Among the innumerable superfluous, unintentional, random, muscular movements of the infant, the movements of the muscles of the larynx, mouth, and tongue take a conspicuous place, because they ally themselves readily with acoustic effects and the child takes delight in them. It is not surprising, therefore, that precisely those vibrations of the vocal cords, precisely those shapings of the cavity of the mouth, and those positions of the lips, often occur which we observe in the utterance of our vowels, and that among the child-noises produced unconsciously and in play are found almost all our consonants and, besides, many that are used in foreign languages. The plasticity of the apparatus of speech in youth permits the production of a greater abundance of sounds and sound-combinations than is employed later, and not a single child has been observed who has, in accordance with the principle of the least effort (_principe du moindre effort_) applied by French authors to this province, advanced in regular sequence from the sounds articulated easily--i. e., with less activity of will--to the physiologically difficult; rather does it hold good for all the children I have observed, and probably for all children that learn to speak, that many of the sounds uttered by them at the beginning, in the speechless season of infancy, without effort and then forgotten, have to be learned afresh at a later period, have to be painstakingly acquired by means of imitation. Mobility and perfection in the _technique_ of sound-formation are not speech. They come into consideration in the process of learning to speak as facilitating the process, because the muscles are perfected by previous practice; but the very first attempts to imitate voluntarily a sound heard show how slight this advantage is. Even those primitive syllables which the child of himself often pronounces to weariness, like _da_, he can not at the beginning (in the tenth month in my case) as yet say after any one, although he makes manifest by his effort--a regular strain--by his attention, and his unsuccessful attempts, that he would like to say them, as I have already mentioned. The reason is to be looked for in the still incomplete development of the sensori-motor central paths. In place of _tatta_ is sounded _tae_ or _ata_; in place of _papa_ even _tai_, and this not once only, but after a great many trials repeated again and again with the utmost patience. That the sound-image has been correctly apprehended is evident from the certainty with which the child responds correctly in various cases by gestures to words of similar sound unpronounceable by him. Thus, he points by mistake once only to the mouth (Mund) instead of the moon (Mond), and points correctly to the ear (Ohr) and the clock (Uhr) when asked where these objects are. The acuteness of hearing indispensable for repeating the sounds is therefore present before the ability to repeat.