  We use the abelian Born-Infeld action for the worldvolume gauge field and
transverse displacement scalars to explore new aspects of D-brane structure and
dynamics. We study several classic gauge field configurations, including point
charges in any worldvolume dimension and vortices in two worldvolume
dimensions, and show that, with an appropriate excitation of the transverse
coordinate field, they are BPS-saturated solutions. The Coulomb point charge
solutions turn out to represent, with considerable fidelity, fundamental
strings attached to the brane (their magnetic counterparts describe D1-branes
attached to D3-branes). We also show that S-matrix for small excitations
propagating on the point charge solution is consistent with (and gives further
illuminating information about) Polchinski's effective open string boundary
condition.
