flexibility and strength of opposition, and the fingers grow more
mobile and controllable. As the body slowly assumes the vertical
attitude, the form of the chest changes till its greatest diameter is
transverse instead of from front to back. The shoulder-blades are less
parallel than in quadrupeds, and spread out till they approximate the
same plane. This gives the arm freedom of movement laterally, so that
it can be rotated one hundred and eighty degrees in man as contrasted
to one hundred degrees in apes, thus giving man the command of almost
any point within a sphere of which the two arms are radii. The power
of grasping was partly developed from and partly added to the old
locomotor function of the fore limbs; the jerky aimless automatisms,
as well as the slow rhythmic flexion and extension of the fingers and
hand, movements which are perhaps survivals of arboreal or of even
earlier aquatic life, are cooerdinated; and the bilateral and
simultaneous rhythmic movements of the heavier muscles are
supplemented by the more finely adjusted and specialized activities
which as the end of the growth period is approached are determined
less by heredity and more by environment. In a sense, a child or a man
is the sum total of his movements or tendencies to move; and nature
and instinct chiefly determine the basal, and education the accessory
parts of our activities.

The entire accessory system is thus of vital importance for the
development of all of the arts of expression. These smaller muscles
might almost be called organs of thought. Their tension is modified
with the faintest change of soul, such as is seen in accent,
inflection, facial expressions, handwriting, and many forms of
so-called mind-reading, which, in fact, is always muscle-reading. The
day-laborer of low intelligence, with a practical vocabulary of not
over five hundred words, who can hardly move each of his fingers