SHOULDER, ./AM/, ! OKI-: ARM, A.\D HAND. 



163 



2. The flexor brevis pollicis, Ilexes first phalanx. 



3. The opponens pnllicis, acts on metacarpal. 



4. The adductor pollicis, adducts the first phalanx. 



The abductor pollicis (Fig. I 1O) is easily isolated. Cut the same near its 

 insertion, and turn it aside so as to preserve the nerve-supply. (Figs. 109 and 

 114.) This muscle arises from the bone at the base of the thumb the os 

 trapezium and the annular ligament. It is inserted into the base of the thumb, 

 proximal phalanx. (Fig. 109.) 



The opponcns pollicis is inserted into the whole length of the thumb meta- 

 carpal bone. (Fig. 109.) It arises from the os trapezium and annular ligament. 

 (Fig. 114.) 



Flexor carpi 



uliiariB 



Pronator quad rat u 



Abductor polllcia 



Outer head of flexor 

 brevis polliciit 



Inner head of flexor 



brevis pollicis first 



division) 



Opponens pollioiB 

 Inner head of flexor 



brevis pollieiB (third 



division) 



Inner head of flexor 

 brevis pollicis (second 

 division) 



Adductor pollicis 



_ Dorsal interosseous 



Third palmar 

 inter oaeeous 



Fourth dorsal 

 mteros8eous 

 Second palmar interoeseous 



Third dorsal intsrosseous 



First palmar interosseoua 



Second dorsal iEteroaueous 



FIG. 114. THE PRONATOR QUADRATUS AND DEEP VIEW OF THE PALM. 



Tlic flexor brci-is pollicis has two heads, and between these two heads lies the 

 tendon of the flexor longus pollicis muscle. The outer, or more superficial head 

 ( Fig. 114), arises from the os trapezium and annular ligament, and is inserted 

 into the base of the first thumb phalanx on the outer side. (Fig. 109.) The 

 deep or inner' head has two parts : (i) A small part that arises from the first 

 metacarpal bone ; (2) a large part that arises from the annular ligament, the os 

 magnum, and the second and third metacarpals. (Fig. 1 14.) 



This latter is described by some authors as the oblique part of the adductor 

 pollicis. The deep part of the flexor brevis is inserted into the base of the first 

 thumb phalanx on the inner side. 



