re peculiarly
different. In a later chapter we shall consider these differences; let
us here consider the points of similarity.

The fact that a boy is a boy makes him heir to all of the
characteristics that man has developed. These characteristics are his
birthright. He responds in a particular way to stimuli because the race
before him has so responded. There is no need here of entering into a
discussion as to how great a controlling factor heredity may be in a
man's life, or how potent environment may be in modifying that life--we
are concerned rather with the result--that man is as he is. It is
essential that we know his characteristics, particularly as they
manifest themselves in youth, so that we may know what to expect in his
conduct and so that we may proceed to modify and control that conduct.
Just as the first task of the physician is to diagnose his case--to get
at the cause of the difficulty before he proceeds to suggest a
remedy--so the first consideration of the teacher is a query, "Whom do I
teach?"

Man may normally be expected to respond in a particular way to a
particular stimulus because men throughout the history of the race have
so responded. Certain connections have been established in his nervous
system and he acts accordingly--he does what he does because he is
_man_. We cannot here go into a detailed discussion of the physiological
processes involved in thinking and other forms of behavior, but perhaps
we may well set down a statement or two relative to man's tendencies to
act, and their explanations:

"The nervous system is composed of neurones of three types: Those
that receive, the afferent; those that effect action, the efferent;
and those that connect, the associative. The meeting places of these
neurones are the synapses. All neurones have the three
characteristics of sensitivity, conductivity, and modifiability. In
order for conduct or feeling or intellect to be present, at least two
neurones must be active, and in all but a few of the human activities
many more are involved. The possibility of conduct or intelligence
depends upon the connections at the synapses,--upon the possibility
of the current affecting neurones in a certain definite way. The
possession of an 'original nature,' then, means the possession, as a
matter of inheritance, of certain connections between neurones, the
possession of certain synapses which are in functional contact an