OSTEOLOGY. 2 7 



The superior extremity has — 



A convex head for articulation with the glenoid cavity. 



An external ox great tuberosity, which shows a summit, crest and 

 convexity. 



An internal or small tuberosity, receiving the insertion of the 

 subscapularis. 



The bicipital groove, between the two tuberosities, and running 

 downward. It consists of two grooves and a central elevation, 

 which allow the passage of the fibro-cartilaginous tendon of the 

 biceps. 



The inferior extremity has — 



A transversely elo7igated articular process, convex from before 

 backward, and divided into two, a larger internal one, the trochlea, 

 and a smaller external, the condyle ; behind and above this a de- 

 pression, which receives the beak of the olecranon in extension, 

 called the olecranon fossa. In front and to the inner side, another, 

 the coronoid fossa, which receives the coronoid in flexion. On 

 the inner side, above the trochlea, the epi-trochlea, a bony eleva- 

 tion. On the outer side, in the same position, the epi-condyle. 



Articulations, 3. 



Scapula, radius and ulna. 



THE FOREARM. 



This consists of two bones, the radius and ulna, united into 

 one at an early age. 



THE RADIUS. 



The I'adius is a long bone articulating above with the humerus, 

 and below with the carpus. 



It shows — 



An external 2.w^ internal border, thick and rounded. 



An anterior surface, smooth and convex. 



A posterior surface, concave, with a rough, triangular surface 

 from the upper to the lower fourth, for attachment of the interos- 

 seous ligament ; above, a transverse groove, to form the radio- 

 ulnar arch, a rough spot at its inferior third. 



The superior extre??iity shows — 



An articular suiface, smooth and concave, divided into a 

 double depression externally, a middle ridge, and an internal 

 depression. 



A well-marked external tuberosity. 



