56 



HUMAN ANATOMY. 



Sigmoid cavity, a shallow concavity at inner side of carpal 

 end, for articulation with ulnar head; 



Styloid process, projects obliquely downward from the ex- 

 ternal surface, for attachment by its apex to external lateral liga- 

 ment of wrist-joint, and by its base to insertion of supinator 

 longus muscle. Its outer surface is marked by two grooves for 

 extensors of thumb ; 



The posterior surface of the lower extremity is also marked 

 by three grooves from without inward for the following: ext. 

 carpi radialis longior and brevior in first, ext. secundi internodii 

 in second, and ext. indicis, ext. communis digitorum, and ext. 

 minimi digiti in third innermost. This surface has also attach- 

 ment of posterior ligament of wrist. 



FIG. 24. 



1, ulna; 2, radius; 3, fibro-cartilage; 4, 5, 6, 7, 8, metacarpal 

 bones; S, scaphoid; L, semi-lunar; C, cuneiform; P, pisiform; R, 

 trapezium; T, trapezoid; M, os magnum; U, unciform. 



It articulates with four bones humerus, ulna, scaphoid, and 

 semi-lunar. 



Its muscular attachments are nine biceps, supinator longus 

 and brevis, flexor digitorum sublimis, flexor longus pollicis, pro- 

 nator quadratus, extensor ossis metacarpi pollicis, ext. primi in- 

 ternodii pollicis, and pronator radii teres. 



Its ossific centres are three one 'each for shaft and each 

 extremity. 



THE HAND. The bones of the hand consist of eight carpus, 

 five metacarpus, and fourteen phalanges; total, twenty-seven 

 bones. 



The carpus consists of eight small bones arranged in two 

 rows first, or proximal row, from the radial side inward are 



