Skip to Main Content



Hematology comes from the Greek words haima, which means blood, and logos, which means a field of study. Hematology is classified as a subspecialty of internal medicine (the branch of medicine that studies and treats, usually by nonsurgical means, diseases of the body's internal organs).

Humanity has known the importance of blood to life since the early days. In primitive times, people who became ill or diseased were thought to be possessed by demons, and bloodletting was done to free them of this possession. The Egyptians, Greeks, and Romans continued the practice of bloodletting. Hippocrates, in the 400s B.C., observed that health depends on the balance between four "humors": blood, phlegm, black bile, and yellow bile. Bloodletting was then done to balance the humors. The practice was popular throughout the Middle Ages and lasted until the early 1800s. Scientific developments in the 17th century, including Anthony van Leeuwenhoek's introduction of the microscope to distinguish blood cells and J.C. Major's first IV injection in humans, elevated the field of hematology and reduced the need for bloodletting. The 18th and 19th centuries brought further developments and innovations by scientists, such as the identification of leukocytes and platelets, successful blood transfusions, and the identification of blood groups A, B, AB, and O.

This exciting, high-tech field in medical research has continued to make dramatic advances in recent decades. Many forms of leukemia that would formerly have caused death within a few months of diagnosis are now curable because of research performed by hematologists.

Related Professions