individual who performs the experiment 

 (Fig. 74). The air-chamber lies in the front part of the sole, near the end 

 of the metatarsus. Accordingly it only registers the pressure exerted upon 

 the anterior part of the foot (Fig. 75). Carlet obtained better tracings by em- 

 ploying soles with two intercommunicating air-chambers placed one lu-ar 

 the heel, the other near the front of the metatarsus. 



Along with these tracings of the pressure exerted by the feet while 

 resting on the ground, Marey and Carlet registered the vertical oscillations 

 of the head, or the horizontal oscillations of the pelvis (Figs. 75, 79), by 

 means of special tambours. 



The chronophotographic method which Marey applied to walking 

 consists in recording on one fixed plate the successive images of a person 

 walking. The photographic apparatus has a lens, and a man is made to 



