William Harvey

by Sir D'Arcy Power

This passage shows one of the minor difficulties that Harvey and all observers in his age had to contend with in the fact that no method existed by which small fractions of time could be measured.[11] The ordinary watch had only a single hand marking the hours, so that neither minutes nor seconds could be registered by them.

The difficulty was one of old standing, and Dr. Norman Moore alluded to it, when he says in regard to Mirfeld’s “Breviarium Bartholomei:” “The mixture of prayers with pharmacy seems odd to us; but let it be remembered that Mirfeld wrote in a religious house, that clocks were scarce, and that in that age and place time might not inappropriately be measured by the minutes required for the repetition of so many verses of Scripture or so many prayers. Thus Mirfeld recommends that chronic rheumatism should be treated by rubbing the part with olive oil. This was to be prepared with ceremony. It was to be put into a clean vessel while the preparer made the sign of the cross and said the Lord’s Prayer and an Ave Maria. When the vessel was put to the fire the Psalm ‘Why do the heathen rage’ was to be said as far as the verse, ‘Desire of Me, and I shall give thee the heathen for thine inheritance.’ The Gloria, Pater Noster, and Ave Maria are to be said, and the whole gone through seven times. Which done let that oil be kept. The time occupied I have tried, and found to be a quarter of an hour.”

In the succeeding chapters Harvey continues his observations on phlebotomy, and draws a conclusion so striking in its simplicity that it appears hard to understand why it had not already occurred to others. He says: “And now, too, we understand why in phlebotomy we apply one ligature above the part that is punctured, not below it: did the flow come from above, the constriction in this case would not only be of no service but would prove a positive hindrance. It would have to be applied below the orifice in order to have the flow more free did the blood descend by the veins from the superior to inferior parts.”

Harvey next returns to the question whether the blood does or does not flow in a continuous stream through the heart—a subject upon which his contemporaries had the wildest notions, for even Cesalpino says: “That whilst we are awake there is a great afflux of blood and spirit to the arteries whence the passage is to the nerves and whilst we are asleep the same heat returns to the heart by the veins, not by the arteries, for the natural ingress to the heart is by the vena cava, not by the artery ... so that the undulating flow of blood to the superior parts, and its ebb to the inferior parts—like Euripus—is manifest in sleeping and waking.” Harvey combats this theory in exactly the same manner as we should do if it were propounded at the present day. He first brings forth his mathematical proof of the circulation, and then continues his surgical observations upon the operation of bleeding. “It is still further to be observed that in practising phlebotomy the truths contended for are sometimes confirmed in another way, for having tied up the arm properly and made the puncture duly, still, if from alarm or any other causes, a state of faintness supervenes, in which the heart always pulsates more languidly, the blood does not flow freely, but distils by drops only. The reason is that with the somewhat greater than usual resistance offered to the transit of the blood by the bandage, coupled with the weaker action of the heart and its diminished impelling power, the stream cannot make its way under the ligature; and further, owing to the weak and languishing state of the heart, the blood is not transferred in such quantity from the veins to the arteries through the sinuses of that organ.... And now a contrary state of things occurring, the patient getting rid of his fear and recovering his courage, the pulse strength is increased, the arteries begin again to beat with greater force, and to drive the blood even into the part that is bound, so that the blood now springs from the puncture in the vein, and flows in a continuous stream....” Thus far, he proceeds, “we have spoken of the quantity of blood passing through the heart and the lungs in the centre of the body, and in like manner from the arteries into the veins in the peripheral parts, and in the body at large. We have yet to explain, however, in what manner the blood finds its way back to the heart from the extremities by the veins, and how and in what way these are the only vessels that convey the blood from the external to the central parts; which done, I conceive that the three fundamental propositions laid down for the circulation of the blood will be so plain, so well established, so obviously true, that they may claim general credence. Now the remaining proposition will be made sufficiently clear from the valves which are found in the cavities of the veins themselves, from the uses of these, and from experiments cognisable by the senses.”

Harvey returns again to his anatomical demonstrations to prove his point. He explains the true uses of the valves in the veins, whose existence, he says, were known to his old teacher “Hieronymus Fabricius, of Aquapendente, a most skilful anatomist and venerable old man.... The discoverer of these valves did not rightly understand their use, nor have succeeding anatomists added anything to our knowledge; for their office is by no means explained when we are told that it is to hinder the blood by its weight from all flowing into the inferior part; for the edges of the valves in the jugular veins hang downwards, and are so contrived that they prevent the blood from rising upwards; the valves, in a word, do not invariably look upwards, but always towards the trunks of the veins, invariably towards the seat of the heart. Let it be added that there are no valves in the arteries, and that dogs, oxen, &c., have invariably valves at the divisions of their crural veins, in the veins that meet towards the top of the os sacrum, and in those branches which come from the haunches, in which no such effect of gravity from the erect position was to be apprehended.”

“The valves are solely made and instituted lest the blood should pass from the greater into the lesser veins, and either rupture them or cause them to become varicose.... The delicate valves, whilst they readily open in the right direction, entirely prevent all contrary movement.... And this I have frequently experienced in my dissections of the veins: if I attempted to pass a probe from the trunk of the veins into one of the smaller branches, whatever care I took, I found it impossible to introduce it far any way, by reason of the valves; whilst, on the contrary, it was most easy to push it along in the opposite direction from without inwards, or from the branches towards the trunks and roots.” He concludes his argument by again pointing out that the uses of the valves can be clearly shown in an arm which has been tied up for phlebotomy, and that the valves are best seen in labouring people.

The fourteenth chapter is devoted to the “Conclusion of the Demonstration of the Circulation.” It runs thus:—

“And now I may be allowed to give in brief my view of the circulation of the blood, and to propose it for general adoption.

“Since all things, both argument and ocular demonstration show that the blood passes through the lungs and heart by the force of the ventricles, and is sent for distribution to all parts of the body, where it makes its way into the veins and pores of the flesh, and then flows by the veins from the circumference on every side to the centre from the lesser to the greater veins, and is by them finally discharged into the vena cava and right auricle of the heart, and this in such quantity or in such afflux and reflux, thither by the arteries, hither by the veins, as cannot possibly be supplied by the ingesta, and is much greater than can be required for mere purposes of nutrition; 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 movement; that this is the act or function which the heart performs by means of its pulse, and that it is the sole and only end of the movement and contraction of the heart.”

Harvey concludes his treatise with a series of reasons which he rightly considers to be of a less satisfactory nature than those he has already adduced. The seventeenth chapter contains much comparative anatomy. It opens with the statement that “I do not find the heart as a distinct and separate part in all animals; some, indeed, such as the zoophytes, have no heart.... Amongst the number I may instance grubs and earth-worms, and those that are engendered of putrefaction and do not preserve their species. These have no heart, as not requiring any impeller of nourishment into the extreme parts.... Oysters, mussels, sponges, and the whole genus of zoophytes or plant-animals have no heart, for the whole body is used as a heart, or the whole animal is heart. In a great number of animals, almost the whole tribe of insects, we cannot see distinctly by reason of the smallness of the body; still, in bees, flies, hornets, and the like we can perceive something pulsating with the help of a magnifying glass; in pediculi also the same thing may be seen, and as the body is transparent, the passage of the food through the intestines, like a black spot or stain, may be perceived by the aid of the same magnifying glass.