The features of the scattering of protons by protons are calculated using the Møller-Rosenfeld version of the meson theory of nuclear forces. A comparison with the experimental material suggests that the neutron-proton interaction is slightly stronger than that between two protons. The predictions of the theory fit the experimental results best when the meson mass is assumed to be about 270 electronic masses. This is significantly larger than that indicated by cosmic-ray measurements, and it is also greater than the values found by using the theory to calculate the features of neutron-proton scattering and the binding energies of the lightest nuclei.