A cartridge comprising both a first container 100 for storage of a first substance and a second container 150, received in the first container, for storage of a second substance. The first container 100 is provided at its distal end with a sealable outlet. A valve 180 is further provided to close both the distal end of the second container 150 and a proximal end of the first container 100. A moveable stopper 166 is also provided to close a proximal end of the second container 150. In use, and for mixing the substances, an operating mechanism drives relative movement between the containers 100, 150, displacing the second substance into a first chamber 102 through the valve 180 when the outlet is closed. The operating mechanism is preferably provided as a part of a mixing device 500 which also comprises a cartridge holder 502, a mixing drive 504 and a delivery drive 506. The operating mechanism driving movement of the mixing drive 504 with respect to the cartridge holder 502 to effect the mixing. The delivery drive further effects the discharging of the mixed substance through displacing the second container 150 relative to the first 100 when outlet is open.
