THE LIMBS. 313 



superficial position to the median nerve. In lower apes, the 

 brachial artery commonly divides a little above the elbow. This 

 position of division is rare in man. In cases of high division the 

 radial, or even the ulnar, may be superficially placed in the fore- 

 arm. 



Internal Saphenous Artery. — In most mammals — in all 

 primates except man — the anastomotica magna of the femoral 

 artery is as large as the popliteal and passes over the inner side of 

 the tibia with the internal saphenous vein to reach the dorsum of 

 the foot, where it forms the dorsalis pedis artery. This vessel is 

 known in them as the internal saphenous artery, and corresponds 

 to the radial artery in the forearm and wrist. The superficial 

 branch of the anastomotica magna rarely assumes such a develop- 

 ment in man ; but the course taken by the internal saphenous 

 artery explains the position of its accompanying vein, the internal 

 saphenous, in front of the internal malleolus. In man only is the 

 internal saphenous vein continued up the thigh to a saphenous 

 opening in the groin. Its primitive termination is in the femoral 

 vein at the lower end of Hunter's canal. 



The Superficial Plantar Arch, formed from the internal plantar 

 artery, is seldom complete in man. The pressure to which it 

 is subjected in the standing posture has led to its partial 

 obliteration. It corresponds to the superficial palmar arch. 



The Supra-condylar Process is well developed in lemurs, the 

 lowest primates, and in mammals of many orders. Its function is 

 unknown. It occasionally appears in man. It is developed from 

 the humerus about two inches above the internal condyle as 

 a hook-like process of bone. It lies in front of the internal 

 inter-muscular septum, and when well developed the brachial 

 artery and median nerve may pass beneath it, as they do in such 

 animals as the squirrel and cat. 



Third Trochanter. — A tubercle may appear in the gluteal ridge 

 which receives this name. It is cartilaginous until the 20th 

 year, when a separate centre of ossification appears in it (Dixon). 

 It is well developed in the horse. 



Ligaments and Joints of the Limbs. — The Inter-articular 

 Cartilages are of doubtful origin. In their first appearance, by 

 the condensation of the mesoblast in the axis of the limb bud, the 

 bones are continuous. The joints are formed between the bones, 



