The interosseous nerve of birds innervates a string of Herbst corpuscles located near the interosseous
membrane between the tibia and fibula. Fibre composition of this nerve was assessed including both
myelinated and unmyelinated axons. The diameter of the whole nerve is ∼100 μm. Complete data were
obtained for 3 nerves. The mean total number of myelinated fibres and unmyelinated axons was 2872±53.
The mean number of myelinated fibres was 280±20 and that for unmyelinated axons was 2600±47. There
was a broad distribution of diameters for myelinated fibres ranging from ∼2 μm to 10 μm with a distinct
peak at ∼3–5 μm and a less prominent second peak at 6–8 μm. Similarly, myelin sheath thickness
distribution showed 2 peaks, one at 0.6–0.8 μm and another at 1.4–1.6 μm. It is suggested that the group
represented by the second peak innervates the Herbst corpuscles. The group of smaller myelinated fibres and
the unmyelinated axons are assumed to innervate other types of receptors, some of which may be
nociceptors.