740 MAMMALIAN ANATOMY 



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The tibial and fibular borders of the tarsus, formed by the meet- 

 ing of the dorsal and plantar surfaces, are well defined in the distal 

 half only, inasmuch ae the proximal heel bone is compressed strongly 

 from side to side. 



The seven bones of the tarsus differ in arrangement from the 

 corresponding carpal bones. Two bones are arranged in the proximal 

 row, four are placed in a transverse distal row, and the seventh bone 

 occupies a position between the two rows and on the tibial side. The 

 two bones which form the proximal row are not side by side, as are the 

 scapho-lunar and cuneiform of the hand, but one is placed dorsal to 

 the other. The other bones do not radiate from the proximal end of 

 the tarsus toward the lateral margins, but are arranged parallel to the 

 long axis of the foot, and in such manner that four lie on the tibial 

 side and one on the fibular side of a longitudinal suture. The dorsal 

 of the two proximal bones is the ankle bone, or the astragalus, and 

 the ventral is the heel bone, or the calcaneum. The scaphoid is the 

 middle bone, which is situated between the two rows. In the distal 

 row, counting from the tibial side, are the entocuneiform, the meso- 

 cuneiform, the ectocuneiform, and the cuboid. 



The tarsal bones are six-sided, and present (a) dorsal and plantar 

 surfaces, which are non-articular, but assist in forming the instep and 

 the sole of the foot respectively ; (b) proximal and distal surfaces, 

 which, except on the astragalus and the calcaneum, articulate respec- 

 tively with the distal and proximal surfaces of adjoining tarsal and 

 metatarsal bones ; and (c) tibial and fibular surfaces, either articulating 

 respectively with the fibular and tibial surfaces of adjoining tarsal 

 bones, or producing the fibular and tibial borders of the tarsus. 



Nomenclature. Tarsus is from tarsos, used by the Greeks for 

 a number of objects with broad flat surfaces, such as the blade of a 

 rudder, a saw, or basket-work for drying fruit. Later, it was applied 

 to the broad part of the hand and of the foot, exclusive of the fingers 

 or the toes, and without any reference to the bones contained therein. 

 It was first used in osteology by Galen, who included in it, however, 

 only the four bones of the distal row, counting the three others as 

 independent elements. The anatomists of the Middle Ages restricted 

 the name to the back part of the foot, which has since borne it. The 

 Germans call the tarsus die Fussivurzel, the French le tarse. 



Three sets of names are employed for the tarsal bones : (1) the 



