e forearm, requiring
the exertion of two units of strength. In this case the biceps must
exert two units of strength more than the triceps, that is, seven units.
In all, the two muscles together exert twelve units of strength to
accomplish the effective result of two units. Six times the needed
strength is exerted. Activity of this kind is naturally fatiguing.

Muscular stiffness increases the difficulty of complex movements. Not
only is unnecessary strength exerted; the stiffness of the joints also
interferes with the freedom and facility of motion. But this unfavorable
condition does not upset the power of coordination. The instinctive
connection between the nerve centers of consciousness and the motor
centers is not broken. Although hampered in their efforts, the muscles
are still able to execute the demands of consciousness.

As an illustration of this analysis of muscular stiffness let us
consider the actions of writing, when performed under the conditions
just described. It is possible to write with the hand and arm in a state
of muscular stiffness. But one does not write so easily, so rapidly, nor
so well with the arm stiff as with the arm normally relaxed. Closer
attention must be paid to the forming of the letters, and more effort
must be put forth to write with the muscles stiffened; yet the result is
not equal to that obtained with less care and labor under normal
muscular conditions.

All that has been said of muscular stiffness applies with especial force
to the vocal organs. Like the rest of the muscular system, the muscles
of the vocal organs are arranged in opposed pairs and sets. The
contraction of all the muscles of the throat, each opposed set or pair
exerting about the same degree of strength, causes a condition of
throat stiffness. Singing is possible in this condition. But the
singer's command of the voice is not so complete and satisfactory as
under normal conditions.

Throat stiffness does not altogether deprive the vocal organs of their
faculty of instinctive adjustment in obedience to the demands of the
ear. To a fair extent the voice is under the command of the singer. The
vocal cords adjust themselves readily enough for the desired pitch;
tones of the various degrees of loudness and softness can be sung in a
fairly satisfactory manner. But the muscles are somewhat hampered in
their contractions, and the response to the demands of the ear is not
quite perfect. This lack of perfect command