The American physiologist Joseph Erlanger (1874-1965) made fundamental discoveries about the way in which nerve impulses are conducted.

Joseph Erlanger, the son of Herman and Sarah Erlanger, was born on Jan. 5, 1874, in San Francisco, Calif. He studied chemistry at the University of California, where he received his bachelor's degree, and then went on to Johns Hopkins University for his medical training. After he was awarded his medical degree (1899), he spent a year as a hospital resident. Between 1900 and 1906 he worked in the department of physiology at Johns Hopkins, successively holding appointments as assistant, instructor, associate, and associate professor.

In 1906 Erlanger moved to the newly established medical school at the University of Wisconsin, where he was the first professor of physiology. Shortly afterward he married Aimee Hirstel. In 1910 he became professor at Washington University, St. Louis, Mo., where he remained until his retirement in 1946.

Erlanger's early interest was in the physiology of the circulation. He studied blood pressure using a sphygmomanometer of his own devising and investigated the effect of pulse pressure on kidney function. The "Erlanger clamp" he designed reversibly to block the conduction of the auriculoventricular nerve bundle and thus was able to define some of the functions of this bundle in carrying impulses between the chambers of the heart. He also elucidated some of the mechanisms by which the flow of blood through the arteries produces sound.

In 1921 Erlanger began his collaboration with Herbert S. Gasser, investigating the properties and functions of nerve fibers. By adapting a new technique to the study of neurophysiology, Erlanger and Gasser proved the hypothesis that thick nerve fibers conduct impulses faster than thin ones. The potential changes in nerves, which are of the order of only a few microvolts, were amplified 100,000 times by means of a newly constructed amplifier and were recorded on a cathode-ray oscillograph, which provided a virtually inertialess recording device. Using this highly sensitive apparatus, Erlanger and Gasser found that nerve trunks contain fibers which conduct electrical impulses at different rates. They defined three groups of fibers: A fibers, those of greatest thickness, which conduct impulses at velocities between 5 and 100 meters per second (mps); B fibers of intermediate thickness, conducting at 3-14 mps; and thin, C fibers, whose conduction velocity is less than 2 mps.

In 1922 Erlanger and Gasser's preliminary observations were published, and the definitive work, "The Compound Nature of the Action Potential of Nerve as Disclosed by the Cathode-Ray Oscillograph," appeared in the American Journal of Physiology in 1924. An augmented version, published in book form in 1937, entitled Electrical Signs of Nervous Activity, has become a physiological classic. For their work they were awarded the Nobel Prize for physiology in 1944.

Erlanger's later work, which continued after his retirement and after his appointment as emeritus professor, was concerned mainly with the properties of single nerve fibers and, to a lesser extent, with synaptic function.

Erlanger was a man of retiring and introspective personality. His only hobby, he said, was "communion with nature." He combined a reflective mind with great manual dexterity, which made him a gifted experimentalist. He died in St. Louis on Dec. 5, 1965.

Further Reading

• There is no detailed biography of Erlanger, but a short account of his life appears in Nobel Lectures: Physiology or Medicine, vol. 3 (1967) and in Lloyd G. Stevenson, Nobel Prize Winners in Medicine and Physiology, 1901-1950 (1953). The best account of his work is Joseph Erlanger and Herbert S. Gasser, Electrical Signs of Nervous Activity (1937). See also Charles Singer and E. Ashworth Underwood, A Short History of Medicine (1928; 3d ed. 1962).