The Head is the only begotten Son of God, the body is His Church; the bridegroom and the bride, two in one flesh. All who dissent from the Scriptures concerning Christ, although they may be found in all places in which the Church is found, are not in the Church; and again all those who agree with the Scriptures concerning the Head, and do not communicate in the unity of the Church, are not in the Church
Encyclical letter of Pope Leo XIII on the Unity of the Church, June 29, 1896, ch. 16, Publications of the Catholic Truth Society, 1896, London, Volume 30, p. 41. http://books.google.com/books?id=pYcQAAAAIAAJ&pg=PA41&dq=%22Head+and+the+body+are+Christ+wholly+and+entirely%22&hl=en&ei=6JVRToOwCYbKsQKKxvTHBg&sa=X&oi=book_result&ct=result&resnum=2&ved=0CC8Q6AEwAQ#v=onepage&q=%22Head%20and%20the%20body%20are%20Christ%20wholly%20and%20entirely%22&f=false
Alternate translation: The whole Christ is Head and Body. The Head, the only begotten Son of God; and His Body, the Church: the Bridegroom and the Bride, two in one flesh. Whosoever dissent from the Holy Scriptures in respect of the Head, even though they be found in all the places in which the Church is marked out to be, are not in the Church. And again, whosoever agree with the Holy Scriptures concerning the Head, and do not communicate with the unity of the Body, are not in the Church, because they dissent from Christ's own witness concerning Christ's Body, which is the Church.
Dr. Pusey, and the Ancient Church (1866), by Thomas W. Allies, Longmans, Green, London, p. 82 http://books.google.com/books?id=Cn-pxLKAcRIC&pg=PA82&dq=%22whole+Christ+is+Head+and+Body.+The+Head,+the+only-begotten+Son+of+God%22&hl=en&ei=gZZRTpHKDqmusQKQ8cnnBg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCoQ6AEwAA#v=onepage&q=%22whole%20Christ%20is%20Head%20and%20Body.%20The%20Head%2C%20the%20only-begotten%20Son%20of%20God%22&f=false
De Unitate Ecclesiae - On the Unity of the Church (c. 401 – 405)
