Note on the Effect on Harvey’s Theory of Faraday’s Discoveries

William Harvey was born in 1578; he inherited much of the old traditional medicine founded on the theories and writings of Aristotle as well as the practice and experiments of Galen, the famous second century AD Roman doctor whose observations were the basis of later anatomical teaching. He thought that the blood travelled in a single circuit reaching even the remotest of its vessels, and demonstrated this by showing that a wound which drained blood from an arterial wound also drained that from the veins, emptying all the blood vessels of the body. But many of the learned anatomists of Harvey’s day disagreed with this, believing that the arterial and venial blood ran in two separate circuits. Though they were unable, like Galen, to find any junction of the two circuits, they argued that there must be one and that therefore there must be a large number of invisible small holes in the cardiac septum separating the right ventricle of the heart from the left through which the blood filtered. Harvey made a very careful examination of the septum and could find no trace of such holes and ridiculed the idea. He also made quantitative measurements of the amount of blood passing through the body in half an hour, and found it to be much greater than the heart could deal with without overheating. To prevent a possible back flow into the right ventricle he stated that the three small valves in its entrance would prevent this, and that another such across the exit from the left ventricle would do the same there. Therefore he reaffirmed Galen’s statement that there had to be a place where both the inflow of arterial blood and the outflow of venous could serve as a kind of pool to which both belonged and into which blood was carried by one vessel and dispatched by the other. Since the pulmonary vein discharges the blood continuously into the lungs and from them it is continually drawn into the right ventricle it must be making a continuous complete circuit and the dirt which it has collected expelled by the lungs. But in the absence of lungs the pulmonary vein would discharge directly into the right ventricle, again making a continuous circuit.

So that one ventricle alone is sufficient to distribute the blood through the body, and this is what happens in creatures which have no lungs and in the early stages of the human foetus, as he found by dissection. He supports this assertion by his own observations on lungless creatures. But the school of Physicians, he said, would not accept the circulation.

Harvey himself had been a practising anatomist and vivisectionist for many years before the publication of his book De motu Cordis in 1628. Many of his arguments came from his own observations and dissection of cadavers and lower animals, which was a common practise in those days and so acceptable to his contemporaries. Others were logical conclusions often destructive of current theories. In his letter to Dr Argent he says: ‘this book of mine is the only one to oppose tradition and to assert that the blood travelled along a previously unrecognised circular pathway of its own.’

He continued: ‘When I meditated even further on the amount of transmitted blood and the very short time it took for its transfer … I then began to wonder whether it had a movement, as it were in a circle; that I afterwards found to be true.’

Two hundred years after this publication Michael Faraday was making his great discoveries on the nature of electricity. In 1831 he reported one of his most famous experiments, inserting a magnetised piece of iron into a coil in which a current was running, which considerably increased the amount of current in the coil. He showed that the reverse was also true, that movement of a conductor bearing a current in a stationary magnetic field produced a similar increase, called the electromagnetic force. This was expressed as Faraday’s Law, that an electromagnetic force is induced in a circuit whenever the magnetic field threading it changes, and that the E.M.F. is proportional to the rate of change of flux. The direction of the induced E.M.F. is stated by Lenz’s Law to oppose the action to which it is due.

A great deal of astronomical and celestial research has revealed that the sun, moon and most of the planets each have their own magnetic fields. So also has the earth, some of which may originate in its core of magnetic material and some in the form of electromagnetic force induced by that of the sun.

The sun’s field has many changes daily, annually and of longer period, and these are reflected in those of the earth, and since according to Harvey’s theory the blood of mammals is a conductor moving in a magnetic field, an E.M.F. must be induced in it when that field changes. The changes in the earth’s field are usually very small, of the order of 3 to 6 oersted, but they are known to increase considerably at times of magnetic storms and other irregularities in that of the sun. Archaeologists and geophysicists are producing much evidence from the ice-cores of Greenland and deep sea cores from the sea bed of great changes in the distant past, amounting at times even to reversals of polarity. These have been reflected also in the formation of rocks. There is no reason to think that our own blood circuits are immune to such changes, and however small they may be the effects they may have on our nervous systems via the blood may be vital and hitherto unexplained.