42 ANATOMY OF THE RABBIT. 
The limbs being more or less independent structures, it is proper 
to apply to them certain terms otherwise applicable to the main 
portion of the body. The chief terms not properly applied else- 
where are proximal, meaning nearer the centre or base ofsattach- 
ment, 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 dorsal and ventral 
surfaces of the fore foot are described respectively as dorsal and 
volar, those of the hind foot as dorsal and plantar. 
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 same time, 
terms applied in the first instance to the human body, in which the 
recognized relatioris are somewhat differenc. In comparison with 
that of a quadrupedal vertebrate, the human body occupies a 
vertical or erect positioa, 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. As in all cases, 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 anterior and posterior 
as applied to a lower form. Since it is unwise to change the form 
of the official terms of human anatomy, it becomes necessary to 
interpret all such terms when used for a quadrupedal mammal 
according to the relations exhibited by man. The human terms 
may in most cases be translated into terms acceptable for com- 
parative anatomy by reading ventral for anterior, dorsal for 
posterior, cranial or oral for superior, and caudal or aboral for 
inferior. The exceptions then apply to those parts of the body 
unaffected by rotation. 
