'Rods and cones' definitions:

Definition of 'Rods and cones'

From: GCIDE

Rod \Rod\, n. [The same word as rood. See Rood.]
1. A straight and slender stick; a wand; hence, any slender bar, as of wood or metal (applied to various purposes). Specifically: (a) An instrument of punishment or correction; figuratively, chastisement. [1913 Webster]
He that spareth his rod hateth his son. --Prov. xiii. 24. [1913 Webster] (b) A kind of sceptor, or badge of office; hence, figuratively, power; authority; tyranny; oppression. "The rod, and bird of peace." --Shak. (c) A support for a fishing line; a fish pole. --Gay. (d) (Mach. & Structure) A member used in tension, as for sustaining a suspended weight, or in tension and compression, as for transmitting reciprocating motion, etc.; a connecting bar. (e) An instrument for measuring. [1913 Webster]
2. A measure of length containing sixteen and a half feet; -- called also perch, and pole. [1913 Webster]
Black rod. See in the Vocabulary.
Rods and cones (Anat.), the elongated cells or elements of the sensory layer of the retina, some of which are cylindrical, others somewhat conical. [1913 Webster]