77 This communication of the Spirit of Christ is the channel through which all the gifts, powers, and extra-ordinary 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 fulness 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.
Source: Mystici Corporis Christi (Vatican.va)