Thethorax in history 6 Circulationand physiology than Galen, and had said almost nothing on medicine, his teaching embraced the whole of the ob:ervable world, and his modes of argument

Thorax, 1978, 33, 714-727

The thorax in history 6 Circulationof the blood

R K FRENCH

From the Wellcome Unit for the History of Medicine, University of Cambridge

Physicians and philosophers

We saw in the last article that the discovery thatblood passes from the heart to the lungs and backagain to the heart was the first break with theGalenic system of physiology. Galen's physiologicalscheme was the theoretical underpinning of hismedical system and was directly related to hisinterpretation of the biological world. Both of thesewere still widely accepted at the end of the six-teenth century, and so to accept the pulmonarytransit meant being based more firmly in theologythan in Galenism, like Servetus, or modifyingrather than rejecting the Galenic system, in theway that Colombo found Galenic answers toGalenic problems.The other intellectual position available at the

time was Aristotelianism. Although Aristotle hadbeen far less precise and satisfactory in anatomyand physiology than Galen, and had said almostnothing on medicine, his teaching embraced thewhole of the ob:ervable world, and his modes ofargument and presentation of evidence reachedfrom the syllogism to the classification of sea-mammals, and formed the basis of university edu-cation that every learned man, physician or not,assimilated up until the seventeenth century.Aristotelianism was presented as a logically inter-related whole in which each successive part of thecurriculum was a development of the one preced-ing, from generally applicable modes of arguing tothe simple motions of the inorganic world andfrom there to the nature of animals and man. Thenatural goal of all this was the complete descrip-tion of the structure and function of man-in aword, the theory of medicine-one of the three orfour' higher faculties (in our terms, postgraduate).But these higher faculties-medicine, law, andtheology-were also professional and practical inleading to a career in civil or ecclesiastical life.University study of medicine normally led tomembership of a professional college, where the

interest lay more than in the universities on prac-tical medicine; and despite the fact that medicinewas a natural culmination of an Aristotelian edu-cation, its chief spokesman in both theory andpractice was Galen. The physicians then hadprofessional reasons for being Galenists: wishing toappear learned, their learning could consist only ofGalen's teaching. Galenism became the pro-fessional orthodoxy of the professional bodies andthe touchstone for the discovery and suppressionof quackery.

So, for both social and intellectual reasons, themedieval disputes between Galenists and Aristote-lians continued well into the seventeenth century.The Aristotelian notion that the heart was thecentre of the body and therefore the source of theveins and arteries not only survived until Harvey'stime but was very influential. Even the mistakennotion that Aristotle said the heart was the originof the nerves2 had a significant part to play in pre-Harveian physiological thought. For our purposesthe most important Aristotelian doctrine still widelyadhered to in the late sixteenth and early seven-teenth centuries was that the arteries and veins(which Aristotle distinguished structurally but notfunctionally) arose from the heart. This cut acrossthe Galenic notion of two distinct blood systems,the nutritive (venous) based on the liver, and therespiratory (arterial) centred on the air-breathingheart, a notion that in turn rested on a pre-Aristotelian idea that the basis of the blood systemwas a fundamental pair of vessels running thelength of the body-the hepatic and splenic.The physiological results of such Aristotelianism

are seen in the works of the Italian peripatetic,Caesalpino,3 whom Italian historians used to claimas the discoverer of the systemic circulation.Firstly, Caesalpino resolved the old question of theorigin of the nerves by asserting that they weresimply fine extensions of the arteries passing intothe brain. This allowed him to accept the neo-Aristotelian cardiac origin of the nerves and the

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The thorax in history 6 Circulation of the blood

superior anatomy of the Galenists who describedin detail the cranial nerves of which Aristotle hadbeen ignorant. He was able to accept the phys-icians' account of the elaboration of spirits in thebrain by means of the arteries. The capillimentathat link the incoming arteries to the outgoingnerves in the brain are a new type of vessel whichrecall strongly the structures described by Servetusin postulating the pulmonary transit (see previousarticle). Servetus had given primacy to the heartand blood for theological reasons, and Caesalpinofor Aristotelian, but the result was the same-namely, that intellectual presuppositions had de-termined body function and this in turn, using the"eye of reason," had determined notions of in-visibly small structures in the anatomy of man. Asa device in physiological thinking, the eye ofreason could not be dispensed with, and althoughseveral people objected to the existence of theGalenic pores in the cardiac septum because theycould not be seen, they were obliged to postulatethe existence of other invisibly small pores in thesubstance of the lung to account for the right-lefttransit of blood that could no longer pass throughthe septum.

Caesalpino is in a similar situation with respectto the second topic we need to examine in hiswritings.4 He accepts the Aristotelian notion thatboth arteries and veins arise from the heart, buthe also accepts Galen's description of the valves ofthe heart, which were unknown to Aristotle. Theresult is extremely interesting: the heart as theseat of the soul is connected to the sense organs,where the sensory capacities of the soul are exer-cised, in the manner described above (the nervesbeing extensions of the arteries). During thewaking period the sense organs are supplied withinnate heat and spirit from the heart, past theaortic valve and through the arteries and nerves,but in sleep, when the sense organs have less needof heat and spirit, and when the blood, cooled,seeks to sink back, then it is the veins that carryit back to the heart, in accordance with the struc-ture of the valves of the vena cava at the heart.This is a clear, but limited, account of a circulationof blood. Its inspiration is the Aristotelian notionthat hot things rise and cold things fall, applied tothe specific requirements of the sense organs (andlungs, which in Aristotelian fashion cool the heart),but it does not relate this slow (daily) circulationto the motions of the heart, quantitatively or quali-tatively. His account also accepts a greater-than-peripheral communication between arteries andveins and admits that blood crosses the cardiacseptum. The relationship of this systemic circuit tothe pulmonary is not clearly defined.

Harvey's background

Nevertheless, before the end of the sixteenth cen-tury there were in the physiological literature aconcise and particular account of the pulmonarytransit and a more general natural-philosophicaldescription of a systemic circulation. Colombo'sbook was a university teaching text and widelyknown. Harvey made clear his debt to Colombo,but does not mention Caesalpino, and the questionof Caesalpino's influence on Harvey is still disputed.A possible link between the two and the two setsof ideas is a commentary by Caspar Hofmann onGalen's most important physiological and ana-tomical text, De Usu Partium.5 Like Caesalpino,Hofmann was an Aristotelian, as was Harvey.Harvey refers to Hofmann who in turn refers toCaesalpino. There was a neo-Aristotelian con-sensus in the pre-Harvey years in which the liverwas divested of its function of generating blood,and the origin of the vena cava was placed in theheart. Sometimes the spleen played a part in theseschemes as a homologue of the liver,6 balancing itin a symmetrical arrangement around the heart.We may recall from the previous article the viewsof Varolius and Ulmus. The heart became thecentre of the body, if not yet the centre of a circlewith these Aristotelians, while at the same time theGalenists had largely adopted the pulmonarytransit.Hofmann elaborated his ideas in a book on the

thorax and its contents, published shortly beforeHarvey's. His work is the culmination of the longhistory of the physician-philosopher debates, andits very title page indicates Hofmann's purpose inthis matter.7 He accepts the pulmonary transit,but of course finds an Aristotelian reason for doingso, claiming that the purpose of the lungs is to coolthe blood, which is perfected and endued with in-nate heat in the heart. Hofmann is struck with thequantitative arguments that the pulmonary vesselsare too large for the simple purpose of nourishingthe lungs, and he extends the argument in exam-ining the quantity of blood that must pass fromthe right side of the heart to the left at everysystole, a quantity that could not be accommodatedby any supposed pores of the septum. Harvey wasto use this quantitative argument to great effect,but strangely, after reading Harvey's book Hof-mann changed his mind about the argument, andclaimed that ebullition of blood in the heart, likemilk rising in a pan, made measurement meaning-less. The repeated cycle of heating and cooling thattook place in the heart and lungs, and that bywhich spirits were produced in the brain from theblood, was referred to as circulatio, a chemists'

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term for distillation (Caesalpino compared thebrain to a chemists' retort) which, although notmeaning circulation in the modern sense, isclear enough evidence of the Aristotelians'general conception of the cyclical processes of thebody.

In distinction to the Aristotelians, the Galenistsseem to have been more concerned with anatomi-cal minutiae. Andre du Laurens, Jean Riolan, andCaspar Bauhin were writers of anatomical text-books which were popular in the pre-Harveianyears and which Harvey himself relied on to aconsiderable extent. Bauhin, like Harvey's teacherFabricius of Acquapendente, was concerned in thediscovery of valves in parts of the body other thanthe heart, and as we saw in an earlier article thediscovery and interpretation of the extra-cardiacvalves (particularly those of the veins) werefundamental in setting the scene for Harvey. Riolanbecame involved in the professional Galenic ortho-doxy of the Paris Faculty of Medicine and insistedon the existence of the Galenic pores in the cardiacseptum in a heart boiled for a long while.8 LikeHofmann, he became a notable opponent ofHarvey's ideas but under their influence suggestedan alternative scheme of circulation, involvinganastomoses between major vessels to allow a cen-tral circulation to proceed, but preserving Galenicphysiology undisturbed in the outer and peripheralparts of the body. This gratuitous postulation ofgross anastomoses was a heavy tread in the sen-sitive area of arterial-venous communication.Harvey could not see his channels of communi-cation any more than the Galenists could seecardiac pores in a fresh heart, and, as we have seen,to deny cardiac pores meant using the eye ofreason to establish invisible pores elsewhere,whether in the lungs or in the flesh of the body.Harvey realised his methodological position herewas open to attack, and where he could do so heavoided "anastomoses" and rose to a rare defenceof his notions against Riolan.9There was no commonly agreed idea of how the

heart worked before Harvey. The Aristoteliansdiffered profoundly from the Galenists, and theGalenists were divided among themselves on thequestion of the porosity of the septum and the pul-monary transit. Yet amid this confusion medicinestill had to be taught, examinations passed, andprofessional colleges entered. The result was thata new formal course of medicine was hammeredout from these disparate elements, which com-bined Aristotelian natural philosophy, Galenicanatomy, and Hippocratic practice. The devicesused to reconcile these three authors recall thoseof the middle ages, and we may call this late

sixteenth and early seventeenth century schoolmedicine "neoscholastic" in contrast to the earlierhumanism of Vesalius.10 The anatomical textbooksof Crooke," Bauhin,12 and Du Laurens'3 presentan assimilated text and consign all the problems-the irreconcilable differences between the ancientauthors and the new discoveries of the time-tomargin notes or separately listed quaestiones. Thenew generation of anatomists, who put themselvesand their discoveries on an equal footing with theancients-Harvey scornfully called them "neo-terics"-had since the time of Vesalius accummu-lated a great deal of anatomical and physiologicalinformation which had been unknown to theancients and which was in many cases inimical totheir ideas.

Harvey

There was no simple orthodoxy against whichHarvey reacted, and indeed he had a very richfield of speculation-including a notion of cir-culation-to draw on. He was himself an Aristote-lian, rather than a Galenist or a neoteric, but hisuse of Aristotle's sound scientific methods pro-duced a result that was dramatically new, andbrought opposition from all three groups. I do notpropose to give a detailed account of Harvey andhis work, for he is a figure who has attracted asmuch attention from historians as any in thehistory of science.'4 Rather, we must see how hiswork fits into the background described in earlierarticles.

Harvey's book of 16281' is set out in the formalstyle of a university dissertation, and the sequenceof topics tells us nothing about Harvey's own pro-gress in his discovery. We are left with his remarksto Robert Boyle, found also in a communicationto Riolan, that it was a consideration of the valvesin the veins that first gave him the idea. We haveseen before that the traditional notion of a valvewas Galenic, and it included the idea that somematerial always flowed back across the valve in the"wrong" way. The analogy of mechanical, water-restraining valves that did not allow a back-flowwas not used in physiology until the late sixteenthcentury, and the English word "valve" expressingthis idea did not enter the language until shortlybefore Harvey in an anatomical digest that hecertainly read. Already convinced by Colombo'sdescription of the pulmonary transit, and believingwith other Aristotelians that the veins arise fromthe heart, Harvey would have quickly seen that toadmit the competence of the venous valves was toreverse the direction of bloodflow in the veins,returning venous blood to the heart from the

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tissues, whence it had been delivered from theheart by way of the arteries.

In his formal exposition of his argument in DeMotu Cordis (as well as in the earlier Lumleianlectures) Harvey approaches the question of cir-culation by insisting on the forceful systole of theheart, against Galen. Galen had said the heart wasnot of the same muscular nature as the skeletalmuscles, and did not act in the same way. Harvey,at least in his earlier days, retained a belief in thethree kinds of fibre16 of which Galen said all hol-low organs were composed, although he wassceptical of the attractive and retentive functiongiven to the straight and oblique fibres respectivelyby Galen. This doubt probably came fromFallopio, under whose criticism Vesalius quiteabandoned the notion of the three sorts of fibre.Harvey, in the book of 1628, denies that the heartis made up of these three sorts, as contemporarythought held, but says that the wall of the heartand the septum consist of circular fibres, whilethe "armlets" (lacertuli)17 consist of oblique fibresserving to pull the apex of the heart to its base.Lacertuli for Harvey were the longitudinal fibrousstructures of the ventricles which he suggests mis-led Aristotle into imagining that the "nerves"arose in the heart. Harvey's emphasis on thesphincter-like circular fibres of the heart was de-signed to refute the idea, illustrated by Vesaliuswith the analogy of osiers and rushes made intothe shape of a pyramid,'8 that the heart contractedby its longitudinal fibres only and thus expandedat its girth while the apex was pulled towards thebase, becoming more capacious.Harvey also substantiates his argument that the

heart is a muscle by reference to the HippocraticOn the Heart. It will be remembered from myfirst article that the author of this book clearlysaid that the blood of the right ventricle is pre-vented from reaching the left ventricle, the seatof the mind; the septum was not thought to bepervious. Probably the septal pores were purelyGalen's invention, introduced to explain his strenu-ously argued claim that the arteries contain bloodand not spirit alone. We have already noted thepossiblility that it was a perusal of some such pre-Galenic work on the anatomy of the heart as theHippocratic On the Heart, combined with Galen'scredible blood-filled arteries, that convinced Ibn alNafis of the pulmonary transit.Having established the heart as a muscle, Harvey

proceeds to show that the arteries are filled pas-sively, and that the pulse is not an active phase ofexpansion along the arterial coat from the heart,as Galen had said. Following this, Harvey arguesfor the pulmonary transit of blood, using

Colombo's anatomical observations of the presenceof blood in the pulmonary vein and left ventricle,the size of the pulmonary vessels, and the argu-ments we have met before. The clinching ana-tomical arguments for the pulmonary transit arethe non-porosity of the septum and the structureof the cardiac valves. Harvey alludes to the notionthat the septum is porous, "But, damme, there areno pores and it is not possible to show such"'9("Sed mehercule porositates nullae sunt, nequedemonstrari possunt").20 Franklin translatesHarvey's caecae porositates as "invisible pores,"but it is perhaps more likely that they are thevisible but not perforate pits (that is, "blind") onthe septal wall that were admitted by all anatomists,but which Galen said were porous, as seen by theeye of reason. At all events, Harvey is thus putinto the position of denying pores to the septumbecause they are not visible, but accepting pores inthe flesh of the lungs (and body) that are equallyinvisible, but which were defensible in terms ofauthority and reason, arguments that anatomistssince Galen had always used, and with whichHarvey's opponents were as well equipped as he.By the idea of the pulmonary transit, the anomalyof the artery-like vein and the vein-like artery isresolved, and Harvey argues energetically for theclose correlation of structure and function: thevenous artery is a vein not only in structure butalso in function. If it served to carry air (as con-temporary but not classical Galenism held) whydid it not have the structure of the harsh artery,that is, the trachea?21 Why suppose that the twosides of the heart have quite different functions,the one sanguineous, the other spiritual, when thestructure of the heart clearly shows it to be oneorgan? How can the lungs and windpipe have thesame function as the left side of the heart whentheir structure is so very different? With Harveycame the final disappearance of the ancient ideaof two fundamental vessels and systems, the venous(nutritive) and arterial (respiratory) that we met inthe first article.Having announced the pulmonary transit,

Harvey turns his attention to the remainingmatters-namely, the amount and the source ofblood passing through the heart and lungs. He tellsus that in attempting to discover how much bloodpassed through the heart, he undertook manyanimal vivisections, and devoted his thought to thesymmetry and size of the ventricle and vessels.22He pondered too on the skilfully-contrived valvesand fibres,23 and arguing like many before himthat Nature does nothing in vain, he concludedthat the amount of blood passing across the valvesin the direction they allowed was greater than that

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which could be supplied from ingested food or ab-sorbed as nutriment by the body. His method ofestimating the amount of blood passing throughthe heart was partly anatomical in that he beganwith the quantity of blood held in the relaxed leftventricle: he says that he has seen two ouncesin the human body. He then estimates the volumeof the contracted ventricle and calculates from thedifference the amount ejected at each systole. Thelatter quantities are entirely theoretical, andHarvey, pe.haps deliberately, remains imprecise.He takes his own lowest estimate and still showsconvincingly that even an eighth part of the bloodcontained in the relaxed left ventricle, ejectedduring contraction, soon totals a very large amountby the heart's repeated action. His only otherdirect measurement at this stage is to discoverthe total amount of blood in a sheep, by way ofshowing that the whole mass of blood must circu-late in a comparatively short time.24Having argued so convincingly for the circu-

lation of the blood, Harvey was then faced withan anatomical problem. How did the blood, reach-ing the fine terminations of the arteries, pass overto the fine venules to be carried back to the heart?The capillaries are of course invisibly small to thenaked eye and, unable to employ Aristotle's prin-ciple of observation, Harvey was forced to employtwo techniques used by anatomists for a long time-the eye of reason and reliance on authority.Harvey is hesitant about postulating direct anas-tomoses between arteries and veins, even on thesmallest level, but his arguments for some kindof passageway are like those used by the championsof the pulmonary transit. The texture of the liverand kidney is far denser than that of the lungs,yet no one denies that the former two organs allowthe passage of great quantities of fluid; why not inthe case of the lung also? Harvey speaks of the"porosities"25 of the lung, and avoids the idea ofa vessel-to-vessel contact. As we have seen, Harveylater wanted to deny any connection with Riolan'sideas, and in a letter to Schlegel he totally deniesthe existence of anastomoses "as such are com-monly understood".26 He elaborates this by ex-plaining that arteries are much smaller than veinsand that the two types of vessel cannot thereforemeet mouth to mouth. Any such connection wouldbe rather like the insertion of the ureters into thebladder, but Harvey prefers to think in terms of"pores of the flesh," the implication being thatblood is extravasated between the arteries and theveins. The problem is really one of terminology:Harvey is prepared to accept that some arteriolesmay enter a venule in the manner of so manyureters inserted into a bladder, but he does not

want to call such a junction an anastomosis. "I donot believe it to be advantageous to the philosophicprinciple to decide something about the works ofNature from the meaning of words, or to summonanatomical disputes before the grammatical tri-bunal."27 He rejects the normal mouth to mouthinosculations of the ancient tradition because hecannot see them, except at three locations-thecerebral choroid plexus, the spermatic preparativeveins and arteries, and the umbilical veins andarteries.

In this letter, however, he has been driven toelaborating his ideas by criticism and inquiry. InDe Motu Cordis he used a large quotation fromGalen's De Usu Partium. In all of the body, saysGalen "the arteries and veins communicate withone another by common openings and exchangeblood and pneuma through certain invisible andextremely narrow passages."28 Now here Harveycannot observe the invisibly small pathways, andis obliged to rely on reason and authority. HisAuthority is Galen, and Harvey makes no objec-tion to Galen's use of the term "anastomosis," orrather, the use of the term in Gadaldinus's editionof Reggio's translation, which is the version usedby Harvey.29Although Harvey's admiration of nature some-

times seems to be as great as Galen's, he seemsfreer of the dominating influence of the idea ofthe perfection of nature as a divine craftsman.There seems no providential reason why the bodyshould vary as much as Harvey's observations toldhim it did, sometimes passing beyond the bound-aries of "normal" variation and approaching thepathological. He was "frankly amazed" that therecould be so much variation in the structure ofhuman hearts, and like Sylvius held that at leastsome change had occurred since Galen. If naturedid nothing in vain she was nevertheless bound bycertain constraints, and was sometimes not quiteas careful as she might have been. She was con-strained not only by simple necessity, such as notbeing able to locate two organs in the same place,but also by considerations of the nobility of organs.so that in the event of a change taking place in thebody over a long period, the less noble organs hadto adjust their position to accommodate the morenoble, as the human kidneys had moved by reasonof the more noble liver. In the microcosm, as in themacrocosm, "the weakest to the wall";30 the leastnoble organs suffer all those above, and the heartwas the most noble of all, the sun of the micro-cosm.3' Sometimes Harvey seems to imply thatvariation in the body, for which there does notseem to be any providential purpose, is due tonature's hastiness or carelessness. The situation of

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the guts is uncertain and variable, for nature"Romidges (rummages) as she can best stow";32the cardiac valves do not "appear to have beenmade with equal skill in all animals in which theyare present. In some they are made relatively care-fully, in others relatively slackly and carelessly,"33

. . in aliis remissius & negligentius."134The principle that nature does nothing in vain

but yet was sometimes rather careless goes handin hand with Harvey's suspicion of reason and hisemphasis on empirical observation. We have seenthat Galen "saw" the pores of the interventricularseptum with the eye of reason by deducing theirexistence from the axiom that nature does notmake a structure without purposes, and a similarmode of reasoning was often used by other anato-mists. While Harvey may have been led to the ideaof circulation, as he told Boyle, by considering thepurpose of Nature in the design and position ofthe venous valves, yet he was always hesitant,because of Nature's occasional negligence and theobserved variability of the body, to reverse theprocedure and assume that an organ must have aparticular form to accord with a purpose ofNature.Harvey also shows his dislike of reason in refus-

ing to acknowledge that his description of thecirculation was incomplete without its final cause.His opponents criticised him for this, that he haddescribed how the blood moves, but not why, andhe replied in the second essay to Riolan that it wasenough in the first instance to establish that cir-culation occurred and later to investigate its pur-pose.35. The true method of procedure, saysHarvey, is observation "stabilised" by reason;through a study of the sensibly manifest, abstrusethings become better known. This is fundamentallyAristotelian, and Harvey's views on scientificmethod, the relative roles of observation andreason, are largely Aristotle's.30 Harvey's words onthis in De Generatione Animalium refer to theneed to keep one's universal concepts in good orderby repeated observation and induction. On theother hand, the Aristotelian method of syllogismis "mere dazzle"37 leading to sophistries, andsophistry breaks up against sense like the wavesof the Sicilian sea against the rocks insideCharybdis.38 In his letter to Hofmann, Harveyrefers indirectly to himself as an analytical phil-osopher proceeding from "facts" to causes. Wehave seen before that the term analysis in academicanatomy was used almost entirely in connectionwith teaching, proceeding from the appearance ofthe whole body often by means of dissection to thenature of its constituent parts, its similars, humours,qualities, and principles. The reverse procedure of

synthesis was also a teaching method, beginningwith those things shown by analysis. Harvey almostcertainly called himself an analytical scientist39because he followed Aristotle's method in thePosterior Analytics;40 here Aristotle recommendsa progress from singulars, most readily known tothe senses, to universals. The idea as used in aca-demic anatomy does not come directly fromAristotle, and although there are some similarities,its lineage is involved. One difference is immedi-ately clear: Harvey is using the term analysis toindicate a mode of research by which new truthsmay be discovered, not a method of teaching. Aneat contrast is provided by his opponent Riolan,who discusses the matter in his commentary onGalen's De Ossibus. This is expressly a didacticand defensive exposition of Galen's osteology, andsince, Riolan claimed, Galen wrote only what istrue or probable4l it is an underlying assumptionof Riolan's discussion that there is little possibilityof making new discoveries. Synthesis, he says, isthe best method of teaching, while analysis "con-firms and demonstrates to sense what the firsttaught theoretically."42 For Riolan synthesis andanalysis form a teaching and learning method thatruns in a circle, beginning and ending in theory.Analysis is secondary, confirmatory, and didactic.For Harvey analysis is a method of scientific investi-gation used in the discovery of new truths, passingfrom singulars most apparent to the senses byinduction to universals and true knowledge.

Mechanism and the new philosophy

Enough has been said on the traditional elementsin Harvey's thought, his Aristotelian methodology,and fundamental concept of life. But Harvey livedthrough one of the most significant periods of intel-lectual change in the history of science, and by theend of his life the intellectual landscape aroundhim had changed almost beyond recognition.

Descartes was a contemporary of Harvey, andsomewhat grudgingly accepted, and then modified,the idea of the circulation of the blood. Both con-senting to and modifying the idea were done in theinterests of Descartes' world-view, with interestingresults. Descartes had early decided that all con-temporary education and knowledge were worth-less, and that future progress must be built onsurer foundations. He consequently returned tofundamental principles of metaphysics and, largelydeductively, created a world-view that was pro-foundly different from the neoclassical synthesisof the schools (though curiously similar in somesuperficial details). The system rested on themutual exclusiveness of soul, non-extended and

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thinking, and matter, extended and non-thinking.In the body the soul was responsible for the intel-lectual operations and voluntary motion. All otherbodily activities were the necessary result of thedisposition of the matter of the body, or in otherwords they were mechanical. Animals, lackingsouls, were simply machines.The idea fitted well into the developing new

philosophy of the seventeenth century, which re-jected Aristotle's qualitative physics and reintro-duced the concept of atoms, or at least funda-mental particles, that had been so objectionable tohim and to Galen. The notion grew up that ulti-mate reality lay in matter and motion, both ofwhich were measurable and could be handled bythe aid of geometry, the only certain science.Aristotle's Qualities and Galen's Faculties werelabelled "occult" because their mode of operationcould not be understood in the new reductionistframework.

In Cartesian physiology,43 then, only voluntarymotions were dependent on the soul, and thereremained a large group of unconscious "vital"motions over which the soul had no control andwhich were relegated to machinery. The most im-portant of these was the beating of the heart, whichdespite Descartes' fresh start remained a funda-mentally important organ, the source of allmotions in the body. Descartes accepted that theblood circulated, but claimed that the mechanismof the heart's action was not a forceful systole, asHarvey and Erasistratus has said, but a forcefuldiastole, as Galen had said. Of course, Descartesrejected Galen's notion along with all the otherapparatus of antiquity, and inserted in its placethe idea that the blood entering the heart vapour-ised by the heat of a fire-without-light placed thereby God. The subsequent expansion forced openthe arterial valves and the blood issued into thebody, where it condensed and returned in liquidform to the heart. Now, although Descartes in-sisted that the fire-without-light was a naturalfire, much like the heat arising in wet hay or byother natural processes, he could make it reallycredible only by assuming it was the direct gift ofGod that maintains or originates it, which is notvery different from the traditional innate heat ofthe heart of almost every Greek writer.

In a similar way Descartes described nervousspirits in purely mechanical terms. He said theyconsisted of fine particles, drawn off from theblood by the rapidity of their motion in accordancewith his laws of motion. Those travelling fastestrose to the brain as the simple result of theirvelocity, and there constituted the nervous spirits,which occupied the nerves and were the agents of

sense and motion. The result is not very differentfrom the contemporary or classical concoction ofanimal spirits from the blood in the brain, exceptthat Descartes has provided a model for the ex-planation of bodily motions that could be indefi-nitely extended and modified.

Descartes' continental influence was consider-able, particularly in France. In England Harvey'swork was accepted before Cartesian mechanism inphysiology was widely known. In conscious emula-tion of Harvey there grew up an English school ofphysiologists who attempted to be experimentaland inductive, without any sharp break with thescientific ideas that had made Harvey so successful.Harvey's influence also meant that several ablemen were investigating further the problems ofcirculation and the action of the heart.One of the most important of the "Harveians"

was Francis Glisson, who carried devotion totraditional ideas to the point of reaction againstthe ever more apparent Cartesian mechanicalrevolution. He is best known for his work on"irritability"-the innate power of the muscle tocontract. All matter, said Glisson, is essentially tosome degree alive and capable of motion.4 Thissimple power exists through a whole hierarchicalrange from inorganic matter to the rationality ofman; in all cases motion presupposes desire, anddesire presupposes perception. Glisson's "simpleperception," "natural appetite," and motion area chain of events that involve sensation only at thelevel of material organisation that provides senseorgans, and which involves conscious volition,appetite, and perception only in the self-consciousmind of man. Glisson's hierarchy related directlyto the traditional grades of soul, the vegetative,sentient, and rational, and his language of caus-ality, matter, and form is that of the schools.Simple and compound perception and appetite areterms elaborated in the same context into currentdoctrines of moral philosophy. All this, and par-ticularly unconscious perception and the primevallife of matter, was incomprehensible to the Carte-sians, for whom all actions of the soul wererational and conscious and all matter was soullessand lifeless. It was, however, much more accept-able in England, where there had been no Cartesianbreak with past ideas and where there was agreater audience for providential explanations.Cartesian corpuscularity was open to the charge ofatheism, as Descartes himself felt, just as Aristotleand Galen had railed against the atomists of theirtime by declaring that there could be no Purpose,no Final Cause, no evidence of a skilful creator ina mindless, fortuitous concourse of atoms. InEngland it seemed that the soul was not only the

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vehicle of personal immortality but the essence oflife and motion in the body.

All this is necessary background to an under-standing of post-Harveian work on the heart. In-deed, the heart proved to be a critical case in thepresentation of mechanical and opposed explana-tions of life. It was the most obvious and necessaryof the vital actions, yet was clearly outside thecontrol of the conscious and rational soul. More,it continued to beat for a while after being excisedfrom the body (the beating of separated vipers'hearts was a scientific curiosity of the time) and sowas absolutely removed from the soul in the brain:was this not good evidence of mechanism? Yet onthe other hand the heart was greatly disturbed inmoments of emotion (which was exercised by thesoul) and it adjusted itself to the needs of the body(it was widely held that the increased pulse offevers was part of the living body's attempt tothrow off the morbific matter): were these notpowers far above those of mere mechanism?The dispute continued for at least a century and

a half after Descartes had introduced the idea ofa mechanical body. By the end of the seventeenthcentury it looked as if mechanism was to becomethe new orthodoxy of medical theory.45 The pump-ing heart and the circulating blood had become thecentral physiological interest. They lay behindother suggestions, such as glandular secretion, sup-posed to be effected by the differential secretion ofparticles of different sizes or shapes in differentglands, depending on the velocity of the particles,or their shape and the shape of the pores in theglandular filter. Given the fact of circulation, cer-tain residual technical questions were left to beanswered. Was the heart capable of sustaining theentire circulation, or did the small arteries assistby the contraction of their muscular coats? Morebriefly, what was the force of the heart? Thequestion was tackled by the Italian mechanistBorelli, but the physics of the time was incapableof formulating the problem, and Borelli's answerwas an impossibly high figure, expressed as weight,while the motion of the blood leaving the heartwas thought of in terms of projectile force. Thebody was increasingly thought of as a hydraulicmachine and the proper physiological questionswere ones of viscosity, friction, velocity, pressure,and all those associated with the passage of fluidsthrough tubes.

This standard interpretation did not containDescartes' fire-without-light in the heart, andinstead the heart was regarded as a muscle likeothers in the body, as Harvey had maintainedagainst Galen. But the standard mechanical pic-ture of the body explained muscle contraction by

assuming that muscles were hollow sacs or chainsof cells of some specified geometrical shape, andthat contraction was effected by the nervous spiritsinflating the cells and so broadening their widthwhile contracting their length. But the nervousspirits, being purely mechanical and with no motiveforce of their own, derived all their power fromthe circulating blood, from which they weremechanically derived. The blood itself derived itscirculating force from the heart, which like othermuscles was supposed to derive its contractionfrom an influx of nervous spirits. It is surprising tous that this perpetual motion machine was acceptedwithout difficulty by several mechanical physi-ologists in the late seventeenth century. It is truethat some began to see the problem of where themotion was coming from, given that the perpetualcircuit must in fact constantly lose motion byfriction and muscular activity, but before theproblems were fully articulated another influence,as great as that of Descartes, altered biologicalthinking: the influence of Newton.46

It took about half a century-the first half ofthe eighteenth-for physiologists to assimilateNewton. Most medical men could not understandthe Principia, but the Opticks (in particular inEnglish) contained a number of broad hints as tohow Newton thought the body worked. Englishphysiological theory was at once filled with etherand particles; vibrations of the first, and short-range attractive and repulsive forces of the secondbeing used to explain nervous transmission, muscu-lar motion, and all "fermentative" or chemicalactions. Later there came some recognition ofNewton's physics, the questions of mass, momen-tum, and the forces necessary to produce or altermotion. Before this physiology had been kinematicor qualitative, and now it became by degreesdynamic and quantitative.

This change from kinematic to dynamic physi-ology gave a curious twist to the establishedpositions mentioned earlier. Those who, likeGlisson, accepted a more or less traditional notionof a soul in the body, and held that the materialsoul was essentially alive and that motion was theprincipal attribute of life, now found that thequestion of the origin of motion in the body wasself-answering: motion was life. Yet mechanism,both Cartesian and Newtonian, did much to en-courage the idea that matter was essentially inertand had to be moved by external forces. So if thebody was a machine, there was an obvious needfor an external supply of motion to make themachine work. Now that Newton had shown howto measure motion in relation to matter, and thatmotion was being constantly lost in the universe

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from friction, collisions between moving bodies,and so on, quantitative considerations showed toothat the body's motions needed constant replenish-ment. Newton had suggested that macrocosmicmotion was replenished by gravity, natural fer-mentations, and other actions, probably motivatedby the omnipresent ether, but those who trans-ferred the problem to the microcosm generallythought that the body was moved by the soul. Theparadox is that it was these traditional "animists"who used quantitative arguments in a penetratingway. The more they could show that the body wasa true hydraulic machine the clearer it was that itneeded an external moving force. The traditional"mechanists" on the other hand denied, in theCartesian tradition, that the soul of the body didanything more than think. They were driven topostulate that the motion of the muscles was dueto some natural or God-given force innate in themuscle itself, a force resulting either from thecomplexity and disposition of matter itself, or froma divine fiat. Again the question of origin andquantity of motion to a certain extent answereditself, and the physiology of the traditional mech-anists was qualitative and kinematic, without eventhe emphasis on the body as a hydraulic machinethat is found in animist writings.The heart was central in this problem. In the

immediate post-Newton period the Scot Pitcairneset up the hydraulic machine model of the bodyfor other Newtonians in Britain. Keill, Jurin, andHales worked on the force of the heart and ex-emplify a change in the practice of Newtonianscience from the mathematical (the influence ofthe Principia) to the experimental (that of theOpticks). Hales was the most experimental anddetermined the blood pressure of a horse by in-serting a tube into the crural artery and observingthe height of the column of blood in the tube.Hales was perpetual curate of Teddington onThames and had a very English view of the ration-ality of the Creator and his Creation. It may wellbe that natural theology of this kind encouragedseveral English thinkers, who had never quite for-gotten the traditional motive faculty of the soul, tooccupy animist positions in the post-Newtonianperiod. Newton's own circle included a number ofScots also, who may have shared these ideas.The situation on the Continent was different,

with the one exception of Montpellier. Here mech-anical doctrines were orthodox until 1735 whenFrangois Boissier de Sauvages began to teach thatthe body was a true hydraulic machine and that asa result it, and particularly the heart, must havea supply of moving force, which could be nothingother than the traditional soul of the Greek medi-

cal writers and the Christian fathers. In particularthe soul was the "healing power of nature" of theHippocratics, and animism could lead away fromthe absurd speculations of the mechanists to a newHippocratic empiricism. The earlier mechanicalteaching at Montpellier, in an effort to introduceNewtonian ideas, had for example explained themotion of the heart on the basis of "libration."While the direct meeting of equal masses movingat equal velocities was assumed to result in totalloss of motion, their indirect meeting was held toproduce constant oscillation about a point. Theheart was said to move in a libration of this typeas a result of all the forces acting upon it: bloodentering, blood leaving, gravity, pressure from thebody, and so on. The result was said to be trueperpetual motion, without any internal or externalinput. Consequently the dynamic problem of theorigin of motion was missed, no account was takenof loss of force in friction, and the whole problemremained essentially qualitative without anyattempt to quantify the forces said to be in action.47

The soul and machinery of the heart

As suggested above, the heart was a critical casein any explanation of animal motion, mechanistor animist. Although widely accepted to be amuscle, it was clearly not under the control of thewill, and more importantly it beat with a uniquealternate motion. Its beat also continued for awhile after excision from the body. The GalenicPulsific Faculty satisfied no-one, and the Cartesianalternate ebullition and condensation did not provepopular (although a similar hypothesis was adoptedby Harvey's opponents to nullify his quantitativearguments: Riolan, Hofmann, and Primerose).One answer was chemical. It was developed by

post-Harveian English physiologists in Oxford whoworked on the heart and on respiration. Boyle andothers recognised similarities between combustionand respiration, and although oxygen as a distinctelement was not discovered, many processes ofwhat we call oxidation found a common explan-ation in the new particulate natural philosophy ofthe time. Lower worked on the heart, but it wasThomas Willis, Sedleian professor of natural phil-osophy at Oxford, who constructed an entirescheme of physiology from the iatrochemistry ofthe time. The contraction of muscles was accountedfor by the effervescence of two particulate "spirits"meeting in the cavities of the muscle, expanding itswidth and contrasting its length. One of the spiritswas derived from blood and was resident in themuscle and the other was sent down the nervesupon a command from the soul; this spirit had

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features in common with the "nitro-aerous" spiritof respiration. Nervous spirit emanating drop bydrop from the nerves ensured the alternating con-traction of the heart. To a certain extent thisanswered the dynamic problem of the source ofthe power of muscular motion by referring it to achemical reaction, but for Willis, writing in themiddle of the second half of the seventeenthcentury, the problem was not heightened byNewtonian physics. Although adopting completelythe corpuscular philosophy of the seventeenth cen-tury, Willis was no mechanist. He claimed thatman had two souls, a higher rational animus occu-pying the nervous system, and a lower materialanima possessed in common with animals and re-sponsible in a traditional way for some of thesentient and vegetative faculties. It was all anEnglish compromise between old and new, and wecan see from Willis's preface to his book on thebrain and nerves48 that his animistic notions werebound up through a natural theological argumentwith traditional Christian views.Another and more directly animistic answer was

put forward, surprisingly enough, by one of themost influential of all mechanists, the ItalianBorelli. Borelli had very successfully applied theprinciples of mechanics to the gross movements ofanimals by considering their limbs as levers and soon, but his attempt to produce a micromechanicsof muscular motion was less successful. It wasagain a question of a hypothetical geometry ofstructure, which he used to show the direction ofa kinematic transfer of motion. But the ultimateorigin of motion was much more difficult to ex-plain, and Borelli was driven to conclude that themotive force of the heart was the same as that ofthe voluntary muscles, which were moved, withoutquestion, by the will, a faculty of the soul.49 Borellisupposed that the embryonic heart at the earlieststage of development could transmit to the soul itsperception of the heaviness and heat of the bloodthat filled it. The soul, although at this stage notrational or conscious, was nevertheless able to actin the best interest of the body, and it accordinglygenerated within the heart a motion designed toremove the unpleasant sensation arising from thecontained mass of blood. This first contraction ofthe heart expelled the blood into the embryonicarteries. The heart was filled again from the veins;again the soul acted, and the future pattern ofsystole and diastole was established. Before longthe motion became habitual to the soul, so thatthe unpleasant stimulus was no longer felt and theresponse was automatic, in the same way as aharpsichordist plays a piece perfectly without beingaware of the motion of each finger in turn. Borelli

makes it clear that this original action of the soulto remove an unpleasant sensation was exercisedby the faculty with which the soul avoided Evil andpursued Good in general. His terminology is thatof the standard moral philosophy or "psy-chology"50 of the time and closely related to theSimple Perception, Appetition, and Motion ofGlisson and to the animists' notion that fever wasthe soul's effort to rid the body of noxious matter.

This doctrine of action and reaction was de-veloped by both animists and mechanists in theeighteenth century. In both cases the "simpleperception" of Glisson or Borelli became "stimu-lus," and the mechanists vigorously denied thatany sort of perception was involved. They insistedthat the response to the stimulus was purelymechanical, much as Descartes had described amechanical reflex action in which the nervousspirits from the sense organs were literally re-flected at the pineal gland in the brain into motornerves. It was indeed a part of the Cartesian in-heritance to deny any soul-directed activity, includ-ing simple perception, at any level lower than theconscious rationality of man. The animists claimedthat the stimulus was perceived at a non-consciouslevel by the living powers of the tissues and thatthe resultant motion was "wise" either in exhibit-ing the habituated action of flight-from-evil, as inBorelli, or in reflecting the wisdom of the Creatorin having united the soul to the body according tocertain fixed and beneficial laws.

It was this dispute on the topic of sensitivity thatsharpened the distinction between the various kindsof non-conscious motions-the "vital" or "in-voluntary." Reflected, or reflex, actions weregenerally admitted to be simple, whether mediatedby simple perception or mechanism. They wereinvariable and beneficial, and in terms of theexperimental results obtained by both schools ofthought eagerly trying to demonstrate their owntheoretical positions, in all major aspects reflexactions were the same to both parties. Secondly,there was a traditional group of actions knownas "sympathetic." These involved a greater degreeof co-ordinated complexity, both physiological andpathological. These motions were apparent mostlyin the abdominal viscera. They had traditionallybeen accounted for by the movement of humoursand by "occult" explanations like similarity offunction of the sympathising parts, similarity oforigin, similarity of substance, spatial proximity,and the use of communicating structures like mem-branes, blood vessels, fibres, and nerves. The de-bate about sensitivity was immediately relevantbecause all except extreme mechanists allowedthat sympathy included some kind of feeling that

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was not necessarily perception or sensation. Thedebate, and particularly the work of Haller,Whytt,51 and others, established that the nerveswere the only sensitive parts of the body and thatthe muscles were the only "irritable"-that is,contractile-part. That the nerves serving thesympathising organs of the abdomen were of atype different from other nerves had been recog-nised by Willis, but it was not until the 1720s thatParfour du Petit showed that the sympatheticnerves were not cranial nerves. French anatomicaltexts like that of Winslow soon described thesympathetic nervous system as distinct from thecentral nervous system, although Haller was stilllooking for the cranial "origin" of the sympathetictrunk later in the century.The most widespread of the mechanical ideas

about the beat of the heart was that of the "medi-cal teacher of all Europe," Hermann Boerhaave.He supposed that the nervous spirits passed downfrom the brain to the heart through nerves which,before entering the muscular substance of theheart, passed down between the ventricles. Whenthe spirit reached the muscular substance, contrac-tion ensued and the nerves were compressed, thushalting the flow of spirit; the cardiac muscles con-sequently relaxed, and the spirit flowed once more.It was difficult to account by this theory for thealterations in heartbeat that accompanied fever,exercise, emotional disturbances. and so on, andBoerhaave's pupils abandoned the idea. Haller52replaced it with a form of the stimulus and re-sponse theory, in which the entering blood arousedthe irritability of the ventricles. The response wasin proportion to the stimulating nature of theblood, which in fevers carried acrid particles, in-creasing the pulse rate. Whytt, from an animistviewpoint, argued that some emotional disturb-ances increase the sensitivity of all parts of thebody, and so the same stimulus of blood in theheart produced a greater response.

Vitalism

Although considering themselves profoundly op-posed on theoretical principles, the animists andthe mechanists for all practical purposes arrived atessentially similar results. The animists, paradoxi-cally insisting that the body was a pure machine, inorder to prove the necessity of a constant supplyof dynamic force to move the inert matter of themachine were obliged to admit that this supply,the soul, acted according to fixed laws. The mech-anists, more aware of dynamic problems afterNewton but refusing to accept an incorporealsource of power, postulated natural forces arising

in matter as a result of its complexity. In otherwords they denied the inertness of matter anddiscussed innate powers like Haller's irritability orvis insita which, he said, was natural but God-given. These biological properties were closer to aposition long since abandoned by the animists, thatof Glisson's innate forces of matter. They wereunquantifiable and diverted biologists' minds awayfrom the dynamic and mathematical problemsfaced by the later animists.

In this way both parties had to a certain extentoccupied each other's territory in theory, and inpractice had reached similar conclusions. Towardsthe end of the eighteenth century the theoreticalpositions were abandoned, and almost the entiremedical world reached some sort of consensus thatwe can call vitalism. The most objectionable aspectof animism had been that the immortal and im-material soul should directly concern itself withmundane physiological activity, and the most re-pugnant aspect of mechanism was that the bodywas a mere machine. Vitalism involved the assump-tion that the uniquely biological properties werethe characteristics of essentially living, but notanimated, matter, that they were unique to physi-ology, which was thus not dependant on physicsas it had been in the periods immediately afterDescartes and Newton, and that they were naturaland not divinely imposed upon matter any more thanthe simple physical qualities of gravity and elasticity.Animism had always had the advantage over

mechanism in that it had a ready answer toquestions about the beneficial result of most bio-logical actions-that is, that they seemed guidedtowards the good of the animal in differing cir-cumstances. Early and extreme animists like Stahlhad insisted that the soul was essentially free, notbound to the body by laws, and able to lead thebody in the best possible way (or even irrespon-sibly). When mechanists faced the problem theiranswer was that the original design of the bodywas that which ensured its continued and adaptableoperations. In a similar way the early vitalistictheories involved a notion of a guiding forceintrinsic to the body, promoting embryonic de-velopment and adapting the body to new circum-stances. Throughout the nineteenth century thisidea was whittled away-for example, by the dis-covery that organic compounds can be synthesisedartificially from inorganic components-until afterDarwin it became possible to refer all biologicalactivity to original design in the evolutionary sense.

General conclusion

In these articles we have examined ideas on the

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structure and function of the thorax and its con-tents, and in particular the heart, over a periodexceeding two thousand years. On reviewing thisperiod the most striking thing is the continuity ofthese ideas. Harvey turned to Erasistratus to sup-port his case against Galen, and the general effectof Harvey's discovery was to overturn the ancientidea of two separate vascular systems in the body,the nutritive and respiratory. In seeking a non-mechanical explanation of the beat of the heartthe eighteenth century animists turned to Hippo-crates. The discovery of the circulation of the bloodwas a conspicuously successful piece of seventeenthcentury science, and one in which we can see somany features of modem science that the interestof the historian of science is drawn to the develop-ment of modern science. Science, in medicine andin other fields, is a dominant feature of our society:how does it compare with that of earlier ages?We must first avoid the superficial conclusion

that our predecessors were simply credulous monksor teachers who accepted without question thesurviving words of the ancients, a conclusion thatmight be suggested by the historical continuity ofideas. The natural philosophers of previous ageswere after all intelligent men, seeking after truth,and we shall be less close to historical prejudiceif we assume that the answers they gave to thescientific problems that faced them were the bestanswers in the circumstances of their "factual"knowledge and their ideas of scientific procedure.Their scientific knowledge came from three majorsources: authority, reason, and observation.Authority, auctoritas, was the work of the authors,auctores, principally the ancient writers whoachieved immense standing in the West as frag-ments of a half-forgotten and superior civilisation.More simply the authorities were used in educa-tion, and most medical men never went beyondtheir education. This knowledge had exactly thesame status as that taught to a modem medicalstudent, who, like his predecessor, has no externalreason to doubt the validity of what he is beingtaught. Only when he goes on to become a re-search scientist can he have an independent assess-ment of the truth of this knowledge. In this respectancient science differed somewhat, for the distinc-tion between teaching and research was not soclearly marked. We noted in an earlier article thatthere was sometimes confusion between teachingand discovery when Galen's remarks on "method"were being interpreted in the middle ages and re-naissance, and although both Aristotle and Galendiscuss the creation of new knowledge by dis-covery, it was often assumed that both of themknew as much as a man could know. In that case

there could be no distinction between teaching anddiscovery for later ages, for "discovery" wassimply the establishment of what the ancients hadsaid, that is, teaching.Yet the most erudite of the later natural phil-

osophers knew that Aristotle and Galen had des-cribed scientific procedures that would lead to newknowledge by the work of later researchers. Yetthese erudite men by inclination were bookish, andthe least likely to put such precepts into action.They were, however, perfectly disposed to developanother aspect of scientific procedure they readabout, that is "reason," the second of the sourcesof knowledge mentioned above. Aristotle had ex-tensively formalised and practised the inductivemode of argument (from many particulars togeneral principles), and Galen had made remarksin the same vein in relation to case histories.Nevertheless, when reason was used in anatomyand physiology in the middle ages and renaissanceit was invariably deductive, beginning with anaxiom such as "nature does nothing in vain" or"opposites cure opposites," and ending with thenecessary shape or function of a part. The reintro-duction of inductivism, following Bacon andothers, was a conscious part of methodological re-form in the later renaissance.

Induction requires observation, the third of thesources of knowledge. Observational and inductive,the biological science of Harvey's predecessorssuch as Fabricius was on a level with that ofAristotle, but it was not yet modern science. Dueweight was given to authority, which however wasconfirmed where possible by observation, andreason was used inductively to categorise and il-luminate relationships between categories, such asanalogous and homologous structures in animals.But modem science has an element lacking equallyin Fabricius's science and in Aristotle's: experi-ment. Aristotle dissected animals, but this was buta small extension of the principle of observation.The Alexandrian anatomists and physiologists,however, vivisected animals and perhaps man. Vivi-section is an extension of observation that almostreaches experiment, if we take experiment to bean abnormal manipulation of nature with a viewto correlating the results with the new situation.In exploring the living body, the Alexandrianscould hardly fail to notice distant and unexpectedparalysis from cutting a particular kind of fibre,and it is clear that they soon began to look forthe unexpected-that is, to experiment. Galen,following the Alexandrians, used experiment ex-tensively and generally to good effect, as in hisserial section of the spinal cord in the living ani-mal. Here he was able to begin his procedure with

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experiment, cutting the cord, and relate the results,localised paralysis and loss of sensation, to the con-clusion, the function and pathways of the nerves.The greater part of Galen's experiments, however,were used at the end of a chain of argument toconfirm his own opinion or reject someone else's:useless to argue with the Erasistrateans, who alwayshad some kind of reason for a counter-argument,so put the matter to the test, ligate and incise theartery to show that it contains blood. Where hisown opinions are uncontested (perhaps becauseunknown) Galen does not support them with ex-periments. The cardiac septal pores were estab-lished by reason but not verified by experiment,whereas Galen does use a hydraulic experiment

4

Figure The only illustration used by Harvey in DeMotu Cordis is this one, of an arm ligatured forphlebotomy. It is taken from a book by Fabricius,Harvey's teacher, who took it in turn from Bauhin'spopular anatomical text. It shows veins swelling distalto the ligature, which prevents blood returning to theheart. According to pre-Harveian thought bloodmoved centrifugally from liver to extremities, and sothe vein should have swelled on the proximal side ofthe ligature. Neither Fabricius, Bauhin, or any oneelse in the preceding two thousand years or so noticedthe anomaly.

that would have been suitable for his purpose inconnection with the disputed action of the kidney.Perhaps then modern medical science differs

from that of Galen principally in this, that experi-ment is used wherever possible to confirm or falsifyevery hypothesis, and to throw up new evidencefor further hypotheses. Additionally modernmedicine relies much more on numerical evidenceand mathematical reasoning. Colombo's discoveryof the pulmonary transit was experimental, andHarvey's argument for the systemic circulation waspartly quantitative, but there was no clear distinc-tion between sense "experience" and "experiment"(the Latin experimentum can mean both) untilafter Newton, and little sophisticated use of experi-ment until Claude Bernard.So the reason for the great continuity of ideas

over the period covered by these articles was thelack of an adequate means of confirming or reject-ing them. Ancient ideas formed not only theteaching curriculum, but the very means of think-ing of the vast majority of educated physicians andnatural philosophers. They were the stock-in-tradeof the practising physician, the hallmark of hisprofessionalism. Harvey himself suggests that itwas this professional and social reason that ac-counted for Riolan's Galenism. Physicians assimi-lated the old ideas in the same way that food wasassimilated in Galenic physiology, so that the ideasbecame part of them, and they literally could notsee evidence that pointed in another direction. Newstructures, like the valves in the veins, were givenold functions. Most remarkable of all, althoughletting blood had been practised throughout theperiod covered by these articles, so firm was theidea of a centrifugal flow of blood in the veinsthat no-one noticed that the veins swelled up onthe wrong side of the ligature (see figure).

Notes and references

1 Pre-reformation universities had both civil andcanon law.

2 Aristotle did not know of the nerves as structuresdistinct from other fibres. See the earlier articlesin this series and Solmsen, F, Greek philosophyand the discovery of the nerves, Museum Hel-veticum, 18 (1961), 150-197.

3 See Peller, S, Harvey's and Caesalpino's role inthe history of medicine, Bull Hist Med, 23 (1949),213-235.

4 Caesalpino's important works are the QuaestionesPeripateticae and the Quaestiones Medicae. Seealso Pagel, W, William Harvey's Biological Ideas,Basel, 1967.

5 Hofmann, C, Commentarii in Galeni De UsuPartium Corporis Humani, Frankfurt-am-Main,1625.

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6 Worth mentioning in this connection is Plater,whose views on the equivalence of the spleen andthe liver were versified by Pincierus, making aplay with Plater's first name Felix ("happy")

Platerus! Happy thou artIn Name and in wit and in art.Your doctrines invariably meanHigh office enjoyed by the spleen

would be an unpoetical rendering. Pincierus, A,Otium Marpurgense, Herborn, 1614, p 160.Plater's views are concisely set out in his DeCorporis Humani Structura et Usu, Basel, 1603.

7 Hofmann, C, De Thorace, Frankfurt, 1627.8 Riolan, J, Anthropographia, Paris, 1618, pp 395-

396.9 Published in the Everyman edition of De Motu

Cordis and his letters; The Circulation of theBlood, trans Franklin. Everyman, 1963.

10 Of course, Vesalius's purposes were not identicalto those of the medical educators, but there doesseem to have been a shift in the intellectualinterest of the time from an analytical search forstructure to a synthetic presentation of the wholeman. The neoscholastic period was coincidentwith a general movement of return to authorityin political, religious, and educational fields. SeeFrench, R K, Anatomical education in a ScottishUniversity, Aberdeen, 1975, and Kearney, H,Scholars and Gentlemen, 1970.

11 Crooke, H, Microcosmographia: A Description ofthe Body of Man. Together with the Controversiesbelonging thereto, London, 1615.

12 Bauhin, C, Institutiones Anatomicae, Basel, 1609(4th edition).

13 Du Laurens (Laurentius), A, Historia Anatomica,Frankfurt, 1602.

14 The reader is recommended particularly to Pagel(1967) and Whitteridge, G, William Harvey andthe Circulation of the Blood, London, 1971.

15 Harvey, W, Exercitatio A natomica de Motu Cordiset Sanguinis in Animalibus, Frankfurt, 1628.

16 Harvey, W, Lectures on the Whole of Anatomy,trans O'Malley, C D et al, Berkeley, California,1961.

17 Harvey (1963) p 107; (1628) p 70.18 Harvey (1628) p 23; (1963) p 28.19 Harvey(I963)p19.20 Harvey (1628) p 18.21 Harvey (1963) p 18.22 Harvey (1963) p 57.23 "ex concinno et diligenti valvularum et fibrarum

artificio," Harvey (1628) p 41.24 Harvey (1963) p 62.25 porositates pulmonum. Harvey (1628) p 3.26 Harvey (1963) p 186.27 Harvey (1963) p 188.28 Galen (1968) vol 1, p 303.

29 Reggio (Galen, De Usu Partium Corporis Humani,Paris, 1528) also uses the term, but it does notappear in Kuhn's Greek text. See Galen OperaOmnia, Leipsig, 1821-33, vol 3, p 455, and Galen,Opera Omnia, (Junta) Venice, 1625, prima classis,151v (used by Harvey).

30 Harvey (1961) p 68.31 Harvey (1963) p 3.32 Harvey (l961) p 54.33 Harvey (1963) p 103.34 Harvey (1628) p 67.35 Harvey (1963) pp 156, 116.36 See Keele, K, William Harvey, London, 1965, pp

103-106.37 Harvey (1963) p 193 (the letter to Morison).38 Harvey (1963) p 167 (to Riolan).39 Harvey (1963) p 120.40 Keele (1965) p 105. See also Entralgo, L, Harvey

and scientific thought, J Hist Med, 12 (1957), 220-234.

41 Riolan, J, Opera Anatomica, Paris, 1649, p 433.42 Riolan (1649) p 438. The italics are the present

writer's.43 Descartes, R, Treatise of Man (1664), ed and trans

by Hall, T S, Cambridge, Mass, 1972.44 Glisson, F, Tractatus de Natura Substantiae Ener-

getica, London, 1672. See also Temkin, 0, Theclassical roots of Glisson's doctrine of irritation,Bull Hist Med, 38 (1964), 297-328.

45 An excellent source for these changes in Englishphysiology is Brown, T M, The Mechanical Phil-osophy and the "Animal Oeconomy"-a Study inthe Development of English Physiology in theSeventeenth and early Eighteenth Century, Prince-ton University Ph D Thesis, 1968.

46 On the general influence of Newton, see Schofield,R E, Mechanism and Materialism, Princeton,1970.

47 This sketch of the introduction of dynamic physi-ology has not been given detailed documentationas an extended treatment of the topic is due toappear in a book on Newton's ether edited byCantor and Hodge.

48 Willis, T, The Anatomy of the Brain and Nerves(1664), ed Feindel, W, two vols, Montreal, 1965.

49 See French, R K, Sauvages, Whytt and the motionof the heart: aspects of eighteenth century ani-mism, Clio Medica, 7 (1972), 35-54.

50 See, for example, Hutcheson, F, MetaphysicaeSynopsis, Glasgow, 1742, published as used atGlasgow in the earlier eighteenth century, andOtto, M H, De Elementa Juris Naturae etGentium (Juris Divini Pars Altera), Halae Magde-burgicae, 1738.

51 See French, R K, Robert Whytt, the Soul andMedicine, London, 1969.

52 Haller, A von, Elementa Physiologiae, eight vols,Lausanne, 1757-1766.

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Thethorax in history 6 Circulationand physiology than Galen, and had said almost nothing on medicine, his teaching embraced the whole of the ob:ervable world, and his modes of argument