Walter Rudolf Hess (born March 17, 1881,Frauenfeld, Switz.—died Aug. 12, 1973, Ascona) was a Swiss physiologist, who received (withAntónio Egas Moniz) the 1949Nobel Prize for Physiology or Medicine for discovering the role played by certain parts of thebrain in determining and coordinating the functions of internal organs.

Originally an ophthalmologist (1906–12), Hess turned to the study ofphysiology, becoming a research assistant first at the Physiological Institute at the University of Zürich in 1912 and then at the University of Bonn in 1915. In 1917 he was appointed professor of physiology and later director of the Physiological Institute (1917–51) at Zürich. He became interested in the study of theautonomic nervous system—those nerves originating at the base of the brain and extending throughout thespinal cord that control the automatic functions such as digestion and excretion. They also trigger the activities of a group of organs that respond to complex stimuli, such as stress.

Using fine electrodes to stimulate or destroy specific areas of the brain in freely moving conscious cats, Hess found that the seat ofautonomous function lies at the base of the brain, in themedulla oblongata and the diencephalon (interbrain), particularly that part of the interbrain known as thehypothalamus. He mapped the control centres for each function to such a degree that he could induce the physical behaviour pattern of a cat confronted by a dog simply by stimulating the proper points on the animal’s hypothalamus. He also studied the mechanisms of goal-directed movements and established the concept of anticipatory motor control on posture to enable voluntary motor action. Among Hess’s books isThe Biology of Mind (1964).

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