les firm to the touch and the body
in a vigorous condition.

Of the many forms of exercise from which one may choose, the question is
again one of individual adaptability and convenience. While the different
forms of exercise vary in their effects and may be made to serve different
purposes, the consideration of these is beyond the scope of an elementary
text. As a rule one will not go far wrong by following his inclinations,
observing of course the conditions under which exercise is taken to the
best advantage.

*General Rules for Healthful Exercise.*--That exercise may secure the best
results from the standpoint of health, a number of conditions should be
observed: 1. It should not be excessive or carried to the point of
exhaustion. Severe physical exercise is destructive to both muscular and
nervous tissues. 2. It should, if possible, be of an interesting nature
and taken in the open air. 3. It should be counter-active, that is,
calling into play those parts of the body that have not been used during
the regular work.(88) 4. It should be directed toward the weak rather than
toward the strong parts of the body. 5. When one is already tired from
study, or other work, it should be taken with moderation or omitted for
the time being. (For exercise of the heart muscle and the muscular coat of
the blood vessels see pages 55 and 57.)

*Massage.*--In lieu of exercise taken in the usual way, similar effects are
sometimes obtained by a systematic rubbing, pressing, stroking, or
kneading of the skin and the muscles by one trained in the art. This
process, known as massage, may be gentle or vigorous and is subject to a
variety of modifications. Massage is applied when one is unable to take
exercise, on account of disease or accident, and also in the treatment of
certain bodily disorders. A weak ankle, wrist, or other part of the body,
or even a bruise, may be greatly benefited by massage. The flow of blood
and lymph is stimulated, causing new materials to be passed to the
affected parts and waste materials to be removed. Massage, however, should
never be applied to a boil, or other infected sore. The effect in this
case would be to spread the infection and increase the trouble.

*Summary.*--Motion is provided for in the body mainly through the muscle
cells. These are grouped into working parts, called muscles, which in turn
are attached to the movable parts of the body. The striated muscles, as a
rule, are attached to the mec