par excellence the function of expression. It is further only a part of the position upon which the psychological theory of expression is based, that all movements are in so far expressive, and that details of expression and its relative fullness are matters of co-ordination. Now, this co-ordination has attained its ripest and most complex form, apart from speech, in movements of the hand. Upon this view it is easy to hold that right-handedness is a form of expressive differentiation of movement, and that it preceded speech, which is a further and more complex form of differentiation and adaptation.
The neurological basis upon which this hypothesis rests is adequate, and affords a presumption as to the psychological development as well. The facts I have now given, for the first time, go some way to support the view: 1. Right-handedness arose before speech in the child H. 2. Imitation by the hand of movements seen arise before articulate imitations of sounds heard;[1] this in spite of the fact that hearing, in its development in the child, becomes perfect before sight. 3. Characteristic differences in children in respect to their general mobility of arm and hand, manual skill, and quickness of manipulation, extend also to speech. As compared with my other child, E, the first-born, H, is remarkably agile and motile generally in her temperament; and her speech development was relatively much earlier and more rapid.
It is further interesting to note that musical ability is associated with speech ability—a connection which would be expected when one takes due account of the expressive character and function of music. As far as theories of the rise of musical expression have gone, they unite in finding its beginnings in the rudimentary emotional expressions of the animals. The singing of birds is undoubtedly connected with their mating instincts. Pathological cases also show a marked connection between musical execution and speech, to the extent that, while musical defect almost invariably involves speech defects, the reverse is much less generally true—a fact which confirms the view that music is an earlier form, but still a form, of expressive reaction.
Late observations also show, as far as they are sufficient, that the center for music expression is also located normally in the left hemisphere for right-handed persons. Oppenheim reports a case[2] of total aphasia with total amusia (lack of musical ability from disease) in which the recovery of speech brought with it musical recovery also. Furthermore, another case of Oppenheim's shows motor aphasia with motor amusia only—i. e., the
