  The Casimir effect in a dispersive and absorbing multilayered system is
considered adopting the (net) vacuum-field pressure point of view to the
Casimir force. Using the properties of the macroscopic field operators
appropriate for absorbing systems and a convenient compact form of the Green
function for a multilayer, a straightforward and transparent derivation of the
Casimir force in a lossless layer of an otherwise absorbing multilayer is
presented. The resulting expression in terms of the reflection coefficients of
the surrounding stacks of layers is of the same form as that obtained by Zhou
and Spruch for a purely dispersive multilayer using the (surface) mode
summation method [Phys. Rev. A {\bf 52}, 297 (1995)]. Owing to the recursion
relations which the generalized Fresnel coefficients satisfy, this result can
be applied to more complex systems with planar symmetry. This is illustrated by
calculating the Casimir force on a dielectric (metallic) slab in a planar
cavity with realistic mirrors. Also, a relationship between the Casimir force
and energy in two different layers is established.
