De motu cordis, William Harvey’s landmark work on circulation, was first published in 1628.

While the publication of new anatomical atlases and illustrations slowed during the first part of the seventeenth century, innovations in experimentation, observation and technology produced major advances in medical knowledge. Ambroise Paré, a military barber-surgeon, revolutionized surgical techniques in the treatment of battlefield wounds. Paré challenged the prominent method of cauterization, or burning, a technique used to close wounds, and developed an alternative treatment that eased patient suffering and facilitated healing. Paré resolved to use only treatments that he directly observed, and in so doing, further cut ties to the authority of the past. Paré broke with tradition yet again by publishing his findings in the vernacular French instead of the more scholarly Latin.

The concept of direct observation led to one of the greatest accomplishments in medical history, and forever altered the teaching of anatomy and physiology. William Harvey, a former student of Fabrizio at the University of Padua, used dissections and experimentation on live animals to accurately describe the circulation of blood. He was inspired in part by Fabrizio's writings on the "little doors" or valves within blood vessels such as veins. Yet it was Harvey's direct observation of the veins and arteries that proved his belief that blood circulates through the body in two systems. His experimentation using a ligature tied tightly around the arm allowed him to create pressure on the flow of blood in the veins. As the ligature was loosened, the veins visibly filled with blood. This helped Harvey to identify that the valves within veins work different from valves within arteries. Harvey published his findings in Exercitatio anatomica de motu cordis et sanguinis in animalibus in 1628.