“If we consider closely all these mysteries of the Cross, those words of the Apostle are no longer obscure, in which he teaches the Ephesians that Christ by His blood made the Jews and Gentiles one ‘breaking down the middle wall of partition . . . in his flesh’ by which the two peoples were divided; and that He made the Old Law void ‘that he might make the two in himself into one new man,’ that is, the Church, and might reconcile both to God in one Body by the Cross...
This communication of the Spirit of Christ is the channel through which all the gifts, powers, and extraordinary graces found superabundantly in the Head as in their source flow into all the members of the Church, and are perfected daily in them according to the place they hold in the Mystical Body of Jesus Christ. Thus the Church becomes, as it were, the filling out and the complement of the Redeemer, while Christ in a sense attains through the Church a fullness in all things. Herein we find the reason why, according to the opinion of Augustine already referred to, the mystical Head, which is Christ, and the Church, which here below as another Christ shows forth His person, constitute one new man, in whom heaven and earth are joined together in perpetuating the saving work of the Cross: Christ We mean, the Head and the Body, the whole Christ.”  Pope Pius XII, Mystici Corporis Christi