We investigate the competition between spinodal decomposition and dynamical
arrest using aqueous solutions of the globular protein lysozyme as a model
system for colloids with short-range attractions. We show that quenches below a
temperature Ta lead to gel formation as a result of a local arrest of the
proteindense phase during spinodal decomposition. The rheological properties of
these gels allow us to use centrifugation experiments to determine the local
densities of both phases and to precisely locate the gel boundary and the
attractive glass line close to and within the unstable region of the phase
diagram