  The long-range $\Lambda N-\Sigma N$ interaction is modeled by a configuration
space meson-exchange potential matrix coupling to channels with $\Delta$ and
$\Sigma(1385)$ isobars. An inner boundary condition, based on $R$-matrix
theory, replaces form factors for short-range effects and includes the effects
of free quark configurations. An excellent fit is obtained to the available
data, with only the energy-independent boundary conditions as free parameters.
The effect of isobar thresholds is shown to be substantial in several partial
waves and is crucial to the understanding of the higher energy $\Lambda N$
elastic scattering data.
