Blood’s life-giving properties did not spur many of those researching or working with it to consider transfusions as a viable treatment. Physicians of the ancient world considered blood to be the carrier of disease; ancient Egyptians practiced bloodletting as a form of treatment. Ancient Greeks thought blood forms in the liver and is carried throughout the body by arteries, and their beliefs were medical canon for centuries. Only as Renaissance physicians gained more knowledge of human anatomy through better experiments did the established ideas began to change.

On this day, June 15, in 1667 Dr. Jean-Baptiste Denis, the physician to King Louis XIV of France, transfused the blood of a sheep into a teenage boy, who recovered after the operation. Denis followed up his experiments on several more individuals, who also survived, likely because the transfused amounts were relatively small.

Several more disparate efforts at transfusion took place over the 17th and 18th centuries: British Physician Richard Lower kept a dog alive by transfusing blood from other dogs, and an apocryphal story holds of an attempted blood transfusion to save the comatose Pop Innocent VIII. More progress was made in the 19th century, when physicians began to understand blood types and internal mechanics — although that knowledge did not stop them from attempting some more off-the-wall experiments, like replacing blood in transfusions with milk.