  In quantum field theory with three-point and four-point couplings the Feynman
diagrams of perturbation theory contain momentum independent subdiagrams, the
``tadpoles'' and ``snails''. With the help of Dyson-Schwinger equations we show
how these can be summed up completely by a suitable modification of the mass
and coupling parameters. This reduces the number of diagrams significantly. The
method is useful for the organisation of perturbative calculations in higher
orders.
