understood. In other words, it gives the key to the liturgical and
mystical meaning of the psalm, with regard to the feast on which it
occurs" (_Cath. Encycl._, art. "Antiphon").

_Psalms._ In the Breviary, before the recent reform, twelve psalms were
recited in the first nocturn of Sundays and on ferias. This recitation
of twelve psalms was, Cassian tells us, caused by the apparition of an
angel, who appeared to the monks and sang at one session twelve psalms,
terminating with _Alleluia_. The event was mentioned at the Council of
Tours, In the new reform, nine psalms are recited at Matins; they
should, the old writers on liturgy tell us, remind us of the nine choirs
of angels who without ceasing sing God's praise.

In the new Psalter, the Psalms have been divided into two large
divisions, Psalms I.--CVIII. being assigned to the night Office, Matins;
and Psalms CIX.--CL. for the day Offices, Lauds to Compline. From this
latter division has been made:--

(1) a selection of psalms suitable by their character and meaning to
Lauds (_vide infra_, psalms at Lauds);

(2) a selection of psalms suitable to Compline;

(3) the psalms long used in the small Hours of Sunday's Office;

(4) the first psalms assigned by Pope Pius V. to Prime on Monday,
Tuesday, Wednesday, Thursday and Friday.

The remaining psalms are divided into seven groups, in simple numerical
order. The psalms of Matins generally come first, and are followed