However much the renewal of classical learning in the fourteenth, fifteenth, and sixteenth centuries may have furthered the development of letters and of art, it had anything but a favourable influence on the progress of science. The interest awakened in the literature of Greece and Rome was shown in admiration not only for the works of poets, historians, and orators, but also for those of physicians, anatomists, and astronomers. In consequence scientific investigation was almost wholly restricted to the study of the writings of authors like Aristotle, Hippocrates, Ptolemy, and Galen, and it became the highest ambition to explain and comment upon their teachings, almost an impiety to question them. Independent inquiry, the direct appeal to nature, were thus discouraged, and indeed looked upon with the utmost distrust if their results ran counter to what was found in the works of Aristotle or Galen. This spell of ancient authority was broken by the anatomists of the sixteenth century, who determined at all costs to examine the human body for themselves, and to be guided by what their own observations revealed to them; and it was finally overcome by the independent genius of two men working in very different scientific spheres, Galileo and Harvey. These illustrious observers were contemporaries during the greater part of their lives, and were some years together at the famous University of Padua. Galileo and Harvey refused to be bound by the teachings of Aristotle and Galen, and appealed from these authorities to the actual facts of nature which any man could observe for himself. Their scientific work is therefore of interest, not only for the innate value of the discoveries they made, but also because it shows them as pioneers in that independent spirit of scientific inquiry to which the great advance in natural knowledge since their time is so largely due.
Harvey’s work, by which his name has been made immortal, strikingly illustrates this. He was the first to show the nature of the movements of the heart, and how the blood moved in the body. He did so by putting on one side authority, and directly appealing to observation and experiment. The completeness of the success with which this independent line was taken, as exemplified in his treatise “On the Movement of the Heart and Blood,” is such as to excite the admiration of every modern physiologist. “C’est un chef-d’œuvre,” says a distinguished French physiologist, Flourens, “ce petit livre de cent pages est le plus beau livre de la physiologie.”[1]
The discovery made by Harvey was this: That the blood passed from the heart into the arteries, thence to the veins, by which it was brought back to the heart again; that the blood moved more or less in a circle, coming back eventually to the point from which it started. In a phrase, there was a Circulation of the Blood. Moreover, this circulation was of a double nature—one circle being from the right side of the heart to the left through the lungs, hence called the Pulmonary or Lesser Circulation; the other from the left side of the heart to the right, through the rest of the body, known as the Systemic or Greater Circulation. Further, that it was the peculiar office of the heart to maintain this circulation by its continuous rhythmic beating as long as life lasts.
This appears very plain and simple to us now—so easy that he who runs may read: as important as simple, for without this knowledge it is no exaggeration to say that a real understanding of any important function of the human body was impossible. And hence it has been contended with much force that not only the science of physiology, but the scientific practice of medicine date from this discovery. “To medical practice,” says Sir John Simon, “it stands much in the same relation as the discovery of the mariner’s compass to navigation; without it, the medical practitioner would be all adrift, and his efforts to benefit mankind would be made in ignorance and at random. . . . The discovery is incomparably the most important ever made in physiological science, bearing and destined to bear fruit for the benefit of all succeeding ages.”[2]
When Harvey first approached the subject, there were all kinds of crude and fantastic ideas regarding the functions and uses of the heart, bloodvessels, and blood—that the heart was the workshop in which were elaborated the spirits, a due supply of which was necessary for many parts of the body; that from the heart the arteries carried spirits, the veins nutriment to the different parts of the body; that the arteries contained blood and air mixed together, or only air; that fuliginous vapours, whatever they may be, passed from the heart along the bloodvessels; that the septum of the heart, by which its two sides are completely separated, was riddled with minute holes, like a fine sieve, through which the blood percolated from the right to the left side; again, that the heart was the organ in which the heat of the body was produced. Another favourite theory was that the blood moved from the heart along certain bloodvessels and back again by exactly the same channels, after the manner of the rise and fall of the tides, to which in fact the movement was likened. More curious still, even the best informed appeared to believe that the arteries terminated in nerves.
Notwithstanding these curious and erroneous speculations there was not wanting exact and wide knowledge of the anatomy of the human body. Indeed, before Harvey was born there had lived and died a most remarkable man known to fame as the “Father of Anatomy.” This was Vesalius. Vesalius’s knowledge of the human body was so profound that the only wonder is that he did not forestall Harvey in the discovery of the circulation. As the result of dissections of the body at the time when they could be carried out only with great difficulty, and often at the risk of severe penalties, Vesalius published, when only twenty-eight years of age, a treatise on Anatomy[3] which cannot fail to excite the astonishment and admiration of any modern acquainted with the subject. This work is illustrated with fine engravings made from drawings by John Calcar, a Flemish artist, and pupil of Titian.[4]
The distribution of the bloodvessels in the lungs and many other parts of the body, the general structure of the heart, the valves in the veins, were all known before Harvey arrived on the scene. More than this, the circulation through the lungs, or the Pulmonary Circulation, appears to have been known to one person at least. Michael Servetus, famous for his martyrdom on account of his religious opinions, in one of his theological works[5] does actually describe the blood as passing from the right side of the heart to the left through the lungs, and gives good reasons for his belief. Servetus, in his early days, had been with Vesalius prosector to John Guinterius of Andernach when Professor of Anatomy at Paris. Guinterius[6] speaks with admiration of the knowledge and abilities of his two young assistants. Like Vesalius, Servetus was therefore well acquainted with the anatomy of the body; but more, he was a physiologist; and no doubt when the cruelty of theological dispute sent him to the stake at the age of forty-four, it deprived physiology of a most promising investigator. The book in which the account of the Pulmonary Circulation is found has a most curious history. All copies of it, except one, were burnt with Servetus. This copy became the property of D. Colladon, one of his judges. After passing through the library of the Landgrave of Hesse-Cassel it came into the hands of a Dr. Mead, who undertook in 1723 to issue a quarto edition of it, but before completion the sheets were seized at the instance of Dr. Gibson, Bishop of London, and destroyed. The Duc de Valise is said to have given 400 guineas for the original copy, and at his sale it brought 3,810 livres. It is now in the National Library at Paris. It may well be questioned therefore whether the discovery of Servetus was ever known to the anatomists, including Harvey, who wrote after his death. One of these was Realdus Columbus, who published a work on Anatomy[7] six years after Servetus died, in which he shows that he clearly understood the valves of the heart, and describes the passage of the blood through the lungs. Columbus has been claimed as the real discoverer of the circulation and as having forestalled Harvey. But neither Servetus nor Columbus had any notion of the Greater or Systemic Circulation. And the latter actually says the heart is not muscular, and speaks of a to-and-fro movement of the blood in the veins.
But a third and much more serious precursor of Harvey as the discoverer has been brought forward in the person of Andreas Cæsalpinus[8] of Arezzo, justly renowned as the earliest of botanists. He actually used the word “circulation” in regard to the passage of the blood through the lungs. The claims of Cæsalpinus have been taken up with enthusiasm, not to say bitterness, in Italy; and in 1876 his statue was erected with much pomp and speechmaking in Rome, and an inscription placed upon it recording that he was the first discoverer of the circulation of the blood. It is much to be regretted that this display was not altogether free from a desire to depreciate Harvey. Wonder may well be expressed at this procedure, even after allowing for well-meant patriotic ardour, when it is learnt that in his works Cæsalpinus speaks of the arteries ending in nerves, of the septum of the heart being permeable, and its valves acting imperfectly, and of the veins carrying blood to the body for its nourishment. The statements made by Cæsalpinus, which at first sight point to his knowledge of the circulation, are altogether discounted on perusal of his works, and it becomes impossible to believe that he had any clear idea of the circulation as we understand it to-day. The misconception has no doubt arisen from the interpretation of isolated passages in the light of what we now know regarding the circulation. Moreover, it is impossible to believe, seeing how well the works of Cæsalpinus were known, that, had he ever been regarded as putting forward in them the doctrine of the circulation as we now understand it, such a new and startling view would not have attracted the attention of the distinguished anatomists who were his contemporaries or immediate successors. But that none of them ever for a moment saw any such doctrine in the works of Cæsalpinus is shown by their writings, and by the surprise with which Harvey’s discovery was received.
Even Shakespeare has been cited as being acquainted with the circulation of the blood, because he refers to its movement. This only illustrates the confusion which has often been made of movement with circulation. From the earliest times it had been believed there was movement of the blood, but there was no clear or correct idea as to the nature of the movement. The view may be ventured that another confusion is responsible for a good deal that has been said about Harvey having been forestalled in the discovery. It is confusing the passage through the lungs of some blood with the whole mass of it. It is difficult to believe, on taking a broad view of all their statements on the subject, that any of Harvey’s predecessors realised that the whole mass of the blood was continually passing through the lungs. Had they done so it is further difficult to see how the systemic circulation should have escaped them. But of this they certainly had no idea.
We may admit all this previous knowledge without its detracting from the greatness and merit of Harvey’s work. Although the same anatomical facts, and even a glimmering of the Pulmonary Circulation may have been present to the minds of his predecessors or contemporaries, yet the genius, the spark of originality by which was discovered the proper relation to one another of the former, the true significance and meaning of the latter, belongs to Harvey and to him alone.