158 



ARTICULATIONS OF THE rPPER LIMB. 



the fifth. Thus to the second, or that of the forefinger, a thin fasci- 

 cukis of fibres passes from the trapezium, and another from the 

 trapezoid bone ; the third receives one from the trapezoid, and from the 

 OS magnum ; the fourtli from the os magnum and also from the unci- 

 form ; but the fifth is connected with the unciform only. The palmar 

 ligaments are not so well defined ; there is a single band to each bone, 

 except that of the little finger. There is likewise an interosseous band 

 in one part of the carpo-metacarpal articulation, connecting the lower 

 and contiguons angles of the os magnum and unciform to the adjacent 

 angle of the third metacarpal bone. This ligament is usually sur- 

 rounded by a part of the general synovial membrane, but sometimes it 

 separates the cavity between the unciform and two inner metacarpal 

 bones from the rest of the joint. 



The first metacarpal bone is unconnected with the others, and is 

 articulated with the trapezium by an external and an internal ligament, 

 a capsular investment, and a distinct synovial membrane. 



METACARPO-PHALANGEAL AND INTERPHALANGEAIi ARTICULATIONS. -553^. 



The rounded head of each of the last four metacarpal bones, being re- 

 ceived into the slight hollow in the extremity of the first phalanx, is 

 maintained in its position by two lateral ligaments, 

 an anterior ligament, and a synovial membrane. 



The lateral ligaments consist of strong fasci- 

 culi of fibres, on each side of the joint, from the 

 metacarpal bone to the contiguous extremity of the 

 phalanx. The direction of the fibres is downwards 

 and forwards. 



Fk. 144. 



^ 



'J M\[ 



Fig. 144. — Longitudinal Axtero-Posterior Section THRocaH 

 the lower part op the radius, semilunar bone, os 

 ]\Iagnum, Met.vcarpal Bone and Phalanges of the Middle 

 Finger, to show the shai-e of the Articular Surfaces 

 and Synovial Cavities between these several Bones. 

 (A. T.) i 



1, synovial cavity of the wrist-joint ; 2, intercai'pal cavity ; 

 3, carpo-metacarpal cavity ; 4, metacarpo-plialangeal cavity ; 

 5 anil 6, jjlialangeal cavities ; 4', 5', and 6', the palmar filiro- 

 cartilaginons plates wliich are att.oched to the base of the several 

 phalanges ; 7, indicates the place of the tendons of the long 

 flexor mnscles ; 8, a transverse .section of the anterior annular 

 ligament ; 9 and 10, transverse retinacnla, or vaginal ligaments 

 of the flexor tendons on the first and second i^halanges. 



The anterior or palmar ligament, or rather 

 fibrous plate, occupies the interval between the 

 lateral ligaments on the palmar aspect of each 

 joint ; it is a thick and dense fibro-cartilaginous 

 structure, which is firmly united to the phalanx but 

 loosely adherent to the metacarpal bone. It is con- 

 tinuous at each side with the lateral ligament, so 

 that the three form one undivided structure which 

 covers the joint, except on the dorsal aspect. Its 

 palmar surface is grooved for the flexor tendon, 

 whose sheath is connected to it at each side ; the other surface, looking 

 to the interior of the joint, is lined by the synovial membrane, and 



