capacity for any kind of work.

No ordinarily intelligent farmer doubts for a moment that all of this is
true in the breeding of stock. He would never expect the same results
from various breeds of cattle or even from all cattle of the same breed.

There is no exception to the rule that the whole life, with every
tendency, is potential in the original cell. An acorn will invariably
produce an oak tree. It can produce no other tree, and it will always
develop true to its own pattern. The tree may be larger or smaller, more
or less symmetrical, stronger or weaker, but always true to the general
pattern of the oak. Variations will be certain, due in part to heredity
and in part to environment.

That the baby had nothing to do with its equipment will readily be
admitted by everyone. The child is born with a brain of a certain size
and fineness. It is born with a nervous system made up of an infinite
number of fine fibers reaching all parts of the body, with fixed
stations or receivers like the central stations of a telephone system,
and with a grand central exchange in the brain. If one can imagine all
of the telephone wires in the world centered in one station, he may have
some sort of a conception of the separate nerves that bring impressions
to the brain and send directions out from it, which together make up the
nervous system of man. None of these systems is perfect. They are of all
degrees of imperfection down to the utterly useless or worse than
useless system. These nerves are of all degrees of sensitiveness and
accuracy in receiving and transmitting messages. Some may work well,
others imperfectly. No one is much surprised when an automobile,
equipped with a mechanism much simpler than the nervous system, refuses
to respond properly.