  We obtain a general rule that the O(1/log m_h) term due to the current
\bar{h}\gamma_\mu\gamma_5h of a mass-m_h quark h in f-flavour theory is
-3\bar{g}^2_f(m_h)/{2\pi^2(33-2f)} times the flavour singlet current of the
residual (f-1)-flavour theory, where \bar{g}_f is the f-flavour running
coupling constant in a mass-independent renormalization scheme. The rule is
applied to the Ellis-Jaffe moment below and well above charm threshold, and to
low-energy Z^0-exchange amplitudes. The singlet axial charge of the proton
common to these experiments is both scale and gauge invariant, but is related
to the axial anomaly and the ``gluon spin'' by a non-perturbative
renormalization factor.
