I also want to thank Scott McCloud for his wonderful pryamid with the three points depicting the "picture plane," "reality," and "meaning." I love the scalene triangle where the border of language bends toward the conceptual edge after passing through the retinal edge along the scale of the representational edge.
References:
Jack Hamm, "Cartooning the Head & Figure" (1967).
Scott McCloud, "Understanding Comics: The Invisible Art" (1994).