354 THE HUMAN MOTOR 



or in radians : 



TC X 129 43:r 



When the oscillation of the right leg has finished and the heel 

 is on the ground, and before the left foot has left the ground, 

 there is a moment during which both feet are on the ground. 

 This is the period of " double support." This period is very 

 short. In normal walking it is only -08 seconds, five times less 

 than that of the oscillation. During this period the weight is 

 transferred to the right leg, which, at this moment, is inclined 

 at about 25 to the vertical, then as the foot comes into full 

 contact with the ground, the leg which was bent straightens at 

 the knee, the lower member takes its full development, and con- 

 sequently the hip describes a curve of increasing radius. When 

 the upright position of the leg is passed the hip commences to 

 describe a curve in the reverse direction. This curve has some 

 resemblance to the trajectory of a point moving in the interior 

 of a semi-cylinder from the bottom to the edge. Marey made 

 records of the sinuous curves by means of measurements of the 

 movement of the pubis. 



By certain muscular contractions, especially of the quadriceps, 

 the knee is stiffened and the whole weight of the body is sup- 

 ported without flexion of the thigh. The foot " unrolls " 

 (deroule) itself from heel to toe, during which " unrolling " the 

 lower member remains straight owing to muscular contraction 

 of hips and femur. It supports the pressure transmitted to it 

 by the rear leg, which pressure is at its maximum in the vertical 

 position. Fischer found, with a subject weighing 58-4 kg. that 

 the pressure varied from 70 kg to 77 kg, a mean increase of 25%. 

 Marey and Carlet measured the pressure on the feet by means of 

 " exploring shoes " ( 212), and found that, in walking, the 

 apparent increase of weight never exceeded 20 kg. But there 

 is also in walking, reaction from the ground, a tangential force, 

 represented by a negative value. Fischer found that its value 

 was 7 kg. at the moment when the rear leg was lifting. It 

 increased immediately to 

 16 kg. and remained at that 

 value during the duration 

 of the period of support. 

 Marey and Demeny used 



a " dynamographic stage " & '" \ /^^*~ ^ 



to measure the vertical and 



horizontal components of Fro. 232.1 



the pressure of the feet. N = perpendicular pressure. 



This apparatus Consists of H = tangential pressure. 



a stage resting on coils of = zero P osition of instrument. 



small rubber tube. The air which is expelled from them acting 



