What gives nerves their silver colour? I always thought the silver colour specific to nerves was due to the myelin sheaths, but I've observed that unmyelinated C fibres display that same silvery appearance. Where does this colour come from? And can you distinguish myelinated from unmyelinated fibre bundles with the naked eye from their colour?

**Short answer**
I think the whitish color is due to the outer layer of nerve bundles: the **epineurium**. This surrounds all nerves, whether they contain myelinated fibers, unmyelinated fibers, or both.

**Background**
Nerves are bundles of axons (Fig. 1). Whether the axons are myelinated or not, the gross anatomy is similar; axons within a nerve are bundled into fascicles and surrounded by perineurium. Those fascicles are again bundled up and surrounded by **epineurium**. It is this epineurium that you probably are seeing and it has a whitish appearance (Fig. 2).

The surface of a nerve therefore does not contain myelin; myelin is present around individual axons and is not exposed. Hence, whether a nerve contains myelinated axons, unmyelinated ones, or both will not determine its outward appearance.

![nerve](
Fig. 1. Anatomy of a nerve bundle. source: EasyNoteCards

![epineurium](
Macroscopic view of a nerve targeted for epineurial repair. source: wikipedia