SYSTEMATIC SYNTHESIS OP TISSUES INTO ORGANS. 229 



the lower arm ; it is furnished with a hook-like process 

 that fits around the lower end of the humerus, and, when 

 the bone is straightened, matches into an excavation in 

 the back part of the humerus. It is also furnished with 

 a process on the lower side of the joint that matches an 

 excavation on the front of the humerus ; thus, the mo- 

 tions of the ulna can be backward and downward nearly, 

 but not quite, to a straight line with the humerus, and 

 forward and upward nearly parallel to, but always at an 

 angle with, it. 



397. THE RADIUS is THE NAME of another bone in 

 the lower arm, situated by the side of the Ulna, and just 

 resting against the lower end of the humerus, but form- 

 ing no part of the elbow-joint; a ligament confines it to 

 its place, but allows it to revolve partly. 



FIG. 173. 



FIG. 172. 



Fig. 172, ulna and radius : 4, point of elbow (olecra- 

 non); 5, process in front of joint (coronoid); 2, cavity 

 fitting around lower end of humerus ; 3, joint of 11 with 

 ulna ; 15, surface of E that turns over on to 8 of the U\ 

 13, attachment of biceps. 



Fig. 173, upper end of ulna : 1, olecranon ; 2, cavity ; 

 3, coronoid ; 4, ligament binding radius in 5, the cavity in which 11 of 172 

 turns. 



398. THE ULNA AND RADIUS are connected through- 

 out their length by a ligament, the surfaces of which af- 

 ford much space for tfte attachment of muscles. 



399. At their lower extremities THE RADIUS is AT- 

 TACHED TO THE ULNA in such a manner that it can turn 

 over on to it, much as the lid of a book turns over. 



400. This ROTARY JOINT OF THE LOWER ARM is the 



most ingenious one in the Body, and the most useful at 



897. Of what ? Describe Fig. 172. Fig. 173. 398. What said of ? 

 9. How ? 400. What is ? 



