The form of quantum theory of reaiation introdnced by Heiaonbarg is diarnaaed from the point of view of the transformation theory of quantum electrodynamics.A general investigation of the connection between Heisenberg's method and Dirac'smethod of variation of parameters is given.The exetension of Heisenberg's methodto eigenvalue problems.which was first carried out by Weissklpf for the self energyof the electron.is presented in such a way as to show more clearly its quantummechanical interpretation.Ageneral proof of the equivalence of We jsskopf's me-tbod and the method of the perturbation theory of stationary stntes in quantumicechanics is given.