The painting presents the Last Supper as a Catholic Mass. From
behind the table, St. John acts as an altar server, placing a
cruet of either wine or water beside the chalice. Both vessels are
of the type used in the Mass even today.
In front of the table, Jesus' left hand holds a paten (also
identical to those used in the divine service) while with his
right he distributes round, white hosts to the apostles, who are
kneeling as all communicants were required to do when receiving
the host. (This requirement ended only in the 20th century.)
Federico da Montefeltro stands on the right behind the kneeling
apostles. The boy behind him could be his son Guidobaldo.
More of the Last Supper
More of the apostles as a group
This image in full resolution