[Illustration: Fig. 23.--Patella, or Knee-Cap.]

49. The Foot. The bones of the foot, 26 in number, consist of
the tarsal bones, the metatarsal, and the phalanges. The
tarsal bones are the seven small, irregular bones which make up the
ankle. These bones, like those of the wrist, are compactly arranged, and
are held firmly in place by ligaments which allow a considerable amount of
motion.

One of the ankle bones, the _os calcis_, projects prominently backwards,
forming the heel. An extensive surface is thus afforded for the attachment
of the strong tendon of the calf of the leg, called the tendon of
Achilles. The large bone above the heel bone, the _astragalus_,
articulates with the tibia, forming a hinge joint, and receives the weight
of the body.

The metatarsal bones, corresponding to the metacarpals of the hand,
are five in number, and form the lower instep.

The phalanges are the fourteen bones of the toes,--three in each
except the great toe, which, like the thumb, has two. They resemble in
number and plan the corresponding bones in the hand. The bones of the foot
form a double arch,--an arch from before backwards, and an arch from side
to side. The former is supported behind by the os calcis, and in front by
the ends of the metatarsal bones. The weight of the body falls
perpendicularly on the astragalus, which is the key-bone or crown of the
arch. The bones of the foot are kept in place by powerful ligaments,
combining great strength with elasticity.

[Illustration: Fig. 24.--Right Tibia and Fibula (Anterior surface.)]