( ( ( The ( normal use ) ) ( of ( this organ ) ) ) ( ( is ( demonstrated ( by ( ( the ( snake 's ) ) ( tongue ( ( ( ( ( ( flicking ( ( in and ) out ) ) , ) ( ( tasting things ) ( that ( it ( touches ( ( with ( its tongue ) ) ( , ( or seemingly ) ) ) ) ) ) ) ) , ) ( sampling ( the air ) ) ) ( around it ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ normal) (NN use)) (PP (IN of) (NP (DT this) (NN organ)))) (VP (VBZ is) (VP (VBN demonstrated) (PP (IN by) (NP (NP (DT the) (NN snake) (POS 's)) (NN tongue) (S (VP (VP (VBG flicking) (PRT (RP in) (CC and) (RP out))) (, ,) (VP (VBG tasting) (NP (NNS things)) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ touches) (UCP (PP (IN with) (NP (PRP$ its) (NN tongue))) (, ,) (CC or) (ADVP (RB seemingly))))))) (, ,) (VP (VBG sampling) (NP (DT the) (NN air))) (PP (IN around) (NP (PRP it))))))))) (. .)))
The normal use of this organ is demonstrated by the snake's tongue flicking in and out, tasting things that it touches with its tongue, or seemingly, sampling the air around it.
(ROOT (S (NP (NNS Snakes)) (VP (VBP use) (NP (PRP$ their) (NN tongue)) (PP (TO to) (NP (NN smell) (NNS things)))) (. .)))
Snakes use their tongue to smell things.