William Harvey

The pursuit of knowledge is a divine calling.

I profess myself of the opinion that the circulation of the blood is to be maintained by argument and ocular demonstration, and not by any other means.

It is absolutely necessary to conclude that the blood in the animal body is impelled in a circle, and is in a state of ceaseless motion; that this is the function of the heart, which, by means of its pulse, impels the blood and distributes it through the whole body.

I have often wondered, and indeed not a little marvelled, that so many and such excellent men, who have written so much and so well concerning the anatomy of the heart and the vessels, have not, in their diligent and careful dissections, observed what I have demonstrated.

The heart, in animals, is the principle of life, the first to live, the last to die, the primary mover, and the fountain of all motion and pulsation.

I began to think whether there might not be a motion, as it were, in a circle.

The blood is not drawn into the arteries by any pulsific faculty of the arteries themselves, but is driven into them by the impulsion of the heart.

The quantity of blood which is transmitted from the vena cava into the arteries, and by them into the whole body, is so great that it cannot be supplied by the ingesta, and must therefore return again to the heart.

The blood, therefore, must needs perform a circular motion in the animal body.

I have not only proposed, but also demonstrated, that the blood is continually moving in a circle.

I am not so arrogant as to imagine that I have discovered anything so great and wonderful as to be beyond the reach of human understanding.

I have not been deterred by the fear of calumny, or by the envy of those who are unwilling to admit anything new.

The blood is not consumed in the periphery, but returns to the heart.

The valves in the veins are so constructed that they permit the blood to flow from the extremities towards the heart, but prevent its return.

I have observed in many dissections, and in living animals, that the blood flows from the arteries into the veins, and from the veins into the heart.

The motion of the blood is so rapid that it cannot be perceived by the eye, but must be inferred from other considerations.

The heart is the sole organ of the pulse, and the arteries pulsate only because they are distended by the blood driven into them by the heart.

The blood is the vehicle of life, and its motion is the cause of all vital actions.

I have not been led to this opinion by the authority of any writer, but by my own observations and experiments.

The circulation of the blood is a truth which, when once admitted, will throw a new light on the whole science of medicine.