Page:First steps in mental growth (1906).djvu/39

, then another contraction followed by slow relaxation and so on—observed in J.'s first week when the child was crying in hunger. Random movements of the arms are most numerous, however, when the infant is lying comfortably in his crib, rolling the head from side to side, bending, stretching, and waving the arms without any purpose or apparent exciting cause.

The physiologist, as we have seen, relates these spontaneous movements to the lowest nerve centers of the spinal cord, medulla and pons, which, in the first weeks of life, are not related structurally by mature fibres to the higher centers of the brain. They are, in Burk's words, "the lowest level movements. They must represent the movements which are racially the oldest…they are movements without higher inhibition, movements as yet without halter or rein, and they tend to disappear just in proportion as the child's capability of executing voluntary movements develops." Yet it must be remembered that these movements, "the flotsam and jetsam of spinal activity "are the ultimate units, and constitute, according to the theory adopted here, an essential preliminary to voluntary movements. They furnish practice in muscle movement, and also a stock of sensations the memory of which serves as a guide when ideational movements arise.