  We present results from an on-going programme to study the dust and ionized
gas in E/S0 galaxies with dust lanes. Our data, together with results from
previous studies of E/S0 galaxies, are used to demonstrate the tight
relationship between these two components. This relationship is discussed in
light of our current understanding of the nature and origin of the interstellar
medium (ISM), and in particular in the context of the interplay between the
different multi-temperature components. We show that focusing on dust obscured
regions as tracers of the ISM, and on their properties, serves as independent
evidence for the external origin of the dust and ionized gas.
