Surgical knowledge depends on long practice, not from speculations.

The seed is the fetus, in other words, a true plant with its parts (that is, its leaves, of which there are usually two, its stalk or stem, and its bud) completely fashioned.

The generation of seeds ... is therefore marvelous and analogous to the other productions of living things. For first of all an umbilicus appears. ... Its extremity gradually expands and after gathering a colliquamentous ichor becomes analogous to an amnion. ... In the course of time the seed or fetus begins to become visible.

In such sad circumstances I but see myself exalted by my own enemies, for in order to defeat some small works of mine they try to make the whole rational medicine and anatomy fall, as if I were myself these noble disciplines.

It is therefore proper to acknowledge that the first filaments of the chick preexist in the egg and have a deeper origin, exactly as [the embryo] in the eggs of plants.