FOREARM AND HAND 123 



turn out to be uninjured, a very striking demonstration may be obtained 

 by inflating them with air by means of the blowpipe. The apertures 

 through which the air is introduced should be made at the proximal margin 

 of the transverse ligament. 



It is said that the mucous sheath which invests the tendons 

 of the flexor digitorum sublimis and flexor digitorum profundus 

 is divided by a vertical partition into two compartments, and 

 that the lateral of these communicates, by means of a small 

 aperture near the upper border of the transverse carpal liga- 

 ment, with the mucous sheath of the tendon of the flexor 

 pollicis longus. 



Flexor Tendons. Open the carpal tunnel by making a 

 vertical incision through the transverse carpal ligament at its 

 middle. The arrangement of the flexor tendons can now be 

 studied, and the mucous sheath dissected from the surface of 

 each. The tendon of the flexor pollicis longus occupies the 

 lateral part of the canal, and gaining the palm turns laterally 

 to reach the phalanges of the thumb. The four tendons of 

 the flexor sublimis are arranged in pairs behind the transverse 

 carpal ligament; those for the little and the index fingers lying 

 dorsal to those for the ring and middle fingers. Of the 

 tendons of fat flexor profundus ^ only that for the index finger is 

 distinct and separate ; the other three, as a rule, remain 

 united until they emerge from under cover of the transverse 

 carpal ligament. 



In the central compartment of the palm the flexor tendons 

 diverge from each other, and two, viz. one from the flexor 

 sublimis, and one from the flexor profundus, go to each of 

 the four fingers. From the tendons of the flexor profundus 

 the lumbrical muscles take origin, and these, with the common 

 volar digital nerves and arteries, will be seen occupying the 

 intervals between the tendons as they approach the roots of 

 the fingers. 



In the fingers the two flexor tendons run distally upon 

 the -velar aspects of the phalanges, and are held in position 

 by the flexor sheaths. These, therefore, must be studied be- 

 fore the insertions of the tendons can be examined. 



Flexor Sheaths. Immediately subjacent to the skin, 

 the superficial fascia and the proper volar digital arteries and 

 nerves lie the fibrous sheaths which bind the flexor tendons 

 to the volar surfaces of the phalanges and to the volar 

 accessory ligaments of the metacarpo-phalangeal and inter- 



