William Harvey

I have often wondered, and indeed not a little, at the great difference of opinion among anatomists and physicians in the matter of the pulse and the motion of the heart.

It is a thing alike wonderful and incredible, to observe how the blood, from the very beginning of its motion, is distributed from the heart through the whole body, and then returns to the heart again.

I am not so mad, nor have I been so caught up in the opinion of others, as to believe that I have discovered anything so great as to be worthy of the name of a new opinion.

I have myself, in my dissections, seen the blood flow from the right ventricle into the pulmonary artery, and from the pulmonary vein into the left auricle.

The circulation of the blood is a new doctrine, and I doubt not but it will meet with its opponents.

All animals, even man himself, are produced from an egg.

The egg is the common origin of all animals.

I have not only affirmed, but also demonstrated, that the motion of the heart is a perpetual circulation of the blood.

The more accurately and industriously I have examined the matter, the more clearly have I perceived the truth.

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

It is only when we have satisfied ourselves by careful dissection that we can truly understand the nature of things.

The heart, like a pump, perpetually propels the blood.

I have not hesitated to present to you, my dear reader, the results of my anatomical observations.

The blood in the arteries is of a more florid colour than that in the veins.

I appeal to the evidence of my senses, and to the testimony of dissections.

The motion of the blood is constant and circular.

Nature does nothing in vain.

The arteries are the channels through which the blood is driven from the heart.

I confess that I have been led to embrace this opinion by a careful consideration of the structure and use of the valves in the veins.

The blood, therefore, moves in a circuit, and is impelled by the heart.