I avow myself the partisan of truth alone. - William Harvey

As art is a habit with reference to things to be done, so is science a habit in respect to things to be known.

Good God! how should the mitral valves prevent the regurgitation of air and not of blood?

...I found the task so truly arduous... that I was almost tempted to think... that the movement of the heart was only to be comprehended by God. For I could neither rightly perceive at first when the systole and when the diastole took place by reason of the rapidity of the movement...