Itself contain the essential elements of speech. Many animals are capable of vocalisation, and in the child the utterance of vowel sounds is the next stage after the cry. The conditions necessary to the existence of speech arose with articulation, and it is intelligence that has converted the vocal instrument into the speaking instrument. For whereas correct intonation depends upon the innate musical ear, which is able to control and regulate the tensions of the minute muscles acting upon the vocal cords, it is intelligence which alters and changes the form of the resonator by means of movement of the lips, tongue, and jaw in the production of articulate speech. The simple musical instrument in the production of phonation is bilaterally represented in the brain, but as a speaking instrument it is unilaterally represented in right-handed individuals in the left hemisphere and in left-handed individuals in the right hemisphere. The reason for this we shall consider later; but the fact supports Darwin's hypothesis. Another hypothesis which was brought forward by Grieger and supported by some authors is summarised by Ribot as follows: "Words are an imitation of the movements of the mouth. The predominant sense in man is that of sight; man is pre-eminently visual. Prior to the acquisition of speech he communicated with his fellows by the aid of gestures and movement of the mouth and face; he appealed to their eyes. Their facial 'grimaces,' fulfilled and elucidated by gesture, became signs for others; they fixed their attention upon them. When articulate
