FOOT. 



45 



and somewhat posteriorly at the upper part (Fig. 27^, Fig. 28*°). 

 It is somewhat twisted in its appearance, and has a slight convexity 

 backwards. The superior extremity or head is thick and large, 

 and depressed upon the upper part by a concave surface, which ar- 

 ticulates with the external condyle of the tibia. Extei'nal to this 

 surface, is a mark for the attachment of the external lateral liga- 

 ment of the knee-joint, terminated behind by a styloid process, for 

 the insertion of the tendon of the biceps. 



The body is prismatic, and has three surfaces, the external of 

 which is the broadest, and commencing upon the anterior part of the 

 bone above, curves around it, so as to terminate upon its posterior 

 side below. The upper two-thirds of this surface gives origin to the 

 peroneus longus and brevis ; the lower third terminates in a groove, 

 which indicates the course of the tendons of these muscles. The 

 internal face looks towards the tibia, and is divided longitudinally 

 by a ridge, to which is attached the interosseous ligament, the space 

 in front of which gives origin to the extensor proprius pollicis, and 

 the extensor communis digitorum ; and the space behind gives origin 

 to the tibialis posticus. The posterior surface is also spiral, and 

 gives origin to the soleus, and the flexor longus pollicis muscles. 



The inferior extremity terminates in the external malleolus^ which 

 is longer and flatter than the internal. Its external surface is super- 

 ficial and triangular ,* its internal has a smooth articular surface for 

 the astragalus. The extremity is pointed, and 

 often called the coronoid process, immediately 

 within which is a rough depression for the 

 external lateral ligament. 



FOOT. 



It consists of the tarsus, metatarsus, and pha- 

 langes. The TARSUS consists of seven bones. 



Os Calais. — This is the largest of the tar- 

 sal bones, and constitutes the heel of common 

 language. Its figure is longitudinal. The 

 superior surface has two articular convexities 

 for the astragalus, separated by a deep groove, 

 in which is fastened the interosseous ligament. 

 The posterior is the larger of the two. 



The iyUernal surface has a deep concavity, 

 called the sinuosity, for the tendons, vessels, 

 and nerves of the sole of the foot. The ex- 

 ternal surface is covered by the skin, and has 

 two grooves for the tendons of the peroneus 

 longus and brevis. The inferior surface has 

 two tuberosities behind, of which the internal 

 is the broader and larger; and also one in front. 



Fig. 29. 



