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girls … lacing’ their girdles too tight, which was why they should be told to ‘cut their laces’. Nature had also created ‘divers offices and divers instruments’ in the digestive tract, so that it could act like a chemical still, with ‘divers Heats [temperatures], vessels, furnaces to draw away the phlegm, raise the spirit, extract oil, ferment and prepare, circulate and perfect’. Considering genitalia, he noted that nature made sex pleasurable, even though it was ‘per se loathsome’. This was so that humans could produce ‘a kind of eternity by generating [offspring] similar to themselves through the ages’. Harvey, whose marriage produced no children, added in a strikingly poetical aside that we are ‘by the string [umbilical cord] tied to eternity’.⁵⁴

      Having covered the philosophical issues, he would move on to the medical ones. His lecture on the thorax would thus begin with some general and orthodox remarks about its function and anatomy, quoting Galen’s observation that the chest provides for the heart, lungs, respiration, and voice. Before it was cut open, he would invite the audience to note the flatness of the human thorax compared to that of the ape and dog, which protrude like a ship’s keel.

      Then he threw out a question to his audience: What is the connection between the width of the chest and the ‘heat’ or vital spirit of the animal? ‘Wherefore [do] butterflies in the summer flourish on a drop of blood?’ Because, would come the answer, the heart and lungs act like a furnace, heating the blood that suffuses energy through the body. The potency of that blood is demonstrated by its effect on the cold-blooded butterfly. ‘Especially in the summer the newt is hotter than the fish,’ he added, gnomically.

      The shape of the chest also revealed important truths about rank. Roman emperors, Harvey noted, were distinguished by having broad chests, which explained their exceptional ‘heat, animation [and] boldness’. His authority for this claim was the Roman biographer Gaius Suetonius Tranquillus, though the only broad chest mentioned in Suetonius’ On the Lives of the Caesars was that of the ‘well chested’ Tiberius, better known for his hot pursuit of young boys than political or military objectives.⁵⁵

      With the medical remarks concluded, it was the time to open up the body, and reveal the mechanics. Traditionally, physicians did not perform the actual dissection, leaving that job to a surgeon. But Harvey believed in getting his hands dirty. His method was to start with the general and work towards the specific, ‘shew as much in one observation as can be … then subdivide according to sites and connections’. Speed and dexterity were essential, not just to complete the course before the body began to putrefy, but to prevent the audience from losing the thread of the argument. There was no time to ‘dispute [or] confute’. ‘Cut up as much as may be,’ he commanded, ‘so that skill may illustrate narrative.’⁵⁶

      Harvey evidently enjoyed playing on the squeamishness of his audience. As a waft of flatus permeated the room, he would recall for the assembled physicians, many of whom had no practical experience of dissections, how cutting up parts of the body, particularly of abscessed livers, provoked ‘nausea and loathing and stench’. The interior of the chest would prove less noxious than the liver, however. Cutting through the ‘skin, epidermis, membrana carnosa’, penetrating ‘sternum, cartilages, ribs’, piercing ‘breasts, nipples, emunctory [lymphatic] glands’,⁵⁷ touching upon respiration, ingestion, hiccoughs, and laughter – prompting a digression on Aristotle’s observation ‘that when men in battle are wounded anywhere near the midriff, they are seen to laugh’ – he would finally come to the pericardium. This was the ‘capsule’ surrounding the heart.⁵⁸ He would make some remarks about the structure and use of the pericardium, and respectfully correct errors made by Vesalius relating to the mediastinum (the compartment between the lungs). He discussed the humour or fluid which ‘abounds’ within the percardial sac, a liquid like ‘serum or urine’, which is ‘provided by nature lest the heart become dry; therefore water rather than blood [issued] from Christ’s wounds’, adding that it was ‘wasted away … in persons hanged in the sun’. Then he revealed the organ within.

      The heart prompted Harvey into raptures. Other organs were usually described with clinical detachment, but not this one. The ‘empire of the heart’ was ‘the principle part of all … the citadel and home of heat, lar [household god] of the edifice [; the] fountain, conduit, head’ of life: ‘All things are united in the heart.’ Then his notes contain what appears to be an innocuous observation, scribbled next to his initials: ‘Query regarding the origin of the veins. I believe from the heart.’ It was the first sign of the intellectual convulsion to come.⁵⁹

      Fundamental to Galen’s physiology was the belief that the veins originate in the liver. Harvey’s dissection showed that this was not the case, but was ‘an error held now for 2000 years’. He did not say this lightly. ‘I have given attention to it,’ he added, ‘because [it is] so ancient and accepted by such great men.’⁶⁰ His notes are ambiguous, but suggest that at some point a live animal was brought into the room, probably stunned with a blow to the head, and strapped to the table for vivisection.⁶¹ Only by such means could Harvey show the audience what he wanted them to see: the beat of a living heart lying in the watery reservoir of pericardial humour. The movements of this glistening organ were complex. He had gazed upon it ‘whole hours at a time’. Initially he had been ‘unable to discern easily by sight or touch’ how it worked, but, by watching the heart as the animal gradually expired, as the muscles began to slacken and the heartbeat slowed, he beheld a revelation, which he now wanted to share with his audience in the most compelling fashion possible. ‘Observe and note,’ he instructed. ‘It seems to me that what is called diastole is rather contraction of the heart and therefore badly defined … or at least diastole [is] distension of the fleshiness of the heart and compression of the ventricles.’⁶²

      Galen saw ‘diastole’, the phase of the heart’s beat when it expands, as the active phase, when it mixes pneuma, or vital spirit, from the lungs with blood to vivify it. Systole, the phase when the heart contracts, was when it relaxed. Galen further concluded that, since the pulse of the arteries did not synchronize with the diastole phase, they must pulse of their own accord, in a manner similar to the ‘pulse’ of the intestine passing food through the digestive system.

      Harvey turned this idea upside down. He argued that the active phase was systole, when the heart contracted, pushing out the blood that had flowed into the heart’s chambers, or ventricles, during diastole. The pulse was thus not ‘from an innate faculty of the arteries, as according to Galen’, but the pressure wave produced by the heart pumping blood at high pressure into the arteries, which explained why they had walls thicker than those of veins.⁶³ ‘From the structure of the heart it is clear that the blood is constantly carried through the lungs into the aorta as by two clacks of a water bellows to raise water,’ Harvey concluded. He was referring to the system of valves used to fill a pair of bellows with water, which is then squirted out under pressure.

      He used another experiment to show where the blood goes to once it has left the heart. Physicians were familiar with applying ‘bandages’ (tourniquets) to the upper arm for blood-letting. They would know how a tourniquet applied very tightly would cut off both veins (which run just beneath the surface of the skin) and arteries (which are deeper in the arm), while a looser tourniquet would restore the flow of the arteries (indicated by the return of the pulse in the wrist) but not of the veins. Harvey noted that when the tourniquet is applied at its tightest, the hand would turn cold, but when it was loosened sufficiently to restore flow through the arteries it would become flushed and swollen, with the veins standing out. The hand would remain in

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