Ventral horn cell counts in a Xenopus with naturally occurring supernumerary hind limbs.

In a Xenopus toad, two partially functioning supernumerary hind limbs developed naturally on the right side and were innervated by the ipsilateral side of the spinal cord. The number of ventral horn cells on the right was 18% higher than on the left while the combined mass of limb muscle on the right was estimated to be a 100% greater. This result corroborates studies with transplanted supernumerary limbs.