The author discusses those aspects of the parent-infant relationship which interrelate with the maturational force inherent in the autonomous ego development of the infant during the first two years of life. The focus is almost exclusively on the biological beginnings of aggression as it is involved in skeletal

muscle maturation, and the relation of this to the development of the ego. The development of the libidinal phases has been thoroughly discussed elsewhere and is minimally dealt with here. Greenacre describes the intricate interrelationships between autonomous ego structure, maturation, environment, and ego development. The important period is that in which the foundation is laid for a healthy separation from the mother, the establishment of a sense of reality, of object relationships, secondary process thinking, and a sense of identity.