[坎贝尔生物学 第1172页] Campbell Biology 12th Edition
cones—about 150,000 cones per square millimeter. The ratio of cones to rods falls with distance from the fovea, with the peripheral regions having only rods. In
cones—about 150,000 cones per square millimeter. The ratio of cones to rods falls with distance from the fovea, with the peripheral regions having only rods. In