  The Green function of the quark-antiquark system in the confining background
field is analysed using the Feynman-Schwinger formalism. The Hamiltonian for
the case of massive spinning quarks is obtained in the form containing
essentially nonhermitian part. The eigenvalue problem for such type of the
Hamiltonian is discussed, and it is shown that no complex eigenvalues arise.
The corresponding no nunitary Foldy-Wouthuysen transformation is performed to
obtain the hermitian Hamiltonian, and the standard spin-orbit interaction term
is recovered.
