Experiments on color vision in mice in relation to the duplicity theory

Summary

• 1. In training experiments with Hering papers three mice gave results indicating color blindness. One specimen confused blue with Hering gray no. 13. Two confused red with gray no. 49; and one gave inconclusive results but seemed not to be able to discriminate between red and a gray slightly darker than no. 49.

• 2. Similar experiments, with a field of artificial colored light of known wave length opposite a non-colored field of variable intensity, demonstrated that four mice were color blind, for the colors employed, and that one specimen could apparently see color. The last is the same mouse which gave doubtful results with Hering papers.One mouse confused blue with a neutral light field of intensity 2.1 Lux; two were unable to distinguish between green and a non-colored field of intensity 27.2 Lux; and one could not discriminate between red and a neutral intensity of 0.04 Lux.

• 3. A single specimen succeeded in discriminating between red and a great number of neutral intensities, though often with some difficulty. Also he chose, not according to relative brightness as did the other specimens, but on the basis of a specific characteristic of the red field. The animal's ability to distinguish between two neutral fields of different intensities was not fine enough readily to suggest that the results with red were due alone to brightness discrimination.

• 4. Examination of preparations of the retinae of the experimental specimens and others has revealed no cones among the rods.

• 5. The retinae of the apparently color-seeing mouse were abnormal in that all elements were small and underdeveloped. Cones may possibly have been present in a partly differentiated condition but could not be identified.

• 6. A discussion of the results is made in regard to the duplicity theory.