section_path: New ideas/Biology and medicine
section_name: Biology and medicine
paragraph_text: Biology and medicine
  
  The writings of Greek physician Galen had dominated European medical thinking for over a millennium. The Flemish scholar Andreas Vesalius demonstrated mistakes in Galen's ideas. Vesalius dissected human corpses, whereas Galen dissected animal corpses. Published in 1543, Vesalius' De humani corporis fabrica was a groundbreaking work of human anatomy. It emphasized the priority of dissection and what has come to be called the "anatomical" view of the body, seeing human internal functioning as an essentially corporeal structure filled with organs arranged in three-dimensional space. This was in stark contrast to many of the anatomical models used previously, which had strong Galenic/Aristotelean elements, as well as elements of astrology.
  
  Besides the first good description of the sphenoid bone, Vesalius showed that the sternum consists of three portions and the sacrum of five or six; and he described accurately the vestibule in the interior of the temporal bone. He verified the observation of anatomist Charles Estienne on the valves of the hepatic veins, described the vena azygos, and discovered the canal which passes in the fetus between the umbilical vein and the vena cava, since named ductus venosus. He described the omentum and its connections with the stomach, the spleen and the colon; gave the first correct views of the structure of the pylorus; observed the small size of the caecal appendix in man; gave the first good account of the mediastinum and pleura and the fullest description of the anatomy of the brain yet advanced.
  
  Before Vesalius, the anatomical notes by Alessandro Achillini demonstrate a detailed description of the human body and compare what he had found during his dissections to what others like Galen and Avicenna had found and notes their similarities and differences. Niccolò Massa was an Italian anatomist who wrote an early anatomy text Anatomiae Libri Introductorius in 1536, described the cerebrospinal fluid and was the author of several medical works. Jean Fernel was a French physician who introduced the term " physiology " to describe the study of the body's function and was the first person to describe the spinal canal.
  
  Further groundbreaking work was carried out by William Harvey, who published De Motu Cordis in 1628. Harvey made a detailed analysis of the overall structure of the heart, going on to an analysis of the arteries, showing how their pulsation depends upon the contraction of the left ventricle, while the contraction of the right ventricle propels its charge of blood into the pulmonary artery. He noticed that the two ventricles move together almost simultaneously and not independently like had been thought previously by his predecessors.
  
  Harvey estimated the capacity of the heart, how much blood is expelled through each pump of the heart, and the number of times the heart beats in half an hour. From these estimations, he demonstrated that according to Gaelen's theory that blood was continually produced in the liver, the absurdly large figure of 540 pounds of blood would have to be produced every day. Having this simple mathematical proportion at hand—which would imply a seemingly impossible role for the liver—Harvey went on to demonstrate how the blood circulated in a circle by means of countless experiments initially done on serpents and fish: tying their veins and arteries in separate periods of time, Harvey noticed the modifications which occurred; indeed, as he tied the veins, the heart would become empty, while as he did the same to the arteries, the organ would swell up. This process was later performed on the human body: the physician tied a tight ligature onto the upper arm of a person. This would cut off blood flow from the arteries and the veins. When this was done, the arm below the ligature was cool and pale, while above the ligature it was warm and swollen. The ligature was loosened slightly, which allowed blood from the arteries to come into the arm, since arteries are deeper in the flesh than the veins. When this was done, the opposite effect was seen in the lower arm. It was now warm and swollen. The veins were also more visible, since now they were full of blood.
  
  Various other advances in medical understanding and practice were made. French physician Pierre Fauchard started dentistry science as we know it today, and he has been named "the father of modern dentistry". Surgeon Ambroise Paré was a leader in surgical techniques and battlefield medicine, especially the treatment of wounds, and Herman Boerhaave is sometimes referred to as a "father of physiology" because of his exemplary teaching in Leiden and his textbook Institutiones medicae (1708).