How do the muscles act? What causes the muscles to act? Do all muscles
act only when we will to have them act?

CHAPTER XXI. HOW TO KEEP THE MUSCLES HEALTHY.--What makes the
right arm of the blacksmith stronger than the left one? How should
exercise be taken? Mention some things in relation to the use of the
muscles which we ought not to do, and state the reasons why. What is the
effect of alcohol upon the muscles? of tobacco? of tea and coffee?

CHAPTER XXII. HOW WE FEEL AND THINK.--With what part of the
body do we think? How many brains does a man have? How is each brain
divided? Of what is the brain largely composed? Where do the nerves
begin? What is the spinal cord? Why does it cause pain to prick the
finger? How many kinds of nerves are there? (_Ans._ Two; nerves of
feeling and nerves of work.) Name some of the different kinds of nerves
of feeling? Name some of the different kinds of work controlled by the
nerves of work. Of what use to the body are the brain and nerves? How
does the brain use the nerves? Of what use is the large brain? What does
the little brain do? Of what use is the spinal cord?

CHAPTER XXIII. HOW TO KEEP THE BRAIN AND NERVES
HEALTHY.--Mention some things which we need to do to keep the brain
and nerves healthy. Mention some things which we ought not to do.

CHAPTER XXIV. BAD EFFECTS OF ALCOHOL UPON THE BRAIN AND
NERVES.--What is the effect of alcohol upon the brain and nerves?
Does alcohol produce real strength? Does it produce real warmth? Does
alcohol make people better or worse? What is the effect of tobacco upon
the brain and nerves? Does the use of tobacco lead to other evil habits?
What about the effect of opium and other narcotics?