to its later name.  Some diptychs which were used afterwards for ecclesiastical purposes, show signs of having had the Consular inscription erased, and the wax removed, while Christian sentiments were written or incised within the book itself.  Parts of the service were also occasionally transcribed on diptychs.  In Milan the Rites contain these passages:  “The lesson ended, a scholar, vested in a surplice, takes the ivory tablets from the altar or ambo, and ascends the pulpit;” and in another place a similar allusion occurs:  “When the Deacon chants the Alleluia, the key bearer for the week hands the ivory tablets to him at the exit of the choir.”

Anastatius, in his Life of Pope Agatho, tells of a form of posthumous excommunication which was sometimes practised:  “They took away from the diptychs... wherever it could be done, the names and figures of these patriarchs, Cyrus, Sergius, Paul, Pyrrhus, and Peter, through whom error had been brought among the orthodox.”

Among ivory carvings in Carlovingian times may be cited a casket with ornamental colonettes sent by Eginhard to his son.  In 823, Louis le Debonaire owned a statuette, a diptych, and a coffer, while in 845 the Archbishop of Rheims placed an order for ivory book covers, for the works of St. Jerome, a Lectionary, and other works.

The largest and best known ivory carving of the middle ages is the throne of Maximian, Archbishop of Ravenna.  This entire chair, with an arched back and arms, is composed of ivory in intricately carved plaques.  It is considerably over three feet in height, and is a superb example of the best art of the sixth century.  Photographs and reproductions of it may be seen in most works dealing with this subject.  Scenes from Scripture are set all over it, divided by charming meanders of deeply cut vine motives.  Some authorities consider the figures inferior to the other decorations:  of course in any delineation of the human form, the archaic element is more keenly felt than when it appears in foliate forms or conventional patterns.  Diptychs being often taken in considerable numbers and set into large works of ivory, has led some authorities to suppose that the Ravenna throne was made of such a collection; but this is contradicted by Passeri in 1759, who alludes to the panels in the following terms:  “They might readily be taken by the ignorant for diptychs....  This they are not, for they cannot be taken from the consular diptychs which had their own ornamentation, referring to the consultate and the insignia, differing from the sculpture destined for other purposes.  Hence they are obviously mistaken who count certain tablets as diptychs which have no ascription to any consul, but represent the Muses, Bacchantes, or Gods.  These seem to me to have been book covers.”  Probably the selected form of an upright tablet for the majority of ivory carvings is based on economic principles:  the best use of the most surface from any square block of material is to cut it in thin slices.  In their architecture the southern mediaeval builders so treated stone, building a substructure of brick and laying a slab or veneer of the more costly material on its surface:  with ivory this same principle was followed, and the shape of the tusk, being long and narrow, naturally determined the form of the resulting tablets.