92 ANATOMICAL TECHNOLOGY. 



the body in the other. Second, these limbs are more elastic than if 

 the several segments were in the same line, and the muscles act 

 upon the bones to better mechanical advantage. 



218. By some writers (Wyman, 75, 253; Coues, 1, 15), and formerly by the senior 

 author (5, 45), this opposed or symmetrical or antitropic relation of the scapula and 

 ilium, and of the propodial and epipodial bones of the arm and leg has been regarded 

 as evidence in favor of a general symmetrical homology between the two limbs. The 

 senior author, however, has admitted (1O, 15) that this antagonistic relation is secondary 

 and telical rather than primary and morphical, and has fully assented to the view that in 

 their normal position both pairs of limbs extend laterad from the trunk, and their flexures 

 are in the do rso- ventral rather than in the cephalo-caudal direction. 



219. To replace the limbs in their normal and primitive posi- 

 tion (see 45), it is necessary to rotate the elbow cephalad and the 

 knee caudad, and then if the commonly accepted view be correct- 

 to lateriduct both limbs until they are at right angles with the 

 meson, as in Fig. 6. 



This rotation will leave the convexities of the elbow and the knee 

 facing dorsad (as in Fig. 7), and that of the ankle, with the plantar 

 aspect of the pes, facing ventrad. In the arm, however, the corres- 

 ponding aspect of the manus the palm will be left facing dorsad, 

 and the ulna and radius will be crossed instead of parallel like the 

 corresponding tibia and fibula. But if the manus be supinated, 

 the ulna and radius will be parallel, and the palm will face ventrad 

 like the sole. 



The restoration just described is assumed to have taken place in 

 the following brief account of some of the bones and their promi- 

 nences : 



220. The proximal end of the humerus presents an elevation, 

 the trocMter or Tuber ositas major (Fig. 45, 46), which is cephalic 

 in the normal position of the parts, but lateral in their natural atti- 

 tude. At the distal end of the same bone (Fig. 46) are two eleva- 

 tions, the epicondylus and epitrocJilea, commonly called external 

 and internal condyles. In the natural attitude, as seen in Fig. 30, 

 the epicondyle shows on the left arm, and the epitrochlea on the 

 right. 



The ulna projects dorsad and proximad of the elbow as a thick 

 process, the olecranon. Just distad of the joint, on the ventral side 

 of the bone, is an elevation the Processus coronoideusfor the 

 attachment of the M. brachialis. 



The proximal end of the radius is the capitettum, while the distal 

 end of each antebrachial bone presents a short Prc. styloideus. 



