  We exhibit the Kontsevich matrix model with arbitrary potential as a BKP
tau-function with respect to polynomial deformations of the potential. The
result can be equivalently formulated in terms of Cartan-Pl\"ucker relations of
certain averages of Schur $Q$-function. The extension of a Pfaffian integration
identity of de Bruijn to singular kernels is instrumental in the derivation of
the result.
