His's line

[hĭsĭz]
n.
  1. An imaginary line extending from the tip of the anterior nasal spine to the hindmost point on the posterior margin of the foramen magnum, dividing the face into an upper and a lower part.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.