86 



THE HUMAN BODY. 



The bone itself, Fig. 39, consists of a central nearly cylin- 

 drical portion or shaft, extending between the dotted lines x 

 and z in the figure, and two enlarged articular extremities. 



Cpi 



FIG. 39. The right humenis, seen 

 from the front. For description, see 

 text. 



FIG. 40. The humerus 

 bisected lengthwise, a, 

 marrow-cavity; 6, hard 

 bone; c, spongy bone; 

 d, articular cartilage. 



On the upper articular extremity is the rounded surface, 

 Cp, which enters into the shoulder- joint, fitting against the 



