194 



HEALTH AND DISEASE 



Humerus (figs. 298, 299). The humerus, or arm-bone, is a bone of 



great thickness and density, and is 

 situated between the scapula or 

 blade -bone above and the radius 

 and the ulna below. Externally 

 the body of the bone is deeply 

 grooved by the furrow of torsion, 

 and presents at about its upper 

 third a somewhat bold pointed pro- 

 jection, the external tuberosity. On 

 the internal surface it presents a 

 rounded prominence, the internal 



Fig. 297. Scapula (Inner Surface) 



' Coracoid Process. 5 Glenoid Cavity. 3 Cartilage 

 of Prolongation. 



tuberosity, into which important 

 muscles gain insertion. 



On the upper extremity are the 

 broad rounded head and several bony 

 prominences. The former, situated 

 behind, is coated with cartilage, and 

 articulates with the glenoid cavity of 

 the scapula or blade-bone to form the 

 shoulder-joint. The latter comprise a 

 double projection of bone on the outer 

 side, termed the great trochanter. On 

 the inner side is the small trochanter 



or tubercle, and between them a prominence which divides the upper 

 front portion of the humerus into two grooves (bicipital groove). The 



Fig. 298. Humerus (Front Aspect) 



' Bicipital Groove. s Small Trochanter. 

 3 Great Trochanter. 4 External Tuberosity. 

 6 Shaft with Furrow of Torsion. 6 Epitrochlea 

 or External Condyle. 7 Supra-eondyloid Fossa. 

 8 Epicondyle or Internal Condyle. 



