428 THE INFERIOR EXTREMITY 



1. Articulationes intertarseee, tarsometatarsere, and intermetatarsese. 



2. Articulationes metatarso-phalangese. 



3. Articulationes digitorum pedis. 



The bones which enter into these articulations are the 

 seven tarsal bones, the metatarsal bones, and the phalanges. 

 The tarsal and metatarsal bones are bound together by inter- 

 osseous, plantar, and dorsal ligaments, and are disposed in the 

 form of two arches, viz., a longitudinal and a transverse. The 

 integrity of these arches is maintained: (i) partly by the 

 forms of the bones ; (2) partly by the tension of the liga- 

 ments ; (3) partly by supporting tendons ; and (4) partly by 

 the tension of the plantar aponeurosis. 



The longitudinal arch presents a greater height and a 

 wider span along the medial than along the lateral side of the 

 foot. The talus lies at the summit of this arch and forms 

 its keystone. The posterior pillar of the longitudinal plantar 

 arch is short and solid, being formed by the calcaneus alone ; 

 the anterior pillar, much longer, is composed of several bones, 

 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 medial three metatarsal bones, 

 and a lateral column composed of the cuboid and the lateral 

 two 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 lie in the plantar concavity ; 

 they are the plantar calcaneo-navicular, the long plantar liga- 

 ment, the plantar cakaneo-cuboid ligament. The various slips 

 of the tendon of the tibialis posterior, as they pass to find 

 attachment to the different tarsal and metatarsal bones, give 

 additional support. The plantar aponeurosis is also an import- 

 ant factor, for, as it extends between the two pillars and is 

 attached to both, 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 plantar surface of its body 



