Julius Bernstein

Julius Bernstein (December 18, 1839 – February 6, 1917) was a German physiologist born in Berlin.

He studied medicine at the University of Breslau under Rudolf Heidenhain (1834-1897), and at the University of Berlin with Emil Du Bois-Reymond (1818-1896). He received his medical degree at Berlin in 1862, subsequently beginning his career in the physiological institute at the University of Heidelberg as an assistant to Hermann von Helmholtz (1821-1894). In 1872 he succeeded Friedrich Goltz (1834-1902) as professor of physiology at the University of Halle. Bernstein remained in Halle for the remainder of his career.

Differential rheotome, used by Bernstein to measure action potentials

Bernstein's work was concentrated in the fields of neurobiology and biophysics. He is remembered for his explanation regarding the origin of the "resting potential" and "action potential" of nerves and muscles. In 1902 he developed the "membrane theory" of electrical potential in biological cells and tissues, a theory that provided the first practical physico-chemical explanation of bioelectric events. This hypothesis is considered to be the first actual quantitative theory in the field of electrophysiology.

Bernstein (1902, 1912) correctly proposed that excitable cells are surrounded by a membrane selectively permeable to K⁺ions at rest and that during excitation the membrane permeability to other ions increases. His "membrane hypothesis" explained the resting potential of nerve and muscle as a diffusion potential set up by the tendency of positively charged ions to diffuse from their high concentration in cytoplasm to their low concentration in the extracellular solution while other ions are held back. During excitation, the internal negativity would be lost transiently as other ions are allowed to diffuse across the membrane, effectively short-circuiting the K⁺ diffusion potential. In the English-language literature, the words "membrane breakdown" were used to describe Bernstein's view of excitation. (From Ion Channels of Excitable Membranes, Third Edition, by Bertil Hille).

His pioneering research laid the groundwork for experimentation on the conduction of the nerve impulse, and the transmission of information in the nervous system. He is credited with invention of a "differential rheotome", a device used to measure the velocity of bio-electric impulses.

Written works

• Untersuchungen über den Erregungsvorgang im Nerven- und Muskelsysteme, Heidelberg: Winter, 1871 - Experiments on the excitation process in nerve and muscle systems.
• Die fünf Sinne des Menschen, Leipzig: Brockhaus, 1875 - The five senses of humans.
• Die mechanische Theorie des Lebens, ihre Grundlagen und ihre Erfolge. Braunschweig: Vieweg, 1890 - The mechanical theory of life, etc.
• Lehrbuch der Physiologie des thierischen Organismus, im speciellen des Menschen. Stuttgart: F. Enke, 1894 - Textbook of physiology on the "animal organism", etc.
• Elektrobiologie: Die Lehre von den elektrischen Vorgängen im Organismus auf moderner Grundlage dargestellt. Braunschweig: Vieweg, 1912 - Book on electrobiology.

References

• Julius Bernstein, Pioneer Neurobiologist and Biophysicist
• Short biography, bibliography, and links on digitized sources in the Virtual Laboratory of the Max Planck Institute for the History of Science
• Short biography
• Early Hypotheses to Explain the Action Potential: Bernstein's hypothesis

Further reading

• Seyfarth E-A. (2006), "Julius Bernstein (1839–1917): pioneer neurobiologist and biophysicist", Biological Cybernetics 94: 2–8