Final answer:
Bloodletting is the medical technique refined during the Middle Ages that involved intentionally causing a person to lose blood as a form of treatment, which remained common until the 19th century.
Step-by-step explanation:
The technique refined by a physician during the Middle Ages that is mentioned in the question is bloodletting. For nearly 2000 years, bloodletting was believed to be the most effective treatment for various illnesses throughout many Western cultures. It was not until the 1800s that the claim of bloodletting's benefits was widely questioned, leading to a shift in medical practices. Educated individuals and physicians recommended bloodletting until well into the 1920s.
Bloodletting is the process of deliberately causing a person to lose blood, with the intent that such a loss would cure or prevent illness. It demonstrates how human knowledge evolves and is refined over time through debate and critical thinking. In the field of medicine, advances are particularly impactful, as they directly affect human health and the treatment of diseases.