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 of attach- 

 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 relations are somewhat different. In comparison wich 

 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. 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. 



