  We construct the canonical constitutive relations for a fluid description of
a system with a spin current, valid in an arbitrary number of dimensions in the
absence of parity breaking or time reversal breaking terms. Our study
encompasses the hydrostatic partition function, the entropy current, Kubo
formula, conformal invariance, and the effect of charge. At some stages of the
computation we turn on a background torsion tensor which naturally couples to
the spin current.
