Mystici Corporis Christi §25

²⁵ In the course of the present study, Venerable Brethren, we have thus far seen that the Church is so constituted that it may be likened to a body. We must now explain clearly and precisely why it is to be called not merely a body, but the Body of Jesus Christ. This follows from the fact that our Lord is the Founder, the Head, the Support and the Savior of this Mystical Body.