This, however, seems to be certain: the ichor, that is, the material I have mentioned that finally becomes red, exists before the heart begins to beat, but the heart exists and even beats before the blood reddens.

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.

Nature has but one plan of operation, invariably the same in the smallest things as well as in the largest, and so often do we see the smallest masses selected for use in Nature, that even enormous ones are built up solely by fitting these together. Indeed, all Nature's efforts are devoted to uniting the smallest parts of our bodies in such a way that all things whatsoever, however diverse they may be, which coalesce in the structure of living things construct the parts by means of a sort of compendium.

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.

Surgical knowledge depends on long practice, not from speculations.