Physical methods have been used in medicine for a long time. In ancient times, for treatment, they used cooling and heating various body parts, fixation of fractured limbs, etc.
A number of scientists, who were physicians and physiologists, in the course of their professional activities and hobbies, worked on physical issues thus strengthening by their works the fusion of these important branches of natural science. The examples of some great scientists are instructive in this respect.
Thomas Young (1773-1829) studied at several universities, where he at first studied medicine and then was attracted to physics. He explained the phenomenon of accommodation of the eye by changing the curvature of the lens; he was the first to explain the phenomenon of light interference and introduced the term "interference" itself, developed the theory of color vision, studied deformation of bodies.
Jean Louis Marie Poiseuille (1799-1869) was a French physicist and physiologist. He studied liquid flow in thin cylindrical tubes and internal friction and was the first to use a mercury manometer to take blood pressure.
Julius Robert von Mayer (1814-1878) was a German physician. As a naval surgeon, during navigation, he noticed that in the tropical and northern latitudes, the color of the venous blood of sailors differs. This gave brought him to a conclusion that there is a relationship between consumption of matter and formation of heat, and that heat and work can be mutually converted. Mayer was one of the first to discover the law of conservation and transformation of energy.
Hermann Ludwig Ferdinand von Helmholtz (1821 - 1894) was a German physician, physiologist, and physicist. He provided a mathematical demonstration to the law of conservation of energy noting its universal nature, developed the thermodynamic theory of chemical processes, achieved sizeable success in the field of physiological acoustics and physiology of vision, and measured the velocity of nervous excitation propagation for the first time.