  The metabolic networks are very well characterized for a large set of
organisms, a unique case in within the large-scale biological networks. For
this reason they provide a a very interesting framework for the construction of
analytically tractable statistical mechanics models.
  In this paper we introduce a solvable model for the distribution of fluxes in
the metabolic network. We show that the effect of the topology on the
distribution of fluxes is to allow for large fluctuations of their values, a
fact that should have implications on the robustness of the system.
