It is worn by bishops, priests, deacons and subdeacons under the other eucharistic vestments, either at Mass or at functions connected with it.
It is worn girdled by bishops and priests in all rites, by subdeacons in the Greek and Coptic rites.
Taking the other orders downwards: deacons wear amice, alb, girdle, stole, maniple' and dalmatic; subdeacons, amice, alb, girdle, maniple and tunicle; the vestment proper to the minor orders, formerly the alb, is now the surplice or cotta.
These are 46 presbyters, 7 deacons, 7 subdeacons, 42 acolytes, 52 exorcists and readers, together with doorkeepers.
The subdeacons, no doubt, became a necessity when the deacons, whose number was limited to seven in memory of their original institution, were no longer equal to their duties in the " regions " of the imperial city, and left their lower work, such as preparation of the sacred vessels, to their subordinates.