XIII 



THE SKELETON 



241 



-j/t 



hd 



cn\ 



the humerus ; its proximal end or head articulates with the 

 glenoid cavity of the pectoral girdle ; the distal or lower 

 extremity has a 

 rounded articular t^^^^d 



prominence in the 

 middle, on either 

 side of which is 

 a small projection, 

 or condyle. A 

 large crest, the 

 deltoid ridge, ex- 

 tends from the 

 head of the hume- 

 rus to about the 

 middle of the ven- 

 tral side. At the 

 distal end of the 

 humerus there is 

 a ridge above 

 each of the two 

 condyles ; the in- 

 ner ridge is much 

 larger in the male 

 than in the female. 

 The skeleton 

 of the forearm 

 consists of the 

 radio-ulna, which 



Fig. 68. — Longitudinal sections of the larger bones 

 of the limbs. A, humerus; B, radio-ulna; C, 

 femur; D, tibio-fibula. t//, condyle; / foramen 

 for artery; yf, fibula; //rf, head; w, marrow; ol, 

 olecranon ; /, bony partition ; ra, radius ; sk, 

 shaft; //, tibia; ul, ulna. (After Parker and 

 Parker.) 



from the fusion of 



arises 



ongi- 



two 



nally distinct bones, the radius and ulna, the line of 

 union between which is very marked, especially at the distal 

 end. The postaxial or ulnar part is produced backward at 

 its upper end to form the olecranon, which fits over the 

 rounded end of the humerus at the joint of the elbow. The 



