Inaugural Medical Dissertation on the Procreation of Male Offspring

the egg of a male fetus resists the spirit of the male seed more than that of a female (36.); therefore, the spirit acts upon and gives life to the former, rather than the latter. But when the plastic spirit A formative force believed to exist within the seed that directed the growth and shaping of the embryo. of the male seed is sufficiently vigorous and abundant, it then acts equally upon the egg of either fetus. However, because the initial structures of the male egg possess a greater receptivity to motion—which can be derived from the fact that the male egg is more swollen and filled with spirited liquor Vital fluids thought to carry the life force. than that of the female (for the male is generally warmer than the female, as noted in §. 34)—the leaping point original: "punctum saliens," a term used by Aristotle and later physicians to describe the first visible motion of the heart in a developing embryo. of the male egg receives motion more quickly and easily, even from an equal force, and begins to move. We see daily that men already born enjoy a greater activity of spirits and possess more strength, which depends upon those spirits. Indeed, anatomical observations original: "extispicia," here referring to the examination of fetal development or dissections. show that the male is completed and grows more quickly in the womb. From this, it also happens that twins of different sexes rarely survive; the male requires more nourishment and spirits for his growth, resulting in the female being deprived of them.

§. XXXVIII.

With this opinion established and so clearly set forth, all other theories on this matter—that is, regarding the power of fathering males—even those most ingeniously devised, collapse of their own accord like a mass resting on a weak foundation. Among these is the theory asserting that the difference in sex depends on the mother’s strong imagination. For the mother's imagination would have to change the parts of one sex into those of another, which is contrary to reason. Nor is an argument correctly drawn from maternal birthmarks original: "naevis maternis," marks or deformities once believed to be caused by a mother's intense cravings or fears during pregnancy., since the change occurring there is not essential to the nature of the child, but merely accidental. However, it is rightly claimed that because of the mother’s imagination and a stronger impression, a fetus may turn out to resemble either the father or the mother. Avicenna A Persian polymath (c. 980–1037) and one of the most significant physicians of the Islamic Golden Age; his works remained medical standards in Europe for centuries. did this when, in his Canon of Medicine, Book I, Canon 98, he said: original: "natus similis est illi, cuius imago intenta cogitatione tempore congressus fuit repraesentata." the newborn resembles the one whose image was represented by intense thought at the time of intercourse. This opinion proposed by Huarte Juan Huarte de San Juan (1529–1588), a Spanish physician known for his work on psychology and physiology. in his Examination of Men's Wits—and held by those who agree with him—is also the product of gross ignorance: namely, that the genitals of the male and female are the same, and are simply pushed outside the body due to a different degree of heat, or