36 ANATOMY OF THE RABBIT 



whole, or in particular parts, the pairs of opposed terms deep and 

 superficial, central and peripheral, or internal and external may 

 be applied. It may be observed, however, that the terms internal 

 and external are sometimes used in the sense of medial and lateral, 

 both in descriptive language and in the names of parts. 



In distinction from the terms medial (medialis) and median 

 (medianus) the term middle (medius) may be used to designate 

 the position of a structure lying between two others, the latter 

 being otherwise designated, for example, as anterior and posterior, 

 lateral and medial, or right and left. 



The limbs being more or less independent structures, it is proper 



to apply to them certain terms not otherwise applicable to the main 



portion of the body. The chief terms which are used principally 



in this connection are proximal, meaning nearer the centre or base 



of attachment, and distal, toward the extremity. In the middle 



segment of the fore limb the respective positions of the bones 



(radius and ulna) are indicated as radial and ulnar. The terms 



tibial and fibular are also applicable, although with less reason, 



to the corresponding segment of the hind limb. The upper and 



lower surfaces of the fore foot are described respectively as dorsal 



and volar, those of the hind foot as dorsal and plantar (or volar). 



In determining the identity of structures in a quadrupedal 



mammal, considerable difficulty may at first arise from the fact 



that descriptive terms, such as those just defined, are frequently 



included in the names of parts, the latter being, at the sarne time, 



terms applied in the first instance to the human body, in which the 



recognized relations are somewhat different. In contrast with 



that of a quadrupedal vertebrate, the human body occupies a 



vertical or erect position, and is to be considered as having been 



rotated upward through ninety degrees on the posterior limbs. 



The latter accordingly occupy for the most part their original 



position, and the human arm largely reassumes this position when 



allowed to hang freely at the side of the body. In all, however, the 



face retains its forward direction. Thus the terms anterior and 



posterior as used in human anatomy mean ventral and dorsal, 



provided they refer to parts of the body, such as the entire trunk 



region, which have been affected by rotation. The terms superior 



and inferior as applied to man are similarly equivalent to anterior 



