[Illustration]

THE MUSCLES.

THE USE OF THE MUSCLES.--The skeleton is the image of death. Its unsightly
appearance instinctively repels us. We have seen, however, what uses it
subserves in the body, and how the ugly-looking bones abound in nice
contrivances and ingenious workmanship. In life, the framework is hidden
by the flesh. This covering is a mass of muscles, which by their
arrangement and their properties not only give form and symmetry to the
body, but also produce its varied movements.

In Fig. 14, we see the large exterior muscles. Beneath these are many
others; while deeply hidden within are tiny, delicate ones, too small to
be seen with the naked eye. There are, in all, about five hundred, each
having its special use, and all working in exquisite harmony and
perfection.

CONTRACTILITY.--The peculiar property of the muscles is their power of
contraction, whereby they decrease in length and increase in thickness.
[Footnote: The maximum force of this contraction has been estimated as
high as from eighty-five to one hundred and fourteen pounds per square
inch.] This may be caused by an effort of the will, by cold, by a sharp
blow, etc. It does not cease at death, but, in certain cold-blooded
animals, a contraction of the muscles is often noticed long after the head
has been cut off.

ARRANGEMENT OF THE MUSCLES. [Footnote: "Could we behold properly the
muscular fibers in operation, nothing, as a mere mechanical exhibition,
can be conceived more superb than the intricate and combined actions that