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matic mechanisms in the retina. There is also little doubt, however, that the curves in question and all specifications based upon them, are potentially convertible into terms of such actual response functions. The characteristic constants of these latter functions must be determined from data auxiliary to the facts

Fig. 3. Color Triangle, Showing Loci of Spectral and Black Body Excitations

(The ordinates give the percentage excitation values for Red and the abscissae those for Violet.)

of color-mixture for the normal eye, such as those of color-blindness and chromatic minuthesis. Attempts to arrive at so-called fundamental excitations, based upon these more comprehensive considerations, have been made by König, Abney, Exner (17) and others,