1553: Servetus discovers circulation, sort of

Michael Servetus (1509?-1553)

Michael Servetus, a Spanish physician, discovered that blood circulates through the body.  He accurately diagrammed the flow of blood through the body, and explained that the lungs cause the arterial blood to be a brighter red in color, and not the heart, as Galen taught. (1, page 474)

He was also the first to speculate that blood does not cross through a septum (or invisible pores) from the right ventricle to the left ventricle as Galen had suggested, but takes another route. He said the blood entered the left ventricle during diastole, and this is where the "vital spirit" is formed, and from there it travels to the arteries. (2, page 63-64)

In his 1806 book, Richard Wright said that past historians and physicians had described Servetus as having wrote about circulation in a book he had published in 1553.  Wright said: (4, page 312

In a book of his entitled, Christianismi Restitutio (The Restoration of Christianity), printed in the year 1553, he clearly asserts, that the blood passes through the lungs, from the left to the right ventricle of th heart, and not through the partition which divides the two ventricles, as was at that time commonly believed.  How he introduces it, or in which of the six discourses into which he divides his book, it is to be found I know not; having never seen the book myself. (4, page 313)

However, despite such an observation, Servetus did not sway too far from Galen in his understanding of the human body.  Wright quotes Servetus historian Dr. Wotton, who wrote:

Servetus saith, that there are three sorts of spirits in the human body, viz. natural, vital, and animal, which are not in reality three, but two distinct spirits only: the arteries communicating by anastomosis, the vital spirit to the veins, in which it is called natural.  The first spirit then is the blood, whose seat is in the liver, and in the veins of the body; the second is the vital spirit, whose seat is the brain and nerves. (4, page 314)

That we may therefore conceive how the blood comes to be the very life; we must first know, that the substantial generation of the vital spirit itself is made and nourished by the inspired air, and te most subtil blood.  The vital spirit hath its origin from the left ventricle of the heart, but its perfection chiefly from the lungs:  it is a fine spirit, produced by the power of a gentle heat, of a bright color, of an igneous quality; and is, as it were, a lucid vapor from te purest blood, having the substance of water, air, and fire.  It is generated by the air which we we inspire, mixt in the lungs with th elaborated subtil blood, which the right ventricle communicates to the left.

Now this communication is not made through the septum of th heart, as 'tis commonly believed; but the subtil blood is driven by a wonderful contrivance, from the right ventricle of the heart, through a long duct, into the lungs, by which it is prepared, and made bright; then it paseth from the vena arteriosa into the arteria venosa; there it mixeth with inspired air, and is purged from its fuligo by expiration.  Lastly, the whole mixture is brought into the left ventricle of the heart by diastole, and is become fit matter to produce the vital spirit...

A little after he adds, that vital spirit therefore is transfused from the left ventricle of the heart into the arteries of t whole body, in such a manner that the most subtil portion of it flies upward, where it is further refined, especially in the plexus retiformis, under the basis of the cerebrum, where the vital spirit begins to be changed into the animal one, drawing nearer to the true nature of a rational soul.

This is that famous passage (adds the author of the history) which is so much taken notice of, on account of the circulation of the blood.  There are indeed several things here that are remarkable, viz. that the blood, in a great stream, passes through a very large and wide duct, from the right ventricle of the heart, into the lungs; that there the blood is purified; and from thence it is driven, by the pulmonary vein, into the left ventricle of the heart; that there is an immediate communication between the arteries and the veins, by anastimosis; that the most pure part of the blood, refined in the lungs, enters the arteries, and from the arteries into the veins, &c.  This shows that Servetus was a great observer of nature, and no doubt would have improved those notions and carried them much further, had he not been prevented by an untimely death' 

This last sentence is important because, for being so brave to announce his suggestions that were opposed to the mighty Galen, he was accused of by the Calvinists of heresy and burned at the stake in 1553. Copies of his book were used as kindling.  His offense was so bad that he was burned "slowly to increase his agony," said Joseph K. Perloff in his 2009 book on the heart and circulation.  (3, page xxiii)

So, the fact that he did not have ample time to prove his theory of circulation, and the fact that so few of his books survived, prevented "its being known to the learned world until so long after," said Wright. (4, page 417-418)(5 page 225)

Regarding the way in which the career and life of Servetus was cut short by the Catholic Church, Wright said:

As to Dr. Wotton's saying 'Well had it been for the church of Christ, if he had confined himself to his own profession;' wherein does this appear? What did Servetus do to injure any church, or disturb tha tpeace of any man living?  Could not he point out what he thought th eerrors of his fellow christians, and endeavor to enlighten mankind, without injuring them?  It is true too many men are offended when their mistakes are pointed out; but ought this to be the case?  He thought for himself, and he made his opinion public; but what harm could arise to the church from his doing this? (4 page 318)

Such questions have been asked over and over, and the only answer to them is: "That's just the way it was."  The aristocracy, the Church, wanted to keep the masses ignorant.

Wright added:

With the Doctor's leave, the world has just cause to bless the memory of Servetus, not only for this important discovery; but also for the noble stand he made for christian liberty and the rights of conscience, against bigots and persecutors; for his steady exertions to discover and promote truth; and for the sacrifice he made of his reputation and his life, in attempting to extirpate deep-rooted errors and prejudices. (4, page 319) 

This is a perfect example of how history is not always fair to the inventors and discoverers of new wisdom.  Sometimes, the person who should get credit is ignored by history, and such was the case with Servetus.

However unfair it was the way Servetus met his end, his work started the ball rolling, so to speak, for circulation to be discovered, and proved,  over the next 100 years following his ill-timed death.

1. Hill, Leonard, Benjamin Moore, Arthur Phillip Beddard, John James Rickard, etc., editors, "Recent Advances in Physiology and bio-chemistry," 1908, London, Edward Arnold
2. Hamilton, William, "A History of Medicine, Surgery and Anatomy," 1831, Vol. I, London, New Burlington
3. Brock, Arthur John, "Galen on the natural faculties," 1916, London, New York, William Heinemann, G.P. Putnam's Sons
4. Wright, Richard, "An Apology for Dr. Michael Servetus: Including an Account of his Life, Persecution, Writings and Opinions: Being designed to eradicate Bigotry and Unchartableness: And to Promote Liberality of Sentiment Among Christians," 1806, London, Printed and Sold by F.B. Wright
5. Perloff, Joseph K, "Physical Examination of the Heart and Circulation," 4th edition, 2009, People's Medical Publishing House-USA, Ltd

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