# Ulisse Aldrovandi, 48

Just as the veins originate from the liver and the arteries from the heart, the softer nerves—regarded as the primary organs of the senses—derive from the brain. From the medulla of the brain, the spinal cord also extends; from there, all the other nerves take their own beginning, communicating sensation and movement to the entire body. All these parts are nourished by menstrual blood, which is drawn through the umbilical veins directed toward the uterus.

Accordingly, during the first six days after conception, the seminal matter held within the womb bears a resemblance to milk. In the nine days that follow, it is transformed into blood, and over the next twelve days, it solidifies. During the remaining eighteen days, up until the forty-fifth, all the limbs achieve their most perfect shape, so that from then on, the fetus only increases in size. This follows the poem by Aegidius:

"Six days as milk, three times three as blood, Twice six form flesh, and three times six shape the limbs."

This is also expressed in another way:

"The seed once cast, for the first six days surely Is like milk; for the nine remaining it becomes blood; then Twelve days solidify it, and twice nine at last Give it its form, etc."

The reader may observe all of these stages in the following figure, which illustrates the initial generation of the fetus. This process, however, is even better expressed by another illustration.

*The initial generation of the fetus.*