, M. Guélin
Centro Astronómico de Yebes (IGN),
Apartado 148, 19080 Guadalajara, Spain
IRAM, Grenoble (France) 
CO using the IRAM 30m telescope, with
spatial resolutions of 13'' and 21'' respectively. The kinematics
of molecular gas in the inner regions of the galaxy is particularly
distorted.
The position-velocity diagram (p-v) taken along the kinematical major axis of
NGC891 is strikingly similar to the Galaxy's longitude-velocity
plot (l-v). As in our Galaxy, we have detected in NGC891 molecular gas circulating
at velocities 'forbidden' by a law based only on circular rotation.
Following the work of Binney et al. (1991) on the interpretation of our
Galaxy's CO l-v diagram, we have developed
a model on the gas kinematics of the inner regions of
NGC891 that explains satisfactorily the major features of the CO p-v diagram.
In our model, the flow of molecular gas is driven by a bar that has
corotation at r
3 kpc and that is viewed at an angle 
45 
from
its major axis. Molecular clouds circulate along x
orbits (elliptical
orbits perpendicular to the bar) between the two Inner Linblad
Resonances (ILR), and partly populate x
orbits (ellipses parallel to the
bar) in the outer regions (from the outer ILR up to the corotation circle).
We can also explain the radial distribution of molecular gas:
the great ring of molecular material at r
4.5--6 kpc
might be associated with the Outer Linblad Resonance of the bar (OLR)
and the adjacent hole of molecular gas inside this radius,
with the corotation circle.
The observed kinematics of molecular
gas in the center of the edge-on spiral NGC5907, as well as
a number of other galaxies, could be also interpreted in terms of
highly elliptical orbits driven by bars or triaxial potentials.