  NGC 2359 is an optical nebula excited by the powerful wind and the radiation
of the Wolf-Rayet star HD 56925. We have investigated the interaction between
this massive star and the surrounding neutral gas by analyzing the large-scale
21cm-HI emission and by mapping the nebula in the J = 1-0 and the J = 2-1 lines
of CO. We found a conspicuous (70 x 37 pc) HI shell, expanding at 12 km/s,
likely produced during the main-sequence phase of the star. The molecular gas
towards NGC 2359 shows three velocity components. Two of these components, A1
and A2, have narrow linewidths (1-2 km/s) and radial velocities of 35-38 and
64-68 km/s, respectively. The third component is detected at radial velocities
between 50 and 58 km/s and has a broader profile (up to 5.5 km/s). Furthermore,
this component is morphologicaly related with the nebula and has a velocity
gradient of a few km/s. We have also estimated the physical parameters of the
molecular gas by means of a LVG modelling of the CO emission. The gas projected
onto the southern HII region of the nebula has low CO column density and is
rather hot, probably up to 80 K. Several profiles of the 13CO J = 1-0 line near
the peak of the emission, together with a weak emission bridge between the
broad and one of the narrow components (component A2), suggest the presence of
a shock front acting in the southern part of the nebula. This shock was likely
produced in a previous RSG/LBV phase of HD 56925.
