Whether only women suffer menstruation.
Further one inquires whether only women suffer menstrua-tion.
1. And it seems not, because the menses are a superfluity of the blood. But this can appear in men just as in women, and therefore, etc.
2. In addition, every viviparous animal [animal productivum sui similis] has some part of itself on which the fetus is nourished. This is the menses, and therefore, etc.
Moreover, that which is converted into menses in a woman is turned into claws, horns, and other such superfluities in other animals, such as brute beasts. But it can happen that it is not converted into things like this. Therefore, it is necessary that their matter be converted into menses.
The Philosopher says the opposite.
One must reply that the menses are a superfluity of the blood, and their color demonstrates this. This is caused by an undigested moisture flowing from individual members to the vessels for the blood. Thus the menses are caused by individual members, just as semen is. But moistures of this sort in the man are consumed owing to the excellence of his heat, and this is why there are no menses in the man. In the same way that part of the menses which is converted into parts of the fetus, and that part on which the fetus is nourished in the uterus, and that part which is converted into milk in the breasts, exist in individual animals. But that part of the menses that flows monthly does not exist in the females of other animals because they have less moisture than women do. This is because they do not take in aliment superfluously and do not live in such leisure or ease, and so the moistures that do exist in them are converted into the superfluities of horns, claws, and hair, as the Philosopher says.
1. To the first argument one must reply that a menstrual flow does not occur in the man for two reasons: namely, both on account of the abundance and excellence of his consuming heat and on account of the paucity of his moisture.
2. To the second argument one must reply that if superfluous blood in other animals is not converted into horns and claws, then this flux does occur in them, but this is against the course of nature. But the fact that they do suffer menses does not contradict the Philosopher since it occurs per accidens, since it arises from some illness in them and beyond the order of nature. This is why, etc.
Whether the moon has dominion over the menstrual flow.
Further one inquires whether the moon has dominion over menstrual flow.
1. And it seems not, because if it did have dominion, then the menstrual flow should increase when the moon waxes. But this is not true, since it grows more at the end of the month, according to the Philosopher.
2. In addition, the moon and every heavenly body act by the power of light. Now, it acts the most when it is most illuminated. If then it had dominion over the flow of the menses, then it would occur on the fourteenth day more than on the thirtieth day.
3. Moreover, the moon does not have dominion over the emission of seed or of other waste products or over the flow of hemorrhoids. Therefore, etc.
The Philosopher says the opposite.
One must reply that the moon does have dominion over the menstrual flow and over everything moist and cold. Nevertheless, one must understand that two things are required for the menses to flow: their collection and their expulsion. The menses are collected when the moon waxes. Thus at the full moon their collection is greatest. But after collection, a disposition for expulsion is required, and they remain in this disposition until the end of the month, and this is why they particularly flow then.
1-2. In this way a solution is apparent to the first and second arguments.
3. To the third, one must reply that sperm is hotter and more aggregated, and this is why it has less regard for the moon, because it is more globular than the menses, which are fluid and watery. Likewise, the other waste products, like urine and things of this sort, are things that are left behind after nature's operation, whereas the menses are something more intended by nature, and this is why the moon has more dominion over the menses than over other superfluities.
Moreover, hemorrhoids are caused by a superfluity of thick blood, because, when such blood is abundant in the body, it descends down below to where there are many veins, namely, in the womb, and then often one or two veins burst, and the blood flows sometimes on account of the opening of these veins. Therefore, this occurs by nature particularly among those living on gross and salty nutriment, like the Jews.And because this blood is thick and has an earthy nature, the moon does not have dominion over its flow in the way it does over the menses.
-  The suggestion that the Jews' diet rendered them especially subject to hemorrhoidal bleeding helped introduce the medieval myth of Jewish male menses. See I. M. Resnick (2000).