THE BONES OF THE LOWER LIMB M7 



to the gracilis, and the lower to the semitendinosus. The external 

 surface is situated between the crest and interosseous border. It 

 is concave over its upper two-thirds, where it gives origin to the 

 tibiaUs anticus. Over the lower third, where it is convex, it turns 

 to the front and supports the extensor tendons, and anterior tibial 

 vessels and nerve. The posterior surface lies between the inter- 

 osseous and internal borders. Superiorly it is crossed by the 

 popliteal or oblique line, which is rough, and extends from the 

 fibular facet downwards and inwards to the internal border at 

 about the junction of the upper third and lower two-thirds. This 

 line gives attachment to the popliteal fascia and part of the soleus, 

 whilst the triangular popliteal surface above gives insertion to 

 the popUteus muscle. The posterior surface below the oblique 

 line presents over its middle third a vertical ridge which divides 

 it into two parts. The outer portion is narrow, and gives origin 

 to the tibialis posticus as low as a point just below the centre of 

 the bone. The inner portion is broad, and gives origin to the 

 flexor longus digitorum over the middle two-fourths of the bone. 

 A little below the oblique line, close to the outer side of the vertical 

 ridge, is the medullary foramen for a large branch of the posterior 

 tibial artery. This foramen, which is the largest of its class, and 

 the canal to which it leads are directed downwards. The posterior 

 surface in its lower third supports the flexor tendons, and posterior 

 tibial vessels and nerve. 



The lower extremity presents a quadrilateral articular surface, 

 concave from before backwards, and wider in this direction exter- 

 nally than internally. It is broader in front than behind, and 

 articulates with the superior surface of the astragcJus. The pos- 

 terior border projects somewhat lower than the anterior. The 

 anterior surface, immediately above the anterior border, is depressed 

 and rough for the anterior ligament of the ankle-joint. The 

 posterior border gives attachment to the posterior ligament of 

 the ankle-joint as far inwards as the groove behind the internal 

 malleolus. It presents the following grooves : one for the tendon 

 of the flexor longus hallucis near the outer end ; one (very faint) 

 near the centre for the posterior tibial vessels and nerve ; and one 

 mainly situated on the back of the internal malleolus for the tendons 

 of the tibialis posticus and flexor longus digitonmi. 



The inner aspect of the lower extremity presents the internal 

 malleolus, which is a strong process having a downward direction. Its 

 internal surface is rough, convex, and subcutaneous. The external 

 surface is covered by cartilage, continuous with that which coats 

 the lower extremity. The plane of this surface is vertical, and the 

 cartilage coats it more deeply in front than behind. It articulates 

 with the internal surface of the astragalus. The anterior border 

 is rough and round for the attachment of the anterior and internal 

 lateral ligaments of the ankle-joint. The lower border is indented 

 by a notch, in front of which is the projection known as the tip, 

 the internal lateral ligament being attached to both of these parts. 



