The frontal lobes form the latest stage in the evolution of the brain. There has been much speculation as to their functions, and they have been described by some as biological luxuries and parasitic growths. It is, however, inconceivable that an organ appearing so late in the scheme of evolution should be completely devoid of function. Since the introduction of pre-frontal leucotomy evidence as to their function has been growing, and it may be said that the consensus of opinion now is that the frontal lobes are concerned with imagination, the social sense, self-consciousness, and the projection of the self into the future; these functions are synonymous with Freud's super-ego, so that, in fact, we may regard the frontal lobes as the seat of the super-ego.