Running differs from walking principally in the fact that at a given moment the body leaves the ground, and passes through space in the same manner as a projectile. The body is inclined more forward, and the centre of gravity is lower than when walking. The lower limbs execute the same alternate movements as in the first mode of progression; but at the moment when the right leg leaves the ground and commences its demi-oscillation, the left, which is bent and only touches the ground at the extremity of the foot, pushes rapidly forward, and with sufficient force to throw the body upward and forward, and the two legs oscillate together during an instant, then the one which left the ground first falls before the other on the point of the toes. The body has made a spring, and the same manoeuvre takes place alternately on each side, and the result is a succession of springs which constitute running.