Surgical knowledge depends on long practice, not from speculations.

Observation by means of the microscope will reveal more wonderful things than those viewed in regard to mere structure and connection: for while the heart is still beating the contrary (i.e., in opposite directions in the different vessels) movement of the blood is observed in the vessels-though with difficulty-so that the circulation of the blood is clearly exposed.

Surgical knowledge depends on long practice, not from speculations.

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.

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.

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.