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Published online by Cambridge University Press: 04 August 2017
Progress in the 50 years since the discovery of ionized gas in NGC 1052 is reviewed. As discovery has proceeded from H II to H I and recently to 107 K gas, the known amount of gas in ellipticals has increased dramatically: from 103–6M⊙ for H II, to 105–9M⊙ for H I in some 15% of E's, to 109–10M⊙ for the X-ray emitting gas. Although a few ellipticals with dust have long been known, recent CCD surveys have revealed dust lanes in nearly half of all E's. The cooler gas — as traced by H I, warm H II, and dust — is generally distributed in the form of a disk that often shows an outer warp. To deduce the true shapes of ellipticals from the geometry and kinematics of such disks has proven a challenging task. There is mounting evidence that many disks consist of gas accreted by mass transfers and mergers, and that some of them may not yet have reached dynamical equilibrium. Some of the major unsolved problems concern the atmospheric balance between sources and sinks of gas, and the importance of cooling flows and galactic winds.