  We analyse the experimental data on near threshold $\pi$, $\eta$, $\omega$,
$\eta'$ and $K^+$ production from $pp$ collisions and show that all information
gained so far is compatible with approximately constant production matrix
elements when including the rescattering between the baryons in the final
states. Different methods to include the final state interactions are discussed
and their range of validity is indicated. We, furthermore, show that Dalitz
plots for the proton-meson invariant mass spectra at different energies should
be suited to distinguish between final state interactions and resonant
production amplitudes.
