208 



TEE ARTICULATIONS. 



ligament. The gfenni.l lip^aments of the four firet dip:it8 are united to each otlier by a tfans- 

 ver«e ligament of tlie metacarpus. Ti.e articulations are consolidated by two lateral ligaments. 



The metacarpo-phalangeal articulations allow flexion and ex- 

 Yis. 134- tension movements, as well -as those of abduction and adduction; 



but the latter are limited by the lateral ligaments. 



7. Articulation of the First with the Second 

 Phalanx, or First Interphalangeal Articulation. 



{Preparation. — Remove the extensor tendon ; throw open the 

 metacaipo-pi.alangeal sheath, and turn down the flexor tendons.) 



This is an imperfect hinge-joint. 



Articular surfaces. — On the inferior extremity of the 

 first phalanx are two lateral condyles, separated by a 

 groove. On the superior surface of the second phalanx 

 are two glenoid cavities, and an antero-posterior ridge. 



The latter surface is completed behind by a glenoidal 

 fihro-cartilage, very dense and thick (Fig. 132, 16), which 

 also acts as a ligament. It is attached, in one direction, 

 to the second phalanx, between the superior articular 

 surface and the kind of fixed sesamoid which margins it 

 behind ; in the other, it is inserted into the first phalanx 

 by means of six fibrous bands (Fig. 135, 4, 5, 6) : two 

 superior, which embrace the inferior, middle, and super- 

 ficial sesamoid ligaments ; two middle, and two inferior, 

 which extend to the sides of the inferior extremity of 

 the first phalanx. This fibro-cartilage is moulded, in 

 front, to the articular surface of the latter bone, and 

 forms, by its posterior face, a gliding surface for the 

 perforans tendon (Figs. 132, 16 ; 134, 5). It is con- 

 founded, laterally, with the two branches of the per- 

 foratus, and receives, in the middle of its superior border, 

 the insertion of the inferior superficial sesamoid liga- 

 ment. 



Mode of union. — Ttvo lateral ligaments (Fig. 135, 

 7), to which are added, behind, the fibro-cartilage just 

 described, and in front the tendon of the anterior extensor 

 of the phalanges. These ligaments are large and thick, 

 and, passing obliquely downwards and backwards, are 

 inserted, superiorly, into the lateral tubercles of the 

 inferior extremity of the first phalanx. They are at- 

 tached, beneath, to the sides of the second phalanx. 

 Their most inferior fibres are even prolonged below that 

 point to reach the extremities of the navicular bone, and 

 constitute the posterior lateral ligaments of the pedal 

 articulation. 



Synovial membrane. — This covers the tendon of the 



ligament ; 7, lateral fasci- 

 culus of the middle inferior sesamoiil ligament; 8, inferior superficial sesamoid ligament ; 9, 

 lateral ligament of the first interphalangeal articulation; 10, section of the terminal branch 

 of the perforafus tendon; 11, section of the lateral cartilage of the foot; 12, postero-inferior 

 surface of navicular bone; 13, section of lateral cartilage, plantar cushion, and wing of pedal hone," 

 14, peiforatus tendon, 15, perforans tendon. 



'osterior view of the 

 metacarpo-phalangeal 

 and inter-phalangeal 

 articulations (right 

 limb). 



1, 3, Outer and inner 

 rudimentary metatarsal 

 bones ; 2, jierforans ten- 

 don and its check liga- 

 ment; 4, suspensory liga- 

 ment ; 5, gliding surface 

 or sVieath for the flexor 

 tendons, f'rmed by the 

 posterior face of the sesa- 

 moid bones, and interse- 

 samoid, transverse, .ind 

 annular ligaments ; 6, 

 section of lateral sesamoid 



