Generally unknown before Harvey. 16. It is thus manifest that several anatomists of the sixteenth century were on the verge of completely detecting the law by which the motion of the blood is governed; and the language of one is so strong, that we must have recourse, in order to exclude his claim, to the irresistible fact that he did not confirm by proof his own theory, nor announce it in such a manner as to attract the attention of the world. Certainly, when the doctrine of a general circulation was advanced by Harvey, he both announced it as a paradox, and was not deceived in expecting that it would be so accounted. Those again who strove to depreciate his originality, sought intimations in the writings of the ancients, and even spread a rumour that he had stolen the papers of Father Paul; but it does not appear that they talked, like some moderns, of plagiarism from Levasseur or Cæsalpin.
His discovery. 17. William Harvey first taught the circulation of the blood in London, in 1619; but his Exercitatio de Motu Cordis was not published till 1628. He was induced, as is said, to conceive the probability of this great truth, by reflecting on the final cause of those valves, which his master, Fabricius de Aquapendente, had demonstrated in the veins; valves whose structure was such as to prevent the reflux of the blood towards the extremities. Fabricius himself seems to have been ignorant of this structure, and certainly of the circulation; for he presumes that they serve to prevent the blood from flowing like a river towards the feet and hands, and from collecting in one part. Harvey followed his own happy conjecture by a long inductive process of experiments on the effects of ligatures, and on the observed motion of the blood in living animals.
Unjustly doubted to be original. 18. Portal has imputed to Harvey an unfair silence as to Servetus, Columbus, Levasseur, and Cæsalpin, who had all preceded him in the same track. Tiraboschi copies Portal, and Corniani speaks of the appropriation of Cæsalpin’s discovery by Harvey. It may be replied, that no one can reasonably suppose Harvey to have been acquainted with the passage in Servetus. But the imputation of suppressing the merits of Columbus is grossly unjust, and founded upon ignorance or forgetfulness of Harvey’s celebrated Exercitation. In the proœmium to this treatise he observes, that almost all anatomists have hitherto supposed with Galen, that the mechanism of the pulse is the same as that of respiration. But he not less than three times makes an exception for Columbus, to whom he most expressly refers the theory of a pulmonary circulation.[650] Of Cæsalpin he certainly says nothing; but there seems to be no presumption that he was acquainted with that author’s writings. Were it even true that he had been guided in his researches by the obscure passages we have quoted, could this set aside the merit of that patient induction by which he established his own theory? Cæsalpin asserts at best, what we may say he divined, but did not know to be true; Harvey asserts what he had demonstrated. The one is an empiric in a philosophical sense, the other a legitimate minister of truth. It has been justly said, that he alone discovers who proves; nor is there a more odious office, or a more sophistical course of reasoning, than to impair the credit of great men, as Dutens wasted his erudition in doing, by hunting out equivocal and insulated passages from older writers, in order to depreciate the originality of the real teachers of mankind.[651] It may indeed be thought wonderful that Servetus, Columbus, or Cæsalpin should not have more distinctly apprehended the consequences of what they maintained, since it seems difficult to conceive the lesser circulation without the greater; but the defectiveness of their views is not to be alledged as a counterbalance to the more steady sagacity of Harvey. The solution of their falling so short is that they were right, not indeed quite by guess, but upon insufficient proof; and that the consciousness of this embarrassing their minds, prevented them from deducing inferences which now appear irresistible. In every department of philosophy, the researches of the first inquirers have often been arrested by similar causes.[652]
[650] Pæne omnes huc usque anatomici medici et philosophi supponunt cum Galeno eundem usum esse pulsus, quam respirationis. But though he certainly claims the doctrine of a general circulation as wholly his own, and counts it a paradox which will startle everyone, he as expressly refers (p. 38 and 41 of the Exercitatio) that of a pulmonary transmission of the blood to Columbus, peritissimo, doctissimoque anatomico; and observes, in his proœmium, as an objection to the received theory, quomodo probabile est (uti notavit Rualdus Columbus) tanto sanguine opus esse ad nutritionem pulmonum, cum hoc vas, vena videlicet arteriosa (hoc est, uti tum loquebantur, arteria pulmonalis) exsuperet magnitudine utrumque ramum distributionis venæ cavæ descendentis cruralem, p. 16.
[651] This is the general character of a really learned and interesting work by Dutens Origine des Découvertes attribuées aux Modernes. Justice is due to those who have first struck out, even without following up, original ideas in any science; but not at the expense of those who, generally without knowledge of what had been said before, have deduced the same principles from reasoning or from observation, and carried them out to important consequences. Pascal quotes Montaigne for the shrewd remark, that we should try a man who says a wise thing, for we may often find that he does not understand it. Those who entertain a morbid jealousy of modern philosophy, are glad to avail themselves of such hunters into obscure antiquity as Dutens, and they are seconded by all the envious, the uncandid, and by many of the unreflecting among mankind. With respect to the immediate question, the passages which Dutens has quoted from Hippocrates and Plato, have certainly an appearance of expressing a real circulation of the blood by the words περιοδος and περιφερομενου αἱματος; but others, and especially one from Nemesius, on which some reliance has been placed, mean nothing more than the flux and reflux of the blood, which the contraction and dilatation of the heart was supposed to produce. See Dutens, vol. ii., p. 8-13. Mr. Coleridge has been deceived in the same manner by some lines of Jordano Bruno, which he takes to describe the circulation of the blood: whereas, they merely express its movement to and fro, meat et remeat, which might be by the same system of vessels.
[652] The biographer of Harvey in the Biographie Universelle strongly vindicates his claim. Tous les hommes instruits conviennent aujourd’hui que Harvey est la véritable auteur de cette belle découverte.... Césalpin pressentoit la circulation artérielle, en supposant que le sang rétourne des extrémités au cœur; mais ces assertions ne furent point prouvées; elles ne se trouvèrent étayées par aucune expérience, par aucun fait; et l’on peut dire de Césalpin qu’il divina presque la grande circulation dont les lois lui furent totalement inconnues; la découverte en était réservée a Guillaume Harvey.
Harvey’s treatise on Generation. 19. Harvey is the author of a treatise on generation, wherein he maintains that all animals, including men, are derived from an egg. In this book, we first find an argument maintained against spontaneous generation, which, in the case of the lower animals, had been generally received. Sprengel thinks this treatise prolix, and not equal to the author’s reputation.[653] It was first published in 1651.
[653] Hist. de la Médécine, iv., 299. Portal, ii., 477.
Lacteals discovered by Assellius. 20. Next in importance to the discovery of Harvey, is that of Assellius as to the lacteal vessels. Eustachius had observed the thoracic duct in a horse. But Asellius, more by chance, as he owns, than by reflection, perceived the lacteals in a fat dog whom he opened soon after it had eaten. This was in 1622, and his treatise, De Lacteis Venis, was published in 1627.[654] Harvey did not assent to this discovery, and endeavoured to dispute the use of the vessels; nor is it to his honour that even to the end of his life he disregarded the subsequent confirmation that Pecquet and Bartholin had furnished.[655] The former detected the common origin of the lacteal and lymphatic vessels in 1647, though his work on the subject was not published till 1651. But Olaus Rudbeck was the first who clearly distinguished these two kinds of vessels.
[654] Portal, ii., 461. Sprengel, iv., 201. Peiresc soon after this got the body of a man fresh hanged after a good supper, and had the pleasure of confirming the discovery of Asellius by his own eyes. Gassendi, Vita Peirescii, p. 177.