Central ( Barclay, 1803 ) : Toward the center of the body. Barclay (1803, pp. 120-121, 164) introduced a formal distinction between central and peripheral (Barclay, 1803), although use of the term as toward the center of the body goes back at least to Aristotle in De Partibus Animalium; see translation of Ogle (1912, 672-34).
Coronal plane ( Barclay, 1803 ) : Synonym for frontal plane (Henle, 1855), named for the human coronal suture, named in turn for the crown of the human head; p. 145. It is commonly used thus in human and other primate anatomy; see Standring (2008, Fig. 1). It is often confusingly used in quadrupeds for transverse plane (Henle, 1855); see coronal plane (Paxinos & Watson, 1982).
Distal ( Barclay, 1803 ) : Toward the end of an object like a tentacle, limb, or nerve; opposite of proximal (Barclay, 1803). Introduced by Barclay (1803, pp. 124-125, 164), also see Standring (2008, p. xxii).
Dorsal ( Barclay, 1803 ) : Toward the back of the body, or away from the belly, in the transverse plane (Henle, 1855); the opposite of ventral (Schulze, 1893); introduced formally by Barclay (1803, pp. 120, 162), who paired it with sternal. At least by the second century Galen had indicated its use, for example, in describing a direction "back toward the dorsum"; see translation by May (1968, p. 701). In Aristotle's De Partibus Animalium, there is reference to "on their [univalves] dorsal surface they have a shell"; see translation by Ogle (1912; 679b, 23-24). Also see Brusca & Brusca (1990, p. 46).
Lateral ( Barclay, 1803 ) : Away from the median plane (Henle, 1855) of the body, in the frontal plane (Henle, 1855); the opposite of medial (Schulze, 1893). Use of the term seems to go at least as far back as the second century and Galen (see, for example, translation by May, 1968, p. 701), but its formal use was introduced by Barclay (1803, pp. 121, 163), who paired it with mesial. Also see Brusca & Brusca (1990, Fig. 4-A).
Longitudinal axis ( Barclay, 1803 ) : The oral-aboral axis (Schulze, 1893) of the body in all animals with a nervous system (Monro, 1783); term probably introduced by Barclay (1803, p. 117); also see Henle (1855, p. 1), Willmer (1990, p. 15). Other synonyms include rostrocaudal axis, central axis, long axis, midsagittal axis, principal axis, and anteroposterior axis, the latter being discouraged as especially ambiguous in comparative anatomy. The longitudinal axis is orthogonal to the transverse axis (Henle, 1855). The concept was clearly described by Aristotle in De Partibus Animalium, where he wrote that "a straight line as an axis has at the upper end the mouth, followed by the gullet, stomach, intestine, and excremental vent"; and that furthermore in some animals like humans, quadrupeds, crustacea, and insects the axis is essentially straight, whereas at the other extreme in animals like the Cephalopods it can be highly curved and thus U-shaped; see translation by Ogle (1912, 685a-686b). Kuhlenbeck (1973, p. 111) provided a nice modern statement of the concept: "Three so-called "axial lines" [longitudinal or rostrocaudal, dorsoventral, and mediolateral] which can be conceived as geodesics and therefore not necessarily ‘straight', provides an essentially nonmetric and non-Euclidean (Euclidoid), ameboid three-dimensional coordinate system (German: "Bezungsmollusk") of anatomical space…"
Proximal ( Barclay, 1803 ) : Toward the origin of an object like a tentacle, limb, or nerve; the opposite of distal (Barclay, 1803). Introduced by Barclay (1803, pp. 124-125, 164), also see Standring (2008, p. xxii).