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More than 2,500 years ago, Hippocrates, the first great physician, developed theories about the practice of medicine and human anatomy. It was the medical ethics that he established, however, that continue to influence medical practice today. The oath that he administered to his disciples is still administered to physicians about to start practice. The "Hippocratic Collection," 87 treatises on medicine, are believed to be the first authoritative record of early medical theory and practice. Hippocratic physicians believed in the theory that health was maintained by a proper balance of four "humors" in the body: blood, phlegm, black bile, and yellow bile.

Greek physician Galen influenced medical thought for more than a thousand years. During the Middle Ages, his works were translated into Arabic and Syriac. The great civilizations of Egypt, India, and China all developed medical theories of diagnosis and treatment that influenced later cultures of their own countries and those of other countries. Monks in monasteries kept medical theories and practices alive during the Middle Ages by carefully preserving and copying medical records from early civilizations. 

Medical research was revived during the Renaissance, with new findings and theories. Swiss physician Paracelsus publicly burned the writings of Galen and Avicenna (a Persian physicist and philosopher), signifying a break with the past. Spanish humanist and physician Juan Luis Vives introduced the concepts of psychology and psychiatry.

Innovations and discoveries in the 1600s and 1700s further advanced the practice of medicine. Examples include: English physician William Harvey's discovery that blood, propelled by the pumping action of the heart, circulates through the body; Dutch lens grinder Anton van Leeuwenhoek's invention of instruments that magnified up to 270 times (he was the first to see bacteria and protozoans). Dutch physician Hermann Boerhaave introduced clinical instruction (teaching at the bedside of patients). Edward Jenner discovered a vaccination against smallpox. Specialization grew rapidly, as did the growth of medical schools, hospitals, and dispensaries.

The 1800s brought more precise medical instruments, such as the stethoscope, the ophthalmoscope, and X-rays. Doctors began to use anesthetics like ether and nitrous oxide and antiseptics. Knowledge of the cell, digestion, metabolism, and the vasomotor system increased. In the 1900s, medical developments included the identification of four blood types, the discovery of insulin, development of antibiotics, and immunizations such as the polio vaccine. Technological advances included the electron microscope, pacemakers, ultrasound, heart-lung machines, dialysis machines, and prostheses, to name only a few.

The specialty of physical medicine and rehabilitation started to take root in the 1930s. Frank H. Krusen, a physician, underwent physical treatment for his own tuberculosis. He researched physical medicine applications and in 1936, established a physical medicine department at the Mayo Clinic. This program became the first residency program in physical medicine in the United States. In 1938, Krusen coined the term physiatrist to describe the physician that specializes in physical medicine; the American Medical Association endorsed this term in 1946. The American Board of Physical Medicine was incorporated in 1947 as the certification body for physical medicine and rehabilitation.

Today, physical medicine and rehabilitation (also known as PM&R) physicians treat numerous medical conditions, including back or neck pain, work or sports injuries, brain or spinal cord injuries, stroke, or bone fractures, amputations, among other conditions. 

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