Abstract: A syringe-type device for inserting a catheter guide wire into a blood vessel includes a syringe in which the plunger has a central passage extending through it. A thin feeder tube fits slidably in the central passage of the plunger and is itself provided with a central passage. The plunger passage is normally blocked by a closure means consisting of a ball bearing received in a seat provided by a rubber tip on inner edge of the plunger body. The needle is inserted into the blood vessel and the plunger is then withdrawn somewhat to permit blood to be observed in the body of the syringe for verification of proper needle positioning. The feeder tube is then slid through the central passage past the closure means to eject the ball bearing and thereby open the plunger passage. The feeder tube is further advanced to bring its inner end into contact with the end wall of the syringe body.