“Ex vivorum dissectione, qualis sit cordis motus.” He minutely describes what he saw and handled in dogs, pigs, serpents, frogs and fishes, and even in slugs, oysters, lobsters and insects, in the transparent minima squilla, “quae Anglice dicitur a shrimp,” and lastly in the chick while still in the shell. In these investigations he used a perspicillum or simple lens. He particularly describes his observations and experiments on the ventricles, the auricles, the arteries and the veins. He shows how the arrangement of the vessels in the foetus supports his theory. He adduces facts observed in disease as well as in health to prove the rapidity of the circulation. He explains how the mechanism of the valves in the veins is adapted, not, as Fabricius believed, to moderate the flow of blood from the heart, but to favour its flow to the heart. He estimates the capacity of each ventricle, and reckons the rate at which the whole mass of blood passes through it. He elaborately and clearly demonstrates the effect of obstruction of the blood-stream in arteries or in veins, by the forceps in the case of a snake, by a ligature on the arm of a man, and illustrates his argument by figures. He then sums up his conclusion thus: “Circulari quodam motu, in circuitu, agitari in animalibus sanguinem, et esse in perpetuo motu; et hanc esse actionem sive functionem cordis quam pulsu peragit; et omnino motus et pulsus cordis causam unam esse.” Lastly, in the 15th, 16th and 17th chapters, he adds certain confirmatory evidence, as the effect of position on the circulation, the absorption of animal poisons and of medicines applied externally, the muscular structure of the heart and the necessary working of its valves. The whole treatise, which occupies only 67 pages of large print in the quarto edition of 1766, is a model of accurate observation, patient accumulation of facts, ingenious experimentation, bold yet cautious hypothesis and logical deduction.
In one point only was the demonstration of the circulation incomplete. Harvey could not discover the capillary channels by which the blood passes from the arteries to the veins. This gap in the circulation was supplied several years later by the great anatomist Marcello Malpighi, who in 1661 saw in the lungs of a frog, by the newly invented microscope, how the blood passes from the one set of vessels to the other. Harvey saw all that could be seen by the unaided eye in his observations on living animals; Malpighi, four years after Harvey’s death, by another observation on a living animal, completed the splendid chain of evidence. If this detracts from Harvey’s merit it leaves Servetus no merit at all. But in fact the existence of the channels first seen by Malpighi was as clearly pointed to by Harvey’s reasoning as the existence of Neptune by the calculations of Leverrier and of Adams.
Harvey himself and all his contemporaries were well aware of the novelty and importance of his theory. He says in the admirable letter to Dr Argent, president of the College of Physicians, which follows the dedication of his treatise to Charles I., that he should not have ventured to publish “a book which alone asserts that the blood pursues its course and flows back again by a new path, contrary to the received doctrine taught so many ages by innumerable learned and illustrious men,” if he had not set forth his theory for more than nine years in his college lectures, gradually brought it to perfection, and convinced his colleagues by actual demonstrations of the truth of what he advanced. He anticipates opposition, and even obloquy or loss, from the novelty of his views. These anticipations, however, the event proved to have been groundless. If we are to credit Aubrey indeed, he found that after the publication of the De motu “he fell mightily in his practice; ’twas believed by the vulgar that he was crackbrained, and all the physicians were against him.” But the last assertion is demonstrably untrue; and if apothecaries and patients ever forsook him, they must soon have returned, for Harvey left a handsome fortune. By his own profession the book was received as it deserved. So novel a doctrine was not to be accepted without due inquiry, but his colleagues had heard his lectures and seen his demonstrations for years; they were already convinced of the truth of his theory, urged its publication, continued him in his lectureship, and paid him every honour in their power. In other countries the book was widely read and much canvassed. Few accepted the new theory; but no one dreamt of claiming the honour of it for himself, nor for several years did any one pretend that it could be found in the works of previous authors. The first attack on it was a feeble tract by one James Primerose, a pupil of Jean Riolan (Exerc. et animadv. in libr. Harvei de motu cord. et sang., 1630). Five years later Parisanus, an Italian physician, published his Lapis Lydius de motu cord. et sang. (Venice, 1635), a still more bulky and futile performance. Primerose’s attacks were “imbellia pleraque” and “sine ictu”; that of Parisanus “in quamplurimis turpius,” according to the contemporary judgment of Johann Vessling. Their dulness has protected them from further censure. Caspar Hoffmann, professor at Nuremberg, while admitting the truth of the lesser circulation in the full Harveian sense, denied the rest of the new doctrine. To him the English anatomist replied in a short letter, still extant, with great consideration yet with modest dignity, beseeching him to convince himself by actual inspection of the truth of the facts in question. He concludes: “I accept your censure in the candid and friendly spirit in which you say you wrote it; do you also the same to me, now that I have answered you in the same spirit.” This letter is dated May 1636, and in that year Harvey passed through Nuremberg with the earl of Arundel, and visited Hoffmann. But he failed to convince him; “nec tamen valuit Harveius vel coram,” writes P. M. Schlegel, who, however, afterwards succeeded in persuading the obstinate old Galenist to soften his opposition to the new doctrine, and thinks that his complete conversion might have been effected if he had but lived a little longer—“nec dubito quin concessisset tandem in nostra castra.” While in Italy the following year Harvey visited his old university of Padua, and demonstrated his views to Professor Vessling. A few months later this excellent anatomist wrote him a courteous and sensible letter, with certain objections to the new theory. The answer to this has not been preserved, but it convinced his candid opponent, who admitted the truth of the circulation in a second letter (both were published in 1640), and afterwards told a friend, “Harveium nostrum si audis, agnosces coelestem sanguinis et spiritus ingressum ex arteriis per venas in dextrum cordis sinum.” Meanwhile a greater convert, R. Descartes, in his Discours sur la méthode (1637) had announced his adhesion to the new doctrine, and refers to “the English physician to whom belongs the honour of having first shown that the course of the blood in the body is nothing less than a kind of perpetual movement in a circle.” J. Walaeus of Leyden, H. Regius of Utrecht and Schlegel of Hamburg successively adopted the new physiology. Of these professors, Regius was mauled by the pertinacious Primerose and mauled him in return (Spongia qua eluuntur sordes quae Jac. Primirosius, &c., and Antidotum adv. Spongiam venenatam Henr. Regii). Descartes afterwards repeated Harvey’s vivisections, and, more convinced than ever, demolished Professor V. F. Plempius of Louvain, who had written on the other side. George Ent also published an Apologia pro circulatione sanguinis in answer to Parisanus.
At last Jean Riolan ventured to publish his Enchiridium anatomicum (1648), in which he attacks Harvey’s theory, and proposes one of his own. Riolan had accompanied the queen dowager of France (Maria de’ Medici) on a visit to her daughter at Whitehall, and had there met Harvey and discussed his theory. He was, in the opinion of the judicious Haller, “vir asper et in nuperos suosque coaevos immitis ac nemini parcens, nimis avidus suarum laudum praeco, et se ipso fatente anatomicorum princeps.” Harvey replied to the Enchiridium with perfectly courteous language and perfectly conclusive arguments, in two letters De circulatione sanguinis, which were published at Cambridge in 1649, and are still well worth reading. He speaks here of the “circuitus sanguinis a me inventus.” Riolan was unconvinced, but lived to see another professor of anatomy appointed in his own university who taught Harvey’s doctrines. Even in Italy, Trullius, professor of anatomy at Rome, expounded the new doctrine in 1651. But the most illustrious converts were Jean Pecquet of Dieppe, the discoverer of the thoracic duct, and of the true course of the lacteal vessels, and Thomas Bartholinus of Copenhagen, in his Anatome ex omnium veterum recentiorumque observationibus, imprimis institutionibus beati mei parentis Caspari Bartholini, ad circulationem Harveianam et vasa lymphatica renovata (Leiden, 1651). At last Plempius also retracted all his objections; for, as he candidly stated, “having opened the bodies of a few living dogs, I find that all Harvey’s statements are perfectly true.” Hobbes of Malmesbury could thus say in the preface to his Elementa philosophiae that his friend Harvey, “solus quod sciam, doctrinam novam superata invidia vivens stabilivit.”
It has been made a reproach to Harvey that he failed to appreciate the importance of the discoveries of the lacteal and lymphatic vessels by G. Aselli, J. Pecquet and C. Bartholinus. In three letters on the subject, one to Dr R. Morison of Paris (1652) and two to Dr Horst of Darmstadt (1655), a correspondent of Bartholin’s, he discusses these observations, and shows himself unconvinced of their accuracy. He writes, however, with great moderation and reasonableness, and excuses himself from investigating the subject further on the score of the infirmities of age; he was then above seventy-four. The following quotation shows the spirit of these letters: “Laudo equidem summopere Pecqueti aliorumque in indaganda veritate industriam singularem, nec dubito quin multa adhuc in Democriti puteo abscondita sint, a venturi saeculi indefatigabili diligentia expromenda.” Bartholin, though reasonably disappointed in not having Harvey’s concurrence, speaks of him with the utmost respect, and generously says that the glory of discovering the movements of the heart and of the blood was enough for one man.
