222 



COLOUR VISION 



Konig's experiments on normal colour vision were carried out in 

 conjunction with Dieterici^ and an abstract was communicated to the 

 British Association in Birmingham in 1886. The curves were calculated 

 from a vast number of matches made with Helmholtz' spectrophoto- 

 meter. An objection to this instrument is that the variations in in- 

 tensity are made by a polarisation method and account is not always 

 taken of the appreciable polarisation of the light by the prism of the 

 spectroscope itself. The observations and calculations were of the 

 same kind as those made for dichromatic systems (v. p. 163), but were 

 necessarily of a more complicated nature. Fig. 59 shows the curves 



720 700 680 660 640 620 600 580 560 540 5 20 500 480 460 440 420 400 380 



a B C P E b F G H 

 Fig. 59. R, G, and V. sensation curves. K, Konig's G-curve; D, Dieterici's G-curve; 

 G-curve of an anomalous trichromat. Abscissae, wave-lengths of the inter- 

 ference spectrum of sunlight; ordinates, arbitrary scale. (Konig and Dieterici.) 



referred to the interference spectrum of sunlight. Konig's and Die- 

 terici's R and F curves coincide ; the G curves are slightly different. 

 The distortion of the G and F curves between 535 /x/x and 475 ju,^ is due 

 to absorption by the macular pigment. 



By far the most exhaustive experiments have been made by Abney, 

 and they will be discussed in greater detail. He has adopted another 

 method of determining the three sensation curves, dependent upon the 

 luminosities of the colours. His results confirm and correct in detail 

 the curves obtained by Konig. The principle of the experiments is as 

 follows^. 



^ Konig and Dieterici, Sitz. d. Akad. d, Wiss. Berlin, 1886 ; Ztsch. f. Psychol, v. Physiol. 

 d. Sinnesorg. iv. 241, 1892 ; m Konig, pp. 60, 214. 



2 Watson, Proc. Roy. Soc. Lond. A, lxxxyui. 404, 1913. 



