For three years Michelangelo devoted himself almost exclusively to this work and from that period of vigour and maturity, of relative calm and satisfying accomplishment, came his most perfect piece of sculpture, the Moses. This statue, originally intended for one of the six colossal figures crowning the upper story of the tomb, in the end was itself the complete expression of the whole monument. The Moses is the older brother of the Prophets of the Sistine, sprung from the same vehement and passionate inspiration, but more commanding, more sure and more master of himself (we shall come upon him again at the completion of the work thirty years later, for Michelangelo was never tired of returning to him). The two Slaves[33] now in the Louvre, who were to be placed against the pilasters of the lower story, immortal symbols of the weariness of living and of the revolt against life,--the voluptuous hero with his beautiful body overcome by deadly torpor and the athlete, vanquished but unsubdued, who writhes in his bonds, "bent like a spring," gathering himself together and hurling his scorn into the face of heaven--both belong to this period. Probably the Caryatid of the Hermitage at St. Petersburg, which was certainly meant for one of the groups of conquerors in the niches, was made at this time as well as the models for many statues. The general subject of the monument according to Condivi and to Vasari who preserved the sayings of Michelangelo himself, was an allegory cold, abstruse and courtier-like, as we must admit the subjects of his undertakings very often were. His nature was timid and lacked independence, but fortunately the force of his passionate feeling carried everything before it. Vainly did he bind himself to lifeless and commonplace programs, vainly attempt to force himself to glorify the established order and the powers that be. At the very first step he took all false pretenses fell away and a furious cry of revolt against the baseness of the world and the bondage of life broke forth. So the statues of this monument which was to express with stale flattery that "all the virtues were prisoners of death now that the pope was dead" became, unconsciously perhaps to their creator, hymns of heroic scorn and expressions of moral grandeur crushed by force yet rising unconquered. But the peculiar quality of these figures compared with the work which was to follow is that they preserve in all their passionate agony a balance and a certain melancholy serenity which the artist of the tombs of the Medici no longer possessed.[34]