i8o 



Anatomy of Skeleton 



that any flattening of the outer arch can only occur with stretching of the long and 

 short plantar ligaments, thus increasing their efficiency. 



The bone is the only tarsal member that normally possesses an epiphysis : this is 



/ins 



FIG. 148. Right os calcis showing the epiphysis. 



situated on its hinder part (Fig. 148) and is a traction epiphysis for the tendo Achillis. 

 It is considered to correspond with the pisiform in the hand. 



The bone is very vascular, and several small foramina can be seen on its sides : 

 those on the inner side are largely arterial, with venous exit on the outer side. 



It is partly ossified at birth. 



CUBOID. 



This bone is really more pyramidal than cuboid in its general shape, for its dorsal, 

 plantar, and anterior surfaces slope towards its narrow and short outer surface or border, 

 with its broad base facing inwards and articulating with the outer cuneiform. The 

 dorsal surface looks outwards and upwards, is roughened slightly by ligamentous fibres 

 connecting it with the adjacent bones, and is covered by the tendons of Peroneus 

 tertius and extensors for the outer toe. The plantar surface is marked by a deep groove, 

 running obliquely across it immediately behind its front margin, for the tendon of 

 Peroneus longus : behind this a thick ridge for the long plantar ligament, some fibres 



of which pass from the ridge over 

 the groove to the metatarsus, and 

 groove for . r ~%'r Ot/ Ter thus help to cover in the tendon. 



' ^T / CV " f!f0rm ' Behind the ridge is a hoUow area for 



the attachment of the short plantar 



ligament. A facetted surface at the 

 outer end of the ridge is for the play 



fdeeci 

 \ 



of the fibro-cartilaginous thickening 

 in the tendon. 



The posterior aspect has a con- 

 cavo-convex articular surface for the 

 os calcis, and the anterior surface 

 has two continuous facets for the 

 two outer metatarsals, the inner 

 quadrilateral and the outer triangular. The outer surface or edge is notched for the 

 peroneal tendon turning into the groove, is overlapped somewhat by the styloid process 

 of the last metatarsal in front, and is covered by the muscular and ligamentous abductor 

 of the outer toe. 



.. 



process. facet for 



Scaph 

 FIG. 149. Left cuboid, from below and from the inner side. 



