towards the desired end of communication.  The lungs developed, roughly speaking, in connection with the necessary biological function known as breathing; the nose, as an organ of smell; the teeth, as organs useful in breaking up food before it was ready for digestion.  If, then, these and other organs are being constantly utilized in speech, it is only because any organ, once existent and in so far as it is subject to voluntary control, can be utilized by man for secondary purposes.  Physiologically, speech is an overlaid function, or, to be more precise, a group of overlaid functions.  It gets what service it can out of organs and functions, nervous and muscular, that have come into being and are maintained for very different ends than its own.

It is true that physiological psychologists speak of the localization of speech in the brain.  This can only mean that the sounds of speech are localized in the auditory tract of the brain, or in some circumscribed portion of it, precisely as other classes of sounds are localized; and that the motor processes involved in speech (such as the movements of the glottal cords in the larynx, the movements of the tongue required to pronounce the vowels, lip movements required to articulate certain consonants, and numerous others) are localized in the motor tract precisely as are all other impulses to special motor activities.  In the same way control is lodged in the visual tract of the brain over all those processes of visual recognition involved in reading.  Naturally the particular points or clusters of points of localization in the several tracts that refer to any element of language are connected in the brain by paths of association, so that the outward, or psycho-physical, aspect of language, is of a vast network of associated localizations in the brain and lower nervous tracts, the auditory localizations being without doubt the most fundamental of all for speech.  However, a speechsound localized in the brain, even when associated with the particular movements of the “speech organs” that are required to produce it, is very far from being an element of language.  It must be further associated with some element or group of elements of experience, say a visual image or a class of visual images or a feeling of relation, before it has even rudimentary linguistic significance.  This “element” of experience is the content or “meaning” of the linguistic unit; the associated auditory, motor, and other cerebral processes that lie immediately back of the act of speaking and the act of hearing speech are merely a complicated symbol of or signal for these “meanings,” of which more anon.  We see therefore at once that language as such is not and cannot be definitely localized, for it consists of a peculiar symbolic relation—­physiologically an arbitrary one—­between all possible elements of consciousness on the one hand and certain selected elements localized in the auditory, motor, and other cerebral and nervous tracts on the other.  If