Jean-Baptiste Denis

Jean-Baptiste Denis (1635-1704)

Jean-Baptiste Denis (*1635 – 1704) was a physician and Professor of philosophy and mathematics.

Denis performed the first documented transfusion of blood from an animal to a man (xenotransfusion) on 15th June 1667

In 1673 Denis created a haemostatic solution. The anti-hemorrhagic liquid that could be taken orally or applied directly to the wounds. His success with this solution first tried out on animals, then on human beings, won him the favour of Charles II. The King invited him to stay in London and offered to give him an appointment as his First Physician, an honour that Denis declined, wishing to return to Paris. 


  • Born 1635/1640
  • Bachelor in Theology, Collège des Grassins
  • Doctor of the Faculty of medicine of Montpellier
  • Physician to King Louis XIV
  • Died October 3 1704

Key Medical Attributions

Blood transfusion [1667] (xenotransfusion)

March 3rd 1667: Denis successfully transfused blood between two dogs. Denis affirmed that the idea of ​​transfusion had been conceived by a Benedictine monk, Dom Robert des Gabets, who had discussed it, in July 1658, in the presence of the “illustrious Company of scholars” that the Count de Montmort had assembled. However while Richard Lower (1631 – 1691) claimed the principle and the first experience of blood transfusion in animals took place in February 1666, in Oxford.

First transfusion: On June 15, 1667: Denis performed the first documented human blood transfusion. He transfused twelve ounces of sheep’s blood into a 15-year-old boy, who had been excessively bled with leeches. The boy survived the transfusion and “rapidly recovered from his lethargy, grew fatter and was an object of surprise and astonishment to all who knew him”

Second transfusion: 45 year-old chair bearer, a robust man who received the blood of a sheep as a paid volunteer. He returned to work the next day as if nothing had happened to him.

Third transfusion: Baron Bonde, a Swedish nobleman, fell ill in Paris while making a grand tour of Europe. He had been abandoned by his physicians; and in despair, his family asked Denis to attempt transfusion of blood as a final recourse. The first transfusion (from a calf) went well and Bonde became able to speak. However, he died during the second transfusion.

Fourth transfusion: Antoine Mauroy, a 34-year-old, newly-wed male house-servant, was prone to running away from his home in suburban Paris and spend his time in debauchery in Paris. A Mr. de Montmors felt sorry for Mauroy’s wife and inquired of Denis whether he could help: calf’s blood, because of the gentle character of a calf, might dampen Mauroy’s spirit. 10 ounces of blood was removed from a vein in his arm, being replaced with five or six ounces of blood from a calf with no obviously untoward (or beneficial) effects.

Two days later, the man was transfused a second time in the presence of several physicians. This resulted in what would now be recognised as a haemolytic transfusion response as a result of inter-species incompatibility.

As soon as the blood entered his veins, he felt the heat along his arm and under his armpits. His pulse rose and soon after we observed a plentiful sweat over all his face. His pulse varied extremely at this instant and he complained of great pains in his kidneys, and that he was not well in his stomach, and that he was ready to choke unless given his liberty. He was made to lie down and fell asleep, and slept all night without awakening until morning. When he awakened he made a great glass full of urine, of a colour as black as if it had been mixed with the soot of chimneys.

Denis J. Philosophical Transactions. 1668; 3(36): 710

On the second day, Mauroy had further haemoglobinuria and epistaxis. However, by the third day his urine had cleared and his mental state had apparently improved so much that he returned home to his wife.

Several months later, Antoine Mauroy again became violent and irrational and his wife persuaded Denis to repeat the transfusion. A transfusion was attempted, but non-cooperation from the patient it was apparently abandoned. The patient died the following night. Reports were that physicians who hated Denis bribed his wife to state that the patient died during the transfusion. Denis was tried for manslaughter but exonerated as and it was established that Mauroy’s wife had been poisoning him with arsenic.

Although the judgment rendered, cleared Denis of any wrongdoing, the court forbade the practice of transfusion of blood in man without permission of the Paris Faculty of Medicine ‘‘for the future no transfusion should be made upon any human body except with the approbation of the physicians of the Parisian Faculty.’’ On January 10, 1670, the French Parliament prohibited transfusions, with the English Parliament rapidly following suit. This ban was still in force in France at the end of the 19th century.

Denis haemostatic solution (essence de Denis, liqueur hémostatique) [1673]

In 1673 that Denis took his place in the history of pharmacy, experimenting with an anti-hemorrhagic liquor over which mystery still hangs. Denis made mention in a publication on April 30, 1673 and the substance of which was reported in English in the Philosophical Transactions 1673.

Denis claimed the essence to be much simpler to use than other methods of cautery such as ‘needle and thread’, ‘hot iron’, or other caustic agents. The essence was applied using soaked pads directly to arterial or venous wounds and experiments performed on dogs, then on other animals, and finally in humans after accidental injuries.

Denis did not provide the formulation of his essence. Some claimed that it was made of potash alum or sulphuric acid and many counterfeits, and some doctors created imitations under the name of Denis.

Denis did not provide the formulation of his essence. When asked he replied “Mine is only found in one place which is on the Quai des Augustins, at the house of Sieur Quenet, a bookseller, under the sign of Hope, at which place it will always be given free of charge to the poor and others, in sealed bottles, so that no one can be abused by such impostors in the future.” and he proposed to deliver them, on request, to hospitals or surgeons who wanted them for their operations.

Denis may have disclosed his secret remedy to Henry Oldenbourg (1619-1677), secretary of the Royal Society; editor of Philosophical Transactions; natural philosopher and widely deemed to be the creator of scientific peer review in 1673

Oldenburg requested the essence be sent to him for testing and on May 30, 1673, published an account of the experiments performed in London by Walter Needham (1631-1691) and Richard Wiseman – two on dogs and two on humans. Of the human subjects, one was a woman who had a breast amputated for ulcerative cancer, the other a male bleeding profusely from scrofulous swellings in the neck that failed cauterisation. In all cases, the hemostasis was carried out using French liquor applied and maintained on the arterial and venous wounds; the results were so extraordinary that Denis was commissioned to London by King Charles II to repeat, in his presence, some experiences.

His British Majesty ordered his surgeons to go to the hospitals to find out if there were any sick or injured on whom to try the new liquor. At the hospital in St. Thomas, in London’s Southwark, two patients were found. One was a woman whose leg had to be amputated due to a malignant ulcer; the other, a sailor with a compound fracture due to have his leg amputated. The results were extraordinary: not only were the artery and severed vein orifices plugged in record time, but the operative suites were better than ever. It was enough to convince King Charles II of the usefulness of the essence for his armies and in his fleet.

History does not say what became of the haemostatic liquor. King Charles II wanted to keep it in England; but Denis declined and returned in Paris in November 1673. The blood-staunching liquor was never heard of again…

Major Publications

Essays on transfusion were published, in the form of letters, in Le Journal des Sçavans (1667), and later translated into English and published in Philosophical Transactions (1668).

Letters transformed into publications in Philosophical Transactions regarding Denis haemostatic solution (1673)


Proclaimed as a physician and Professor of philosophy and mathematics…however, there is no evidence of medical degree, matriculation or degrees in either philosophy or mathematics as researched and recorded in 1668 by Pierre-Martin de la Martinière in Remonstrances charitables du Sieur de la Martinière à Monsieur Denis: the story of the death of one called Mauroy and the contradictory sentence given by Mr. Denis the criminal lieutenant of April 17, 1668, against the transfusers

  • * Date of birth variably recorded as 1635 or 1640
  • ** Surname *Denis or Denys in various publications and dictionaries.


BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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