76 



DISSECTION OF THE HAND. 



origin, 

 insertion, 



relations, 

 and use. 



Tendon of 

 long flexor 

 of thumb ; 



its insertion. 



Dissection 

 of deep 

 arch, 



and of 

 muscles of 

 thumb and 

 little linger. 



Five mus- 

 cles to 

 thumb. 



Abductor : 



attach- 

 ments, 



relations, 



and use. 

 Dissection. 



ligament ; the outer two springing each from a single tendon, while 

 the inner two are connected each with two tendons. They are 

 directed to the radial side of the fingers, to be inserted into the ex- 

 panded extensor tendon on the dorsal aspect of the metacarpal phalanx 

 (%. 30, c). 



These muscles are concealed for the most part by the tendons 

 and vessels that have been removed ; but, as already seen, they are 

 subcutaneous for a short distance between the processes of the 

 palmar fascia. 



Action. The lumbricales assist in bending the metacurpo- 

 phalangeal joints, and, by their insertion into the extensor tendons, 

 they straighten the interphalangeal joints. 



Tendon of the flexor longus pollicis. Beneath the annular ligament 

 this tendon is external to the flexor profundus ; and in the hand it 

 inclines outwards between the outer head of the flexor brevis and 

 the adductor obliquus pollicis (fig. 31), to be inserted into the last 

 phalanx of the thumb. The common synovial membrane surrounds 

 it beneath the annular ligament, and sends a prolongation, as before 

 said, into its digital sheath. 



Dissection (fig. 31). The deep palmar arch with the deep 

 branch of the ulnar nerve, and some of the iuterosseous muscles, 

 will come into view if the flexor profundus is cut above the wrist, 

 and thrown with the lumbricales muscles towards the fingers ; but 

 in raising the tendons the student should preserve the fine nerves 

 and vessels entering the inner two lumbrical muscles. 



The short muscles of the thumb and little finger are next to be 

 prepared. Some care is necessary in making a satisfactory separation 

 of the different small thumb-muscles ; but those of the little finger 

 are more easily defined. 



SHORT MUSCLES OF THE THUMB (fig. 31). These are five in 

 number. The most superficial is the abductor pollicis (A) ; and 

 beneath it is the opponens pollicis (B), which will be recognised by 

 its attachment to the whole length of the metacarpal bone. To the 

 inner side of the last is the short flexor (c) ; below this and below 

 the tendon of the long flexor is the adductor obliquus (c') ; and the 

 wide muscle coming from the third metacarpal bone is the adductor 

 transversus (D). 



The ABDUCTOR POLLICIS (A) is the most superficial muscle, and 

 is about an inch wide. It arises from the upper part of the annular 

 ligament 011 the outer side, and from the tuberosity of the scaphoid 

 bone ; and it is inserted into the base of the first phalanx of the 

 thumb at the radial margin, sending a slip to join the tendon of the 

 extensor longus pollicis. 



The muscle is subcutaneous, and rests on the opponens pollicis ; 

 it is joined at its origin by a slip from the tendon of the palmaris 

 longus, and often by one from the extensor ossis metacarpi pollicis. 



Action. The abductor pollicis moves the thumb in. the direction 

 of its radial border away from the index finger. 



Dissection. The opponens pollicis will be seen on cutting 

 through the abductor. To separate the muscle from the short 



