  We review the evidence for cosmic ray acceleration in the superbubble/hot
phase of the interstellar medium, and discuss the implications for the
composition of cosmic rays and the structure and evolution of the interstellar
medium. We show that the bulk of the galactic supernovae, their expanding
remnants, together with their metal-rich grain and gas ejecta, and their cosmic
ray accelerating shocks, are all confined within the interiors of superbubbles,
generated by the multiple supernova explosions of massive stars formed in giant
OB associations. This superbubble/hot phase of the ISM provides throughout the
age of the Galaxy a cosmic ray source of essentially constant metallicity for
acceleration by the shocks of many supernovae over time scales of a few Myr,
consistent with both the Be/Fe evolution and ACE observations of Ni-59/Co-59.
We also show that if the refractory cosmic ray metals come from the sputtering
of fast refractory grains then the accompanying scattering of ambient gas by
these fast grains can also account for the relative abundance of cosmic ray
volatiles.
