  The effect from quark masses and transversal motion on the Gottfried,
Bjorken, and Ellis-Jaffe sum rules is examined by using a quark-parton model of
nucleon structure functions based on an improved scaling variable. Its use
results in corrections to the Gottfried, Bjorken, and Ellis-Jaffe sum rules. We
use the Brodsky-Huang-Lepage prescription of light-cone wavefunctions to
estimate the size of the corrections. We constrain our choice of parameters by
the roughly known higher twist corrections to the Bjorken sum rule and find
that the resulting corrections to the Gottfried and Ellis-Jaffe sum rules are
relevant, though not large enough to explain the observed sum rule violations.
