202 



THE SKELETON. 



the external calcaneo-astragaloid ligament ; and in front of the tubercle it presents 

 a narrow surface marked by two oblique grooves, separated by an elevated ridge 

 which varies much in size in different bones ; it is named the peroneal tubercle, and 

 gives attachment to a fibrous process from the external annular ligament. The 

 superior groove transmits the tendon of the Peroneus brevis ; the inferior, the 

 tendon of the Peroneus longus. 



The internal surface is deeply concave ; it is directed obliquely downward and for- 

 ward, and serves for the transmission of the plantar vessels and nerves into the sole of 

 the foot; it affords attachment to part of the Flexor accessorius muscle. At its upper 

 and fore part it presents an eminence of bone, the lesser process or sustentaculum 

 tali, which projects horizontally inward, and to it a slip of the tendon of the 

 Tibialis posticus is attached. This process is concave above, and supports the 



Peroneal tubercle 

 Groove for 

 Peroneus brecis. 



Groove for \ "^^fj^^^^For triido 



Peroneus longus. Tubercle for ext. lat. lig. Achillis. 



For astragalus. 



Sustentaculum For cuboid. 



tali. 

 Groove for Flex. 



long, hallucis. 

 FIG. 139.-The left os ealcis. A. Postero-external view. B. Antero-internal view. 



anterior articular surface of the astragalus ; below, it is grooved for the tendon of 

 the Flexor longus hallucis. Its free margin is rough, for the attachment of part of 

 the internal lateral ligament of the ankle-joint. 



The anterior surface, of a somewhat triangular form, articulates with the 

 cuboid. It is concave from above downward and outward, and convex in the 

 opposite direction. Its inner border gives attachment to the inferior calcaneo- 

 navicular ligament. 



The posterior surface is rough, prominent, convex, and wider below than above. 

 Its lower part is rough, for the attachment of the tendo Achillis and the tendon of 

 the Plantaris muscle; its upper part is smooth, and is covered by a bursa which 

 separates the tendons from the bone. 



Articulations. With two bones : the astragalus and cuboid. 



Attachment of Muscles. To eight : part of the Tibialis posticus, the tondo 



