thing about as well as another, just as the high-grade boys and
girls can do one thing about as well as another; but in the former
there is a limit to the possible development which is exceeded in
the latter. Among both classes of children the full development
depends upon suitable environment, but what is suitable for one may
not be suitable for the other.

From a consideration of these differences in degree and difference
in kind we may see that there is no course of training or treatment,
no method of instruction, no trick for the mother or for the teacher
that will be usable for all children under all circumstances, to
make them all come up to some preconceived uniform standard. On the
other hand, if we consider the differences as worth developing, and
even emphasizing, it must be obvious that the training and the
treatment should be adapted to the individual child so far as
possible. Starting out with essentially different human beings,
uniform treatment will not make them all alike, nor will _any_
treatment make them all alike. But starting out with a particular
human being, we can learn to treat him in such a way as to make him
develop into a more desirable person than he would become if he were
neglected or if he were treated differently. And that is the main
problem, after all.

The relation between heredity and environment may perhaps be made
clear by an extreme illustration from the physical side. Here are
two full-grown men, both five feet and four inches tall. We observe
that they are both short. Now, the shortness of one of them turns
out to be the result of heredity,--that is, he belongs to a strain
of short people. No amount of feeding or of exercise or of special
régime could have made him more than a quarter or half an inch