LECTURE III. 129 



hand prone or supine, for whilst the radius 

 is revolving upon its axis above, it travels 

 round the ulna below, and carries with it 

 the hand. 



The surface, which the fore-arm presents 

 to make the joint of the wrist, is an oblong 

 cavity of little depth. It is formed chiefly 

 in the radius, and partly in a piece of car- 

 tilage, continued from the end of that bone 

 over the extremity of the ulna. The side 

 surface of the radius, which is applied to 

 the ulna, is hollowed out into a semi- 

 circular cavity, receiving a corresponding 

 convex surface of the ulna; so that the 

 hand and the cartilage, continued from 

 the radius, moves round upon the end of 

 the ulna. 



The wrist is composed of eight little bones 

 placed in two rows. They form an arch 

 slightly convex on the back of the hand. 

 There are projections in front on either 

 side, forming its basis or spring. These 

 are secured together by the carpal ligament 

 which is of prodigious strength. There is 



K 



