Thomas Aquinas was almost entirely responsible for writing the Office of Corpus Christi, a feast officially instituted by Pope Urban IV. The introit was taken from Psalm LXXX, which prefigures the Eucharist: "And he fed them with the fat of wheat..."
Jean Colombe has shown Christ leaning forward from the waist to give communion to a kneeling apostle, probably Peter. Behind him, the younger beardless figure perhaps represents John. The others await their turn with joined hands.
The hall in which the ceremony takes place is decorated with rather unusual sculpture. Within a capital letter, Christ presents the Eucharist above a chalice that is related to the same communion.

small image (23KB) --- large image (212KB) --- Christ gives communion to Peter (large) (181KB) --- Initial letter with the escutcheon of the Duc of Savoie (large) (205KB)