. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 438 Comparative Animal Physiology Granit used the technique of placing microelectrodes on single tertiary neurones of the retina before they enter the optic nerve (Fig. 141). Then he stimulated the area of sense cells connected to this fiber with light of known wave length and intensity and varied the intensity at each wave length until he determined the threshold of the fiber for that particular wave length. In this manner he was able to obtain sensitivity curves for individual visual units. Each unit consisted
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 438 Comparative Animal Physiology Granit used the technique of placing microelectrodes on single tertiary neurones of the retina before they enter the optic nerve (Fig. 141). Then he stimulated the area of sense cells connected to this fiber with light of known wave length and intensity and varied the intensity at each wave length until he determined the threshold of the fiber for that particular wave length. In this manner he was able to obtain sensitivity curves for individual visual units. Each unit consisted of the tertiary fiber and all sense cells and secon- dary neurones from which it received impulses. It was found that the units were not all the same. Some gave both the normal scotopic (dark-adapted) and photopic (light-adapted) sensitivity curves as the state of adaptation was appropriately changed, and this indicated that the same tertiary fiber received impulses from both rods and cones. Other tertiary fibers apparently received impulses only from cones. The sensitivity curves from exclusively cone units also seemed to be of several types, some with a narrow range and a peak in RCX3S CONES. I 2 3 E NON-FUNCTIONAL IN PBOTANOPIA X NON-FUNCTIONAL IN DEUTERANOPIA Fig. 142. An explanation of color vision and color blindness based on the findings of Granit and his collaborators and on the histology of the retina. Ei, Ea, Ea, Et, recording electrode positions; B, blue-sensitive cones; G, green-sensitive cones; Y, yellow-sensitive cones; R, red-sensitive cones. From ;* the blue, others with a narrow range and a peak in the green, yellow or red and still others with a wide range and a peak which coincided with the nor- mal photopic visibility curve. The above typesi of data can be explained by assuming that there are cones with narrow sensitivity curves with peaks in the red, yellow, green, and blue, and that these are connected both singly and in combination to tertiary
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