The author stresses the importance of the muscular system in the development of early ego functions. By producing motion, the muscles contribute to the differentiation of self from non-self; by movement, the infant is able to discover gratifications and disappointments; by coördination, skill is developed which brings a sense of power. Sprague also emphasizes the smooth muscles of the larynx and their importance for speech. He points out that the striped muscles always remain personalized, while the smooth may become impersonalized and externalized. In regression all phases, the development of muscular sensitivity and activity are of importance. There are no references to the psychoanalytic literature on this subject.