MUSCLES OF THE HAND 



403 



The unci-pisiformis. — A short, thick band of muscle which runs from the pisiform to the 

 tip of the hamulus of the os hamatum (unciform) parallel with the pisohamate (pisi-unciform) 

 ligament. It is innervated by the ulnar nerve. 



The flexor carpi radialis brevis (radio-carpeus) . — An abnormal muscle found in about 5 per 

 cent, of bodies (Le Double). It arises from the lateral or the volar surface of the distal half 

 of the radius. Some of the fibre-bundles may spring from the pronator quadratus, the fascia 

 of the forearm, or the ulna. It is inserted into the carpus or metacarpus, and occasionally even 

 into the first phalanx of the index finger, etc. It is supphed by a branch of the volar interosse- 

 ous nerve. It serves to flex the wrist. It is said to represent the tibialis posterior of the leg. 



BURS^ 



B. m. flexoris carpi ulnaris. — Between the tendon of this muscle and the pisiform bone. 

 B. m. flexoris carpi radialis. — Between the tendon of this muscle and the tubercle of the 

 navicular bone. 



Fig. 374. — Synovial Sheaths of the Tendons of the Long Flexors of the Fingers 

 A. Frequent type; B. normal type; C. foetal type. (After Poirier and Charpy.) 



A bursa is often found between the tendon of the deep flexor of the index finger and the 

 carpus. This bursa is frequently in communication with the radial and ulnar tendon sheaths. 

 A bursa is also often found between the deep and superficial tendons of the index finger. 



Synovial Tendon Sheaths 

 (Figs. 366 and 374) 



Vagina tendinis m. flexoris carpi radialis. — About the tendon as it passes beneath the 

 transverse carpal Ugament. 



Vaginae tendinum mm. flexorum digitorum. — The osteo-fibrous canals of the digits are 

 lined by a synovial membrane which is reflected by means of a fold (cul-de-sac) to the tendons at 

 each end and over the vincula tendinum, in which blood-vessels and nerves for the tendons are 

 contained. The synovial cavity of the first and usually that of the fifth digit communicate 

 with those of the palm. 



In the wrist and palm two large synovial sacs may usually be recognized, although the 

 number may be raised to five or reduced to one. 



The radial sac, vagina tendinis m. flexoris pollicis longi, surrounds the long flexor tendon 

 of the thumb in the wrist and palm and usually communicates with that of the thumb. In the 

 palm a well-marked mesotendon usually extends to the deep ulnar side of the tendon from the 

 parietal layer of the sheath. 



The ulnar sac, vagina tendinum mm. flexorum communium, surrounds the tendons of the 

 long flexors of the fingers. It begins proximal to the transverse carpal ligament and extends 

 nearly or quite to the synovial sheath of the little finger on the ulnar side and on the radial 

 side to the centre of the palm. 



3. Musculature of the Hand 



(Figs. 366, 368, 375-379) 



The intrinsic muscles of the hand are taken up in the following groups: — 



a The subcutaneous muscle of the palm. 

 b The muscles of the little finger, 

 c The muscles of the thumb. 

 d The lumbrical muscles. 

 e The interosseous muscles. 



