THE MUSCLES. 167 



D. Muscles on the Hand. 

 . a . Muscles of the ball of the Thumb (thenar). 

 o. Attached to the outer side of Os Metacarpi I. or Phalanx I. 



322. 1. Abductor pollicis brevis. 



Pos. : the most superficial on the outer border of os metacarp. 

 /., separated from opponens beneath it, by a fascia. Or. : Lig> 

 carpi volare propr. (radial side) Tuber Trapezii. Ins. : Basis 

 of /. phalanx. Use. : abducts the thumb from the index finger. 



323. 2. Opponens pollicis. 



Pos. : beneath the former muscle ; internal portion only covered 

 with skin ; above flex, pollicis brevis and tendon of the longus. 

 Or. : like the former muscle. Ins. : Radial border of os metacarp. 

 I. ' Use : to draw the thumb inwards and forwards (towards the 

 little finger). 



324. , 3. Flexor pollicis brevis. 



Pos. : oblique downwards and outwards, on the external border 

 covered by abduct, brevis, on the internal united with adduct. 

 pollicis. Or. : the same as before, and from the tendinous sheath 

 of flexor radial carpi. Ins.: Os sesamoideum externum and 

 Phalanx I. (covered externally by the tendon of adduct. pollicis). 

 Use: to draw the phalanx inwards and forwards (M. opponens 

 internus). 



)3. Attached to the Ulnar side of the first phalanx of the 

 Thumb. 



325. 4. Adductor pollicis. 



Pos. : triangular, between Os metacarpi I. and //., covered by 

 the tendons of flexor dig. prof, and lumbricales. The deep 

 portion (Cap. prof und. M. flex. poll, brev.) close to the former 

 muscle; the superficial close beneath the skin. Or.: 1. Os meta- 

 carpi III. (the entire anterior border). 2. Os trapezium (anterior 

 superior part). Ins. : Os sesamoideum internum and Phalanx I. 

 Use : to draw the thumb towards the index finger. 



Nerves: (first to the fourth) medianus and ulnaris. 



b. Muscles on the ball of the little finger (hypothenar.}. At- 

 tached to the ulnar side. 



326. 5. Abductor digiti minimi. 



Pos.: on the internal (ulnar) border of Os metacarpi F., 

 covers oppon. dig. V. Or.: Os pisiforme and aponeurosis of 



