The pattern of the electrical response of the visual cortex to the stimulation of optic nerve or lateral geniculate body has been analyzed into three components representing the activity of three conducting pathways composed of three different sized fibers. The three components of the cortical response to geniculate stimulation can be selectively potentiated by continuous illumination of the retina with monochromatic lights. The red light enhances predominately the first component, green the second and blue the third. It is concluded that the nerve impulses for red are probably transmitted mainly by large sized fibers, those for green by medium and large sized fibers and those for blue by small fibers.Chang H. T. IV. - Triple conducting pathway in the visual system and trichromatic vision. In: L'année psychologique. 1949 vol. 50. pp. 135-144