Antiphonarium. There were not standard editions of these old books, and
great diversities of use and text were in existence.

_Divisions of the Divine Office_.--How is the daily Office divided?
The Office is divided into the night Office and the day Office. The
night Office is so called because it was originally recited at night.
It embraces three nocturns and Lauds. The day Office embraces Prime,
Terce, Sext, None, Vespers, and Compline.

_Parts or Hours of the Office_.--How many parts or hours go to make
up the Office? Rome counts seven, and seven only; and this is the number
commonly counted by liturgists and theologians. They reckon Matins and
Lauds as one hour.

The old writers on liturgy ask the question: "Why has the Church
reckoned seven hours only?" Their replies are summarised well by
Newman: "In subsequent times the hours of prayer were gradually
developed from the three or (with midnight) the four seasons above
enumerated to seven, viz.:--by the addition of Prime (the first hour),
Vespers (the evening), and Compline (bedtime) according to the words of
the Psalm--'Seven times a day do I praise thee, because of thy righteous
judgments.' Other pious and instructive reasons existed, or have since
been perceived, for this number. It was a memorial of the seven days of
creation; it was an honour done to the seven petitions given us by our
Lord in His prayer; it was a mode of pleading for the influence of that
Spirit, who is revealed to us as sevenfold; on the other hand, it was a
preservative against those seven evil spirits which are apt to return to
the exorcised soul, more wicked than he who has been driven out of it;
and it was a fit remedy of those successive falls which, scripture says,
happen to the 'just man' daily." (_Tracts for the Times_, No. 75.