Analysis of the structure of the brain stem of mammals by means of a modified D'Arcy Thompson procedure.

In his famous book, 'On Growth and Form', D'Arcy Thompson demonstrated that the shapes of related animals, or parts thereof, can be transformed into each other by a simple graphical procedure, called the method of coordinates. In this procedure, an object is inscribed in a net of Cartesian coordinates. It appeared that the shape of related objects could be characterized by means of simple, harmonious deformations of the initial orthogonal system of coordinates. Here, I demonstrate that: (1) the central nervous system contains a built-in, natural coordinate system; (2) differences in shape and proportion of cross sections through the brain stem of various mammals can be easily analyzed with the aid of this coordinate system, and (3) sets of structures in the mammalian brain stem, which are closely related to the neocortex, but form part of entirely different functional systems, form spatially constrained complexes, and have the capacity to expand jointly and harmoniously within these complexes.