. Psychology, descriptive and explanatory [microform] : a treatise of the phenomena, laws, and development of human mental life . hysical basis of the psychical fusion which takes place between the light-and color-sensations and the tactual and muscular sensations of the eye. The retina is a wonderful nervous mosaic, having its various elementsarranged in some nine or ten layers. In one of these layers a great multi-tude of elongated bodies are arranged side by side, like rows of palisades,with their largest extension in the radial direction. These are called rods and cones, and in the jjlace
. Psychology, descriptive and explanatory [microform] : a treatise of the phenomena, laws, and development of human mental life . hysical basis of the psychical fusion which takes place between the light-and color-sensations and the tactual and muscular sensations of the eye. The retina is a wonderful nervous mosaic, having its various elementsarranged in some nine or ten layers. In one of these layers a great multi-tude of elongated bodies are arranged side by side, like rows of palisades,with their largest extension in the radial direction. These are called rods and cones, and in the jjlace of clearest vision (the yellow-spot), whereonly cones appear, not less than one million are supposed to be set in asquare -j^o inch. The retina of the eye thus appears adapted to an astonish-ingly minute work of analysis, but of a diflferent character from that per-formed by the organ of Corti in the ear. While we are confident that in the excitation of the optic nerve, throughthe rods and conns, chemical changes in the pigments of the eye, under theaction of the light upon them, bear an important i)art, the exact number of. Taken from Wuudt, and see my Elements of PhyBiological P?j-chology. p. 338 f. TTIKOKY OF COLOU-SENSATION 109 those visual substances, and the precise nature of the cliange wrought in themand of the infiucnco they exert upon the nervous elements of the retina, arestill matters of doubt. Other forms of stimulation l)esides light (objective) excite sensations ofthis class. Among them are various mechanical and electrical stimuli, suchas any shock to the eye by a blow, moderate pressure on a limited area ofthe eyeball by the finger-nail or by a blunted stick (the disks of light withdarkly colored edges, called pltosplienex), or a weak electrical current sentthrough tlie eye. Moreover, the changing blood-supply excites the nervouselements of the retina so that they are rarely or never inactive ; and thus themost varied and gorgeous cotoring is often seen with th
Size: 1583px × 1578px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectpsychology, bookyear1
