1. Small doses (1-10mug) of colchicine injected into the ventral horn of the spinal cord of the chicken caused paralysis in the legs. 2. Colchicine had no effect on the incorporation of leucine into proteins of the spinal cord but markedly decreased the total amount of protein flowing into the axons of the sciatic nerve. 3. This axonal flow of protein proceeded at two rates: a high rate (300mm/day) and a low rate (2mm/day). Although both groups of proteins were affected, the slow transport of protein was more profoundly blocked by colchicine. 4. The results suggest that axonal flow is dependent on the neurotubular system in the axon.