THE POSTERIOR RADIO ULNAR REGION 



485 



pollicis, its tendon passing through the same groove on the outer side of the 

 styloid process, to be inserted into the basj of the first phalanx of the thumb. 



Relations. The same as those of the Extensor ossis metacarpi pollicis. 



The Extensor longus pollicis (ra. extensor pollicis longus) is much larger 

 than the preceding muscle, the origin of which it partly covers in. It arises 

 from the outer part of the posterior surface of the shaft of the ulna, below the 

 origin of the Extensor ossis metacarpi pollicis, and from the interosseous mem- 

 brane. It terminates in a tendon which passes through a separate compartment 



Tendon of Ext. 

 carpi rad. longior 



Tendon of Ext. 

 communis digitorum 



Tendon of Extensor indicis 



First Lumbrical 



Ligamenta brevia 



Tendon of Ext. ossis 

 metacarpi pollicis 



Trapezium 



Radial artery 



Tendon of Ext. brevia pollicis 



Tendon of Ext. long, pollicis 



Flexor sublimis digiiorum 

 Flexor prof undus digitorum 



Ligamenta longa 



FIG. 363. The tendons attached to the right index finger. 



in the annular ligament, lying in a narrow, oblique groove at the back part of 

 the lower end of the radius. It then crosses obliquely the tendons of the Extensor 

 carpi radialis longior and brevior, being separated from the other Extensor tendons 

 of the thumb, by a triangular interval, in which the radial artery is found, and is 

 finally inserted into the base of the last phalanx of the thumb. 



Relations. By its superficial surface, with the same parts as the Extensor ossis metacarpi 

 pollicis; by its deep surface, with the ulna", interosseous membrane, the posterior interosseous 

 nerve, radius, the wrist, the radial vessels, and metacarpal bone of the thumb. 



The Extensor indicis (m. extensor indicis proprius) (Figs. 359 and 362) is 

 a narrow^, elongated muscle placed on the inner side of, and parallel with, the 



