  We present the analysis of the point source content of a low galactic
latitude region selected from the ROSAT all-sky survey. The test field is
centered at l = 90deg, b = 0deg and has an area of 64.5 deg2. A total of 128
soft X-ray sources are detected above a maximum likelihood of 8. Catalogue
searches and optical follow-up observations show that in this direction of the
galactic plane, 85% of the sources brighter than 0.03 PSPC cts/s are identified
with active coronae. F-K type stars represent 67% (+/-13%) of the stellar
identifications and M type stars account for 19% (+/- 6%). These results
together with those of similar optical campaigns demonstrate that the soft
X-ray population of the Milky Way is largely dominated by active stars. The
modelling of this population suggests that most of the stars detected by ROSAT
in this direction are younger than 1 Gyr. The small number of unidentified
sources at low X-ray flux put rather strong constraints on the hypothetical
X-ray emission from old neutron stars accreting from the interstellar medium.
Our observations clearly rule out models which assume no dynamical heating for
this population and a total number of Nns = 10^9 neutron stars in the Galaxy.
If accretion on polar caps is the dominant mode then our upper limit may imply
Nns ~ 10^8.
