Empedocles affirms, that heat and cold give the difference in the generation of males and females. Hence is it, as histories acquaint us, that the first men originated from the earth in the eastern and southern parts, and the first females in the northern parts. Parmenides is of opinion perfectly contrariant. He affirms that men first sprouted out of the northern earth, for their bodies are more dense; women out of the southern, for theirs are more rare and fine. Hippo, that the more compacted and strong sperm, and the more fluid and weak, discriminate the sexes. Anaxagoras and Parmenides, that the seed of the man is naturally cast from his right side into the right side of the womb, or from the left side of the man into the left side of the womb; there is an alteration in this course of nature when females are generated. Cleophanes, whom Aristotle makes mention of, assigns the generation of men to the right testicle, of women to the left. Leucippus gives the reason of it to the alteration or diversity of parts, according to which the man hath a yard, the female the matrix; as to any other reason he is silent. Democritus, that the parts common to both sexes are engendered indifferently; but the peculiar parts by the one that is more powerful. Hippo, that if the spermatic faculty be more effectual, the male, if the nutritive aliment, the female is generated. CHAPTER VIII. BY WHAT MEANS IT IS THAT MONSTROUS BIRTHS ARE EFFECTED. Empedocles believes that monsters receive their origination from the abundance or defect of seed, or from its division into parts which are superabundant, or from some disturbance in the motion, or else that there is an error by a lapse into an unsuitable receptacle; and thus he presumes he hath given all the causes of monstrous conceptions. Strato, that it comes through addition, subtraction, or transposition of the seed, or the distension or inflation of the matrix. And some physicians say that the matrix suffers distortion, being distended with wind. CHAPTER IX. HOW IT COMES TO PASS THAT A WOMAN'S TOO FREQUENT CONVERSATION WITH A MAN HINDERS CONCEPTION. Diocles the physician says that either no genital sperm is projected, or, if there be, it is in a less quantity than nature requires, or there is no prolific faculty in it; or there is a deficiency of a due proportion of heat, cold, moisture, and dryness; or there is a resolution of the generative parts. The Stoics attribute sterility to the obliquity of the yard, by which means it is not able to ejaculate in a due manner, or to the unproportionable magnitude of the parts, the matrix being so contracted as not to have a capacity to receive. Erasistratus assigns it to the womb's being more callous or more carneous, thinner or smaller, than nature does require. CHAPTER X. WHENCE IT IS THAT ONE BIRTH GIVES TWO OR THREE CHILDREN.