104 



DISSECTION OF THE UPPER LIMB. 



lateral band 



Very little 

 motion. 



Dissection. 



Articular 

 surfaces. 



and contact. 



Synovial 

 sacs, two 



or three. 



Interosseous 

 ligaments, 



metacarpal, 

 and carpal. 



Metacarpo- 

 phalangeal 

 articula- 

 tions ; 



Dissection 

 of finger- 

 joints. 



lateral 

 ligaments ; 



On the ulnar side of the metacarpal bone of the middle digit is 

 a longitudinal lateral band, which is attached above to the os mag- 

 num and unciform, and below to a rough part on the inner side of 

 the base of the above mentioned bone. Sometimes this band 

 isolates the articulation of the last two metacarpals with the 

 unciform bone from the remaining carpo-metacarpal joint ; but 

 more frequently it is divided into two parts, and does not form a 

 complete partition. 



This band may be seen by opening from behind the articulation 

 between the unciform and the last two metacarpal bones ; and by 

 cutting through the transverse ligaments joining the third and 

 fourth metacarpals so as to allow their separation. 



Movement. Scarcely any appreciable antero-posterior movement 

 exists in the articulations of the bases of the metacarpal bones of 

 the fore and middle fingers ; but in the ring and little fingers the 

 motion is greater, with a slight degree of opposition. 



Dissection. The articular surfaces of the bones in the carpo- 

 metacarpal articulation may be seen by cutting through the rest of 

 the ligaments on the posterior aspect of the hand. 



Articular surfaces. The metacarpal bone of the forefinger has 

 a broad, notched articular surface, which receives the prominence 

 of the trapezoid bone, and articulates laterally with the trapezium 

 and os magnum. The middle finger metacarpal articulates with 

 the os magnum. The metacarpal bone of the ring finger touches 

 the unciform bone and the os magnum. And the little finger bone 

 is opposed to the unciform. 



Synovial sacs. Usually two synovial sacs are interposed between 

 the carpal and metacarpal bones, viz., a separate one for the bone 

 of the thumb, and offsets of the common carpal synovial sac (p. 102) 

 for the others. Sometimes there is a distinct synovial sac for the 

 articulation of the two inner metacarpals with the unciform bone. 



Interosseous ligaments. The interosseous ligaments between the 

 bases of the metacarpal bones may be demonstrated by detaching 

 one bone from another ; and those uniting the adjacent carpal bones 

 may be shown in the same way. 



UNION OF METACARPAL BONE AND FIRST PHALANX (fig. 45). 

 In this joint the convex head of the metacarpal bone is received 

 into the glenoid fossa of the phalanx, and the two are united by 

 the lateral, anterior and posterior ligaments. 



Dissection. For the examination of this joint it will be requisite 

 to clear away the tendons and the tendinous expansion around it. 

 A lateral ligament on each side, and an anterior thick band are to 

 be defined. One of the joints may be opened to see the articular 

 surfaces. 



The same dissection may be made for the articulations between 

 the phalanges of the fingers. 



The lateral ligaments (a) are triangular in form ; attached above 

 to the lower part of the tubercle on the side of the head of the 

 metacarpal bone, and below the phalanx and to the anterior 

 ligament. 



