Thus far, the path integral approach didn't avail us of any novel results. For that, one must venture further than the ideal model. As a first departure from this limited model, we now consider the constraint of spatial obstructions. The ideal model assumed no constraints on the spatial configuration of each additional monomer, including forces between monomers which obviously exist, since two monomers cannot occupy the same space. Here, we'll take the concept of obstruction to encompass not only monomer-monomer interactions, but also constraints that arise from the presence of dust and boundary conditions such as walls or other physical obstructions.