Page:Popular Science Monthly Volume 6.djvu/145

Rh curves of pressure of the four feet, drawn at two different levels: the uppermost are the curves of the anterior limbs; those below, of the posterior limbs. In each series the curves of the left foot are drawn with dotted lines, those of the right with full lines.

 —R A, reactions of the fore-limbs; R P, reactions of the hind-limbs. A G and A D, curves and notations of the fore-limbs; P D and P G, curves and notations of the hind-limbs.

The moment when the curve begins its rise represents the commencement of the pressure of the foot on the ground; the point at which the curve begins to descend represents the moment when the rise of the foot commences. It is seen from these tracings that the feet AG and PD, left fore-foot and right hind-foot, strike the ground at the same time. The simultaneous lowering of the curves of the two feet shows that they also rise from the ground simultaneously.