264 



A MANUAL OF ANATOMY 



border, is very short and narrow, and presents a notch leading to 

 the peroneal groove on the plantar surface. The dorsal surface 

 is rough, and is directed upwards and outwards. The plantar 

 surface presents in front the deep peroneal groove, which is directed 

 inwards and forwards, and lodges the tendon of the'peroneus longus. 

 Behind the groove is a stout, oblique ridge for the long plantar 

 ligament. This ridge becomes enlarged externally into a tubercle, 

 which is covered by cartilage on its anterior and outer aspects for 

 the play of the sesamoid cartilage, or bone, usually present in the 

 tendon of the peroneus longus. The surface behind the ridge gives 

 attachment to the short plantar ligament, a slip of the tendon of 

 the tibialis posticus, and some fibres of the flexor brevis hallucis, 

 but the latter may spring from the internal surface. 



Dorsal Surface 

 I 



Posterior Surface for , 



Os Calcis 



Calcaneal Process 



For 4th Metatarsal 



- For External Cuneiform 



Posterior Surface 

 for Os Calcis 



Fig. 156. — The Right Cuboid Bone. 

 A, External View ; B, Internal View. 



Articulations. — Posteriorly with the os galcis, anteriorly with the 

 fourth and fifth metatarsal bones, internally with the external 

 cuneiform, and sometimes with the navicular, and at the lower and 

 inner angle occasionally with the astragalus. 



Structure. — ^The structure is that of a short bone. 



The tarsus as a whole is convex superiorly, and concave interiorly, 

 from before backwards as well as from side to side. The part in 

 front of the astragalus and os calcis constitutes the instep, and the 

 entire tarsus forms two columns — an inner, comprising the astrag- 

 alus, navicular, and three cuneiform bones, and an outer, representing 

 the OS calcis and cuboid. 



Varieties. — The number of tarsal bones is sometimes increased to eight, 

 \vhich is brought about in one or other of the following ways : (i ) the external 

 tubercle on the posterior border of the astragalus may form a separate ossicle, 

 called the 05 trigonum : {2) the tuberosity of the navicular may form a 



