We give an alternative proof that the partition function Zn(tl) of the hermitian one-matrix model at finite N is a particular Wronskian type tau-function of the KP hierarchy, and is related to the orthogonal polynomials Pn(λ, t) by Pn(λ, t) = λ^nZn(tl + l^(-1) λ(-1))/Zn(tl)We also derive a bilinear relation for the Baker-Akhiezer function of the matrix model, generalizing the bilinear identity of the KP hierarchy.