It is St.Paul who develops extensively this theme and represents Jesus Christ as an immense organism, a body, of which Jesus is the Head and men the various members (Epistles to Corinthians, Colossians, Ephesians, and Romans). Christ the Incarnate Word is the New Adam, Head of humanity which is redeemed in Him, and He constitutes with it a body, which is the mystical Christ. This Body in a large sense embraces all mankind, because Christ died for the salvation of all, but in a strict sense, it is the Church, which man enters through Baptism, to be ingrafted onto Christ and thus participate in the super-natural life, which flows from the Head into the members by the action of the Holy Spirit, who is the soul of the Mystical Body. The unity of this organism is so real and deep that St.Paul does not hesitate to say (Gal 3:28) “You are all one in Christ”, as St.Thomas translates, you are with Christ one sole mystical person. Here “mystical” is not opposed to real, but stands for a supernatural reality, although not a physical one. Christ in us, is for St.Paul the great mystery that God reveals in the Gospel: through it we live in Christ, who continues in us His passion, death, and resurrection. On this mystery rest the Redemption and the Church.
I can not immediately recall the saint or saints that have taken on the sufferings of someone specifically, and they were cured. The latest canonized saint that could fit into this category is St.Padre Pio. From the testimonies of different witnesses, and his responses one is led to believe that he took on their sufferings. He certainly took on the sufferings of Christ Himself, by his own admission. The sufferings of many faithful, especially in the lives of the Saints manifest this partaking of suffering for the sake of humanity in union with Christ and His suffering. Perhaps our Book Club members can supply some of the specifics of Saints who took on the sufferings of individuals. Many years have passed, and so has some of my memory.