"The Missal, or Mass Book, contains all the prayers said by the priest during the Holy Sacrifice. Most of these prayers are very ancient, coming down from the first ages of the Church. Mass is celebrated in Latin, not because this is essential, but because it secures uniformity of worship in all parts of the world; because modern languages are constantly changing in form and meaning; because Latin has come down to us from antiquity, thus showing the antiquity of the Mass, and reminding us that the faithful of today are assisting at the same divine service as the Christians of the first centuries. There can be no objection to the use of Latin by the priest: first, because the prayers he says are addressed to God; and secondly, because the people may follow what he is saying through the translations in their prayers books, or better in their Missals. From a literary and devotional viewpoint the Missal is one of the most beautiful books in the world; for its contents are made up of a great variety of the most excellent passages from the Old and New Testaments of Holy Scripture, and of most appropriate and elevating prayers composted by saints, doctors and liturgists of the Church. The Missal also embraces in outline the chief mysteries and doctrines of our holy faith, and is therefore a treasury of religious and moral instruction."
-The Catholic Sunday Missal, c. 1934