introducer

plural introducers

1. Someone or something that introduces.

   The impartial observer of mankind is compelled to acknowledge that anger is the bane of society, the introducer of discord into the families of rich and poor, the disjoiner of friendships, the destroyer of conjugal and domestic bliss.

   1850, The Cottager's Monthly Visitor, volume 30, page 314

2. medicineA device used to introduce an object into the body.