“Running,” says one of our gymnasiarchs, “only differs from walking
by the rapidity of the movement.” This is quite incorrect. Running is
precisely intermediate to walking and leaping; and, in order to pass
into it from walking, the motion must be changed. A series of leaps
from each foot alternately must be performed, in order to constitute
it; the foot which is left behind quits the ground before the foot
in advance is firmly fixed, so that the centre of gravity remains
uncertain in passing from one leg to the other, which forms a series of
leaps, and renders a fall a common occurrence.