Peter Lombard

"And because she is not given as slave-girl or as one to lord it over him, in the beginning she was not formed either from the highest part, nor from the lowest, but from the side of man, for the sake of conjugal partnership. If she had been made from the highest, as from the head, she might seem created for domination; but if from the lowest, as from the feet, she might seem to be created for subjection to slavery. But because she is taken neither as mistress, nor as slave-girl, she is made from the middle, that is, from the side, because she is taken for conjugal partnership."