What the hell are C-fibers?

They are free nerve endings.

C-fibers are unmyeliniated and as a result, have a slower conduction velocity; lower than 2 m/s. These fibers are associated with chronic or dull pain. C-fibers are associated with sensations of cold, as well as mechanical and chemical stimuli. The density for cold receptors in the skin is greater than the density of warm-receptors (by a factor of 5). It is thought that most or all C fibers are nocireceptors (responding only to noxious stimuli).

In contrast:

Aδ fibres are thin, myelinated fibers with a large conduction velocity (2 to 30 m/s) and are associated with acute pain. In a real life situation, this is the sharp pain that triggers reflexes which result in the "pulling away" from the stimuli (ie: yanking hand away from hot stove). A certain proportion of Aδ fibers are also associated with sensations of heat and pressure.

Discussion questions:

1) Should philosophers switch to Aδ fibers firing as physical correlates for pain?

2) Do you think Kripke was a masochist based on his use of C rather than Aδ fibers?