280 THE ARTICULATIONS 



The second metatarso-jihalanfieal joint is a quarter of an inch in front of hoth 

 the first and third metatarso-phalangeal joints. 



The third nietatarso-i)halangeal joint is a quarter of an inch in front of the 

 fourtli, and the fourth three-eighths of an incli in front of tlie fifth. 



The head of the fifth metatarsal is in hne with the neck of the fourth. 



Thus the outer side of the longitudinal arch of the foot is shorter than the inner; 

 it is also distinctly shallower. 



(6) The Metatarso-phalangeal Joints of the Great Toe 



The metatarso-phalangeal joint of the great toe difiers from the rest in the 

 following particulars: — 



( 1 ) The ]x>nes are on a larger scale, and the articular surfaces are more extensive. 



(2) There are two grooves on the plantar surface of the metatarsal lione, one 

 on each side of the median line, for the sesamoid bones. 



(o) The sesamoid bones replace the fibro-cartilaginousor sesamoid plate. They 

 are two small hemispherical bones developed in the tendons of the flexor brevis 

 hallucis, convex below, but flat above where they play in grooves on the head of 

 the metatarsal bone; they are united by a strong transverse ligamentous liand, 

 which is smooth below and forms ]iart of the channel along which the long flexor 

 tendon plays. They are firmly united to the base of the phalanx b}'' strong short 

 fibres, but to the metatarsal bone they are joined by somewhat looser fibres. 

 Laterally they are connected with the lateral ligaments and the sheath of the 

 flexor tendons. They provide shifting leverage for the Jiexxir brevis haUuci>! as 

 well as for the flexor longus hallucis. 



The arteries come from the digital and interosseous branches; and the nerves 

 from the cutaneous digital, or horn small twigs of the nerves to the interossei 

 muscles. 



The movements permitted are: flexion, extension, alxluction, adduction, and 

 circumduction. 



Flexion is more free than extension, and is limited by the extensor tendons and 

 dorsal ligaments; extension is limited b}' the flexor tendons, the plantar fibres of the 

 lateral ligaments, and the sesamoid plates. The lateral motion is possible from the 

 shai)e of the bony surfaces, but is very limited, being most marked in the great toe. 

 It is limited by the lateral ligaments and sesamoid plates. 



9. THE INTERPHALANGEAL JOINTS 

 Class. — Diarthrosis. Subdivision. — Gii)f/li/mus. 



The articulations between the first and second, and second and third ]ilialanges 

 of the toes are similar to those of the fingers, with this important dift'ercnce, 

 that the l>ones are smaller and the joints, especially l)etween the second and third 

 phalanges, are often ankylosed. The ligaments which unite them are: — 



Two lateral. Dorsal. Glenoid ligament. 



The two lateral ligaments are well marked, and i)ass on each side of the joints 

 from a little rough dei)ression on the head of the proximal, to a rough border on 

 the side of tlie base of the distal phalanx of the joint. 



Tlie dorsal ligament is thin and membranous, and extends across the joint 

 from one lateral ligament to the other beneath the extensor tendon, with the deej) 

 surface of which it is connected, and by which it is strengthened. 



The glenoid ligament covers in the joint on the ))lantar surface. It is a fibro- 

 cartilaginous ])late, connected at the sides with the lateral ligaments, and with the 

 l>ones l)y short ligamentous fibres; the plantar surface is smooth, and grooved for 

 the flexor tendons. 



The arteries and nerves are derived from the corresjionding digital branches. 



The only movements permitted at these joints are iiexion and extension. 



