Lower studied medicine at Oxford at the same time as Robert Boyle and Thomas Willis. He assisted Willis in the dissections of the brain, published in 1664 as Cerebri anatome. In 1665 he received his medical degree, and moved to London where he became an active member of the Royal Society. He was the first to effect the intravenous transfusion of blood from one animal to another in 1665. The first human transfusion was performed in Paris by J.B. Denys in 1667, who appropriated Lower's technique, and shortly thereafter by Lower himself in England. In Tractatus de corde Lower attempted to explain the function of anatomical structures through experiments. His dissections of the cardiovascular system made significant observations that virtually completed the work of Harvey on the heart. With the assistance of Robert Hooke, Lower proved experimentally that venous blood is changed to arterial blood in the lungs through its contact with air (ch. 3). Other important observations include the scroll-like structure of the cardiac muscle, and the notion of the heartbeat as a muscular mechanism. Recognised as an important and authoritative work, the Tractatus was reprinted three times in London, seven times on the Continent, and was translated into French. An English translation did not appear until 1932.