Segregation of muscle and cutaneous afferent fibre terminals in the brachial spinal cord of the frog.

Separate filling with cobalt of individual nerves of the arm revealed that cutaneous afferent fibres terminate in an oval-shaped area at the superficial part of the dorsal horn, while muscle afferent fibres terminate in a triangle-shaped area lying deeper in the gray substance of the frog spinal cord. In a few cases, flexor muscle afferents also emit a small number of short collaterals to the ventral part of the oval-shaped area. In the medulla, cuaneous afferents project onto the dorsal part and muscle afferents onto the ventral part of the cuneate nucleus. Muscle afferents only terminate in the cerebellum.