It is clear from (25) that fluid effects in cannot increase the overall compliance eigenvalues simultaneously for both the quasi-bulk and the quasi-shear modes. Rather, if one increases, the other must decrease. Furthermore, it is certainly always true that the presence of pore liquid either has no mechanical effect or else strengthens (i.e., stiffens) the porous medium in compression. But this effect on the bulk modulus has been at least partially accounted for in A*11 = 1/9K* through the original contribution derived by Gassmann (1951). So presumably the contribution of to compliance cannot be so large as to negate completely the liquid effects on the undrained bulk modulus.