  It is shown that the ten generators of the Poincare group acting in the Fock
space of nucleons and mesons and based on standard Lagrangians can be
blockdiagonalized by one and the same unitary transformation such that the
space of a fixed number of nucleons is separated from the rest of the Fock
space. The existence proof is carried through in a formal power series
expansion in the coupling constant to all orders. In this manner one arrives at
effective generators of the Poincare group which act in the two subspaces
separately.
