  We have measured the Shubnikov-de Haas oscillations in high-mobility Si MOS
structures over a wide range of the carrier densities n > 0.77x10^{11}/cm^2.
This range includes the critical density n_c of the metal-insulator transition
(2D MIT) for two samples studied. The periodicity of oscillations clearly
demonstrates that the electron states remain fourfold degenerate down to and at
the 2D MIT. Both the effective spin susceptibility \chi* and mass m* remain
finite and show no signatures of divergency at the critical density for both
samples studied. To test possible divergency of \chi*(n) and m*(n) at even
lower densities, we have analyzed the data on \chi*(n) and m*(n) in terms of a
critical dependence \chi*, m* ~ (n/n_0 -1)^{-\alpha}. Our data suggest that
\chi* and m* may diverge at n_0 < 0.5x10^{11}/cm^2 (r_s > 12), which is
significantly smaller than n_c.
