THOEACIC LIMBS 589 



arcuate outer edge of the distal articular surface. From side to side 

 the distal surface is strongly concave, the outer part facing in great 

 measure inward. From before backward its inner half is concave, 

 while the outer half is distinctly convex. It articulates with the 

 proximal surface of the scapho-lunar bone. 



The styloid process is a blunt conical tubercle extending several 

 millimetres below the distal articular surface. Its outer posterior 

 surface is rough, and its base forms the partition between the grooves 

 for the extensor ossis metacarpi pollicis and extensor carpi radialis. 

 Its outer anterior surface, which is triangular N and rough, begins at 

 the abrupt termination of the outer border of the extremity. Its 

 inner lower surface is smooth, and forms the saddle-shaped outer part 

 of the distal surface which fits in the shallow concavo-convex surface 

 on the upper surface of the scapho-lunar. 



FIG. 450. 



For EXTENSOR COM- 



MUNIS DIGITORUM 

 Far EXTENSORES CARPI RADIALIS f\^^~^\ I FffT EXTENSOR INOICIS. 



LONGIOR ana BREVIOR. 



FOr EXTENSOR OSSIS META- 



CARPI POLLICIS. ' .VHBH \ im\ i. \ ' UZna. 



Outer Border. 



With Scapho-lunar. 

 LEFT RADIUS AND ULNA, LOWER ENDS. 



Nomenclature. The word radius was introduced into osteology 

 by Celsus. It was applied to any rod-like object. Galen called the 

 radius kerkis, a word used by Homer to denote a weaver's shuttle. 

 The colloquial German word is die Speiche ; the French use le radius. 



Determination. If the radius be held with the anterior concave 

 surface uppermost and the head toward the student, the styloid process 

 will be on the side to which the bone belongs. 



Articulation. The radius articulates with the humerus, the ulna, 

 the scapho-lunar, and slightly with the pisiform. 



Muscular Attachments. To the anterior surface are attached 

 the insertion of the supinator brevis, and the fibres of origin of the 

 radio-ulnar head of the flexor profundus digitorum and the pro- 

 nator quadratus ; to the anterior border, the insertion of the supi- 

 nator brevis, the pronator teres, and the supinator longus ; to the 

 external and posterior surfaces, the supinator brevis and fibres of 

 origin of the extensor ossis metacarpi pollicis; to the internal border, 



