Structure, Degeneration and Repair of Nerve Fibres*

Abstract

NERVE fibres have become greatly elongated for their function of conduction, but each yet remains essentially a bag, surrounded by a membrane, with the nucleus separated in a special region, the nerve cell body, at one end. It is difficult to obtain a true representation of the immense disproportion between the length and breadth of these cells. The cell body of a mammalian motor fibre is an irregular star-shaped structure about 1/10 mm. in diameter. Attached to this is the axon process which is 1/50 mm. in diameter or less, and yet often as much as 1 metre in length. Even in the very shortest peripheral nerve fibres, the axon is 1,000 times as long as it is broad. In very many motor fibres in man the disproportion is 10,000 times. But some of the longest sensory fibres, more than 1 metre in length, are less than a tenth of the thickness of these motor fibres and the disproportion here must often approach one million times.