Irenaeus, Bishop of Lyons, (early 100's AD) used the following depictions for the 4 Gospels:
MATTHEW:Lion
Christ as the Royal Power
MARK:Calf
Christ as the Sacrificial Order
LUKE:Human Face
Christ's Advent as a Human
JOHN:Eagle
Christ as the Gift of the Spirit over the Church
And the Word was made flesh, and dwelt among us, (and we beheld his glory, the
glory as of the only begotten of the Father,) full of grace and truth.
John 1:14