In keeping with the suggestion in Hartmann's paper, The Technical Implications of Ego Psychology (1951), that 'technical progress might depend on a more systematic study of the various functional units within the ego', Zetzel presents a developmental model of the psychic apparatus relating early object relations to definitive aspects of ego structure and function. This is then related to psychoanalytic treatment. In psychoanalysis the therapeutic alliance that must first be established is equivalent to the relationship of the infant to the mother before structuralization of the psychic functions can take place. Further, just as psychic development contains both progressive and regressive manifestations at all stages, so progress in analysis involves controlled regression necessary to the mastery of conflict and increased adaptation. Finally, just as healthy development leads to independence and autonomy, a satisfactory termination of analysis implies the same.