Term: cone

Definition: These elements are shorter and less abundant than rods, except in the fovea centralis, where they are the only visual cells present. They are shaped like bottles sitting on the outer limiting membrane with their necks extending into spaces between rods (Figs. 188e and 190B). Their length increases from the periphery of the retina to the macula lutea. Like rods, cones present two segments. The short, cone-shaped, higly variable outer segement is covered with a very thin hyaline film, and its contents are homogeneous and quite refractive in fresh tissue. In contrast, its superimposed lamellae may be easily dissociated. The inner segment is much longer as well as much thicker, and its granular cytoplasm is lightly stained by carmine, hematoxiline, and the basic aniline dyes.