In Communion, the wine or juice REPRESENTS Jesus' blood; the Cracker/Wafer REPRESENTS Jesus' broken body. You are correct that those who hold to transubstantiation DO wind up cannibalzing the Son of God (though I don't believe it takes place, so they're not, really). Most Protestants hold to the parts of communion as REMINDERS of what Christ has done for us. 'This do in REMEMBRANCE of Me.'