  A Jacobi matrix with matrix entries is a self-adjoint block tridiagonal
matrix with invertible blocks on the off-diagonals. The Weyl surface describing
the dependence of Green's matrix on the boundary conditions is interpreted as
the set of maximally isotropic subspace of a quadratic from given by the
Wronskian. Analysis of the possibly degenerate limit quadratic form leads to
the limit point/limit surface theory of maximal symmetric extensions for
semi-infinite Jacobi matrices with matrix entries with arbitrary deficiency
indices. The resolvent of the extensions is explicitly calculated.
