DISSECTION OF THE UPPER EXTREMITY 115 



ligament of the radius (ligamentum annulare radii) (0. T. orbicu- 

 lar ligament) and the sacciform recess (recessus sacciformis). 



(b) Distal radio-ulnar joint. 



What bony surfaces are concerned? Study carefully 



(ba) Joint-capsule (capsula articularis}. 



(bb) Articular disk (discus articularis) (0. T. triangular fibro- 



cartilage). 

 (be) Saccular recess (recessus sacciformis). 



(c) Interosseous membrane and oblique cord. 



Study exact form and attachments. What vessels and nerves are 

 related to the interosseous membrane? 



In what movements are the radio-ulnar articulations con- 

 cerned! Study carefully the movements of pronation and supi- 

 nation (a) when the forearm is extended, (b) when it is flexed. 

 What muscles are concerned in these movements ? 



Saw through the ulna at the junction of its distal and middle 

 thirds ; cut through the membrana interossea. Draw the distal 

 fragment of the ulna medialward ; open the recessus sacciformis. 

 The proximal surface of the discus articularis can be seen and 

 its attachments carefully examined. 



Carpometacarpal Joints (Articulationes carpometacarpeae). 



How many of these are there ? What bony surfaces are con- 

 cerned in their formation? In order to examine these joints 

 thoroughly, remove the Mm. interossei from the metacarpal 

 bones and detach the tendons of the flexor muscles and the Mm. 

 lumbricales from the fingers. Do not disturb the extensor ten- 

 dons at present. Clean the carpometacarpal and the intermeta- 

 carpal ligaments carefully. Study in the four ulnar carpometa- 

 carpal articulations the following : 



(a) Joint-capsules (capsulae articular es] . 



(b) Strengthening ligaments : 



(ba) Dorsal carpometacarpal ligaments (ligamenta carpometacar- 



pea dorsalia). 



(bb) Volar carpometacarpal ligaments (ligamenta carpometacar- 



pea volaria). 



Note the special carpometacarpal joint for the thumb 

 (articulatio carpometacarpea pollicis). Study its capsula 

 articularis. 



Intermetacarpal Joints (Articulationes intermetacarpeae). 



These joints are amphiarthroses. What is an amphiarthro- 

 sis ? Study 



(a) Joint-capsules (capsulae articulares) . 



(b) Strengthening ligaments: 



