Possibly, but strychnine is a fairly rapid drug in its action. 
( Possibly ( , ( ( but strychnine ) ( ( is ( ( a ( ( fairly rapid ) drug ) ) ( in ( its action ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Possibly)) (, ,) (NP (IN but) (NN strychnine)) (VP (VBZ is) (NP (NP (DT a) (ADJP (RB fairly) (JJ rapid)) (NN drug)) (PP (IN in) (NP (PRP$ its) (NN action))))) (. .)))
Strychnine is a very fast moving water current. 
( Strychnine ( ( is ( a ( ( ( very fast ) moving ) ( water current ) ) ) ) . ) )
(ROOT (S (NP (NNP Strychnine)) (VP (VBZ is) (NP (DT a) (ADJP (ADVP (RB very) (RB fast)) (JJ moving)) (NN water) (NN current))) (. .)))