tructural or functional peculiarities of the
individual mind. The least modified form is that known as "talking to
one's self" or "thinking aloud." Here the speaker and the hearer are
identified in a single person, who may be said to communicate with
himself. More significant is the still further abbreviated form in which
the sounds of speech are not articulated at all. To this belong all the
varieties of silent speech and of normal thinking. The auditory centers
alone may be excited; or the impulse to linguistic expression may be
communicated as well to the motor nerves that communicate with the
organs of speech but be inhibited either in the muscles of these organs
or at some point in the motor nerves themselves; or, possibly, the
auditory centers may be only slightly, if at all, affected, the speech
process manifesting itself directly in the motor sphere. There must be
still other types of abbreviation. How common is the excitation of the
motor nerves in silent speech, in which no audible or visible
articulations result, is shown by the frequent experience of fatigue in
the speech organs, particularly in the larynx, after unusually
stimulating reading or intensive thinking.

All the modifications so far considered are directly patterned on the
typical process of normal speech. Of very great interest and importance
is the possibility of transferring the whole system of speech symbolism
into other terms than those that are involved in the typical process.
This process, as we have seen, is a matter of sounds and of movements
intended to produce these sounds. The sense of vision is not brought
into play. But let us suppose that one not only hears the articulated
sounds but sees the articulations themselves as they are being executed
by the speaker. Clearly, if one can only gain a sufficiently high degree
of adroitness in perceiving these movements of the speech organs, the
way is opened for a new type of speech symbolism--that in which the
sound is replaced by the visual image of the articulations that
correspond to the sound. This sort of system has no great value for most
of us because we are already possessed of the auditory-motor system of
which it is at best but an imperfect translation, not all the
articulations being visible to the eye. However, it is well known what
excellent use deaf-mutes can make of "reading from the lips" as a
subsidiary method of apprehending speech. The most important of all
visual speech s