  The BRST-invariant formulation of the bosonic stretched membrane is
considered. In this formulation the stretched membrane is given as a
perturbation around zero-tension membranes, where the BRST-charge decomposes as
a sum of a string-like BRST-charge and a perturbation. It is proven, by means
of cohomology techniques, that there exists to any order in perturbation theory
a canonical transformation that reduces the full BRST-charge to the string-like
one. It is also shown that one may extend the results to the quantum level
yielding a nilpotent charge in 27 dimensions.
