nerve cells in the brain from which they come that the hand is being
burned. The cells which feel cannot do anything for the hand, but some
of their branches run over to another part of the brain, which sends
nerves down to the muscles of the arm. These cells, through their nerve
branches, cause the muscles to contract. The cells of feeling ask the
cells which have charge of the muscles to make the muscles of the arm
pull the hand away, which they do very quickly.

~17.~ So you see the nerves are very much like telegraph or telephone
wires. By means of them the brain finds out all about what is happening
in the body, and sends out its orders to the various organs, which may
be called its servants.

~18. An Experiment.~--A man once tried an experiment which seemed very
cruel. He took a dove and cut open its skull and took out its large
brain. What do you think the effect was? The dove did not die at once,
as you would expect. It lived for some time, but it did not know
anything. It did not know when it was hungry, and would not eat or drink
unless the food or water was placed in its mouth. If a man gets a blow
on his head, so hard as to break his skull, the large brain is often
hurt so badly that its cells cannot work, and so the man is in the same
condition as the poor dove. He does not know anything. He cannot think
or talk, and lies as though he were asleep.

~19.~ By these and many other facts we know that the large brain is the
part with which we remember, think, and reason. It is the seat of the
mind. We go to sleep because the large brain is tired and cannot work
any longer. We stop thinking when we are sound asleep, but sometimes we
do not sleep soundly, and then the large brain works a little and we
dream.