rch forbade those who fast to partake of those foods which
both afford most pleasure to the palate, and besides are a very great
incentive to lust. Such are the flesh of animals that take their rest
on the earth, and of those that breathe the air and their products,
such as milk from those that walk on the earth, and eggs from birds.
For, since such like animals are more like man in body, they afford
greater pleasure as food, and greater nourishment to the human body,
so that from their consumption there results a greater surplus
available for seminal matter, which when abundant becomes a great
incentive to lust. Hence the Church has bidden those who fast to
abstain especially from these foods.

Reply Obj. 1: Three things concur in the act of procreation, namely,
heat, spirit [*Cf. P. I., Q. 118, A. 1, ad 3], and humor. Wine and
other things that heat the body conduce especially to heat: flatulent
foods seemingly cooperate in the production of the vital spirit: but
it is chiefly the use of flesh meat which is most productive of
nourishment, that conduces to the production of humor. Now the
alteration occasioned by heat, and the increase in vital spirits are
of short duration, whereas the substance of the humor remains a long
time. Hence those who fast are forbidden the use of flesh meat rather
than of wine or vegetables which are flatulent foods.

Reply Obj. 2: In the institution of fasting, the Church takes account
of the more common occurrences. Now, generally speaking, eating flesh
meat affords more pleasure than eating fish, although this is not
always the case. Hence the Church forbade those who fast to eat flesh
meat, rather than to eat fish.

Reply Obj. 3: Eggs and milk foods are forbidden to those who fast,
for as much as they originate from animals that provide us with
flesh: wherefore the prohibition of flesh meat takes precedence of
the prohibition of eggs and milk foods. Again the Lenten fast is the
most solemn of all, both because it is kept in imitation of Christ,
and because it disposes us to celebrate devoutly the mysteries of our
redemption. For this reason the eating of flesh meat is forbidden in
every fast, while the Lenten fast lays a general prohibition even on
eggs and milk foods. As to the use of the latter things in other
fasts the custom varies among different people, and each person is
bound to conform to that custom which is in vogue with those among
whom he is dwelling. Hence Jerome says [