Two statoacoustic ganglion (SAG) cells holding a common perikaryal myelin sheath in between in the chick

Ganglion cells of the eighth cranial nerve in vertebrates have perikaryal myelin sheaths. The present electron microscopic study showed a case of two statoacoustic ganglion (SAG) cells holding a common perikaryal myelin sheath in between in the chick. Observations of numbers and terminals of myelin lamellae suggested that the sheath would be composed of an abortive lamella sandwiched between respective perikaryal myelin sheaths of the two SAG cells. The outer surface of the two perikaryal sheaths was covered by a continuous basal lamina. The process of common myelin sheath formation is discussed.