TARSUS. 175 



rower, of an elongated oval form, convex longitudinally, and often subdivided 

 into two by an elevated ridge : of these the posterior one articulates with the lesser 

 process of the os calcis ; the anterior one, with the upper surface of the calcaneo- 

 scaphoid ligament. The internal surface presents at its upper -part a pear-shaped 

 articular facet for the inner malleolus, continuous above with the trochlear surface ; 

 below the articular surface is a rough depression, for the attachment of the deep 

 portion of the internal lateral ligament. The external surface presents a large 

 triangular facet, concave from above downwards, for articulation with the external 

 malleolus ; it is continuous above with the trochlear surface, and in front of it is 

 a rough depression for the attachment of the anterior fasciculus of the external 

 lateral ligament. The anterior surface, convex and rounded, forms the head of the 

 astragalus; it is smooth, of an oval form, and directed obliquely inwards and 

 downwards ; it is continuous below with that part of the anterior facet on the 

 under surface which rests upon the calcaneo-scaphoid ligament. The head is sur- 

 rounded by a constricted portion, the neck of the. astragalus. The posterior sur- 

 face is narrow, and traversed by a groove, which runs obliquely downwards and 

 inwards, and transmits the tendon of the Flexor longus pollicis. 



To ascertain to which foot it belongs, hold the bone with the broad articular 

 surface upwards, and the rounded head forwards ; the lateral triangular articular 

 surface for the external malleolus will then point to the side to which the bone 

 belongs. 



Articulations. With four bones : tibia, fibula, os calcis, and scaphoid. 



THE SCAPHOID. 



The Scaphoid or Navicular bone, so called from its fancied resemblance to a 

 boat, is situated at the inner side of the tarsus, between the astragalus behind and 

 the three cuneiform bones in front. This bone may be distinguished by its boat- 

 like form, being concave behind, convex and subdivided into three facets in front. 



The anterior surface, of an oblong form, is convex from side to side, and sub- 

 divided by two ridges into three facets, for articulation with the three cuneiform 

 bones. The posterior surface is oval, concave, broader externally than internally, 

 and articulates with the rounded head of the astragalus. The superior surface is 

 convex from side to side, and rough for the attachment of ligaments; the 

 inferior, somewhat concave, irregular, and also rough for the attachment of 

 ligaments. The internal surface presents a rounded tubercular eminence, the 

 tuberosity of the scaphoid, which gives attachment to part of the tendon of the 

 Tibialis posticus. The external surface is broad, rough, and irregular, for the 

 attachment of ligamentous fibres, and occasionally presents a small facet for 

 articulation with the cuboid bone. 



To ascertain to which foot it belongs, hold the bone with the concave articular 

 surface backwards, and the broad dorsal surface upwards; the broad external 

 surface will point to the side to which the bone belongs. 



Articulations. With four bones : astragalus and three cuneiform ; occasionally 

 also with the cuboid. 



Attachment of Muscles. Part of the Tibialis posticus. 



THE CUNEIFORM BONES. 



The Cuneiform Bones have received their name from their wedge-like shape. 

 They form with the cuboid the most anterior row of. the tarsus, being placed 

 between the scaphoid behind, the three innermost metatarsal bones in front, and 

 the cuboid externally. They are called the first, second, and third, counting from 

 the inner to the outer side of the foot, and, from their position, internal, middle, 

 and external. 



THE INTERNAL CUNEIFORM. 



The Internal Cuneiform is the largest of the three. It is situated at the inner 

 side of the foot, between the scaphoid behind and the base of the first metatarsal 



