Theses medicae de divina et admiranda hominis in utero formatione

LIII.
In pregnant women, the menses do not flow, because then Nature withdraws all the blood and transmits it into the uterus for the nutrition of the fetus.

LIIII.
The fetus is nourished, however, by the purest blood, which it draws from the entire blood mass: unless the entire blood is corrupt and vicious.

LV.
The nutrition of the fetus is accomplished in this way: into that circular flesh, which we said grows onto the interior membrane of the uterus like a liver from the influx of blood, certain vessels, which are called umbilical, are inserted by the infinite mouths of small branches, through which the fetus receives both blood for nutrition, and spirit and vital heat.

LVI.
This blood is drawn into the infant's liver, and is better concocted there, and distributed through the entire body. For it is not nourished through the mouth, since no path for food is open to it, and the fetus cannot yet digest food taken through the mouth.

LVII.
Galen thought that the umbilical vessels (which are one vein and two arteries) arise from the vessels of the uterus, and are not only contiguous to them but also continuous. To which opinion both Aristotle himself in the second book On the Generation of Animals, and also reason and sense, are opposed. For those mouths do not reach the internal membrane of the uterus, but that circular flesh lies between them and the membrane: furthermore, if there were a continuity of vessels, how great a profusion of blood would arise in childbirth from their rupture?

LVIII.
Therefore, such is the origin of the umbilical vessels. The vein arises from the trunk of the portal vein, as soon as it emerges from the hollow of the liver; the arteries, however, arise from the great artery running through the loins, and, enveloped in two membranes, they are produced a very long way in man.

LIX.
Nature made the umbilical vessels very long for this reason: so that the animal, if by chance it were stuck in the female parts, could draw spirit from the mother and survive longer.

LX.
Nutrition is completed in the same way as in adults, by attraction, retention, concoction, and assimilation. Also, the same excrements are generated as in adults, namely urine, feces, and sweat.

LXI.
Urine is excreted through the pudendum and is received and