  We extend the considerations of a previous paper on black hole statistical
mechanics to the case of black extended objects such as black strings and black
membranes in 10-dimensional space-time. We obtain a general expression for the
Euclidean action of quantum black p-branes and derive their corresponding
degeneracy of states. The statistical mechanics of a gas of black p-branes is
then analyzed in the microcanonical ensemble. As in the case of black holes,
the equilibrium state is not thermal and the stable configuration is the one
for which a single black object carries most of the energy. Again, neutral
black p-branes obey the bootstrap condition and it is then possible to argue
that their scattering amplitudes satisfy crossing symmetry. Finally, arguments
identifying quantum black p-branes with ordinary quantum branes of different
dimensionality are presented.
