  The isostaticity theory for stress transmission in macroscopic planar
particulate assemblies is extended here to non-rigid particles. It is shown
that, provided that the mean coordination number in $d$ dimensions is $d+1$,
macroscopic systems can be mapped onto equivalent assemblies of perectly rigid
particles that support the same stress field. The error in the stress field
that the compliance introduces for finite systems is shown to decay with size
as a power law. This leads to the conclusion that the isostatic state is not
limited to infinitely rigid particles both in two and in three dimensions, and
paves the way to an application of isostaticity theory to more general systems.
