An injection device including a barrel, a hollow plunger having a portion structured and arranged to move within the barrel, a needle unit, and a safety system that one of automatically causes the needle unit to retract into the plunger when the plunger reaches a substantially fully depressed position and utilizes a frangible or breakable seal arranged within the plunger. This Abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.
