( ( ( ( ( ( ( The function ) ( of ( the ( digestive gland ) ) ) ) ( ( is not ) ( fully understood ) ) ) , ) but ) ( it ( probably ( contributes ( to ( ( ( digestion and ) absorption ) ( of food ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (NN function)) (PP (IN of) (NP (DT the) (JJ digestive) (NN gland)))) (VP (VBZ is) (RB not) (VP (ADVP (RB fully)) (VBN understood)))) (, ,) (CC but) (S (NP (PRP it)) (ADVP (RB probably)) (VP (VBZ contributes) (PP (TO to) (NP (NP (NN digestion) (CC and) (NN absorption)) (PP (IN of) (NP (NN food))))))) (. .)))
The function of the                      digestive gland is not fully understood, but it probably contributes                      to digestion and absorption of food.
(ROOT (S (NP (NP (DT The) (JJ main) (NN function)) (PP (IN of) (NP (DT the) (JJ human) (NN digestive) (NN system)))) (VP (VBZ is) (S (VP (TO to) (VP (VB break) (PRT (RP down)) (NP (NP (NNS foods)) (PP (IN for) (NP (NN absorption)))) (PP (IN into) (NP (DT the) (NN blood))))))) (. .)))