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.