276 DISSECTION OF THE HAND. 



The third is directed to the radial side of the index finger, and gives a 

 branch to the most external lumbrical muscle. 



The fourth furnishes a nerve to the second lumbrical muscle, and di- 

 vides to supply the contiguous sides of the fore and middle fingers. 



The Jifth, like the fourth, is distributed by two branches to the opposed 

 sides of the middle and ring fingers : it communicates with a branch of the 

 ulnar nerve. 



On the fingers. On the sides of the fingers the nerves are superficial to 

 the arteries, and reach to the lust phalanx, where they end in filaments for 

 the ball and the pulp beneath the nail. In their course forwards the nerves 

 supply chiefly tegumentary branches : one of these is directed backwards 

 by the side of the metacarpal phalanx, and after uniting with the digital 

 nerve on the back of the finger (p. 262), is continued to the dorsum of the 

 last phalanx. 



Dissection. The tendons of the flexor muscles may be followed next to 

 their termination. To expose them the ulnar artery should be cut through 

 below the origin of the profunda branch ; and the small superficial volar 

 branch (of the radial) having been divided, the palmar arch is to be thrown 

 towards the fingers. The ulnar and median nerves are also to be cut be- 

 low the annular ligament, and turned forwards. 



A longitudinal incision is to be made through the centre of the annular 

 ligament, without injuring the small muscles that arise from it, and the 

 pieces of the ligament are to be thrown to the sides. 



Finally the sheaths of the fingers may be opened for the purpose of ob- 

 serving the insertion of the tendons. 



FLEXOR TENDONS. Beneath the annular ligament the tendons of the 

 deep and superficial flexors are surrounded by a large and loose synovial 

 membrane, which projects upwards into the forearm and downwards into 

 the hand, and sends an offset into the digital sheath of the thumb and that 

 of the little finger. 1 



Flexor sublimis. The tendons of the flexor sublimis are superficial to 

 those of the deep flexor beneath the ligament ; and all four are nearly on 

 the same level, instead of being arranged in pairs, as in the forearm. 

 After crossing the palm of the hand they enter the sheath of the fingers 

 (fig. 82, e), and are inserted each by two processes into the margins of the 

 middle phalanx, about the centre. When first entering the digital sheath, 

 the tendon of the flexor sublimis conceals that of the flexor profundus ; 

 but near the front of the first phalanx it is split for the passage of the 

 tendon of the latter muscle. 



Dissection. To see the tendons of the deep flexor and the lumbrical mus- 

 cles, the flexor sublimis must be cut through above the wrist, and thrown 

 towards the fingers. Afterwards the areolar tissue should be taken away. 



Flexor profundus. At the lower border of the annular ligament the ten- 

 dinous mass of the flexor profundus is divided into four pieces, though in 

 the forearm only the tendon of the forefinger is distinct from the rest. 

 From the ligament the four tendons are directed through the hand to the 

 fingers, and give origin to the small lumbricales muscles. At the root of 

 the fingers each enters the digital sheath with a tendon of the flexor sub- 

 lirnis, and having passed through that tendon, is inserted into the base of 

 the last phalanx. 



1 Theile refers the notice of this fact to M. Maslieurat-Lagdmard, in No. 18 of 

 the "Gazette Me"dicale," for 1839. 



