A R T1CULA TIONS. LIGAMENTS. 



433 



Locate tlie lesser sig moid cavity. 



It is on the outer part of the ulrfa, at the junction of the olecranon and coro- 

 noid processes ; it is limited in front and behind by the anterior and posterior lips 

 of the cavity. It contains the head of the radius. It is covered by articular 

 cartilage. 



THE INTEROSSEOUS MEMBRANE. 



This you will see extending from the interosseous ridge of the ulna to that of 

 the radius. It is limited above by the ulnar origin of the supinator brevis ; below, 



Capsule of elbow-joint 

 Cushion of fatty tissue 



Membranous tissue joining the 

 orbicular ligament to the neck 

 of the radius 



RADIUS 



Orbicular ligament 



Capsule of elbow 



FIG. 301. ORBICULAR LIGAMENT. 

 (The head of the radius removed to show the membranous connection of this ligament with the radius.) 



Orbicular ligament 



External lateral 

 ligament 



Posterior ligament 



FIG. 302. EXTERNAL VIEW OK THE ELBOW-JOINT. 



by the ulnar sigmoid of the radius. It is a modified form of radio-ulnar perios- 

 teum. It is an intermuscular septum between the flexor and extensor muscles 

 on the forearm. It has a posterior and an anterior surface, a radial and an ulnar 

 attached border. On its anterior surface you will find the origin of a part of the 

 flexor profundus digitorum, and the flexor longus pollicis and pronator quadratus 

 muscles. Between these you will see the anterior interosseous nerve and vessels. 



