FOREARM AND HAND 



133 



sheath of the flexor digitorum sublimis and the flexor digitorum 

 profundus, the sheath of the flexor pollicis longus and the 

 sheath of the flexor carpi radialis. 



If the sheaths are uninjured they can be distended with air 

 by means of a blowpipe, or by fluid forced in through a syringe. 

 If they have been injured they can still be explored with a blunt 

 probe. 



Examine, first, the common sheath of the flexor tendons of 

 the fingers. Pick up a fold of the medial part of its anterior 

 wall within the forceps, and introduce the blowpipe or the 

 needle of the syringe into the base of the fold. Notice that as 



Cephalic vein 

 Lateral cutaneous nerve 



of the forearm v 

 Brachio-radialis 



Radial artery 



Medial cutaneous nerve 

 of the forearm 

 ' Median nerve 



Palmaris longus 



Radial nerve, 



superficial 



branch 



Extensor carpi 

 radialis longus 



.Ulnar artery 



Ulnar nerve 

 Medial cutane- 

 ous nerve of 



' the forearm 



^-Flexor carpi 

 ulnaris 



"Basilic vein 



Dorsal interosseous nerve 



Extensor digitorum communis 



Supinator muscle Anconaeus 



Supinator muscle Tendon of biceps brachii 



Dorsal cutaneous nerve of the forearm 



FlG. 57. Transverse section through the Proximal Third of the 

 left Forearm. 



the air or fluid enters it the sheath is distended, at first "proximally, 

 to about 25 mm. above the transverse carpal ligament, then the 

 distension passes distally, behind the transverse carpal ligament, 

 to the middle of the palm and along the little finger, as far as 

 the terminal phalanx, showing that the common flexor sheath 

 is continuous with the flexor sheath of the little finger. It may 

 also extend along the thumb, for, in a certain number of cases, 

 the sheath of the flexor pollicis longus communicates with the 

 common flexor sheath . 



The sheath of the flexor carpi radialis is not easily distended 

 because it is enclosed for the greater part of its extent in an 

 osteo-fibrous canal. It extends from a short distance proximal 

 to the transverse carpal ligament to the base of the metacarpal 

 bone of the index finger. Open it at the proximal border of the 

 i 9 a 



