92 Dr, E. Rose on the Doctrine 



It follows that colour-blindness can occur with regard to both 

 ends of the spectrum, and reduce it to one-half (about r 8 7 ) — a 

 result which will convince even one who has only bad instruments 

 at his disposal. 



Apart from the circumstance that such people are naturally 

 blind in light of another colour, any colour-blindness is of itself 

 amblyopia, a weakness of vision which shows itself externally 

 in the visage, and for, the most part so pronounced that it has 

 led my friends, healthy in other respects, to visit oculists, — a 

 result not surprising, as almost (in Mr. M for example) half the 

 source of light is inactive, from which secondary disturbances 

 again result. But that is not the only evil of colour-blindness. 

 Is it immaterial whether with progressive colour-blindness the 

 world finally appears in almost homogeneous light ? Is it an 

 advantage to see everything monochromatic ? Is the chromatic 

 aberration of the eye a defect which is common to humanity ? 



As I was walking through the streets with Mr. M, whose 

 power of accommodation and sharp-sightedness are enviable, he 

 suddenly grasped my arm. The sun had shone out, and without 

 being led he could go no further. After he had gradually accom- 

 modated himself to the dazzling brightness by closing the eyelid, 

 he continued the walk with continual spasm of the eyelids and 

 nystagmus, which he did not before have — like a rabbit which has 

 the magnesium light reflected on its retina by a mirror. I had 

 previously noticed that his younger brother had nystagmus ; and 

 his mother had assured me that four absent ones had it too. 

 Hence they had consulted all the most important oculists, and, 

 as this was without success, some less important ones also — 

 not without pain, so that now it gave me the most terrible trouble 

 to get hold of the brother, who intentionally kept out of the 

 way. In fact he also saw five intervals, and was just like his 

 brother; so that I do not hesitate to consider chronic spasm 

 of the eyelids and nystagmus a frequently overlooked conse- 

 quence of colour-blindness. In any case we must assume that 

 man naturally sees nothing distinctly, because for each homoge- 

 neous constituent of the light he must accommodate differently, 

 just as the telescope must be adjusted specially for each Fraun- 

 hofer's line. The chromatic aberration of the eye is the normal 

 condition, and it is not without injury that this beneficent shield 

 is wanting to the colour-blind. Weakness of sight and dazzling, 

 with their host of secondary ailments, are the direct consequences 

 of colour-blindness, quite apart from chromatic delusions, which 

 are not so serious as in the case of colour-mistake *. 



The result of this investigation might be summed up by 



* Farbenirrsinn, implying that the mistake is one of sensation, not of 

 judgment. — Ed. 



