springiness--by resorting to her favorite device, the use of muscular
engines. The arch is necessarily constructed of a number of bones which
can move on each other to a certain extent, so that the foot may adapt
itself to all kinds of roads and paths. It is true that the bones of the
arch are loosely bound together by passive ties or ligaments, but as
these cannot be lengthened or shortened at will, Nature had to fall back
on the use of muscular engines for the maintenance of the foot as an
arched lever. Some of these are shown in Fig. 8. The foot, then, is a
lever of a very remarkable kind; all the time we stand or walk, its
rigidity, its power to serve as a lever, has to be maintained by an
elaborate battery of muscular engines all kept constantly at work. No
wonder our feet and legs become tired when we have to stand a great
deal. Some of these engines, the larger ones, are kept in the leg, but
their tendons or piston cords descend below the ankle-joint to be fixed
to various parts of the arch, and thus help to keep it up (Fig. 8).
Within the sole of the foot has been placed an installation of seventeen
small engines, all of them springing into action when we stand up, thus
helping to maintain the foot as a rigid yet flexible lever.

We have already seen why our muscles are so easily exhausted when we
stand stock-still; they then get no rest at all. Now, it sometimes
happens in people who have to stand for long periods at a stretch that
these muscular engines which maintain the arch are overtaxed; the arch
of the foot gives way. The foot becomes flat and flexible, and can no
longer serve as a lever. Many men and women thus become permanently
crippled; they cannot step off their toes, but must shuffle along on the
inner sides of their feet. But if the case of the overworked muscles
which maintain the arch is hard in grown-up people, it is even harder in
boys and girls who have to stand quite still for a long time, or who
have to carry such burdens as are beyond their strength. When we are