  On the basis of the non-perturbative Heisenberg's quantization scheme and
using some simplifications and assumptions the reduction from the gluon-quark
Lagrangian to a scalar-fermion Lagrangian is made. The corresponding field
equations have a regular spherically symmetric solution which can be interpret
as a simplified model of nucleon. Some properties of such "nucleon" are
discused: the presence of a mass gap and spin $\neq \hbar /2$. The mass gap
describes the difference between the "nucleon" and the "nucleon" without quark
field (a scalar glueball). The presence of spin $\neq \hbar /2$ can be
connected with the spin problem of nucleon.
