passive immunity: an impermanent form of acquired immunity in which antibodies against a disease are acquired naturally (as through the placenta to an unborn child) or artificially (as by injection of antiserum)
acquired immunity: immunity to a particular disease that is not innate but has been acquired during life; immunity can be acquired by the development of antibodies after an attack of an infectious disease or by a pregnant mother passing antibodies through the placenta to a fetus or by vaccination
common cardinal vein: the major return channels to the heart; formed by anastomosis of the anterior and posterior cardinal veins