PELVIC LIMBS 



747 



FIG. 564. 



neum 



It is an oblong, irregular bone, with the greatest length double 

 the greatest width from the tibial to the fibular -side. It is wider at 

 the distal than at the proximal end. The greatest width, however, is 

 found just distal to the middle, where a prom- 

 inence known as the lesser process projects 

 laterally to the tibial side. The average width 

 is scarcely one-third the length. The proximal 

 narrower portion is compressed from side to side, 

 and the distal wider portion is flattened from 

 the dorsal to the plantar side. The distal part 

 is sometimes called the greater process of the 

 bone. The plantar aspect is smooth ; the dorsal 

 aspect is irregular, and marked by eminences 

 and depressions. The calcaneum presents for 

 examination six surfaces, the dorsal, the plan- 

 tar, the internal or tibial, the external or fibular, 

 the proximal, and the distal. 



The dorsal surface (Fig. 565) consists of a 

 proximal and a distal portion of nearly equal 

 length. Inasmuch as the proximal or posterior 

 part of both the external and the internal sur- 

 face slopes from the plantar edge dorsally and 

 to the middle line of the foot, the proximal part 

 of the dorsal surface becomes little more than 

 a border, which is rounded from side to side and 

 concave from end to end. It is separated be- 

 hind from the proximal surface by the cres- 

 centic proximal margin, which is sometimes 

 sharp and everted. When the sole of the foot 



is wholly on the ground this surface faces outward as well as upward. 

 The part of the dorsal surface distal to this portion becomes wider 

 and more prominent ; it is convex and slopes abruptly to the plantar 

 side and passes into the distal part of the dorsal surface. On this 

 sloping portion are two facets for articulation with the astragalus. 



The fibular facet begins on the tibial or internal surface of the 

 bone near its dorsal border, and is directed distally and to the fibular 

 side. It is twice as long as wide, and strongly convex from end to 

 end, except just at the distal end, which passes into the wide part 



POSITION OF CALCANEUM. 



