1. An inhabitant, 19 year-old male, of Sado Island, and his sister, 16 years of age, were found to posses all conventional criteria of total colour-blindness. Spectroscopic examination, however, revealed they had more on less rudimentary colour discriminative power.
2. The brother was dichromic, his spectrum being composed of“ darkened blue” (Up to 495mμ) and “darkened khahki” (550. 700mμ) with a zone of minimum chromaticity at 495.550mμ. The sister was found trichromit. She saw the spectral range up to 485mμ as “darkened blue”. From 485mμ to 500mμ was minimum in chromaticity. A “darkened yellow” began at 500mμ and farther ahead it blended into a “ darkened red”, which continued up, to 690mμ.
Possibility is indicated that the totally cokiur-blind generally retain rudimentary colour sensation, since previous cases had been diagnosed as such without spectral perusal, such as performed by the present authors.
Hereditary relation was also discussed.