Wal·ler \ˈwäl-ər\ , Augustus Volney (1816–1870), British physiologist. Waller began in private practice, but after several years he decided to devote full time to research, first in Bonn and then in Paris. For a time he was professor of physiology in Birmingham, England. He is best known for pioneering a major technique for unraveling the complex structure of the nervous system using the type of nerve degeneration that is now associated with his name. By cutting the nerves in the frog's tongue, Waller discovered in 1849 that degeneration occurred throughout the axon's distal segment, and he concluded from this that the nerve cell body is the axon's source of nutriment. The method became a major means of tracing the origin and course of nerve fibers and tracts.