  We construct a field-theoretic description of two coupled spin-1 Heisenberg
chains, starting with the known representation of a single spin-1 chain in
terms of Majorana fermions (or Ising models). After reexamining the
bosonization rules for two Ising models, taking particular care of order and
disorder operators, we obtain a bosonic description of the spin-1 ladder. From
renormalization-group and mean-field arguments, we conclude that, for a small
interchain coupling, the spin-1 ladder is approximately described by three
decoupled, two-frequency sine-Gordon models. We then predict that, starting
with decoupled chains, the spin gap decreases linearly with interchain
coupling, both in the ferromagnetic and antiferromagnetic directions. Finally,
we discuss the possibility of an incommensurate phase in the spin-1 zigzag
chain.
