hat sense is walking voluntary? In what sense is it reflex?

12. How does secondary reflex action lessen the work of the nervous
system?

13. State the special functions of the nerves, ganglia, spinal cord, bulb,
cerebellum, and cerebrum.

14. State the importance of the formation of correct habits.

[Fig. 143]

Fig. 143--Nerve board for demonstrating nerve pathways.

PRACTICAL WORK

*To demonstrate Nerve Pathways.*--A smooth board, 2x6 ft., is painted
black, and upon this is drawn in white a life-size outline of the body.
Pieces of cord of different colors and lengths are knotted to represent
mon-axonic and di-axonic neurons. These are then pinned or tacked to the
board in such a manner as to represent the connections in the different
kinds of nerve pathways. Fig. 143 shows such a board with connections for
a reflex action and a voluntary action of the same muscle.

*Study of the "Knee Jerk" Reflex.*--A boy is seated on a chair with the
legs crossed. With a small pointer he is given a light, quick blow on the
upper margin of the patella at the point of connection of the tendon. The
stroke will usually be followed by a reflex movement of the foot. Does
this take place independently of the mind? (The one upon whom the
experiment is being performed should assume a relaxed condition and make
no effort either to cause or prevent the movement.) Can the movement be
inhibited (prevented)? Repeat the experiment, effort being made to prevent
the movement, but not by contracting opposing muscles.

Other reflex actions adapted to class study are those of the eyes, such as
the closing of the lids on moving objects near them and the dilating of
the pupils when the eyes are shaded. The involuntary jerking of the head
on bringing the prongs of a vibrating tuning fork in contact with the end
of the nose is also a reflex action which can be studied to advantage.

*To determine the Reaction Time.*--Have several pupils join hands, facing
outwards, making a complete circle, excepting one gap. Give a signal by
touching the hand of one pupil at the end of the line. Let this pupil
communicate the signal, by pressure of the other hand, to the next pupil
and so on around, having the last pupil raise the free hand at close of
the experiment. Note carefully the time, preferably with a stop watch,
required to complete the experiment and divide this by the number of
pupils, to get the aver