274 



THE ARTICULATIONS 



this aspect; where there are two articular facets, the fibres extend upward between them nearly 

 as far as their carpal facets. That between the fourth and fifth is the weakest. 



The synovial membrane is prolonged downward from the common carpal sac. 



The arteries to the intermetacarpal joints are twigs from the volar and dorsal metacarpal 

 arteries; the twigs pass upward between the interosseous muscles. 



The nerves are derived from the ulnar and the deep branch of radial (posterior interosseous). 



The Union of the Heads of the Metacarpal Bones 



The distal extremities of these bones are connected together on their palmar aspects by 

 what is called the transverse ligament [Ug. capitulorum]. This consists of three short bands 

 of fibrous tissue, which unite the second and third, third and fourth, and the fourth and fifth 

 bones. They are rather more than 6 mm. (J in.) deep, and rather less in width, and limit the 

 distance to which the metacarpal bones can be separated. They are continuous above with the 

 fascia covering the interosseous muscles; below, they are connected with the subcutaneous 

 tissue of the web of the hand. They are on a level with the front surface of the bones, and are 

 blended on either side with the edges of the glenoid ligament in front, with the lateral hgaments 



Fig. 305. — Anterior and Posterior Views of Ligaments of the Fingers. 



Transverse ligament 

 ^=='*3'S between the heads 



t' _s of the metacarpal 

 'f^ bones 

 __L- Accessory volar ligament 



^PCollateral ligament 



Areolar tissue 

 capsule 

 Collateral ligament 



[ V % 



-Glenoid ligament 

 -Collateral ligament 



-Flexor tendon 



Areolar tissue 

 capsule 

 Collateral ligament 



Extensor tendon 



-Flexor tendon 



Slips of the extensor, 

 tendon 



of the metacarpo-phalangeal joint, and also with the sheaths of the tendons. In front, a lum- 

 brical muscle passes with the digital arteries and nerves; while behind, the interossci muscles 

 pass to their insertions. 



10. THE METACARPO-PHALANGEAL JOINTS 

 (a) The Metacarpo-phalangeal Joints of the Four Medial Fingers 

 Class. — Diarthrosis. Subdivision. — Condylarthrosis. 



In these joints the cup-shaped extremity of the base of the first phalanx fits 

 on to the rounded head of the metacarpal bone, and is united by the following 

 ligaments (in addition to the articular capsule) : — 



Collateral. 



Volar accessory. 



The volar accessory (or glenoid) ligament (fig. 305) is a fibro-cartilaginous plate which 

 seems more intended to increase the dcplli of tlic phalangeal articular facet in front, than to 

 unite the two bones. It is much more firmly attached to the margin of the phalanx than to the 

 metacarpal bone, being only loosely connected with the palmar surface of the latter by some 

 loose areolar tissue which covers in the synovial membrane, here prolonged some little distance 

 upon the surface of the bone. At the sides, it is connected with the collateral ligaments and the 



