Jean-Baptiste Denys was born in Paris around 1643, and after qualifying from Montpelier, worked as personal physician to Louis XIV of France.
Denys was following the work of early controversial human anatomists, notably Andreas Vesalius in the 16th Century, who contravened guidelines set by the Royal Colleges of Physicians banning human dissection. Vesalius not only performed autopsies, which flouted religious principles of medicine, but he performed them publically to ensure as many apprentices, practitioners and lay-people as possible could attend and learn.
His work, published as De Humani Corporis Fabrica in 1543, and dedicated to Holy Emperor Charles V, not only blew holes in the theories of Galen, which had formed the back-bone of anatomy and medicine for over 1400 years, but they propelled the study away from religion and myth into science. They also gave credibility to the practice of anatomy as a recognised branch of medicine, rather than a derogatory practice associated with surgeons, charlatans and butchers. This elevation obviously had a positive effect of the view, and the subsequent training of surgeons.
Vesalius’ most crucial discovery was that Galen’s theory on the blood circulatory system, was entirely incorrect. It had been stated that the arteries carried the rich blood upwards to the important organs, the brain and heart, and the veins downwards to the lesser organs. And that there were two ventricles to the heart interspersed with a series of holes to interconnect the two sides. Sadly he only went so far as to admit he couldn’t find these holes and did not investigate further, choosing instead to believe that the blood diffused through the transecting skin from one side to the other. Based on his work, later anatomists discovered valves that regulated the blood flow through veins one-directionally, without reflux.
In 1628, British Physician William Harvey, mapped and documented the entire human circulatory system and their properties for the first time, and used his findings to attempt the first human blood transfusions. Initial attempts proved fatal. In 1665, Richard Lower, also British, performed the first successful blood transfusion. Sadly it was canine in origin, rather than human, but after bleeding a dog almost to death, Lower successfully transfused blood from another dog, via a tied artery and both survived.
On June 15th 1667, Jean-Baptiste elaborated on this procedure by performing the first successful transfusion of blood from a sheep to a 15 year old boy, resulting in the survival of both specimens. He later repeated the process with an older man, again successfully. It would however be another 151 years before the first human to human transfusion took place, in 1818 when obstetrician James Blundell saved the life of a haemorrhaging female during childbirth with a transfusion from her husband. 83 years later, Austrian doctor Karl Landsteiner discovered the ABO typing of blood groups, and the principles of compatibility. Following the Great War, in the 1920’s, anticoagulation methods were introduced to prolong storage, and voluntary blood donation was introduced.
The process of determining the viability of blood transfusion from structure and theory to practice had taken around 300 years.