The present disclosure relates to a syringe for mixing two substances which have been retained separately inside the syringe, for instance in a storage condition. In particular the present disclosure relates to a syringe for 1) retaining a dry composition in a vacuum, and 2) mixing the dry composition with an aqueous medium to form a flowable substance. One embodiment relates to a syringe for retaining and mixing first and second substances comprising: a barrel comprising a sealable and/or closable distal outlet and a vacuum chamber for holding a first substance, a plunger incorporating a reservoir chamber for holding a second substance and configured to be axially displaced through a proximal end of the barrel, a membrane separating the vacuum chamber and the reservoir chamber, and a pointed member, such as one or more needles, for penetrating the membrane.
