TARSUS. m 



THE CUBOID. 



The Cuboid bone is placed on the outer side of the foot, in front of the os calcis, 

 and behind the fourth and fifth metatarsal bones. It is of a pyramidal shape, its 

 b;tso being directed upwards and inwards, its apex downwards and outwards. 

 It may be distinguished from the other tarsal bones, by the existence of a deep 

 groove on its under surface, for the tendon of the Peroneus longus muscle. It 

 presents for examination six surfaces ; three articular, and three non-articular : 

 the non-articular surfaces are the superior, inferior, and external. 



The superior or dorsal surface, directed upwards and outwards, is rough, for the 

 attachment of numerous ligaments. The inferior or plantar surface presents in 

 front a deep groove, which runs obliquely from without, forwards and inwards ; 

 it lodges the tendon of the Peroneus longus, and is bounded behind by a promi- 

 nent ridge, terminating externally in an eminence, the, tuberosity of the cuboid, 

 the surface of which presents a 'convex facet, for articulation with the sesamoid 

 bone of the tendon contained in the groove. The ridge and surface of bone 

 behind it are rough, for the attachment of the long and short plantar ligaments. 

 The external surface, the smallest and narrowest of the three, presents a deep 

 notch, formed by the commencement of the peroneal groove. 



The articular surfaces are the posterior, anterior, and internal. The posterior 

 surface is smooth, triangular, concavo-convex, for articulation with the anterior 

 surface of the os calcis. The anterior, of smaller size, but also irregularly trian- 

 gular, is divided by a vertical ridge into two facets ; the inner facet, quadrilateral 

 in form, articulates with the fourth metatarsal bone; the outer one, larger and 

 more triangular, articulates with the fifth metatarsal. The internal surface is 

 broad, rough, irregularly quadrilateral, presenting at its middle and upper part a 

 small oval facet, for articulation with the external cuneiform bone ; and behind 

 this, occasionally, a smaller facet, for articulation with the scaphoid ; it is rough 

 in the rest of its extent, for the attachment of strong interosseous ligaments. 



To ascertain to which foot it belongs, hold the bone so that its under surface, 

 marked by the peroneal groove, looks downwards, and the large concavo-convex 

 articular surface backwards, towards the holder ; the narrow non-articular surface, 

 marked by the commencement of the peroneal groove, will point to the side to 

 which the bone belongs. 



Articulations. With four bones: the os calcis, external cuneiform, and the 

 fourth and fifth metatarsal bones ; occasionally with the scaphoid. 



Attachment of Muscles. Part of the Flexor brevis pollicis. 



THE ASTKAGALUS. 



The Astragalus (fig. 113), next to the os calcis, is the largest of the tarsal bones. 

 It occupies the middle and upper part of the tarsus, supporting the tibia above, 

 articulating with the malleoli on either side, resting below upon the os calcis, and 

 joined in front to the scaphoid. This bone may easily be recognized by its large 

 rounded head, the broad articular facet on its upper convex surface, and by the 

 two articular facets separated by a deep groove on its under concave surface. It 

 presents six surfaces for examination. 



The superior surface presents, behind, a broad smooth trochlear surface, for 

 articulation with the tibia ; it is broader in front than behind, convex from before 

 backwards, slightly concave from side' to side. In front of the trochlea is the 

 upper surface of the neck of the astragalus, rough for the attachment of liga- 

 ments. The inferior surface presents two articular facets separated by a deep 

 groove. The groove runs obliquely forwards and outwards, becoming gradually 

 broader and deeper in front : it corresponds with a similar groove upon the upper 

 surface of the os calcis, and forms, when articulated with that bone, a canal, filled 

 up in the recent state by the calcaneo-astragaloid interosseous ligament. Of the 

 two articular facets, the posterior is the larger, of an oblong form, and deeply 

 concave from side to side : the anterior, although nearly of equal length,, is. nar- 



