THOEACIC LIMBS 553 



degree. The lower extremity consists of three parts, two lateral 

 prominences and a middle prominence. The two lateral prominences, 

 one on each side, are called the outer and inner condyles. The area 

 between them comprises a lower transverse roller-shaped articular emi- 

 nence, bounded in front and behind by a depressed non-articular space. 

 When the bone is held vertically the inner sharp edge of the articular 

 eminence is the lowest point of the extremity. The inner condyle is 

 the larger, and it appears to project slightly further downward. The 

 widest part of the extremity is between the points of the condyles, 

 considerably above the line of the articular surface. From this point 

 it becomes narrow as it ascends to join the shaft and as it descends to 

 join the articular eminence. 



Above the inner condyle is the supracondyloid foramen, which, 

 strictly speaking, is a canal piercing the side of the bone obliquely 

 from behind, forward, downward, and inward. The bridge of bone 

 limiting it laterally is known as the internal supracondyloid ridge. 

 The canal itself is twice as high vertically as it is wide transversely. 

 Its length from before backward is equal to its height. Its outer 

 wall is considerably shorter than the inner wall. The relation of 

 the greatest width to the greatest antero-posterior length varies, but 

 averages as seventy-five is to forty-five. 



The greatest antero-posterior diameter of the lower extremity is 

 through the outer part of the articular eminence, and exceeds but 

 slightly the same diameter at the inner end of the eminence. The 

 anterior surface of the articular eminence lies in front of the rest 

 of the lower extremity and the anterior surface of the shaft, and its 

 posterior surface lies in front of the posterior surface of the extremity 

 and of the shaft. 



The inner condyle is an oblong tuberosity projecting outward and 

 slightly backward from the posterior part of the inner end of the lower 

 extremity. It has the appearance of a downward prolongation of the 

 side of the shaft, applied to the inner end of the articular mass. For 

 facility of study it may be said to have four surfaces. 



The anterior surface (Fig. 430) is the continuation of the smooth 

 terminal part of the internal surface of the shaft, bridging the supra- 

 condyloid foramen. It is bounded on the median side by the anterior 

 supratrochlear fossa and the vertical end of the articular eminence, on 

 the inner side by the edge which it makes with the posterior surface, 



