  We carry out a comparative analysis of the transversities and the
longitudinally polarized parton distribution functions in light of the first
empirical extraction of the transversity distributions recently done by
Anselmino et al. It is shown that the precise determination of the isoscalar
tensor charge, which is defined as the 1st moment of the isoscalar combination
of the transversity distributions, is of fundamental importance for clarifying
the internal spin structure function of the nucleon.
