Four Creatures

At the begining of Mass the Book of the Gospel is often processed into the church and placed on the alter. The book is often decorated with four symbolic creatures; angel, lion, ox, and eagle. These symbols come from the visions of the prophet Ezekiel and the Revelation of St John. The book of Revelation describes:

In the center and around the throne, there were four living creatures covered with eyes in front and in back. The first creature resembled a lion, the second was like a calf, the third had a face like that of a human being, and the fourth looked like an eagle in flight. The four living creatures, each of them with six wings, were covered with eyes inside and out. Day and night they do not stop exclaiming: “Holy, holy, holy is the Lord God almighty, who was, and who is, and who is to come.”
 
In our tradition these creatures are associated with the authors of the four gospels; St Matthew with the angel, St Mark with the Lion, St Luke with the Ox, and St John with the Eagle.  This tradition goes back to the early centuries of the Church. These depictions have been common in the Latin West and can be found in the famous Book of Kells, or the Psalter pictured above from around the year 1200, along with many Gospel Books used today.
 
The voice of a lion crying out in the wilderness became associated with St Mark’s Gospel because that is how his gospel begins, with John the Baptist preaching from the desert that now is the time to prepare for the Lord is coming. St Matthew first laid out the human geneology of Christ and so the human face has become linked to that narrative. St. Luke started his narrative with Zechariah a priest of the Jerusalem Temple and father of John the Baptist. The image of the Ox evoked temple sacrifices and the priestly origin of the Baptist. St. John had a soaring view of who Christ was which he decribed in his prologue and thus was associated with the symbol of the eagle.