[en] In a calculation of the P-state deuteron wavefunctions, coupled Schroedinger-like equations are used, which are the adiabatic limit of Gross' relativistic equations for the wavefunctions. The P-state wavefunctions can be expressed as purely-relativistic potentials acting on the S and D wavefunctions. Standard nonrelativistic wavefunctions, slightly modified, were used for the S and D wavefunctions. All wavefunctions were normalized according to a fully relativistic normalization condition. In position-space the P-state wavefunctions are small and short range; in momentum-space they are large at high momenta, and even become comparable to the D-state. The four Blankenbecler-Cook npd form factors and the four Bewtra form factors are also calculated. Over the rather extensive range in position-space where single pion exchange dominates the nuclear force, the P-state wavefunctions are proportional to the percentage of pseudoscalar coupling in a mixed pseudoscalar-pseudovector pion-nucleon coupling. In the adiabatic limit the relativistic formalism produces an infinite hard core. Deuteron photodisintegration has been studied near the N* peak at 270 MeV. Besides virtual excitation of the N*, our calculation includes the gauge-invariant Born terms. The full calculation with spin does not yield the correct energy dependence, and we discuss why this is so. A scalar model is much more satisfactory, especially if an artificially low N* mass is used. For use in calculating photodisintegration, an isobar model of pion photoproduction near the first resonance was constructed. Besides the Born terms, direct and crossed N* exchange and the omega are included. The effects of using an energy-dependent width for the N* is explored, and it is argued that the N* width must be set equal to zero in crossed contributions. The usual N* propagator is incorrect when the N* is off-shell. Alternative propagators are discussed