O'Day has pointed out1 that his histological preparations provide definite evidence for the presence of cones in the retina of the guinea pig. I welcome this statement, although I have myself, as he indicated, relied on authors who have denied it. Occasionally one finds evidence for red modulators in the eye of the guinea pig (see, for example, Fig. 140, p. 281, of my recent summary2). Such modulators, I maintain, should be ascribed to cones if the histological differentiation of the cells into rods and cones is going to mean anything at all to retinal physiology. There are more of them in the eye of the rat. Since, however, some histologists deny the presence of cones in the eye of the rat (see ref. 2), and others refuse to accept them in the guinea pig, the physiologist must try to stand on his own feet.
O'Day, K., Nature, 160, 648 (1947).
Granit, R., âœSensory Mechanisms of the Retinaâ (Oxford Univ. Press, 1947).
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GRANIT, R. Visual Cells of the Guinea Pig. Nature 160, 838 (1947). https://doi.org/10.1038/160838b0