awareness through movement

42 AWARENESS THROUGH MOVEMENT
are mainly inherited, by contrast with the Rhinic system described
above, which is entirely inherited and remains unchanged from individual
to individual, except in cases of basic evolutionary changes.
Instincts are not as stationary and definite as we often think; they
vary, and there are small instinctual differences between individuals.
In some cases the instinct is weak, and a certain amount of individual
experience is needed for action to proceed, as where, for instance,
a newborn child fails to suck until its lips are stimulated with
the nipple. In some cases, instinct permits a fair degree of adjustment
to circumstances and the first hint of ability to change with a
changing environment is found—in short, the birth or dawn of the
ability to learn. Thus, for instance, birds accustom themselves to
building nests of new materials when they are moved to strange surroundings.
But the adjustment is difficult, and not all individuals succeed
equally well; some do not manage to adjust at all. The adjustment
of instincts to the demands of new surroundings may go so far
as to approach what we are accustomed to call understanding and
learning.
Fine differentiation is a human prerogative
A third group of structures of the brain is concerned with activities
that distinguish man from animals. This is the Supralymbic system,
which is much more highly developed in man than in any of the higher
animals. It is this system that assures the delicate differentiation of the
muscles of the hand, thereby multiplying the possible number of patterns,
rhythms, and shades of any operation. This system turns the
human hand into an instrument capable of playing music, drawing,
writing, or doing many other activities. The Supralymbic system imparts
an equal sensitivity to the muscles of the mouth, throat, and breathing
apparatus. Similarly, here the power of differentiation multiplies the
number of different sound patterns that it is possible to produce, resulting
in the creation of hundreds of languages and a great variety of ways
of singing and whistling.