  Using Monte Carlo integration methods, we describe the behavior of the exact
four-spinon dynamic structure function $S_{4}$ in the antiferromagnetic spin
1/2 Heisenberg quantum spin chain as a function of the neutron energy $\omega$
and momentum transfer $k$. We also determine the four-spinon continuum, the
extent of the region in the $(k,\omega)$ plane outside which $S_{4}$ is
identically zero. In each case, the behavior of $S_{4}$ is shown to be
consistent with the four-spinon continuum and compared to the one of the exact
two-spinon dynamic structure function $S_{2}$. Overall shape similarity is
noted.
