308 A MANUAL OF ANA TOMY. 



of the last two sets of phalanges through their connections 

 with the common extensor aponeurosis. 



DISSECTION. 



Divide the abductor pollicis and reflect its portions ; cut through the annu- 

 lar ligament, note the relations of the tendons of the long flexor muscles and 

 the median nerve, also the extension up under the ligament of the synovial 

 sac of these tendons. 



Divide the ulnar artery and nerve just below their deep palmar branches; 

 sever the connections of the superficial arch at the base of the thumb and turn 

 the digital nerves and arteries and the tendons of the sublimis and profundus 

 digitorum, with the lumbricales, below the web of the fingers. 



Clean the rest of the thumb and little- finger muscles, the deep palmar arch 

 and its branches. 



The Inner Head of the Plexor Brevis Pollicis. (Adduc- 

 tor Obliquus.) Fig. 67. 



Origin. From the sheath of radial flexor of carpus, os 

 magnum, and bases of second and third metacarpal bones. 



Insertion. Into the inner side of the base of the first 

 phalanx of the thumb with the adductor pollicis ; and by a 

 separate fasciculus into the outer side of the base of the 

 same bone with the outer head of the flexor brevis pollicis. 



Nerve Supply. By the deep branch of the ulnar from 

 the eighth cervical nerve. 



Action. To adduct and flex the carpometacarpal and 

 metacarpophalangeal articulations acting with the adductor 

 pollicis muscle. 



Adductor Pollicis. (Adductor Transversus^ Fig. 67. 



Origin. From the lower two-thirds of the front of the 

 third metacarpal bone. 



Insertion. Into the inner side of the base of the first 

 phalanx of the thumb, with the inner head of the flexor 

 brevis muscle, and into the inner portion of the aponeurosis 

 of the extensor longus pollicis. 



