  We present seven epochs of spectroscopy on the quadruply imaged quasar SDSS
J1004+4112, spanning observed-frame time delays from 1 to 322 days. The spectra
reveal differences in the emission lines between the lensed images.
Specifically, component A showed a strong enhancement in the blue wings of
several high-ionization lines relative to component B, which lasted at least 28
days (observed frame) then faded. Since the predicted time delay between A and
B is <30 days, our time coverage suggests that the event was not intrinsic to
the quasar. We attribute these variations to microlensing of part of the broad
emission line region of the quasar, apparently resolving structure in the
source plane on a scale of ~10^{16} cm at z=1.734. In addition, we observed
smaller differences in the emission line profiles between components A and B
that persisted throughout the time span, which may also be due to microlensing
or millilensing. Further spectroscopic monitoring of this system holds
considerable promise for resolving the structure of the broad emission line
region in quasars.
