HOLY THURSDAY is the most complex and profound of all religious observances, saving only the Easter Vigil. It celebrates both the institution by Christ himself of the Eucharist and of the institution of the sacerdotal priesthood (as distinct from the 'priesthood of all believers') for in this, His last supper with the disciples, a celebration of Passover, He is the self-offered Passover Victim, and every ordained priest to this day presents this same sacrifice, by Christ's authority and command, in exactly the same way. The Last Supper was also Christ's farewell to His assembled disciples, some of whom would betray, desert or deny Him before the sun rose again.
On Holy Thursday there is a special Mass in Cathedral Churches, attended by as many priests of the diocese as can attend, because it is a solemn observance of Christ's institution of the priesthood. At this 'Chrism Mass' the bishop blesses the Oil of Chrism used for Baptism and Confirmation. The bishop may wash the feet of twelve of the priests, to symbolize Christ's washing the feet of his Apostles, the first priests.