  Galactic extinction is tested using galaxy number counts at low Galactic
latitude obtained from five band photometry of the Sloan Digital Sky Survey.
The spatial variation of galaxy number counts for low extinction regions of
$E(B-V) < 0.15$ is consistent with the all-sky reddening map of Schlegel,
Finkbeiner, & Davis (1998) and the standard extinction law. For higher
extinction regions of $E(B-V) > 0.15$, however, the map of Schlegel et
al.(1998) overestimates the reddening by a factor up to 1.4, which is likely
ascribed to the departure from proportionality of reddening to infrared
emissivity of dust. This result is consistent with the analysis of Arce &
Goodman (1999) for the Taurus dark cloud complex.
