  A simple relativistic model of heavy-quark-light-quark mesons is proposed. In
an expansion in inverse powers of the heavy quark mass we find that all zeroth
and first order heavy quark symmetry relations are satisfied. The main results
are: - the difference between the meson mass and the heavy quark mass plays a
significant role even at zeroth order; - the slope of the Isgur-Wise function
at the zero recoil point is typically less than $-1$; - the first order
correction to the pseudoscalar decay constant is large and negative; - the four
universal functions describing the first order corrections to the semileptonic
decay form factors are small; - these latter corrections are quite insensitive
to the choice of model parameters, and in particular to the effects of
hyperfine mass splitting.
