All of the poisons caused uterine contractions, EXCEPT:

Ergot, Quinine, Lead are collectively called as 'Ecbolics'. They stimulate uterine contractions. The only true ecbolic known is ergot. Ergots act only on the uterus which has already begun to contract. Arsenic does not cause uterine contraction. It is used in 'aboion stick' which is introduced into the uterus. Because of irritation due to juices or rupture of membranes due to force of stick, the products of conception are expelled out.