The b1 structure function is an observable feature of a spin-1 system
sensitive to non-nucleonic components of the target nuclear wave
function. The contributions of exchanged pions in the deuteron are
estimated and found to be of measurable size for small values of x. A
simple model for a hidden-color, six-quark configurations (with~ 0.15%
probability to exist in the deuteron) is proposed and found to give
substantial contributions for values of x>0.2. Good agreement with
Hermes data is obtained. Predictions are made for an upcoming JLab
experiment. The Close & Kumano sum rule is investigated and found to be
a useful guide to understanding various possible effects that may
contribute.