CARPUS. 



39 



RADIUS, 



Placed on the outer side of the ulna, is slightly curved and pris- 

 matic. 



The superior extremity has a rounded head,'^ the rim of which is 

 smooth, and partly plays in the lesser sigmoid cavity. The upper 

 surface of the head has a cup-like depression for articulation with 

 the humerus. Beneath the head is the neclt^^'^ the narrowest part of 

 the bone. Below the neck, and on the inner side, is the tuhercle^^^ 

 a prominence, rough below and smooth above, for the insertion of 

 the biceps muscle. 



The body is prismatic ; anteriorly^ the surface gradually increases 

 in breadth,^" giving origin to the flexor longus pollicis, and receiving 

 the insertion of the pronator quadratus muscle. The posterior sur- 

 face is occupied by the extensor major of the thumb and the indicator 

 muscle. The external surface is curved, and has a roughness about 

 the middle for the insertion of the pronator radii teres muscle, above 

 which and below the tubercle is the space occupied by the insertion 

 of the supinator radii brevis muscle. 



The inferior extremity is thick and triangular. The surface of 

 the extremity*^ is concave and divided by a ridge. It articulates with 

 the scaphoid and lunare. Continuous with this articular surface, is a 

 smaller one on the internal aspect of the extremity for articulation 

 of the ulna. Externally there is a sttjloid process, ^^ for the connexion 

 of the external lateral ligament. 



Into a ridge contiguous to the palmar surface of the bone is in- 

 serted the supinator radii longus. Upon the dorsal view of this 

 extremity, are three large grooves, each divided into smaller ones. 

 The groove near the supinator ridge transmits the tendons of the 

 extensor ossis metacarpi pollicis and the extensor minor pollicis; the 

 groove in the middle is the broadest and most shallow, transmitting 

 the tendons of the radial extensors ; and the groove nearest the ulna 

 transmits the tendons of the extensor communis, indicator, and exten- 

 sor major pollicis. The portion of the groove occupied by the latter 

 is very deep. 



HAND. 



The hand consists of the carpus, metacarpus, and digiti. 



The CARPUS or wrist is oblong, the greatest diameter being trans- 

 verse. The dorsal surface is convex, and the palmar surface is 

 concave with four prominences. This concavity transmits the flexor 

 tendon. 



It consists of eight bones arrayed in two rows. The bones of the 

 superior row are the scap)hoid, lunare, cuneiform, and 2nsifor7n. 

 Those of the inferior row are the trapezium, trapezoides, mag- 

 7ium, and unciform. 



