St. Jerom, in strong but indiscreet language, expresses the most important use of fasting and abstinence:
"Non quod Deus universitatis Creator et Dominus, intestinorum
nostrorum rugitu, et inanitate ventris, pulmonisque ardore
delectetur, sed quod aliter pudicitia tuta esse non possit."
(Op. tom. i. p. 137, ad Eustochium [Ep. 22, tom. i. p. 94,
ed. Vallars.].)
See the twelfth and twenty-second Collations of Cassian, de Castitate and de Illusionibus Nocturnis.