Hering

HERING, Ewald (Ewald Heririg, 1834-1918), German physiologist, professor in Prague and Leipzig. The name of Hering in physiology is associated with an original theory of color vision, which arose parallel to Helmholtz's theory of vision (see) and had a large number of supporters. According to Hering, in the endings of the visual nerves and in the cells connected with them—cones—there are special substances capable of decomposing under the influence of light. The decomposition of one substance gives us the sensation of white color; the process of its restoration gives the sensation of darkness—black color. The second substance, under the influence of light rays, gives the sensation of red color; the restoration of this substance under the influence of complementary rays, which Hering considers to be green, gives the sensation of green color. The third substance decomposes under the influence of yellow color and is restored under the influence of blue rays. Thus, at the basis of all visual processes lie processes of two kinds. The process of decomposition, which proceeds in the black-and-white substance, in the red-and-green, in the yellow-and-blue, is the process of dissimilation (D-process). The reverse process, restoring the primary substance, is called assimilation (A-process). From the combination of processes occurring in these three substances, Hering derives the processes of color vision. Incidentally, Hering is the author of the explanation, by means of the light theory, of the phenomena of contrast, which, according to Helmholtz, should be phenomena of a central character. Hering's views in recent times have undergone significant changes, and one has to abandon the original theory of Hering, since there is a series of facts contradicting this theory. For example, it can be proved that in the retina the sensations of red and green colors occur not in the same place and not at the same depth. Furthermore, it can be proved that the electromotive force of the retina, arising upon illumination, obeys a different law than that required by Hering's theory. Thus, at present his theory, which played a huge role in physiological optics, can no longer claim, as before, the leading role. Hering's view on assimilation and dissimilation extends not only to vision but to all processes of living matter: A- and D-processes are observed everywhere and parallel to each other (see Biotonus). From the interplay of these processes are composed all the properties that living matter possesses. Hering is the author of an extensive monograph devoted to vision and summarizing his views on this subject. The most important works of Hering: "0ber das Gedachtnis als eine allgemeine Punktion der organisierten Materie" (Wien, 1870); "Raumsinn des Auges, Augenbewegungen" (Handb. der Physiologie, hrsg. v. L. Hermann, Band III, T. 1, Leipzig, 1879; Russian edition - St. Petersburg, 1888); "Grundzuge der Lehre vom Lichtsinn" (Handb. der gesamten Augenheilkunde, begründet v. A. Graefe u. Th. Saemisch, Band III, Berlin, 1920).