It has long been known that the stimulation of one sense organ influences in some degree the sensitivity of the organs of another sense. But whether the influence is exerted upon the receptors or upon their central areas in the cortex has not been with certainty determined. This behavior of the nervous system may readily be inferred from its synaptical arrangement and intemunciatory constitution whereby all parts are susceptible of communication with each other. These ideas have thus been summsrized by Sherrington (12): "All parts of the nervous system are connected together and no part of it is probably ever capable of reaction without affecting and being affected by various other parts, and it is a system certainly never absolutely at rest." The two senses which seem to be best adapted for the purpose of measurement are those of hearing and vision. As long ago as 1888, Urbantschitsch (13) observed that sounds of different tones may act differently upon the sensitivity of the visual apparatus for various colors, but no definite quantitative relation between sound and color was detected by him. In later investigations Lazarev (11) concluded that the visual sensi- bility of the retinal periphery, that is of rod vision, increased under the influence of acoustical stimulation of the ear. Yakovlev (15) found that stimulation of the ear by sound conspicuously enlarged the area of the field of cone vision especially for green light. Kravkov (8) observed that under the influence of sound the critical frequency of flicker of white light increases for central or cone vision, and diminishes for peripheral or rod vision. In a recent investigation Yakovlev (16) has studied in much detail the influence of acoustic stimulation, both by musical tones of frequency 780 cycles per second and noises of 75 decibels in loudness, upon the limits of the areas of the retinal fields for extreme red, orange-red, green, and blue colors. The colors were not spectral but were obtained from Wratten color filters. The maximum transmissions of the filters were at 700 m/~, 680 m#, 540 m~, and 440 m~ respectively. Two observers were employed and from their measurements the following results were obtained. Under the influence of both tones and noises the color field for extreme red was unaltered, that for orange-red was dlmluished, and those for green and blue enlarged in area. Noise was more effective as a stimulus than musical tones, possibly because of its greater intensity, and under its influence the color fields were diminished and enlarged to the greatest extent. In a more detailed research Kravkov (9) has investigated the influence of acoustic stimulation of the ear upon the light, or rod, and the color, or cone, sensibility of the 105