Topographic divisions of cerebrospinal axis ( Swanson & Bota, 2010 ) : Since Classical Antiquity at least six fundamentally different ways to divide the cerebrospinal axis (Meckel, 1817) have been used, although today there is rather broad consensus about a set of major topographic divisions. The set of divisions is arranged in a hierarchical parceling scheme that is based primarily on structural differentiation of the neural tube (Baer, 1837) and its end product in adult macrostructure or gross anatomy (Swanson, 2000). There are 10 elementary divisions at the bottom: cerebral cortex (Bauhin, 1605), cerebral nuclei (Swanson, 2000), thalamus (His, 1893a), hypothalamus (Kuhlenbeck, 1927), tectum (Schwalbe, 1891), tegmentum (Swanson, 2000), cerebellum (Aristotle), pons (Haller, 1747), medulla (Winslow, 1733), and spinal cord (Galen, c162-c166). There is considerably more controversy about smaller topographic divisions below the level of the ten elementary divisions. The 17 terms in the hierarchy below cerebrospinal axis (Meckel, 1817) are very useful "building blocks" that may be combined in many ways to create new terms, like brainstem, which can have different meanings depending on which elementary divisions are included (Swanson, 2000, Tab. 1).