Biological materials such as vaccines can be stabilized in certain glassy materials soluble in water. It has been proposed to form these glassy materials as a powder suspended in a non-aqueous liquid for injection into a patient. This method is complicated by the need to find suitable compatible liquids and to stop the glassy particles from congregating in liquid. These problems have been obviated by supporting the glassy material on a porous membrane remote from the eluant. When the biological material requires administration, the eluant can be passed across the membrane dissolving the glass and causing the substance to be carried by the liquid into the patient.