Girolamo Fabrizzi [Fabricius Ab Aquapendente] was one of the most illustrious Italian physicians of the 16th century. He studied under Falloppio and later became professor of surgery and anatomy at the University of Padua.
Fabricius published "De venarum ostiolis" (On the Valves of the Veins) in 1603, in which he described the existence of membranes or valves inside the veins. This work also appeared in his "Opera omnia".
In his book Fabricius wrote there are " thin little membranes on the inside of the veins distributed at intervals over the limbs . At times they are single, at times we find two of them together. Their mouths are directed towards the root of the veins [that is, towards the heart], and in the other direction [that is, away from the heart] they are closed."
Fabricius thought that these valves were designed to decelerate the blood velocity in the venous system and failed to understand their exact function: "In my opinion these valves are formed that they may to a certain extent delay the blood and so prevent the whole of it flowing to the feet, the hands or the fingers and collecting there." Fabricius still believed in the Galenic theory of blood motion with ebb and flow of blood in the veins. He believed that nutrient blood was carried through the veins and the impurities were extracted from the tissues and brought back through the same venous system.
The observation of the valves in the veins ultimately led to the idea of unidirectional blood flow and influenced greatly Harvey's vision and his accurate description of blood circulation which appeared in "De motu cordis" in 1628. Harvery gave credit to Fabricius' work and the similarity between the illustrations in their works suggests that Harvery was greatly inspired by Fabricius.
Illustration indicating the structure of the veins and their valves in the human arm after the placement of a ligature. The veins of the arm were then dissected and opened longitudinally demonstrating the existence of the valves.
Engravings demonstrating the presence of valves in the veins of lower extremity.
Singer C. The discovery of the circulation of the blood. London, Bell, 1922.