What is "axial line"

Axial \Ax"i*al\, a.

1. Of or pertaining to an axis; of the nature of, or resembling, an axis; around an axis.

   To take on an axial, and not an equatorial, direction.
   --Nichol.

2. (Anat.) Belonging to the axis of the body; as, the axial skeleton; or to the axis of any appendage or organ; as, the axial bones.

   Axial line (Magnetism), the line taken by the magnetic force in passing from one pole of a horseshoe magnet to the other.
   --Faraday.

An axial line is the line between two adjacent dermatomes that are not represented by immediately adjacent spinal levels. Although dermatomes are shown to be discrete segments on dermatomal maps (like in the image opposite), they are in fact not; adjacent dermatomes overlap with one another. This is one of the reasons for the variety of different dermatomal maps proposed. However, at axial lines, adjacent dermatomes do not overlap. An example of an axial line would be the line between the S2 and L4 dermatomes on the calf.