  We discuss the role of the so-called Darwin-Foldy term in the evaluation of
the proton and deuteron charge radii from atomic hydrogen spectroscopy and
nuclear scattering data. The question of whether this term should be included
or excluded from the nuclear radius has been controversially discussed in the
literature. We attempt to clarify which literature values correspond to which
conventions. A detailed discussion of the conventions appears useful because a
recent experiment [R. Pohl et al., Nature vol. 466, p. 213 (2010)] has
indicated that there is a discrepancy between the proton charge radii inferred
from ordinary ("electronic") atomic hydrogen and muonic hydrogen. We also
investigate the role of quantum electrodynamic radiative corrections in the
determination of nuclear radii from scattering data, and propose a definition
of the nuclear self energy which is compatible with the subtraction of the
radiative corrections in scattering experiments.
