Quantitative compensation by lateral motor column neurons in response to four functional hindlimbs in a frog tadpole.

An analysis of the lateral motor columns of a frog tadpole with 4 functional unilateral hindlimbs revealed a 58% increase in the number of neurons on the overloaded side as compared to the control side of the spinal cord. An accompanying, apparently selective, increase in the number of very large neurons suggests that spinal motor centers respond to peripheral overload through a variable combination of neuronal number and size in providing for adequate innervation.