unit_ of the multiplex man. Then, of course, all his units should be
taught to work _together_ to make his success certain with his
all-around capability fully developed and coordinated.

[Sidenote: The Discriminative-Restrictive Method]

Luther Burbank worked out "discriminative-restrictive" methods of growth
that may be applied as successfully to men as to plants. He could not
have built up the ability of a prune tree to produce _delicious_ fruit
if he had not fed into the tree structure, or instrument of production,
a sufficient quantity and high quality of the _particular plant foods of
deliciousness_. He restricted his experimental prune trees to the
development of specific delicious qualities, by giving them no food
except that _discriminatively_ selected for his purpose. That is, he
made them develop in one way and in one way only, when he was making a
particular test.

Similarly, as has been stated before, you can develop the specific _man_
qualities you need to succeed. You must _feed_ to a particular mind
center, through the related brain center, _selected sense impressions_.
These can come only from the coordinated set of _muscles_ governed by
that mind-brain center. Then you should _exercise_ the specific brain
center and set of muscles in the production of mental reflexes, or the
mind fruit. Acts of courage, for example, are the fruit of brave
thoughts.

[Sidenote: Brain Development]

A particular brain center, of course, will be strengthened both by the
_food_ of sense impressions it is given, and by the _exercise_ of
handling messages to and from the mind. The brain, or physical
instrument of the mind, is like an intermediary or go-between of the ego
and the body. It is of the utmost importance that it should do its work
efficiently. Otherwise the full capability of neither the outer nor the
inner man can be utilized.

If Brown passes something to Jones, who passes it along to Smith; then
Smith passes it back to Jones to be re-passed to Brown--Jones, the
middle