  It is shown that solvable mixed spin ladder models can be constructed from
su(N) permutators. Heisenberg rung interactions appear as chemical potential
terms in the Bethe Ansatz solution. Explicit examples given are a mixed
spin-1/2 spin-1 ladder, a mixed spin-1/2 spin-3/2 ladder and a spin-1 ladder
with biquadratic interactions.
