Theses medicae de divina et admiranda hominis in utero formatione

VII.
Through the union and intercourse of these, a certain matter is conferred, namely seed, in which their power and potency is contained, and from which something third is effected.

VIII.
This seed flows from both parents; yet it has a condition entirely different in the constitution of the fetus: for the male [seed] obtains the rationale partly of matter and partly of the efficient [cause], but the female [seed] obtains the rationale of matter alone.

IX.
That women emit seed can be taught chiefly by this reason, that they have received testicles and seminal vessels twisted with frequent bends and circuits; which, like nothing else, were certainly not created by nature in vain.

X.
Since this seed is only a passive principle and cannot effect anything by itself, it was not held as seed by Aristotle.

XI.
For seed is accepted in two ways by Aristotle: first for that fluid which is excreted by all who generate, from which as matter all spermatic parts are formed, and it is called by the philosopher sōma spermatikon spermatic body or hē gonēs the seed/generation, and hōrismēnon spermatikon determined spermatic [matter]: which we also say exists in women. Secondly, for the effective principle, which lies hidden in the mass of the seed itself: which Aristotle calls sometimes gonein to generate, sometimes gennētikēn generative, or plastikēn dynamin formative power, sometimes eidē kai logon spermatikon formative patterns and spermatic reason, and by other names. We establish with the philosopher that this exists only in men.

XII.
Therefore, when Aristotle says that the seed of the man is excreted and slips back into the womb, it is not to be understood of the former, which provides matter to the spermatic parts and is achōriston inseparable; but of this latter, which as an efficient [cause] does not enter into the constitution of the thing.

XIII.
Many dispute much about the generation and nature of the seed of women. Aristotle thinks it is nothing other than the useful excrement of the ultimate nourishment which was destined for the nutrition of individual parts. Hence it can produce from itself parts similar to those of which it was the excrement. For it is potentially such as that from which it was decided was actually.

XIV.
Others [maintain] it is not excrement, but a portion of purer and fatter...