752 MAMMALIAN ANATOMY 



tendon. The dorsal margin consists of an inner or tibial slightly 

 concave part which passes obliquely outward and upward to meet the 

 proximal part of the dorsal surface of the bone, and a shorter outer 

 or fibular part which runs nearly vertically to meet the tibial part in 

 a dorsal angle. 



On the plantar surface (Fig. 587) the proximal margin is trans- 

 verse and rounded, but well defined. The tibial margin begins at the 

 inner tuberosity of the heel, runs distally as an indistinct border, and 

 becomes apparent as a ridge dividing the groove on the plantar sur- 

 face of the lesser process from the plantar surface proper. The fibular 

 margin is less marked proximally, inasmuch as the fibular surface is 

 concave and passes gently into the plantar surface ; its distal part is 

 well defined, running at first distally to the fibular side as far as the 

 peroneal tubercle, and then distally and to the tibial side. The greater 

 part of the plantar surface is convex from side to side ; it is depressed 

 at the distal end, on a line running obliquely from the tibial side, 

 distally and to the fibular side, parallel with the distal end of the 

 fibular border. 



Nomenclature. Calcaneum is derived from calx, the heel. Os 

 calcis is used, and also os calcaris, from calcara, a spur, because the 

 spurs are worn on the heel. The German equivalent is das Fersenbein, 

 the French le calcaneum. 



Determination. When the calcaneum is held with the dorsal 

 surface uppermost and the distal surface toward the student, the lesser 

 process is on the side to which the bone belongs. 



Articulation. The calcaneum articulates with the astragalus, the 

 cuboid, and the scaphoid. 



Muscular Attachments. The calcaneum affords origin on its 

 dorsal surface to the extensor brevis digitorum ; on the plantar sur- 

 face to the abductor minimi digit! and the plantar head of the flexor 

 longus digitorum. 



Ossification. The calcaneum appears to be developed from a 

 single centre of ossification. 



THE SCAPHOID. 



General Description. The Scaphoid is the first bone on the 

 inner or tibial side of the second row of the tarsus (Fig. 568). It lies 

 distal to the astragalus, proximal to the three cuneiforms, and on the 



