THE PERCEPTION OF LIGHT AND COLOR. 



183 



Region of spectrum. 



Extreme red 



Orange 



Yellow 



Green 



Blue 



Ratio. 



3. 



5. 



9. 

 196 

 625 



It should be remarked that these ratios 1 were determined for an 

 eye kept for twenty minutes in darkness. If an eye not adapted had 

 been tested the above ratios would have been reduced, as it is well 

 known that its luminous sensibility is much less. It is, however, a very 

 interesting fact that the quantity of light necessary for the perception of 

 color remains very nearly constant. Furthermore, if one adds white light 

 to a monochromatic light, the quantity of the latter necessary for the 

 recognition of its color remains almost invariable. If the results 

 obtained by M. Charpeutier and M. Parinaud are compared, it will be 

 seen that they differ but slightly. According to M. Parinaud, red cannot 

 give rise to a luminous sensation without color, even in indirect vision, 

 and, on the other hand, in the yellow spot all the colors appear at first 

 sight as colored. Although M. Charpeutier denies these propositions, 

 he nevertheless recognizes that chromatic sensibility is best developed 

 at the center of the retina. M. Parinaud, on his side, formally recog- 

 nizes the decrease of chromatic sensibility from the center to the periph- 

 ery of the retina, and even his denial that red can produce a luminous 

 sensation without color is not absolute, since he recognizes that certain 

 parts of the retina can not perceive this color. 



As we have stated above, the German physicists and physiologists 

 took up the study of the same phenomena after the French savauts, 

 and, judging from the excellent reviews published by M. Victor Henri 

 in successive volumes of " L'Annee Psychologique," the phenomena 

 observed across the Ehine are in exact agreement with the enuncia- 

 tions of M. Parinaud. It is, however, to be regretted that his fre- 

 quent visits to the German laboratories have prevented M. Henri from 

 reminding Koenig and Yon Kries to respect the rights of priority of 

 Charpeutier and Parinaud. Professor Kuel, of Ghent, in reviewing the 

 researches of Von Kries in " Les Archives d'Ophtalmologie," adds to his 

 analysis the following reflections: "It seems tome that the authors 

 across the Ehine are too neglectful of the preponderating merit which 

 our French collaborators have had in the elaboration of these new 

 ideas." Without wishing to dwell longer than necessary on this detail, 

 [ have thought that it should not be passed over in silence. 



The first publication of Von Kries on this subject appeared in 1894, 

 and (thanks to the review by M. Victor Henri) we will be able to sum- 

 marize his results. Hillebrand had shown in 1889 that if the eye be 

 adapted to obscurity, a spectrum whose brightness is continuously 



1 La Revue Ge"nerale, etc., July 15, 1898, p. 214. 



