To take another example of the association of ideas or the co-
ordination of mental images necessary to the production of speech,
let us suppose, for instance, that the child has been in the habit
of petting the dog and hearing him called by name "Dot" at the
same time. Now, if the dog be placed out of the child's sight and
yet in a position where the hand of the child can reach and pet
him in a familiar way, this sense of touch, like the sense of
sight, will set up a train of thought that results in the child
making his childish attempt to speak the name of the dog "Dot."

In other words the excitation of any sensory organs sets up a
series of sensory impulses which are transmitted along the sensory
nerve fibres to the brain, where they are referred to the
cerebellum or filing case, locating a set of associated impulses
which travel outward from the motor area of the brain and result
in the actions, or series of actions, which are necessary to
produce a word.

It will make the action of the brain clearer if the reader will
remember the sensory nerve fibres as those carrying messages only
TO the brain, while the motor nerve fibres carry messages only
FROM the brain.

To make still clearer this association of ideas so necessary to
the production of speech, suppose this same child hears the word
"Dot" spoken in his presence. He will, in all probability, begin
to repeat the word, and to search diligently for his pet dog. Thus
it will be seen that in this case the sound of the dog's name has
stirred up a train of mental images, one of these being a visual