Download Seeing Red: Harvey and the Circulation of the Blood

Lecture 14 Seeing Red: Harvey & the Circulation of the Blood
© Darrin Durant 2004
Seeing Red: Harvey & the Circulation of the Blood
Questions: Was Harvey (1578-1657) a ‘modern’, an ‘ancient’, or ‘both’?
Maybe none of the above? What made his claim ‘reasonable’?
Figure. 1: Theories are Under-Determined by data/observation/evidence
Data
Observations
Evidence
Theory1
Theory2
Theory3
Theoryn
Metaphors
Analogies
Networks: hypotheses &
auxiliary assumptions
Figure. 2: Theories are Networks (webs, nets)
Forceful systole
Material nature of blood
Blood is moving
Arithmetic argument is appropriate
Inferences from animals appropriate
Circulation
of the
Blood
 Aristotelian anatomy: goal is to discover causes
 No vein/artery distinction; blood vessels originate in heart;
heart as central organ.
 Method: 1. Inspection produces history, 2. generate a cause,
3. demonstrate completeness
 Galen (ca. 129-200 A.D)
 Venous blood = nutritive; arterial blood = vital
 Movement of blood = parts of body attract nutrients
 Right to left ventricle = pores in septum
rejects observation in favour of theory
 Diastole ([natural] expansion) = active phase
 Vesalius (1514-1564), De Fabrica Corporis Humani (1543)
 Criticized Galen’s reliance on non-human material
 1543 (1st ed) = Pores in septum cannot be seen, but the
Creator does work in mysterious ways
nd
 1543 (2 ed, 1555) = septum is impermeable
 Pulmonary Transit not thought possible (veins
filled with air and soot), but raises status of anatomy
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Lecture 14 Seeing Red: Harvey & the Circulation of the Blood
© Darrin Durant 2004
 Realdus Columbus (ca. 1515-59)
 Discovered, not the ‘lesser circulation’, but the pulmonary
transit of the blood (blood used up, new blood comes to lungs)
 Septum as impermeable
 Heart’s active phase = contraction (systole) = ejection
 Fabricius (1533-1619) and the ‘Aristotle project’ at Padua
 Get scientia via study of parts, organs & processes
 Vesalius incomplete; only Aristotle as predecessor
 Project?: about eye, ear, larynx in general; the animal
in general. Work on speech extends Aristotle.
 De Venarium Ostiolis (1603): On the Little Doors in the
Veins. Their purpose?: delay blood flow and prevent
flooding in extremeties; provide nutrients.
 Extends Aristotle’s project:
1. Inspection produces history, 2. Inquire into actions of the
parts, 3. Specify usefulness (use or cause of parts),
4. Demonstrate completeness (is #3 valid?)
*** Harvey & ‘The Way of the Anatomist’ ***
 Establish anatomy in one of two ways
1. By inspection (autopsia)  More certain, descriptive
a. Observation, sense, practical, in person
b. Autopsia = seeing for oneself
2. By instruction (doctrina)  More noble (final causes)
a. Reason, theory, books, tradition
 Harvey: establish the action of the heart and of the circulation by
anatomical demonstration
 The fact of circulation v. the cause of circulation
 E.g.: We may not know the cause of a plague, but would we
deny its existence?
 E.g.: Can you see an hypothesis?
 Only the purpose of circulation was a matter for theoria
 Harvey establishes circulation in the way of the anatomist, and uses
Aristotelian ideas to elucidate the purpose of circulation
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Lecture 14 Seeing Red: Harvey & the Circulation of the Blood
© Darrin Durant 2004
*** Harvey’s Argument ***
 Since all the blood is being actively pushed out of the heart in one
direction, and the volume of blood produced is greater than could be
used up and replaced by the body, it must circle back.
 Stated in Chap. 8 of De Motu Cordis (1628)
 How did Harvey make this look reasonable?
 Why did he think it was ‘compelling’ [‘logical’]?
 If it was ‘compelling’, why spend Chap. 9-14 defending it?
 Chap. 1-7: inconsistencies in Galen’s view of the movement of air and
blood to heart, and sooty vapours away from it; action of auricles and
ventricles of heart, pulmonary transit of blood.
 On the basis of vivisectional and anatomical evidence:
- With each beat of the heart, there is a significant transfer of
blood in one direction from the veins, through the heart and
the lungs, into the arteries
- The systole (contraction) of the heart forces blood out into the
aorta
- ‘X’ = Doctrine of Forceful Systole
 Nothing terribly novel yet
 Chap. 8: novelty of the circulation of the blood
 Given ‘X’, the doctrine of forceful systole
 The constantly beating heart would put out more blood than
the veins could supply, or the arteries could hold (too much blood
leaves the heart for it to be used up and replaced).
- The sum of the parts (accumulation of blood over time,
resulting from blood expelled by heart into aorta) cannot be
greater than the whole (total amount of blood produced from
the ingested food and drink)
- The amount produced is greater
- ‘Y’ = such an abundant flow is impossible . . . unless . . .
 The blood must, of necessity, return to the heart through the
veins
- ‘Z’ = necessity of the venous return
 There is a circular movement of the blood
 That ‘X’ (systole of heart forces blood out into the aorta)
Therefore ‘Y’ (such a flow is impossible)
Because ‘Y’, Therefore ‘Z’ (the necessity of a venous return)
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Lecture 14 Seeing Red: Harvey & the Circulation of the Blood
© Darrin Durant 2004
*** Problems with That ‘X’, Therfore ‘Y’, Therfore ‘Z’ ***
 What is the material nature of the blood put out by the heart?
 Vitalistic model: Galen
 Arterial blood mixed with pneuma (forced air)
 Arterial blood much lighter & rarified than Venous blood
 Arterial tree an open system?
 Blood like ‘frothy milk’?
 Movement of blood?: faculty of ‘attraction’ exercised by
organs + ‘pulsatile faculty’ transmitted
 Hydraulic model: spirit is in the blood
 Squeeze a container of liquid, and its contents will be
vigorously expelled
 Blood like ‘boiling water’?
 Expulsion – impulse – transmitted – pulse
 (Galenic) Orthodoxy
 Heart alters the blood’s nature
 An active diastole (expansion)
 Vivisectional evidence irrelevant because it shows the body
under unnatural conditions
 Caspar Hofmann (1625-27)
 Accepted ‘X’
 But: Organs attract their nutrients out of both Arteries/Veins
And: Pulse = stagnant blood ‘concussed’ by left ventricle
 Therefore denies ‘Y’
 Only enough blood put out to replace what had been
taken up by flesh
 Both output of heart & the pulse ‘managed’ by God
 Harvey assumes the arterial blood is moving
 Disturb nature by cutting?
 Emilio Paragiano (1621)
 Accepts ‘X’ and ‘Y’
 But: - The aortic valve is incompetent (allows blood from the
aorta into the heart during diastole
- Blood moves backwards (‘flux and reflux’)
 Thus redefines ‘X’, and Therefore denies ‘Z’
 1629: during systole spirit, not blood, leaves the heart
 Thus no sum great enough to create problem of ‘Y’
 Thus redefines ‘X’ so ‘Y’ not a problem
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Lecture 14 Seeing Red: Harvey & the Circulation of the Blood
© Darrin Durant 2004
*** Ligature Experiments as Reinterpretation ***
 Ligating the arm in preparation for bloodletting
 Veins below ligature swell, veins above do not swell
 Galenic physiology
 Blood moves outward to nourish the flesh
 Ligature created an unnatural situation
 Blood attracted to ligature, hence pain results in blood
flowing in a direction opposite to its natural course
 Harvey
 Ligature thwarts the natural return of blood to the heart,
via the veins
 Harvey agreed with Galenists that there was an active
principle in the blood causing the heart to beat
 But: ‘Z’ made ‘attraction’ unnecessary in
explaining ligature effects
*** Quantitative Argument ***
 Chap. 9 of De Fabrica
 Output of Heart (oc), multiplied by pulse over time (pt), gave a
volume of blood exceeding a reasonable volume (v) of blood in the body
or capable of being created by the body
 oc x pt > v
 Hofmann, 1636
 ‘Y’ makes nature appear purposeless and foolish
 Harvey’s argument is based upon reasoning and the
calculation of things that cannot be seen, rather than visible
demonstration
 Harvey being an accountant, not an anatomist
*** Inferences from Animals & Negative Evidence ***
 Inferences from eels, frogs, snakes, and so on, appropriate?
 Inferior animals to noble man . . .
 Chap. 16: rapid spread of poisons explained by ‘Z’
 Snake bite = unnatural condition?
 Cannot ‘see’ connections between veins and arteries
 Rejects observation in favour of theoria and other
demonstrated facts
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Lecture 14 Seeing Red: Harvey & the Circulation of the Blood
© Darrin Durant 2004
*** Plemp versus Descartes ***
 Vopiscus Fortunatus Plemp (Univ. of Louvain, Prof. Of Medicine)
 1638: opposes circulation (‘Z’)
 Tie off leg veins in a dog, and if Harvey is right, the leg
should swell dramatically. It does not, thus Harvey is wrong
 1644: same experiment proves circulation
 Rene Descartes, 1637
 Disagreed with Harvey, not on ‘Z’, but on heart’s movement
being caused by a pulsatile faculty in blood
 Heat in the heart vaporizes drops of blood as they enter the
ventricles, causing them to expand, thus blood leaves heart during
diastole
 Plemp versus Descartes
 Plemp: Remove a heart from an animal while it is beating, cut
it into pieces, and it still beats, in the absence of blood
 Descartes: ferment left in blood causes individual pieces to
expand and thus move
 ‘Fact’ = the beating pieces
 Descartes to Plemp: Does this fact mean the soul (pulsatile
faculty is the soul’s agent) can be divided into pieces?
 Plemp to Descartes: No, it is an unnatural situation, in which a
spirit acts on behalf of the soul, for a short time
 Descartes on Plemp: saving the soul by importing spirit
 Plemp on Descartes: importing ferment to avoid faculty
 A priori commitments: Descartes’ mechanism, Plemp’s faculties
 Response to ‘fact’ was to modify theoretical model
Conclusion
 Whenever you read of experimental debates, redraw them in terms
of Figure 1 (under-determination)
 Whenever you read of theories, redraw them in terms of Figure 2
(theories as nets, or webs)
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