Path integral of relativistic strings

The field-theoretical aspects of the path integral for the string Lagrangian in the manner of Polyakov are discussed. It is shown that the Becchi-Rouet-Stora (BRS) symmetry is consistent with the conformal anomaly, and the generalized Virasoro condition arises from the BRS invariance. The ghost number current, however, contains an anomaly. It is also noted that the conformal degree of freedom at $D<\mathrm{}26\mathrm{}$ corresponds to the "unphysical" mode to be canceled by the Faddeev-Popov ghosts in the $S$ matrix in the conventional field-theoretical sense.