264 



OSTEOLOGY. 



TUBEROSITY 



GROOVE FOR PERON^US 



LONG US 



A 



GROOVE FOR TUBEROSITY 



PERON.EUS LONGUS 



B 



its middle and close to its dorsal border. This is for articulation with the lateral 

 side of the third cuneiform ; anterior and posterior to this the surface is rough for 

 ligaments. Not infrequently, behind the facet for the third cuneiform, there is 



NAVICULAR a small articular 



THIRD CUNEIFORM (occasional) surface for the 



navicular, as is the 

 case normally in 

 the gorilla, whilst 

 posteriorly and on 

 the plantar aspect 

 the projecting in- 

 ferior angle is 

 sometimes pro- 

 vided with a facet 

 on which the head 

 of the talus rests. 

 (Sutton, " Proc. 



Anat. Soc./' Journ. Anat. and Physiol. vol. xxvi. p. 18.) The anterior surface is oval or 

 conical in outline ; sloping obliquely from the medial side laterally and backwards, 

 it is divided about its middle by a slight vertical ridge into two parts, the medial of 

 which articulates with the base of the fourth metatarsal bone, the lateral with that 

 of the fifth. The posterior surface, also articular, has a semilunar outline, the convex 

 margin of which corresponds to the dorsal roundness of the bone. The inferior 

 lateral angle corresponds to the tubercle on the lateral border of the bone, whilst 

 the inferior medial angle forms a pointed projection which is sometimes called 

 the calcanean process. This surface articulates with the calcaneus by means of a 

 saddle-shaped facet, which is convex from side to side, and concave from dorsal 

 to plantar margins. 



The tarsus as a whole may be conveniently described as arranged in two 



FIG. 269. THE RIGHT CUBOID BONE. 

 A. Lateral Side. B. Medial Side. 



FIG. 270. RADIOGRAPHS OF THE F<ETAL FOOT. 



1. About fifth month. No ossification in the tarsus visible. 



2. About sixth month. Appearance of a nucleus for the calcaneus. 



3. About seventh month. Nucleus for calcaneus well developed. 



4 and 5. About eighth month. Centre for talus, as well as for calcaneus, is now seen. 



6. About birth. Centres for the talus and calcaneus are well developed ; there is also a considerable centre 

 for the cuboid, and the appearance of a centre for the third cuneiform is now displayed. 



columns ; the medial, corresponding to the medial border of the foot, comprising 

 the talus, navicular, and three cuneiforms, and forming a base for the support of 

 the medial three metatarsal bones and their phalanges. The lateral column, 

 formed by the calcaneus and cuboid, supports the fourth and fifth metatarsal bones, 

 together with their phalanges. The dorsal surface of the anterior portion of the 



