the belly does not properly extend into the head, unless we assume that the mouth represents an extended belly element. Therefore, in common use, those brain parts that lie close to the base of the cranium, and through it to the mouth cavity, are called ventral – i.e., at its bottom or lower side, as defined above – whereas dorsal parts are closer to the enclosing cranial vault. Reference to the roof and floor plates of the brain is less prone to confusion, also allow us to keep an eye on the axial flexures mentioned above. Dorsal and ventral are thus relative terms in the brain, whose exact meaning depends on the specific location. Rostral and caudal: rostral refers in general anatomy to the front of the body (towards the nose, or rostrum in Latin), and caudal refers to the tail end of the body (towards the tail; cauda in Latin). The rostrocaudal dimension of the brain corresponds to its length axis, which runs across the cited flexures from the caudal tip of the spinal cord into a rostral end roughly at the optic chiasma. In the erect Man, the directional terms "superior" and "inferior" essentially refer to this rostrocaudal dimension, because our body and brain axes are roughly oriented vertically in the erect position. However, all vertebrates develop a very marked ventral kink in the neural tube that is still detectable in the adult central nervous system, known as the cephalic flexure. The latter bends the rostral part of the CNS at a 180-degree angle relative to the caudal part, at the transition between the forebrain (axis ending rostrally at the optic chiasma) and the brainstem and spinal cord (axis roughly vertical, but including additional minor kinks at the pontine and cervical flexures) These flexural changes in axial dimension are problematic when trying to describe relative position and sectioning planes in the brain. There is abundant literature that wrongly disregards the axial flexures and assumes a relatively straight brain axis. Medial and lateral: medial refers to being close, or relatively closer, to the midline (the descriptor median means a position precisely at the midline). Lateral is the opposite (a position more or less separated away from the midline). Note that such descriptors (dorsal/ventral, rostral/caudal; medial/lateral) are relative rather than absolute (e.g., a lateral structure may be said to lie medial to something else that lies even more laterally). Commonly