  It is argued that, in the two dimensional principal chiral model, the
Wess-Zumino term can be induced quantum mechanically, allowing the model with
the critical value of the coupling constant $\lambda^2 = 8\pi/|k|$ to turn into
the Wess-Zumino-Novikov-Witten model at the quantum level. The Wess-Zumino term
emerges from the inequivalent quantizations possible on a sphere hidden in the
configuration space of the original model. It is shown that the Dirac monopole
potential, which is induced on the sphere in the inequivalent quantizations,
turns out to be the Wess-Zumino term in the entire configuration space.
