Born at Venice, of the patrician family of Emiliani, Jerome unreservedly gave himself up to the influence of divine grace "which on the ruins of the corrupt man, raised him as a new man made in the image of God" (Secret). Filled with the Spirit of adoption, which makes us children of the Father, he was chosen by heaven to be the Father of orphans and of the poor (Collect). As Jesus had asked the young man in the Gospel to do, he left everything and, like his Master, made little children come unto him (Gospel). He founded at Somascha, between Milan and Bergamo, a Congregation whose object was to educate youth in orphanages and colleges. Wherefore the Introit, applying to him the words of Jeremias, shows him full of compassion for children who, thanks to him, learned to praise the Lord. Dividing his bread with those who were hungry, and covering the naked, he opened asylums for the poor and gave them abundant alms with the help of the nobility of Pavia and Milan (Epistle, Gradual, Alleluia).
He died of the plague in 1537, having borne on his shoulders the plague-stricken to their burial place (Offertory).
Let us have recourse to the Father of mercies so that we may be filled like St. Jerome, with holy charity for the poor and for children.
Effusum est in terra jecur meum super contritione filiae populi mei, cum deficeret parvulus et lactens in plateis oppidi. * Laudate, pueri, Dominum: laudate nomen Domini.
My liver is poured out upon the earth, for the destruction of the daughter of my people, when the child and the suckling fainted away in the streets of the city. * Praise the Lord, ye children: praise ye the name of the Lord.
(Lamentations 2:11 and Psalm 112:1 from the introit of Mass)
Deus, misericordiarum pater: per merita et intercessionem beati Hieronymi, quern orphanis adjutorem et patrem esse voluisti: concede; ut spiritum adoptionis, quo filii tui nominamur et sumus, fideliter custodiamus.
O God, the Father of mercies, grant, by the merits and prayers of blessed Jerome, whom Thou didst raise up to be the father and helper of orphans, that we may faithfully keep the spirit of adoption, whereby we are both in name and in deed Thy children.
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/08343a.htm