330 INFERIOR EXTREMITY 



viz. the navicular, the cuboid, the three cuneiforms, and the 

 metatarsus. Further, the anterior pillar may be considered 

 as being formed of a medial column composed of the navicular, 

 the three cuneiform, and the three medial metatarsal bones, 

 and a lateral column composed of the cuboid and the two 

 lateral metatarsal bones. The weight of the body is trans- 

 mitted to the summit of the arch through the talus, and the 

 most important ligaments concerned in the prevention of 

 excessive flattening of the arch are the plantar calcaneo- 

 navicular^ the two plantar calcaneo-cuboid ligaments^ and the 

 various slips of the tendon of the tibialis posterior as they 

 pass to find attachment to the different tarsal and meta- 

 tarsal bones. The plantar aponeurosis also acts powerfully 

 in this way : connecting as it does the extremities of the 

 two pillars of the plantar arch, it operates, as the late Sir 

 George Humphry once pointed out, in the same manner 

 as the " tie-beam " of a roof. The transverse arch of the 

 foot is seen to best advantage across the line of the tarso- 

 metatarsal articulations. 



Dissection. The muscles and tendons which have hitherto been only 

 partially detached from the bones of the foot should now be completely 

 removed and the ligaments defined. 



Taloid Articulations. The talus articulates by means 

 of the large posterior facet on the distal surface of its body 

 with the corresponding posterior facet on the proximal surface 

 of the calcaneus. Its head, on the other hand, is received 

 into a large socket which is formed for it by the sustentaculum 

 tali of the calcaneus, the navicular, and two ligaments which 

 pass between the calcaneus and the navicular viz. one 

 below, the plantar calcaneo-navicular, and another on the 

 lateral side, the lateral calcaneo-navicular ligament. These 

 two taloid articulations are quite distinct. 



The ligaments which hold the talus in its place are five 

 in number. Four are attached to the calcaneus and one to 

 the navicular bone. They are : 



1. Lig. talo-calcaneum interosseum. 



2. Lig. talo-calcaneum laterale. 



3. Lig. talo-calcaneum mediale. 



4. Lig. talo-calcaneum posterius. 



5. Lig. talo-naviculare dorsale. 



The talo-calcanean interosseous ligament is by far the most 

 powerful. It occupies the tarsal canal, and consists of strong 



