78 



posterior surface at a concave edge externally ; the inner concave bor- 

 der of the shaft is thick and rounded. A short rough ridge is continued 

 from the middle of the anterior proximal tuberosity obliquely down- 

 wards and inwards. Fine reticular risings mark the smoother parts of 

 the anterior surface. A broad but shallow groove runs from the lower 

 part of the outer concave edge downwards upon the anterior surface 

 of the expanded distal end of the bone. The outer malleolus pro- 

 jects as a somewhat square-shaped protuberance. The opposite side of 

 the distal end, or the inner malleolus, forms a less prominent convex 

 tuberosity. The posterior surface of the tibia is smooth at the con- 

 cavity beneath the overhanging fibular articulation, and along the outer 

 half of the posterior surface as far as the rugged rising which overhangs 

 the distal articular surface. The inner half of the back part of the tibia 

 presents a rough elevated tract, which extends across its upper part a little 

 below the convex boundary of the condyloid articular surface : a thick 

 rough ridge extends downwards to the middle of the internal concave 

 border of the shaft : a narrow ridge descends along the middle of the upper 

 half of the posterior surface and then divides, the inner branch extending 

 obliquely to the angle terminating the concavity of the inner margin of the 

 shaft. Below this rid^e a wide and deep canal extends obliquely from 

 above downwards and inwards, its lower edge being about an inch above 

 the distal articular margin : this deep posterior excavation forms a well- 

 marked character of the internal malleolus, and indicates prodigious 

 strength in the flexors of the toes and adductors of the foot. 



The distal articular surface of the tibia presents the most singular mo- 

 difications : it is divided into three compartments, which are well-defined, 

 although the synovial surface is uninterrupted. The external compart- 

 ment is semi-elliptical, flat, nearly horizontal, inclining from without 

 inwards and downwards ; it forms the lower surface of the outer distal 

 protuberance of the bone, and rests upon a corresponding surface at the 

 lower part of that excavation of the fibula which receives the said protu- 

 berance. The second compartment of the distal articulation of the tibia 

 is slightly concave, of a crescentic figure, with the bones directed inwards 

 and forwards : its plane is more nearly horizontal than the fibular facet. 



