68 



ANATOMY OF THE RABBIT 



the various segments of the limb with one another, 

 muscles may be subject to considerable variation. 



Individual 



Equivalence of Limb Muscles 



As already indicated, the skeletons of anterior and posterior 

 limbs are serially equivalent part for part. This is true also of the 

 related muscles and their actions upon the parts of the limb. The 

 respective actual positions of the proximal, middle, and distal 

 segments, however, are rather different in the front as compared 

 with the hind limb of a mammal, a condition easily discernible 

 from the fact that the elbow is directed backward, the knee forward. 

 Similarly there are peculiarities of the muscles and muscle surfaces, 

 owing to this difference in position and to a twisting which has 

 occurred in the anterior limb but not in the posterior one, as ex- 



Fig. 38. Schematic representation of the respective positions of the 

 segments in the mammalian limbs. A, neutral; B, anterior limb; C, posterior 

 limb. Explanation in text: tr.p., transverse plane. Radial or tibial side of 

 limb shaded, ulnar or fibular unshaded. 



plained below. There are also conventional ideas prevailing in 

 anatomy as to flexion and extension, that is bending or straighten- 

 ing parts of the limb, and as to flexor and extensor muscles and 

 surfaces. For example, ventral bending of the hand is called flexion 

 and the reverse movement is extension. A continuation of the 

 latter movement, however, results in bending the hand dorsally 

 and may be distinguished as dorsiflexion, which is accomplished by 

 extensor muscles, the original flexion then being distinguished as 

 ventral or palmar flexion. At the ankle, the foot in the normal 

 position of rest is approximately at a right angle or at an acute angle 

 to the leg. Further bending of the upper surface of the foot towards 

 the leg is called flexion, or better dorsiflexion, while bringing the 



