t, seeing the end in the
beginning, and will be the means eventually of leading the body into its
greatest accomplishments.

*Summary.*--The nervous system, on account of its delicate structure, is
liable to injury through wrong methods of using it and also through the
introduction of drugs, or poisons, into the body. There are also found in
our methods of living and systems of education conditions that tend to
waste the nervous energy. To protect the nervous system from all these
threatened dangers requires, among other things, the power of
self-control. This enables the individual to direct his life according to
his highest ideals and to free himself from habits known to be injurious.
Children must have their nervous systems safeguarded by parents and
teachers. Especially must they be kept from becoming enslaved to some
drug, such as alcohol or the nicotine of tobacco.

*Exercises.*--1. In what respect is the hygiene of the nervous system the
hygiene of the entire body?

2. Of what value in the hygiene of the nervous system is the power of
self-control? How is the habit of self-control formed?

3. Name several forms of activity that waste the nervous energy.

4. Name several influences that react unfavorably on the nervous systems
of children.

5. How may too much reading prove injurious to the nervous system?

6. What forms of physical exercise are beneficial to the brain worker?

7. Why is the use of alcohol even in small quantities to be regarded as a
dangerous practice?

8. Name several causes of nervousness.

9. What are the unanswerable arguments for preventing the use of tobacco
by the young?

10. Why do cigarettes have a more harmful effect upon the body than other
forms of tobacco?

11. Enumerate conditions in the schoolroom that dissipate the nervous
energy of pupils; that economize it.

CHAPTER XX - PRODUCTION OF SENSATIONS

Our study of the nervous system has shown that impulses arising at the
surface of the body are able, through connecting neurons, to bring about
various activities. Moving along definite pathways, they induce motion in
the muscles, and in the glands the secretion of liquids. It is now our
purpose to consider the effect produced by afferent impulses upon the
brain and, through the brain, upon the mind.(114) This effect is
manifested in a variety of similar forms, known as

*The Sensations.*--Sensations constitute the lowest forms of mental
activity. Roughly spea