MONOCHROMATIC VISION 



189 



and Gertz (1). Gertz used a special method and was convinced that if 

 there were a central scotoma it was less than 50'. There was a central 

 scotoma in nine cases: Konig (1), Nagel (1), UhthofT (3), Grunert (3), 

 and Hessberg (1). Bjerrum and Ronne were unable to decide with 

 certainty; in Bjerrum's case the blind spot could not be demonstrated. 

 The positive cases include those with macular changes and albinism, 

 but several had quite normal fundi. Whether all cases have an 

 absolute central scotoma or not, it is certain that foveal vision is 

 very defective even as compared with parafoveal, as is admitted by 

 Hess. 



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Fig. 



54. 



Achromatic scotopic luminosity curve of a deuteranope. 

 ....... Luminosity curve of a monochromat. Abscissae, wave-lengths of the 



prismatic spectrum of gaslight ; ordinates, arbitrary scale, (v. Kries.) 



The spectrum appears to the totally colour-blind as a monochromatic 

 strip, which is usually described as grey. No colour distinctions are 

 made, but the luminosity varies in different parts. The part which 

 appears to them brightest is what the normal call green, and when the 

 luminosity curve is worked out it is found to agree in a very remarkable 

 manner with the normal achromatic scotopic luminosity curve. This 

 fact was first discovered by Hering and Hillebrand 1 and has received 

 conclusive confirmation, notably in the researches of Konig and 



1 Sitz. d. Wiener Akad. XCVTU 70, 1889. 



