Note 57 — BOOK I.

It was a very ancient practice of Christian worship to place the silver, or ivory dittici, upon the altars during the service of the mass, and when the sacred ceremony was over, they were folded up in the manner of a book, and taken elsewhere. The same figure was retained, even in the introduction of the largest altar pieces, which likewise consisted of two wings, and were portable. This custom, of which I have seen few remnants in Italy, has been long preserved in the Greek church. At length, by degrees, artists began to paint upon one whole panel. (See Buonarroti Vetri Antichi, p. 258, &c.)