THE METATARSO-PHALANGEAL 279 



7. THE IXTERMETATARSAL ARTICULATIONS 

 Class. — Di((rthroi<iK. Subdivision. — Arthrodia. 



The bases of the metatarsal hones are firmly held in |)osition V)y dorsal, plantar, 

 and interosseous ligaments. The first occasionally articulates by means of a distinct 

 facet with the second metatarsal (figs. 183 and 184, Section I). 



The dorsal ligaments are broad, membranous bands passing between the four 

 outer toes on their dorsal aspect; but in place of one between the first and 

 second metatarsal bones a ligament extends from the internal cuneiform to the 

 base of the second metatarsal bone (page 277). 



The plantar ligaments are strong, thick, well-marked ligaments Avhich connect 

 the bones on their plantar aspect. 



The interosseous ligaments are three in number, very strong, and are situated 

 at the points of union of the shaft with the bases of the bones, and fill up the 

 sulci on their sides. They limit tlic synovial cavities in front of the synovial facets. 



The common synovial membrane of the tarsus extends between the second and 

 third, and third and fourth bones; that of the cubo-metatarsal joint extending 

 between the fourth and fifth. 



The arterial and nerve-supply is the same as for the tarso-metatarsal joints. 



The movements consist merely of gliding, so as to allow the raising or widening 

 of the transverse arch. Considerable flexibility and elasticity are thus given to the 

 anterior part of the foot, enabling it to become moulded to the irregularities of the 

 ground. 



The Union of the Heads of the Metatarsal Bones 



The heads of the metatarsal bones are connected on their plantar aspect by 

 the transverse ligament, consisting of four bands of fibres passing transversely 

 from bone to bone, blending with the fibro-cartilaginous or sesamoid plates of the 

 metatarso-phalangeal joints, and the sheaths of the flexor tendons where the}^ are 

 connected with the fibro-cartilages. It differs from the corresponding ligament 

 in the hand by having a band from the first to the second metatarsal bone. 



8. THE METATARSO-PHALAXGEAL ARTICULATIONS 



{(C) The Metatarso-phalanctEal Joints of the Four Outer Toes 



Class. — Diaii?trnsis. Subdivision. — Condylarthrosis. 



These joints are formed by the concave proximal ends of the first phalanges 

 articulating with the rounded heads of the metatarsal bones, and united by the 

 following ligaments: — 



Two lateral. Dorsal. Plantar sesamoid plate. 



The two lateral ligaments are strong bands passing from a ridge on each side 

 of the head of the metatarsal bone to the sides of the proximal end of the first 

 phalanx, and also to the sides of the sesamoid plate Avhich unites the two bones 

 on their plantar surfaces. On the dorsal aspect they are united by the dorsal 

 ligament. 



The dorsal ligament consists of loose fine fibres of areolo-fibrous tissue, extend- 

 ing between the lateral ligaments, thus completing a capsule. It is connected by 

 fine fibres to the under surface of the extensor tendons, which pass over and 

 considerably strengthen this portion of the capsule. 



The plantar sesamoid plate helps to deepen the shalktw facet of the phalanx 

 for the head of the metatarsal bone, and corresponds to the glenoid ligament of 

 the fingers. It is firmly connected to the lateral ligaments and the transverse liga- 

 ment, and is grooved inferiorly where the flexor tendons pass over it. It serves to 

 prevent dorsal dislocation of the phalanx. 



