Air built

Built in the air, without any solid foun dation; chimerical, as, an air - built castle. Air'-cas'ing, n. Anair-tight casing around a pipe, etc., at a little distance from it, intended to secure the interpo sition of air as a non-conductor of heat or cold. Air-cavities, n. pl. ( Bot .) See AIR-CELLS. Air-cells, AIR-CHAMBERS, AIR-CAVITIES, AIR-SACS, AIR PASSAGES, n. pl. (Physiol.) Cavities connected with the respiratory system of animals. In the Mammal i a , and specially in Man , the bronchi, after entering the lungs, diverge into innumerable ramifications, which become more and more minute, pervading every part of the pulmonary structure. They lead to minute cavities called intercellular pa ages, and these last, after numerous bifurcations, terminate each by a cul-de-sac, or air-cell. It will be understood from this that the air which enters