Walter Rudolf Hess

A Swiss neurophysiologist, Walter Rudolf Hess (1881-1973) won the 1949 Nobel Prize for Physiology or Medicine (with Antonio Egas Moniz) for discovering the role played by certain parts of the brain in coordinating the functions of internal organs.

The son of Professor Clemenz Hess, Walter Rudolf Hess was born at Frauenfeld, Switzerland, on March 17, 1881. In 1900 he became a medical student at the University of Lausanne, and after more study in Switzerland and Germany, he graduated from the University of Zurich in 1906. He became a practicing ophthalmologist, but in 1912 he turned to physiology. In 1917 Hess was appointed professor of physiology and director of the Institute of Physiology at the University of Zurich.


The Experiments

Hess soon became interested in the study of the autonomic nervous system, the nerves that originate at the base of the brain and extend throughout the spinal cord. These nerves control such functions as digestion and also trigger the response of organs to such stimuli as stress. In 1925 Hess began work on the influence of the diencephalon (interbrain)—especially the hypothalamus—in relation to the regulation of involuntary activities that enable the individual to function as an integrated organism.

At the time, it was known that the autonomic nervous system was divided into the sympathetic and the parasympathetic and that these two divisions were in general mutually antagonistic. Involuntary muscles and glands were supplied by two types of fibers, one excitatory and the other inhibitory. But much less was known about the action of the central origins of the autonomic nervous system in the brain, mainly in the hypothalamus. A few scientists had observed the reactions in animals following stimulation of poorly localized areas of the hypothalamus. It thus came to be realized that the hypothalamus, through the autonomic nervous system, controlled the automatic functions of the body, such as the blood supply to muscles and organs, mechanism of heat regulation, activity of the gastrointestinal tract, and the regulation of basal metabolism, of the sugar content of the blood, and of blood pressure. But to a large extent, the exact areas responsible for such functions had never been precisely localized.

Hess developed his own brilliant technique for the investigation of such problems. Others had used needle electrodes implanted in the hypothalamus to pass an electric current to a desired area, but locations were generally not precise. Hess implanted his electrodes accurately under general anesthesia. The needle electrode, insulated except at the very tip, was connected to a frame fixed to the skull. When the animal had recovered from the operation, a very weak current was passed through the electrode, and the animal's reaction, giving the result of stimulation at the site of the tip of the electrode, was very carefully recorded. After repeated observations of this type, the minute area around the tip of the electrode was coagulated by a current, and the animal's reaction was again recorded. At autopsy, serial sections were made of the animal's brain in order to identify the exact situation at the tip of the electrode. The correlation of these clinical and anatomical findings involved a very careful recording technique. Hess's experiments were carried out on a scale never previously attempted.

Hess proved conclusively that bodily functions, triggered by the sympathetic division of the autonomic nervous system, are related to the posterior and middle parts of the hypothalamus. Stimulation of a certain area of the hypothalamus of a cat produces all the symptoms of rage. Stimulation of another defined area produces parasympathetic, not sympathetic, effects; the cat relaxes and falls asleep. By these methods Hess mapped out the influence of the hypothalamus, and for his work he was awarded a Nobel Prize, with Antonio Egas Moniz, in 1949.

After his official retirement in 1951, Hess continued to work in the Institute of Physiology. He was already the author of several books, and in 1956 he published an atlas of sections of the hypothalamus and the thalamus. In 1962 he published a work that related his research to psychosomatic phenomena and the behavior pattern of the individual (2d ed., 1968). Hess received many honors, including honorary degrees from four universities and in 1971, the Johannes Müller Medal. He died in Locarno, Switzerland, on Aug. 12, 1973.

Further Reading on Walter Rudolf Hess

There is a biography of Hess in Nobel Lectures, Physiology or Medicine, 1942—1962 (1964), which also includes his Nobel Lecture. For the physiology of the autonomic system and hypothalamus see J. F. Fulton, Physiology of the Nervous System (3d ed. 1949). For the historical aspects see J. Beattie in W. E. LeGros Clark and others, The Hypothalamus (1938).