Chapter 19 — Part II: The Sacraments — Penance
Section 58. By the holy Fathers it is also called compunction of heart, and hence they preferred to entitle their works on contrition treatises On Compunction of Heart; for as ulcers are lanced with a knife in order to allow the escape of the poisonous matter accumulated within, so the heart, as it were, is pierced with the lance of contrition, to enable it to emit the deadly poison of sin.