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1. a straight, slim mass of substance.
2. one of two types of visual cells, cylindrical segments that contain rhodopsin; together with the cones they form the light-sensitive elements of the retina. See also eye and vision. Called also retinal rod.
Corti's r's pillar cells.
Harrington rod a rigid contoured metal rod used in Harrington instrumentation.
olfactory rod the slender apical portion of an olfactory bipolar neuron, a modified dendrite extending to the surface of the epithelium.
retinal rod rod (def. 2).