The delivery device 12 comprises a barrel 16 and a plunger 22 received within the barrel. A resilient element 35 mounted in a passageway 33 in a bush 28 at the forward end of the plunger provides a measured degree of frictional resistance to the plunger, to prevent it returning under its own weight to the retracted position. The resilient element may be a ring 35 which is annular in a relaxed condition but resiliently deforms into an oval (see figure 5) in use, and only contacts the inside of the barrel at the axial ends. The resilient element may alternatively be a C-shaped resilient element (262, see figure 13) which engages in a slot 231 extending around most of the periphery of the bush. A clutch mechanism is operable between the plunger and the barrel. In the engaged condition of the clutch, the plunger is advanced by rotation relative to the barrel. An axial load on the plunger disengages the clutch mechanism, allowing the plunger to be advanced axially whilst rotating the driven member.
