Fourteen men were appointed in the spring of 1784 to examine animal magnetism as d’Eslon practised it: nine in the commission of the Faculty of Medicine and the Academy of Sciences that Franklin headed, and five in a parallel commission of the Royal Society of Medicine. Thirteen of them signed a report that said the fluid did not exist. The fourteenth published his own. His name was Antoine-Laurent de Jussieu; he was thirty-six, a physician by training and a botanist by vocation, of the family that had run the Jardin du Roi for two generations; five years later his Genera plantarum would give botany the natural system of classification it still uses. In 1784 he was the one examiner who refused to say he had seen nothing. The translations from his report are mine.

Why he would not sign

“I was named, on 5 April 1784, to examine the doctrine, the procedures and the effects of animal magnetism, practised by M. Deslon,” his report begins. “The Report of MM. Mauduyt, Andry and Caille, with whom I was charged with this examination, has not been signed by me, and I owe an account of my motives, so that I am not credited with an opinion different from my own.”

His objection was to the amount of looking. The commission, he thought, “demanded of us, not a simple judgment founded on a few isolated facts, but a methodical exposition of numerous and varied facts”. He agreed with his colleagues on the method in principle, and his statement of it is as clear as Lavoisier’s: the decisive experiments had to exclude friction and strong pressure, which were causes in themselves; they had to guard against “the imagination of the persons submitted to the experiments, either by acting upon them without their knowledge, or by choosing for these trials children, men deprived of reason, or even animals.” Without that precaution “the question would remain undecided; the adversaries of Magnetism would attribute everything to the imagination; and its partisans would be entitled to object that their opinion is no better founded than the one which admits the magnetic fluid.”

But negative results on a few healthy people, he argued, could not decide a question about an agent that was said to act only on the sensitive and the sick. The right course was to begin in the treatment rooms, “where many patients are gathered, where one can see much”, and then to verify what one had seen with isolated experiments repeated many times. “This course seemed to me the best; I frequented M. Deslon’s rooms; to avoid illusion, I wished to see a great deal, and to operate often myself; and although occupied elsewhere with more agreeable labours and public functions, I gave these a considerable time.” His colleagues had made a few experiments in common and thought them sufficient for a judgment. “I did not subscribe to it.”

Four kinds of fact

He sorted what he had seen into four classes, and the sorting is the most careful thing anyone wrote about the baquet in 1784.

The first were general facts whose cause could not be fixed: the heat and the pains patients reported, the yawning, the sweats, the crises with their three stages of excitement, suspension and release. He had seen crises begin at the tub with no other procedure; he had been told by some patients that they never had them elsewhere and by others that they did. He had tried the poles and found no regular correspondence. He had produced sweats in three men in an hour by passing his finger upward in front of them, against the rules. He recorded, without conclusion, a young man who in crisis became mute, walked the room, and magnetised other patients with a touch, and who on waking “remembered nothing of the past, and no longer knew how to magnetise.” Of these facts he said that some must belong to a physical cause and the rest could be either an unknown fluid or the imagination, “and until the fluid is demonstrated, the latter opinion must prevail, as older and better proven.”

The second class were negative facts, “more numerous” but “all uniform”: an epileptic girl without reason, magnetised for an hour before the commissioners by various procedures, felt nothing; five of Mauduyt’s electrical patients felt nothing; a part of d’Eslon’s own patients felt nothing; “I was magnetised myself several times, and always without success.” From these he concluded “that the fluid, if it exists, has not on most men, whether healthy or sick, an action which can manifest itself by sensible signs.”

The third class were facts that depended on the imagination, and here he gave his colleagues everything the blindfold had shown. A man subject to crises, magnetised by Jussieu himself for a long time while they talked of interesting things, felt nothing but heat and said the conversation had often stopped the magnetism working on him. A lady attending her convulsing husband felt only a slight warmth though Jussieu magnetised her as he had before with success. D’Eslon’s most devoted patients all fell into crisis at the same time though he could touch them only one by one, and a single look from him when one came round was enough to bring it back. A woman’s expectoration stopped when d’Eslon left the room and started when he came back, with no touch at all. A new patient whom Jussieu was the first to magnetise took three days to begin starting; on the third day she went on after he stopped, stopped when he left the room, started when he returned, started again when she saw him in the courtyard and again when she met him at the foot of the stairs. Then the two blindfolded men at Mauduyt’s house, examined by all the commissioners: the half-paralysed man who, once blindfolded, “rambled about the effects, announced sensations at points of the body which were not being magnetised, even when one was in complete inaction, and rarely designated the magnetised parts”; and the second man, who had the same effects magnetised or not, with the difference that “of the total of the experiments then made on him, a third only offered a correspondence between the magnetic action and the sensation stated.” His conclusion for the class: “the imagination forewarned, put at fault, heated by diverse causes together, acts with enough force upon man to produce in him the greatest effects without the help of any external agent.”

Everything so far is the Franklin commission’s case, made by a man who had spent more hours in the halls than any of them.

The fourth class

Then he set down the facts he could not fit, “because if they are true, they give rise to ideas different from those first presented by the preceding article. A single positive fact, which would evidently demonstrate the existence of an external agent, would destroy all the negative facts, which establish only its non-action, and would balance those which assign everything to the imagination.”

At the tub, opposite a woman whose blindness from two thick films had been verified by the commissioners a month before, he waited a quarter of an hour while she sat quietly, occupied with the iron pointed at her eyes. “At the moment when the noise of voices was sufficient to put her hearing at fault, I directed, at the distance of six feet, a rod at her stomach, which I knew to be very sensitive. At the end of three minutes she appeared uneasy and agitated; she turned round on her chair, asserted that someone, placed behind or beside her, was magnetising her, although I had previously taken the precaution of sending away all those who might have made the experiment doubtful.” Her unease stopped almost as soon as he stopped. Fifteen minutes later he did it again, “which offered exactly the same result.” He listed the precautions, admitted the hour was late and a third trial might have increased conviction, and moved on. A woman whose crisis was a deep sleep, and who started at any sudden noise, started also at magnetic passes made in front of her face without noise. A woman in a spasm, eyes closed, whose head followed his withdrawn finger “mechanically in every sort of direction” and who snatched her hand away when his other hand came within an inch of it. Patients who jumped when a finger was moved behind their backs without their knowledge, a thing the newly admitted physicians tried first, “with mistrust”, from outside the circle, before they dared operate openly. He said of all this: “These facts are few in number and little varied, because I have been able to cite only those which were well verified, and about which I had no doubt.”

From them he concluded that the body was acted on by causes internal and moral, like the imagination, and causes external and physical, “like friction, contact, and the action of a fluid emanating from a like body”. And he asked what the fluid was. Friction and contact carry heat. “Would this heat be the fluid whose existence is so debated?” The rest of the report is a theory: that there is in animate bodies a principle of motion which is animal heat, identical when it leaves the body with the electric fluid, tending always to equilibrium, passing from the body that has more to the body that has less, and acting more on the delicate than the robust. “Heat, ceaselessly active, is therefore that true part emanated from bodies, that unknown and contested agent, which establishes the physical influence of man on man.” He proposed, in effect, to rename animal magnetism as the medicine of touch, give it to instructed physicians, and try it slowly, first in slight and recent complaints, with the caution that tonics given too long or at the wrong time “produce irritation, erethism, convulsion.”

He gave his own cases, and they are modest. A servant at a country house, with a pain down her thigh for two days after a chill and no idea what magnetism was, had her warmth brought back by a finger on the stomach and another on the painful part, sweated all night, and was back at work in two days. A laundress with a frozen shoulder, brought to the treatment by one of the commissioners, had recovered movement and lost most of her pain in two months. Several hypochondriacs digested better. Some quartan fevers had stopped, “which at least ceased without other help.” Of the serious cases he was plain: the treatment “always appeared more harmful than advantageous to consumptives”; its action on scrofulous tumours was “very slow and almost insensible”; one dropsical woman was relieved and not cured, another’s swelling went up and down, a third had to be tapped of fourteen pints and swelled again. “I cannot attest any complete cure, because I have not verified those which have been announced to the public.”

What his dissent was

Jussieu’s animal heat is not a fluid anyone would defend now, and his evidence for the fourth class is a handful of observations, uncontrolled, on patients he had himself sometimes magnetised before. He said as much. His report is remembered, when it is remembered, as the one that gave the magnetisers a respectable name to quote, and d’Eslon quoted it at once: the one commissioner, he wrote in September, who “alone thought it right to follow my treatments with constancy.”

But the dissent is worth reading for what it is, which is an argument about sample and method from inside the finding, not against it. He accepted the blindfold and what it showed. He thought thirteen men had stopped at the point where the question got interesting: having shown that belief could produce the effects, they had not shown that nothing else could, and the way to show that was more experiments of exactly the kind they had invented, on more people, repeated. He refused to put his name to “a simple judgment founded on a few isolated facts”. He was wrong about the agent and right about the method, and the Report that printed the tree and the paper partition as “entirely conclusive” could have used a signatory who insisted on doing them twice.

Sources

• Antoine-Laurent de Jussieu, Rapport de l’un des commissaires chargés par le Roi de l’examen du magnétisme animal, Paris: Veuve Hérissant and Théophile Barrois, 1784. All quotations, translated by the author of this entry. archive.org
• Charles d’Eslon, Observations sur les deux rapports de MM. les commissaires, Paris, 1784, page 1, note 1, for Jussieu as the commissioner who followed his treatments. archive.org
• Rapport des commissaires de la Société royale de médecine, Paris, 1784, signed 16 August 1784 by Poissonnier, Caille, Mauduyt and Andry, without Jussieu. archive.org