  For the first time, a wide range of collective magnetic g-factors g$_{\rm
R}$, obtained from a novel analysis of experimental data for
multi-quasiparticle configurations in high-K isomers, is shown to exhibit a
striking systematic variation with the relative number of proton and neutron
quasiparticles, N$_{\rm p}$ - N$_{\rm n}$. Using the principle of additivity,
the quasi-particle contribution to magnetism in high-K isomers of Lu - Re, Z =
71 - 75, has been estimated. Based on these estimates, band-structure branching
ratio data are used to explore the behaviour of the collective contribution as
the number and proton/neutron nature (N$_{\rm p}$, N$_{\rm n}$), of the
quasi-particle excitations, change. Basic ideas of pairing, its quenching by
quasi-particle excitation and the consequent changes to moment of inertia and
collective magnetism are discussed. Existing model calculations do not
reproduce the observed g$_{\rm R}$ variation adequately. The paired superfluid
system of nucleons in these nuclei, and their excitations, present properties
of general physics interest. The new-found systematic behaviour of g$_{\rm R}$
in multi-quasi-particle excitations of this unique system, showing variation
from close to zero for multi-neutron states to above 0.5 for multi-proton
states, opens a fresh window on these effects and raises the important question
of just which nucleons contribute to the `collective' properties of these
nuclei.
