THE CUNEIFORM BONES. 



261 



FOR SECOND CUNEIFORM 



the edges of which are striated. Into this surface the tendo calcaneus is inserted. 

 The lowest surface is rough and striated, and is confluent below with the medial 

 and lateral processes; this is overlain by the dense layer of tissue which forms 

 the pad of the heel. 



Os Naviculare Peclis. 



The navicular bone (O.T. scaphoid), of compressed piriform shape, is placed on 

 the medial side of the foot, between the head of the talus posteriorly and the 

 three cuneiform bones anteriorly. The bone derives its name from the oval or 

 boat-shaped hollow on its posterior surface, which rests upon the head of the 

 talus. Its anterior aspect is furnished with a semilunar articular area, which is sub- 

 divided by two faint ridges into three wedge-shaped facets for articulation, 

 medio-laterally, with the first, second, and third cuneiform bones. The dorsal 

 surface of the bone, 

 convex from side to 

 side, is rough for the 

 attachment of the liga- 

 ments on the dorsal 

 aspect of the foot. On 

 its plantar aspect the 

 bone is irregularly con- 

 cave ; projecting down- 

 wards and backwards 

 from its lateral side 

 there is often a pro- 

 minent spur of bone, 

 the plantar process, to 

 which is attached the 

 plantar calcaneo-navicular ligament. The lateral surface is narrow from before 

 backwards, and rounded from above downwards. In 70 per cent, of cases (Manners 

 Smith) it is provided with a facet which rests upon a corresponding area on 

 the cuboid. Behind this, in rare instances, there is a facet for the calcaneus. The 

 medial surface of the bone projects beyond the general line of the medial border 

 of the foot, so as to form a thick rounded tuberosity (tuberositas ossis navicularis), 

 the position of which can be easily determined in the living. To the medial and 

 plantar surface of this process an extensive portion of the tendon of the tibialis 

 posterior muscle is inserted. 



' FOR HEAD OK 



PLANTAR PBOCESS TALUS 



u PLANTAR PROCESS 



O 



TUBEROSITY 



FIG. 261. THE RIGHT NAVICDLAR BONE. 

 A. Seen from behind. B. Seen from the front. 



The Cuneiform Bones. 



The cuneiform bones, three in number, are placed between the navicular 

 posteriorly and the bases of the first, second, and third metatarsal bones anteriorly, 

 for which reason they are now named the first, second, and third cuneiforms 

 (O.T. internal, middle, and external). More or less wedge-shaped, as their name 

 implies, the first is the largest, whilst the second is the smallest of the group. 

 Combined, they form a compact mass, the posterior surface of which, fairly regular 

 in outline, rests on the anterior surface of the navicular ; whilst anteriorly they 

 form a base of support for the medial three metatarsals, the outline of which is 

 irregular, owing to the base of the second metatarsal bone being recessed between 

 the first and third cuneiforms, as it articulates with the anterior surface of the 

 shorter second cuneiform. 



The first cuneiform bone, the largest of the three, lies on the medial border 

 of the foot between the base of the metatarsal bone of the great toe anteriorly, 

 and the medial part of the anterior surface of the navicular posteriorly. In form 

 the bone is less characteristically wedge-shaped than its fellows of the same 

 name and differs from them in this respect, that whilst the second and third 

 cuneiforms are so disposed that the bases of their wedges are directed upwards 

 towards the dorsum of the foot, the first cuneiform is so placed that its base is 



