  The Walecka model contains essentially two parameters that are associated
with the Lorentz scalar (S) and vector (V) interactions. These parameters are
related to a two-body interaction consisting of S and V, imposing the condition
that the two-body binding energy is fixed. We have obtained a set of different
values for the nuclear matter binding energies at equilibrium densities. We
investigated the existence of a linear correlation between $B_N$ and $\rho_0$,
claimed to be universal for nonrelativistic systems and usually known as the
Coester line, and found an approximate linear correlation only if $V?S$ remains
constant. It is shown that the relativistic content of the model, which is
related to the strength of $V?S$, is responsible for the shift of the Coester
line to the empirical region of nuclear matter saturation.
