108 SPECIAL ANATOMY. 



boundary of the incisura semilunaris to that of the Capitulum Ulnce and the 

 Cartilage triangularis ; lies beneath lig. capsulare carpi et antibrachii. 



2. Carlilago-triangularis lies with its apex in the angle between Capitul. et 

 Proc. styloideus ulnce, with its base on the inferior border of the incisura semi- 

 lunaris, and fills up the interval between the two bones ; its apex, lig. subcru- 

 entum, unites with the proc. styloid. UlruB over it a synovial capsule. 



Appendant : 3. Lig. interosseum. A membrane in the space between the 

 central pieces of the radius and the ulna, from the Crista radii to the Crisia 

 ulnae / serves for attachment of muscles, extensor brevis, abductor and flexor 

 longus pollicis, extensor indicis proprius, flexor digit, comm. profund. has above 

 and below spaces through which the interosseal vessels and nerves perforate, 

 and for rn. supinator brevis. The fibres of the ligament cross from the radius 

 inwards and downwards. 



Movements : 



Rotation ; the radius alone moves. 1. Forwards, pronation. 

 a. At the superior radio-ulnar articulation. The internal portion 

 of the capitul. radii rolls from before backwards; its escape is 

 prevented by the small projection on the foss. sigmoid. min.; 

 but, however, it sometimes happens, particularly in children while 

 falling, at the same time that the hand is held. b. At the inferior 

 radio-ulna art. The fossa semilunaris radii rolls backwards and 

 forwards; should the capsular ligament lacerate, the capitulum 

 ulnse passes out backwards. 



2. Backwards, Supination. a. At the superior articulation: 

 The capit. radii rolls from behind, forwards, and comes in contact 

 with the anterior projection of the Fossa sigmoidea minor. 

 Luxation is very rare. b. At the inferior articulation: Fossa 

 semilunaris radii rolls from before, backwards; the capitulum 

 ulnas may escape forwards, if the capsular ligament is lacerated. 



In pronation the once parallel body of the radius is drawn 

 over the ulna, and crosses it, since the superior extremity remains 

 on the outer side, and the inferior passes to the inner. The in- 

 terosseous ligament is relaxed. 



In supination the radius returns back again into its parallel 

 position, with respect to the ulna, and the ligam. interosseum is 

 stretched. 



123. V. Connection of the Fore-arm with the Hand, 

 Jlrticulatio carpi. 



The wrist-joint, articulatio carpi, forms a free, ball and socket 

 joint. 



Articular surfaces: 1. Of the radius and ulna, concave, elon- 

 gated transversely. 2. Of the carpus os. naviculare, lunatum, 

 et cuneiforme forming a head. 



That portion of the articular surface, belonging to the Ulna, 



