ver, is compensated in increased velocity.

There are upward of four hundred muscles in the human body. Some of
these are _voluntary_ in their motions, as those I have described, while
others are _involuntary_, as the action of the heart and the respiratory
muscles. Had the action of these depended upon the will, as does the
action of the muscles of locomotion, the circulation of the blood and
the process of breathing would cease, and life would become extinct
whenever sleep or any other cause should overcome the attention. Here,
then, we have another beautiful illustration of the wisdom and
beneficence of the Creator in so ordering that those muscles which are
essential to the continuation of life shall perform their functions
without the control or attention of the individual.

The study of the muscular system involves an exposition of the
principles by which exercise should be regulated, and can scarcely fail
to excite the attention of the general reader, and especially of those
who, as parents or teachers, are interested in the education of the
young.

The muscles enable us to move the frame-work of the system. Their chief
purpose obviously is to enable us to carry into effect the various
resolutions and designs which have been formed by the mind. But, while
fulfilling this grand object, their active exercise is, at the same
time, highly conducive to the well-being of many other important
functions. By muscular contraction, the blood is gently assisted in its
course through the smaller vessels to the more distant parts of the
body; and by it the important processes of digestion, respiration,
secretion, absorption, and nutrition are promoted; and by it the health
of the whole body is immediately and greatly influenced. The mind itself
is exhilarated or depressed by the proper or improper use of muscular
exercise. It thus becomes a point of no slight importance to establish
general principles by which that exercise may be regulated.

In every part of the animal economy, the muscles are proportioned in
size and structure to the efforts required of them. Whenever a muscle is
called into frequent use, its fibers increase in thickness within
certain limits, and become capable of acting with greater force and
readiness. On the other hand, when a muscle is little used, its volume
and power decrease in a corresponding degree.

In order to secure the most beneficial results from exercise, reference
should be had to the t