an begotten of such semen would be more akin to
the cow and the pig, than to his father or other relations.

Obj. 4: Further, Augustine says (Gen. ad lit. x, 20) that we were in
Adam "not only by seminal virtue, but also in the very substance of
the body." But this would not be, if the semen were produced from
surplus food. Therefore the semen is not produced therefrom.

_On the contrary,_ The Philosopher proves in many ways (De Gener.
Animal. i, 18) that "the semen is surplus food."

_I answer that,_ This question depends in some way on what has been
stated above (A. 1; Q. 118, A. 1). For if human nature has a virtue
for the communication of its form to alien matter not only in
another, but also in its own subject; it is clear that the food which
at first is dissimilar, becomes at length similar through the form
communicated to it. Now it belongs to the natural order that a thing
should be reduced from potentiality to act gradually: hence in things
generated we observe that at first each is imperfect and is
afterwards perfected. But it is clear that the common is to the
proper and determinate, as imperfect is to perfect: therefore we see
that in the generation of an animal, the animal is generated first,
then the man or the horse. So therefore food first of all receives a
certain common virtue in regard to all the parts of the body, which
virtue is subsequently determinate to this or that part.

Now it is not possible that the semen be a kind of solution from what
is already transformed into the substance of the members. For this
solution, if it does not retain the nature of the member it is taken
from, it would no longer be of the nature of the begetter, and would
be due to a process of corruption; and consequently it would not have
the power of transforming something else into the likeness of that
nature. But if it retained the nature of the member it is taken from,
then, since it is limited to a certain part of the body, it would not
have the power of moving towards (the production of) the whole nature,
but only the nature of that part. Unless one were to say that the
solution is taken from all the parts of the body, and that it retains
the nature of each part. Thus the semen would be a small animal in
act; and generation of animal from animal would be a mere division, as
mud is generated from mud, and as animals which continue to live after
being cut in two: which is inadmissible.

It remains to be said, there