  We show that the current quark mass should vanish to be consistent with the
QCD color confinement: a bag model leads us to Heun's equation, which requests
that not only the energy but also the string tension should be quantized. This
is due to the presence of higher order singularity which requests higher
regularity condition demanding that parameters of the theory should be related
to one another. As a result, the Hadron spectrum is consistent with the Regge
trajectory only when quark mass vanishes. Therefore, in this model, the chiral
symmetry is a consequence of the confinement.
