Marcello Malpighi used the microscope to examine the major organs of the body and the brain. He discovered capillaries and contributed to the understanding we have today of the vascular system of the body. He found that capillaries made it so blood could flow back to the heart.
The Royal Society experimented successfully with blood transfusions. As time went on, however, blood transfusions became dangerous and eventually illegal.
Atony van Leeuwenheuk began building more refined microscopes. He built over 500 microscopes in his lifetime. He is considered the first microbiologist there ever was.
James Lind found that citrus was the best treatment for seamen with scurvy. He didn't necessarily discover that citrus was helpful in treating scurvy, but he did verify citrus to be the most effective treatment of scurvy.
William Smellie gave many lectures and eventually published his refinery of the midwife. He helped transform this ancient idea of "midwifery".
Joseph Priestly discovered nitrous oxide, commonly known as "laughing gas" today. Nitrous oxide is an analgesic.
William Withering discovered the active ingredient, foxglove, that streats foxglove. He went on to publish his findings in "The Account of the Foxglove"
William Jenner created the vaccination for smallpox. In 1796 he successfully inoculated a woman and her son from smallpox.
Sir Humphry Davy discover the isolation of potassium and sodium as well as calcium, strontium, barium, and magnesium. Today these elements are used in what we call electrolysis.
Laennec invented and built the first stethescope. He discovered that using a tube worked better at hearing the beating of the heart than the common ear-to-chest method.
Horace Wells was a dentist who allowed nitrous oxide to be used on him so that he could understand better the effects of the gases. He found them to be a successful way of blocking pain.
Florence Nightingale implemented sanitation during the Crimean War. She saw a dramatic decline of deaths and illnesses due to enforcing and educating on the importance of sanitation in the medical community.
Theodor Boveri and Walter Sutton discovered that chromosomes bear heredity. They expounded upon the previous genetic experiments of Mendel's laws.
Archibald Garrod found that genetic defects cause inherited disease. He was able to identify the defects in genes in their correlation with serious disease inheritance.
Hermann Muller discovered that x-rays can cause genetic mutations. His findings contributed to modern medicine today by helping us understand the effects and dangers of radioactivity.