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.

For Nature is accustomed to rehearse with certain large, perhaps baser, and all classes of wild (animals), and to place in the imperfect the rudiments of the perfect animals.

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.

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.

We are many small puppets moved by fate and fortune through strings unseen by us; therefore, if it is so as I think, one has to prepare oneself with a good heart and indifference to accept things coming towards us, because they cannot be avoided, and to oppose them requires a violence that tears our souls too deeply, and it seems that both fortune and men are always busy in affairs for our dislike because the former is blind and the latter only think of their interest.

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.