  We describe a way in which spin of quarks can enter a consistent QCD string
theory. We show that the spin factor of the 4d massless, spin 1/2 fermions is
related to the self-intersection number of a 2d surfaces immersed in the 4d
space. We argue that the latter quantity should appear in a consistent
description of the QCD string. We also calculate the chiral anomaly and show
that the self-intersection number corresponds to the topological charge
$F{\tilde F}$ of QCD.
