  We propose a technique to test the idea that non-standard dynamics, rather
than dark matter halos, might be responsible for the observed rotation curves
of spiral galaxies. In the absence of non-luminous matter, a galactic disk's
rotational velocity and its vertical velocity dispersion can be used jointly to
test the self-consistency of the galaxy's dynamics. A specific illustrative
example, using recent measurements of the disk kinematics of M33, shows this to
be a promising approach to assess the viability of Modified Newtonian Dynamics
(MOND).
