Now the opposite of the male is the female. . . . In human beings the male is much hotter in its nature than the female. On that account, male embryos tend to move about more than female ones, and owing to their moving about they get broken more, since a young creature can easily be destroyed owing to its weakness. And it is due to this self-same cause that the perfecting of female embryos is inferior to that of male ones. . . . We should look upon the female state as being as it were a deformity, though one which occurs in the ordinary course of nature.