cle he clutches the
handle bars in a vise-like grip. His knees are so stiff as to bend only
with a great exertion of strength. To steer the wheel the learner must
put forth his most powerful muscular efforts. A half-hour lesson in
bicycle riding often tires the beginner more than an afternoon's ride
does the experienced cyclist.

This condition of muscular stiffness is due to the contraction of
antagonist groups of muscles, involving practically the entire body. In
one sense the excessive muscular contractions are involuntary; yet it
would not be easy to define where the voluntary element of the
contractions leaves off.

A similar excessive expenditure of strength may be seen in the attempt
of an illiterate laborer to sign his name. He grips the pen as though it
were a crowbar, and puts forth enough strength to handle a twenty-pound
weight. Learning to dance, or to skate, or to row a boat, is usually
accompanied in the beginning by this form of muscular stiffness.

As skill is acquired by practice in the performance of complex
activities, the undue muscular tension of the initial stage is gradually
relaxed.

There is another way in which the radiation of nerve impulse may be
caused, entirely distinct from the lack of use or skill. Muscular
stiffness may be induced in the case of activities so thoroughly
habitual as to be normally performed automatically. The cause of
muscular stiffness now to be considered is the attempt to perform
complex activities mechanically, that is, by consciously directing the
individual component movements and muscular contractions involved in the
actions. Involuntary contractions of associated and antagonist muscles
take place under these conditions, in addition to the voluntary exercise
of the muscles normally exerted in the movements.

This fact may be illustrated by attempting to write a few lines, and
forming every stroke of each letter by a distinct exercise of the will.
If you keep up this attempt for ten minutes you will find that you press
upon the paper with many times your accustomed weight. The hand stiffens
in consequence of the close attention paid to its movements. This
stiffness will extend to the arm, and even to the shoulder, if the
exercise be continued long enough and with sufficient intensity of
attention to the hand.

Another good illustration of this form of muscular stiffening may be
found by walking upstairs, and paying the same kind of attention to the
muscular