  Spiral galaxies are studied using a simple global disc model as a means for
approximate determination of mass profiles. Based on rotation curves and the
amount of gas (HI+He), we find global surface mass densities consistent with
measurements and compare them with B-band surface brightness profiles. As a
result we obtain mass-to-light ratio profiles. We give some arguments for why
our approach is reliable and sometimes better than those assuming ad hoc the
presence of a massive non-baryonic dark matter halo. Using this model, we study
galaxies NGC 7793, 1365, 6946 and UGC 6446. Based on a rotation curve from The
HI Nearby Galaxy Survey (THINGS) we also study galaxy NGC 4536 and compare the
results with those we published elsewhere for the same galaxy.
