Theses medicae de divina et admiranda hominis in utero formatione

XXI.

Aristotle and Hippocrates sometimes call it gonē seed/procreation. The uterus embraces this from all sides and warms it with its own heat: yet this embrace is not yet truly called conception.

XXII.

A woman is said to have truly conceived when the power of procreation that lies hidden in the seed is excited to action by the innate power and faculty of the uterus. This is the proper action of the uterus, namely, to excite the dormant power of the seed that lies hidden within it, and to stimulate it to action.

XXIII.

There is disagreement even among the most learned regarding what that power is, and what kind of power it is, which lies hidden in the seed, and which the philosopher calls spermatikēn spermatic or gennētikēn generative. The Stoics thought it was the soul of the world; Simplicius called it common nature or the creating power. Others understand it as the sun, which, with its warmth, animates all the particles of our world prepared by secondary causes: whence Aristotle says: The sun and man generate a man. Aristotle says that something more divine corresponds to the elements and the proportion of the elements of the stars.

XXIIII.

Those seem to me to think piously who understand by dynamin plastikēn plastic power that divine power of procreation implanted by God in all living things, and attributed to each individual by His most effective word (Increase and multiply).

XXV.

This faculty uses heat and spirit as if they were instruments, by which, running through the entire mass of the seed, it first delineates and distinguishes all parts of the body in a rough fashion, like a certain painter.

XXVI.

And this is the first movement of the seed, by which it is brought into act, and that which was before dynamei in potentiality begins to become, namely, animated.

XXVII.

Individual parts are fashioned from a convenient and suitable material, namely, the nobler ones from the purest, and the ignoble ones from the less pure: for seed is by no means simple and homoiomeres composed of similar parts, but consists of dissimilar parts, according to the diversity of the generated parts.

XXVIII.

This distinction, however, does not occur through the segregation of dissimilar parts and