ng up three mental pictures--an auditory picture, or a picture
of the sound of the word; a graphic or visual picture, or a picture of
the appearance of salt and a third, which we have called a motor-memory
picture, which represents the muscular movements necessary to speak the
word. A little later on, after you had gone to school and learned to
write, you added to these pictures a fourth, the movements of the hand
necessary to write the word "salt."

At the sight of the mother, a child may, for instance, be heard to say
the word "Mom" while at the sight of the pet dog whose name is "Dot,"
be heard to say "Dot" in his childish way.

Here we have the first example in this child of the association of
ideas. The child has heard, repeatedly, the word "Mama" used in
conjunction with the appearance of the smiling face of his mother. Thus
has the child acquired the habit of associating the word "Mama" with
that face--and the sight of the countenance after a time recalls the
sound of the associated word. Thus a visual image of the mother
transmitted to the child through the medium of the eye, links up a
train of thought that finally results in the child's attempt to say
"Mama."

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