10 Influential Physicians and Medical Researchers

Physicians throughout history have made groundbreaking contributions to medicine, significantly shaping medical practice, knowledge, and understanding. Today that tradition of innovation and compassion to alleviate human suffering is carried on by new generations of physicians, some striving to cure cancer, others working to advance health equity, and still others achieving deeper understanding across a vast array of issues pertaining to human health and disease. Physicians today stand on the shoulders of those who came before. Here we reflect on individuals who helped lay the foundations of medicine through their curiosity, perseverance, and achievements.

Hippocrates

Often regarded as the father of medicine, Greek physician Hippocrates (c. 460–375 bce) was revered for his ethical standards in medical practice. He emphasized the importance of clinical observation and meticulous documentation of patient conditions and symptoms, moving medicine away from superstition and toward a more scientific and empirical approach. He is best known for the Hippocratic oath, which laid the ethical foundation for medical practice and which, it is suspected, he did not write.

• Hippocrates was born on the island of Cos (Kos), Greece.
• One of the earliest proponents of the idea that “food is medicine,” Hippocrates often prescribed specific diets, along with exercise and changes in environment, as treatments—an approach that resonates with modern preventive medicine.
• Some modern medical terms are derived from Hippocratic ideas and writings, including the terms diagnosis, sepsis, and trauma.

William Harvey

William Harvey (1578–1657) was a pioneering English physician best known for his discovery of the circulation of blood throughout the human body. His work fundamentally changed the understanding of the cardiovascular system and laid the foundation for modern physiology. Harvey demonstrated that the heart works as a pump to circulate blood throughout the body in a closed loop. His observations contradicted the long-held Galenic view, which suggested that blood was consumed by the body and produced anew by the liver. Harvey’s book De Motu Cordis (1628; On the Motion of the Heart and Blood in Animals) presented experimental evidence to support his theory of circulation. The book is considered to be one of the most important works in the history of medicine.

• Harvey’s deduction of the circulatory path of blood through the body directly contradicted the teachings of Galen, whose ideas on blood flow had been accepted since the 2nd century.
• Harvey served as a physician to King James I and King Charles I of England.
• During a civil disturbance in London in the early 1640s, Harvey’s lodgings were ransacked, and many of his manuscripts, notes, and books were lost.

Edward Jenner

English physician Edward Jenner (1749–1823) is often considered to be the father of immunology, owing to his pioneering work in developing the smallpox vaccine—the world’s first successful vaccine. Jenner demonstrated that inoculation with material from lesions caused by cowpox, a relatively mild disease, could protect against smallpox, a highly contagious and deadly disease. This process became known as vaccination, a term derived from the Latin vacca, meaning “cow.” Jenner’s work on vaccine development not only led to the eventual eradication of a deadly disease, saving countless lives, but also had profound implications for public health and immunology.

• Although Jenner is credited with developing the first scientifically documented vaccine and pioneering the practice of vaccination, other forms of immunization against smallpox had been evident in different cultures long before his work.
• Unlike many scientists of his time, Jenner did not seek to profit from his discovery. He published his findings and methods freely and encouraged others to adopt and refine his techniques.
• Jenner wrote a poem titled “Address to a Robin,” a lament expressing his frustration with critics of vaccination.

Elizabeth Blackwell

Elizabeth Blackwell (1821–1910) was the first woman to receive a medical degree in the United States, breaking significant barriers in an otherwise then male-dominated field. In 1849, when Blackwell graduated first in her class from Geneva Medical College in New York state, women were largely excluded from formal medical education and practice. Her determination and dedication had a profound impact on the fields of health care, medical education, and women’s rights. Through her efforts, she not only set an example but also made it possible for future generations of women to pursue careers in medicine.

• Blackwell was admitted to Geneva Medical College because the faculty, unsure how to respond to her application, left the decision to the all-male student body, who voted to accept her as a prank. Little did they know that she would excel academically and graduate at the top of the class.
• In 1857, with her sister, Emily, and colleague Marie Zakrzewska, Blackwell founded the New York Infirmary for Indigent Women and Children (later part of NewYork-Presbyterian Lower Manhattan Hospital).
• Blackwell pursued medicine in part because she was determined not to marry, which she feared would stifle her intellectual development.

Joseph Lister

English scientist Joseph Lister (1827–1912) is widely regarded as the father of modern surgery for his pioneering work in antiseptic medicine and the prevention of infections in surgical wounds. Lister found an effective antiseptic in carbolic acid, which he used to interpose a chemical barrier between the wound and the surrounding environment, including the surgeon’s hands and instruments. He introduced antiseptic techniques to sterilize surgical instruments, clean wounds, and disinfect the air and the operating room. While his method based on such techniques is no longer employed, his principle that bacteria must never gain entry into an operation wound remains the basis of surgery to this day.

• Listerine mouthwash, an antiseptic product used for oral health and hygiene, is named for Lister.
• Lister’s father, Joseph Jackson Lister, was a successful wine merchant who also invented an achromatic lens that compensated for chromatic aberration in the compound microscope.
• In 1897 Lister was made Baron Lister of Lyme Regis; the honor made Lister the first British surgeon to receive a peerage.

Alexander Fleming

In 1928 Scottish bacteriologist Alexander Fleming (1881–1955) discovered penicillin, igniting what became known as the antibiotic revolution—a transformative period in medicine that fueled the development and widespread use of antibiotics to treat bacterial infections. Fleming’s work on penicillin was subsequently taken up by a team of scientists, led by Howard Florey at the University of Oxford, who eventually brought the drug into use during World War II. Fleming’s discovery saved countless lives. In 1945 he was awarded a share of the 1945 Nobel Prize for Physiology or Medicine.

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• Fleming discovered lysozyme, an antibacterial enzyme found in tears and saliva, in 1921—before he discovered penicillin—already solidifying a place for himself in the history of bacteriology.
• In 1945, the year Fleming was awarded the Nobel Prize, he warned in an interview with The New York Times that overuse of penicillin could result in antibiotic resistance.
• Fleming was an amateur watercolor painter and a member of the Chelsea Arts Club. He created some paintings with bacteria, having grown microbes of varying natural pigments in petri dishes.

Jonas Salk

American physician and medical researcher Jonas Salk (1914–1995) was an essential figure in medical history, owing to his development of the first effective polio vaccine, which saved millions of lives and helped to nearly eradicate the devastating disease. Salk’s commitment to humanitarian principles, his decision to forgo personal profit from his discovery, and his continued advocacy for public health have made him a symbol of scientific innovation and selflessness.

• During World War II, before his work on the polio vaccine, Salk developed one of the first vaccines against influenza.
• The clinical trial for Salk’s polio vaccine, conducted in 1954, remains one of the largest medical experiments ever conducted. It involved more than a million children in the United States, who became known as the “Polio Pioneers.”
• In 1963 Salk founded the Salk Institute for Biological Studies in La Jolla, California, which continues to be a leading research center globally in biology and genetics.

Paul Ehrlich

German scientist and physician Paul Ehrlich (1854–1915) revolutionized medicine through key advances in the areas of chemotherapy, hematology, and immunology. He discovered the first effective treatment for syphilis: a substance initially known as preparation 606 and later called Salvarsan. He also introduced the concept of a “magic bullet”—a drug that would specifically target and destroy pathogens while leaving healthy cells unharmed. His pioneering ideas about targeted therapy, the immune response, and drug dosage continue to inform medical research today.

• Ehrlich developed various methods of staining blood cells to allow for better visualization. Several of his techniques continue to be used in the diagnosis of blood disorders, infections, and leukemia.
• The term chemotherapy was coined by Ehrlich to describe the treatment of diseases, including infections and cancer, by chemical compounds.
• Ehrlich was awarded a share of the 1908 Nobel Prize in Physiology or Medicine for his work on immunity.

Christiaan Barnard

Christiaan Barnard (1922–2001) of South Africa was a pioneering cardiac surgeon whose successful performance of the world’s first human heart transplant marked a significant milestone in medical history. His work demonstrated the feasibility of heart transplantation, advanced cardiac surgery techniques, and raised public awareness and support for organ transplantation. Despite facing numerous challenges and controversies, Barnard’s contributions have had a profound and lasting impact on the field of transplant surgery, inspiring future generations of surgeons and transforming the treatment of heart disease.

• Barnard was known for popularizing innovation and particularly the idea of taking bold steps—which often require a willingness for taking calculated risks—in the face of uncertainty.
• Barnard was motivated in part to become a doctor after his younger brother died from a heart condition in childhood.
• To address ethical concerns around the timing of organ donation, Barnard and his team worked to determine the moment of brain death accurately. Their efforts contributed to early discussions on the medical and ethical criteria that define death.

Anthony Fauci

American doctor and scientist Anthony Fauci (1940– ) is a pivotal figure in public health and medicine. His substantial contributions to the study and control of infectious diseases, his leadership in the face of multiple public health crises, and his advocacy for science-based responses to health challenges have established Fauci as a trusted source of medical expertise. In particular, as a researcher, he did work that was instrumental in the development of effective treatment strategies for HIV/AIDS. Later, as an adviser to various U.S. presidents, he led research efforts to better understand and treat infectious diseases such as Ebola, SARS, MERS, Zika, and influenza. During the COVID-19 pandemic, Fauci played a central role in guiding the U.S. and global response. His work has saved countless lives and continues to shape public health policy and practice worldwide.

• Fauci’s career as the director of the National Institute of Allergy and Infectious Diseases (NIAID) stretched across five decades, from 1984 to 2022.
• Fauci is an avid runner who ran marathons for part of his life.
• Fauci was one of the most cited scientists in the world, with more than 1,400 scientific publications to his name.