140 COLOUR VISION 



It was shown by Sachs 1 that in man the extent of the pupil reaction 

 varies with the subjective luminosity of the light. Similarly Abelsdorff 2 

 showed that the maximal pupillomotor effect for the light-adapted eye 

 was at 600 /z^u,, for the dark-adapted eye at 540 H/JL. Hess found the 

 photopic and scotopic values for cats and rabbits about the same as for 

 man. 



It appears therefore that mammals have the same spectral limits 

 as man ; that they have a similar capacitv for dark adaptation ; and 

 that their luminosity curves are similar. 



Birds. Lloyd Morgan 3 experimented with chickens. A chicken 

 which picked out bits of yolk of hard-boiled egg from the white was given 

 pieces of orange peel, which it found distasteful. Afterwards for some 

 time it was suspicious of yolk. On the other hand after having learned 

 to avoid bad-tasting black and yellow caterpillars, it did not object to 

 wasps, but probably points of difference other than colour were apparent 

 to it. 



J, P. Porter 4 investigated the colour vision of the English sparrow and 

 other birds by feeding experiments. A number of glasses of like size 

 and shape were covered inside and out with coloured papers, including 

 dark and light grey. The glasses were placed in a row on a board, and 

 food was always put in the same coloured glass, the position of which 

 was changed. The sparrow and cowbird learned to pick out the right 

 vessel. Rouse 5 investigated pigeons by Graber's method of allowing 

 a choice between compartments illuminated by different coloured glasses. 

 The pigeons showed a preference for green and blue. A greater rapidity 

 of breathing was recorded under green and blue lights than under 

 others. 



Hess experimented with birds of diurnal habits (chickens, pigeons) 

 and nocturnal habits (owls) in the same manner as for mammals. 



For diurnal birds com or rice grains were scattered over a matt 

 black surface, part of which was illuminated by a spectrum. They 

 usually pecked at the grains in the orange and red first, then those in 

 the green and yellow, and some in the blue-green. Those in the green- 

 blue, blue and violet were left untouched. Dark-adapted chickens 



1 Arch.f. d. ges. Physiol LIT. 79, 1892 ; Arch.f. Ophth. xxxix. 3, 1893 ; Ztsch.f. Psychol. 

 a. Physiol. d. Sinnesory. xxn. 388, 1900. 



- Ztsch. f. Psychol. u. Physiol. d. Sinnesorq. xxi. 451. 1900; Arch. f. Augenhlk. XLI. 

 155, 1900; Arch.f. Anal. u. Physiol. 561, 1900. 



3 Habit and Instinct, London, 189fi. 



4 Amer. J. of Psychol. xv. 313, 1904 ; xvn. 248. 1900. 



5 Harvard Psych. Studies, u. 580 ; 1900. 



