ANOMALOUS TRICHROMATIC VISION 183 



protanopes {profanomal, Nagel) Bonders and Konig do not record any 

 case, V. Kries one only^, whereas NageP, Guttmann^, and Abney and 

 Watson record a considerable number. The two last have exceptional 

 opportunities as examiners for the Board of Trade. Their results, 

 of which only a very small proportion have been published, will be 

 discussed later (Part III). 



v. Kries and his pupils made a series of investigations on the 

 ratio of green to red in the matches with intermediate homogeneous 

 lights for normal and anomalous trichromats. The quotients of long 

 series of average ratios is given in the following table, I for v. Kries 

 (normal) and Lotze (abnormal), II, for Halben (normal) and Lotze 

 (abnormal), III, for Polimanti (normal) and Zehender (abnormal). 



The table shows conclusively that the anomaly is the result of a 

 physiological condition, not of physical conditions, such as macular 

 pigmentation as suggested by Hering*. If it were due to the latter 

 cause all the quotients of any series would be the same. On the 

 contrary the quotients of partial deuteranopes diminish 23ari passu 

 with the diminution in wave-length of the comparison homogeneous 

 light. 



The divergence is even more marked for the partial protanope 

 (Levy) ; here the quotients also vary with the wave-length, increasing 

 up to 589 [xfji and then diminishing. 



If the results are compared with Breuer's^ for macular pigmentation 

 we find that his ratio of green to red for central fixation (1° field) was 

 I'l times that for paracentral fixation (3° field, 3° — 6° paracentral). 

 The difference therefore between normal and anomalous trichromats 



^ Levy, Dissertation, Freiburg, 1903. 



2 Klin. MonatsU. f. Augenhlk. xlii. 356, 1904. 



3 Ztsch.f. Sinnesphysiol. XLn. 24, 250, 1907 ; XLni. 146, 199, 255, 411, 1909 

 « Lotos, \^. 142, 1885. 



^ Ztsch.f. Psychol, u. Physiol, d. Sinnesorg. xm. 464, 1897. 



