stimulus

(stim’u-lus), pl. stim’uli [L. “ goad ”]. Any agent, act, or influence that produces func- tional or trophic reaction in an irritable ti ue. adequate 8., one that acts specifically upon the end-organs ont:, as light upon the retina. Called also homologous s. chemic s., one which induces a chemic change in a ti ue: for example, nitric acid or silver nitrate locally applied. electric s., a galvanic, induced, or other electric current or shock, as applied to a responsive ti ue. heterologous 5., one which produces an effect or sensation when applied to any part whatever of a nerve-tract. homologous 8. See adequate s. mechanic 8., a stimulant application of mechanic force, as in friction or pinching. thermal s., application of heat.