A piston turned hand pressure into a measured dose
The useful trick was not a sharp tip but a close-fitting piston inside a tube. As the user pushed the piston forward, it reduced the space holding the ointment and drove the paste toward the opening. Pulling the piston back made room for another load. In modern terms, the device worked by displacement: the moving piston pushed material out by taking up the space it had occupied.
That arrangement suited ointments, which are too thick to pour like a liquid. A spoon or fingertip can smear a salve, but a tube-and-piston device can deliver it through a narrow outlet and place it more directly. The user supplied the force by hand, so the amount and speed depended on how far and how firmly the piston was pushed.
Why the simple design mattered
A syringe is often pictured with a hollow needle, but that is only one possible attachment. Without a needle, the Roman device was closer to a reusable dispenser: a tube held the medicine, and a piston moved it out. Its usefulness came from controlling where a sticky substance went, rather than from injecting it into the body.
The underlying principle is easy to recognize because it solves the same practical problem as many later dispensers. When a thick substance will not flow freely, pushing from behind gives it a directed path out. The Roman syringe made that everyday bit of mechanics useful for applying medicine.
