On June 15, 1667, French physician Jean-Baptiste Denys, performed the first successful human blood transfusion. Before he performed a blood transfusion on humans, Denys was already experimenting with blood transfers between animals including calves, dogs, and sheep. These were well documented and published in the Royal Society’s Philosophical Transactions.
While his first human blood transfer was successful, it was far from ideal. Denys was presented with a 15-year-old boy who was drowsy and feverish after being leeched twenty times by other physicians. As a result, the boy lost too much blood.
To perform the transfusion, Denys used 12 ounces of sheep blood. Blood was taken from the sheep’s carotid artery and was introduced to the boy’s bloodstream through a vein in his inner elbow. Denys recorded the transfusion’s success, reporting that the boy fully recovered and even gained weight. He was said to be “an object of surprise and astonishment to all who knew him.”