me'dium, pi. me'dia

[L. neuter of medius, middle.] 1 Anything through which an action is performed, a means. 2. substance, either solid or liquid, containing nutrient material for the cultivation of microorganisms; a culture-medium. 3. The liquid vehicle holding a substance in solution or suspension. 4. substance used for treating or mounting histological specimens. 5. substance through which impulses or impre ions are transmitted, clear'ing m., one used in histology for making specimens translucent or transparent. cul'ture m., medium (2). disper's ion m., exter'nal m., external phase.* pa 'ive m., one which produces no change in the specimens placed in it.