BONES OF THE FOOT. 



345 



obliquely outwards to the second metatarsal, 

 the other from the third cuneiform obliquely 

 inwards to the same bone. We find, moreover. 

 two plantar ligaments, one short *nd direct, 

 passing from the second cuneiform bone to the 

 second metatarsal, the other much longer and 

 more oblique, coming from the first cuneiform. 

 Lastly, this articulation has an interosseous liga- 

 ment, which is extended from the lateral facet 

 on the external surface of the first cuneiform to 

 a corresponding one on the internal surface of 

 the second cuneiform. 



Each of the remaining tarso-metatarsal arti- 

 culations has its dorsal ligaments, of which 

 those of the third and fourth are direct, and that 

 of the fifth is extended obliquely outwards 

 from the cuboid to the fifth metatarsal bone. 

 In all three, the place of plantar ligament is 

 supplied by the sheath of the long peroneal 

 tendon, and the fifth receives additional strength 

 from fibres given off from the tendon of the 

 peroneus brevis. In the third there is an 

 interosseous ligament between the third and 

 fourth metatarsal bones, and from the anterior 

 part of the external surface of the third cunei- 

 form to the fourth metatarsal. 



The five tarso-metatarsal articulations have 

 four synovial membranes amongst them : the 

 first, as has already been mentioned, has a 

 distinct one ; the second lines the contiguous 

 surfaces of the first and second cuneiform bones, 

 and is prolonged over the mortise-shaped cavity 

 and the articular portions of the second meta- 

 tarsal. The third lines the articular portions 

 of the third cuneiform and third metatarsal, 

 and is prolonged on either side of the latter in 

 the form of two culs-de-sac into the space 

 between the latter bone and the second meta- 

 tarsal on the inside, and the fourth on the 

 outside. In fine, the fourth synovial membrane 

 is common to the fourth and fifth tarso-meta- 

 tarsal joints. 



Mttatarsal articulations. The four external 

 metatarsal bones are articulated with each other 

 by means of the contiguous articular facets on 

 the lateral surfaces of their posterior extremi- 

 ties. They are maintained in apposition by 

 interosseous ligaments which pass from one 

 metatarsal bone to the other, being inserted 

 into rough surfaces immediately above the 

 articular portion of each bone. Moreover, 

 these joints have dorsal and plantar ligaments, 

 which consist of ligamentous fibres directed 

 transversely from one bone to the other. The 

 plantar ligaments are considerably stronger and 

 thicker than the dorsal. 



The anterior extremities of the five meta- 

 tarsal bones, although not articulated together 

 by surfaces which play upon each other, are 

 yet connected by a common transverse ligament 

 which passes from one bone to the other, being 

 attached to the plantar surface of each bone, 

 and covered by the sheaths of the flexor ten- 

 dons. 



Metatarso-phalangeal articulations. The 

 convex articular surface of the anterior extre- 

 mity of each metatarsal bone is adapted to the 

 concave surface on the posterior extremity of 

 each posterior or metatar^a! phalanx. A sepa- 



rate synovial membrane lines the articular sur- 

 faces of each joint ; and two lateral ligaments, 

 one on either side, maintain the surfaces in 

 apposition. On the dorsal aspect each joint is 

 strengthened and protected by the extensor 

 tendons ; and on the plantar a strong, thick, 

 almost cartilaginous substance is extended 

 from the metatarsal bone to the phalanx. This 

 substance protects the joint inferiorly ; it is 

 grooved on its inferior surface, and contributes 

 to form the sheath for the flexor tendon, which 

 runs along the plantar surface of each toe. 



The metatarso-phalangeal articulation of the 

 great toe presents some points of difference 

 from the others ; its surfaces are more exten- 

 sive, and on the plantar aspect the head of the 

 metatarsal bone has a pulley-like form, from 

 the existence of a ridge in its centre, on either 

 side of which there is a superficial depression : 

 each depression receives a sesamoid bone, 

 which, being formed in the substance of the 

 inferior ligament, thus contributes greatly to 

 strengthen the joint in this situation. 



Articulations of the toes. These are gin- 

 glymoid joints, all closely resembling each 

 other both in the forms of the articular surfaces, 

 and also in the bonds of union by which the 

 contiguity of these surfaces is maintained. 

 The articular surfaces are pulley-like ; an in- 

 ternal and an external lateral ligament belong to 

 each joint ; and the plantar aspect of each is 

 protected by a ligamentous structure similar to 

 that a'ready described in the metatarso-phalan- 

 geal joints'. 



Motions of the metatarsal joints. At the 

 tarsal extremities the metatarsal bones enjoy 

 but a very limited mobility in consequence of 

 the strong and compact manner in which they 

 are articulated with the tarsus ; their motions 

 consist in a very limited and scarcely percepti- 

 ble gliding upwards and downwards. At their 

 phalangeal extremities, however, the metatar- 

 sal bones are capable of a greater, although 

 still a very limited, degree of motion. 



Motions of the metatarso-phalangeal joints. 

 These are flexion and extension, with a slight 

 degree of lateral inclination or abduction and 

 adduction, and also, of course, circumduction 

 or the rapid succession of the preceding four. 

 The lateral motions are very limited, being 

 most manifest in the joint of the great toe. 

 Flexion is limited by the extensor tendon and 

 the superior fibres of the lateral ligaments ; 

 extension by the inferior fibres of the lateral 

 ligaments, by the inferior ligament, and by 

 the flexor tendon. 



Motions of the phalangeal joints. Flexion 

 and extension only are enjoyed by these joints, 

 the extent of which is principally controlled 

 by the lateral ligaments and by the due anta- 

 gonism of the flexor and extensor muscles. 



Viewing the human foot as a whole, we 

 cannot fail to notice how admirably it is 

 adapted as an instrument of support, and for 

 the purposes of progression. For the former 

 end the solid and yet elastic mechanism of 

 the tarsus is mainly useful ; this part is placed 

 immediately under the tibia, which transmits 

 the weight of the body to the astragalus, the 



