  The QCD-motivated constituent string model is extended to consider the
baryon. The system of three quarks propagating in the confining background
field is studied in the Wilson loop approach, and the effective action is
obtained. The resulting Lagrangian at large interquark distances corresponds to
the Mercedes Benz string configuration. Assuming the quarks to be heavy enough
to allow the adiabatic separation of quark and string junction motion and using
the hyperspherical expansion for the quark subsystem we write out and solve the
classical equation of motion for the junction. We quantize the motion of the
junction and demonstrate that the account of these modes leads to the effective
"swelling" of the baryon in comparison with the standard potential picture. We
discuss the effects of the finite gluonic correlation length which do not
affect the excited states but appear to be substantial for the baryonic ground
state, reducing the "swelling" considerably and leaving room to the short range
Coulomb force in the three quark system.
