German physicist, doctor, physiologist, psychologist, acoustician. From 1842 to 1852, Helmholtz studied the growth of nerve fibers. At the same time, he actively studied the physiology of vision and hearing. Helmholtz also created the concept of “unconscious inferences”, according to which actual perception is determined by the “habitual methods” already available to the individual, due to which the constancy of the visible world is preserved, while muscle sensations and movements play an essential role. He develops a mathematical theory to explain the shades of sound with the help of overtones. Helmholtz is the author of a number of works in the field of physiology on the nervous and muscular system. Helmholtz discovered heat formation in the muscle (1845-1847), studied the process of muscle contraction (1850-1854), measured the rate of propagation of excitation in nerves (1850), determined the latent period of reflexes (1854), formulated the theory of accommodation of the eye (1853), and developed the theory of color vision (1859-1866).