  We study the electromagnetic vertex of a nucleon in next-to-leading order
chiral perturbation theory (CPT). We consider the case where one of the
nucleons at the $\gamma$NN vertex is off its mass shell. We define relevant
measures for the off-shell dependence in the limited kinematical range allowed,
and analyze their expansion in the pion mass. The leading nonanalytic
contributions are calculated to estimate their size.
