  A dynamical valence and sea quark mixing model is shown to fit the baryon
ground state properties as well as the spin content of the nucleon. The
relativistic correction and the $q^3{\leftrightarrow} q^3q\bar{q}$ transition
terms induced by the quark axial vector current
$\bar{\psi}\vec{\gamma}\gamma^5\psi$ in this model space is responsible for the
quark spin reduction.
