TIBIA. 



1G7 



pollicis muscles. Immediately 

 below the oblique line is the 

 medullary foramen, which is di- 

 rected obliquely downwards. 



The Lower Extremity, much 

 smaller than the upper, is some- 

 what quadrilateral in form, and 

 prolonged downwards on its in- 

 ner side, into a strong process, 

 the internal malleolus. The 

 inferior surface of the bone 

 presents a quadrilateral smooth 

 surface, for articulation with the 

 astragalus ; narrow internally, 

 where it becomes continuous with 

 the articular surface of the inner 

 malleolus, broader externally, 

 and traversed from before back- 

 wards by a slight elevation, se- 

 parating two lateral depressions. 

 The anterior surface is smooth 

 and rounded above, and covered 

 by the tendons of the Extensor 

 muscles of the toes; its lower 

 margin presents a rough trans- 

 verse depression, for the attach- 

 ment of the anterior ligament of 

 the ankle-joint. The posterior 

 surface presents a superficial 

 groove directed obliquely down- 

 wards and inwards, continuous 

 with a similar groove on the pos- 

 terior extremity of the astragalus ; 

 it serves for the passage of the 

 tendon of the Flexor longus polli- 

 cis. The external surface presents 

 a triangular rough depression, 

 the lower part of which, in some 

 bones, is smooth, and covered 

 with cartilage in the recent state, 

 and articulates with the fibula; 

 the remaining part is rough for 

 the attachment of the inferior 

 interosseous ligament, which 

 connects it with the fibula. 

 This surface is bounded by two 

 prominent ridges, continuous 

 above with the interosseous 

 ridge; they afford attachment 

 to the anterior and posterior 

 tibio-fibular ligaments. The 

 internal surface is prolonged 

 downwards to form a strong py- 

 ramidal-shaped process, flattened 

 from without inwards, the inner 

 malleolus ; its inner surface is 

 convex and subcutaneous. Its 



Fig. 110. Bones of the Right Leg. Posterior Surface. 



'it/laid j)i-oces3 



