  We show that the thermodynamic Bethe ansatz equations for one-dimensional
integrable many-body systems can be reinterpreted in such a way that they only
code the statistical interactions, in the sense of Haldane, between particles
of identical or different momenta. Thus, the thermodynamic properties of these
systems can be characterized by the generalized ideal gases recently proposed
by one of us. For example, the Yang-Yang $\delta$-function gas is a gas with
specific statistical interactions between particles of different momenta, while
the Calogero-Sutherland system provides a model for an ideal gas of particles
with a fractional statistics.
