The inequality by Pólya
and Schiffer considered in this paper is concerned with the sume of the n first
reciprocal eigenvalues of the problem Δu + λu = 0 in G,u = 0 on ∂G. First we
extend this inequality to the problem of an inhomogeneous membrane Δu + λρu = 0
in G,u = 0 on ∂G. Then we prove a sharper form of it for a class of homogeneous
membranes with partially free boundary. The proofs are based on a variational
characterization for the eigenvalues and use conformal mapping and transplantation
arguments.