bag

Any saclike structure, b. of waters. That portion of the amniotic sac with its fluid which presents in the cervix uteri during the first stage of labor. Barnes' bag. See under Barnes, ink bag. A pyriform gland in certain molluscs, lying in or near the liver. It secretes adark-colored fluid which the animal ejects when alarmed. [Early mid. Engl., bagge, bag, from old Fr., bague, sack.]