s of ice. And, to particularize still more, it would be
necessary for him to learn how to pass different liquids. Water and
thick molasses in pails should not be handled alike.

Similarly the various brain centers, as passers of different sense
impressions and mental reflexes in and out, require, each of them--like
Jones--the _specific_ exercises that will develop _their several
particular_ abilities. The _individual brain unit_ (as of courage,
memory, judgment, etc.) is strengthened only by handling the in and out
business of _its_ coordinated muscles and mind center. Also, while a
particular set of muscles and coordinate mind center are strengthening
their brain center by the exercise they give _it_, they are both being
developed by the same exercise of passing along sense impressions and
thoughts to each other through the brain--like Smith and Brown.

[Sidenote: The Process Of Growth]

Returning to the comparison of Burbank's methods with man development,
we perceive again how the principle of discriminative-selective training
is applied to accomplish the growth of certain characteristics needed
to assure a man's success. The plant wizard in his initial tests gave
to his undeveloped prune trees particular food and conditions and
treatment selected for the purpose of imparting specific qualities of
deliciousness. A prune _somewhat improved_ in deliciousness was
the first result. Then from the product of that _improved_ prune
he started _another_ cycle of development. He fed the selected food
of deliciousness to the improved prune tree, and a fruit _more_
delicious resulted. His work was simply plant breeding by the
discriminative-restrictive method. Brain breeding is a similar process
of _particularized, cumulative_ development.

[Sidenote: Begin With Specific Training of The Outer Man]

All the foregoing rather complicated explanation of "psychological
processes" has seemed necessary to make a clear impression of the _right
training methods_ for building within you any quality you need to assure
your success. You must begin by training your _outer_ man.

You can develop a particular mind-brain center (such as the center of
courage) only by the discriminative-restrictive training of those
portions of your _body_ which are directly related in activity and
responsiveness to that mind-brain unit of the multiplex YOU. Training of
_any other_ set of muscles will not develop the particular mind-brain
center you want t