UPPER EXTREMITY AND THORAX, ANTERIOR. 311 



ing, also usually three in number, pass to the back of the 

 hand through the second, third, and fourth interosseous 

 spaces, to end in the dorsal anastomoses. 



The Tendons of the Long- Flexor Muscles of the Fin- 

 gers. 



After opening the sheath of one or two fingers and hav- 

 ing seen its formation, notice how the long flexor tendons 

 are attached to the phalanges. It will be seen that the 

 flexor sublimis tendon lies anterior to the profundus until 

 the middle of the first phalanx is reached, where it divides 

 into two parts, which pass around and reunite behind the 

 deep tendon, over the base of the second phalanx. The 

 tendons again divide and pass to their insertion into the 

 sides of the second phalanx. 



The tendons within their sheaths are surrounded by syn- 

 ovial membrane. These synovial sacs reach from the in- 

 sertion of the long flexor tendons to the heads of the 

 metacarpal bones. The synovial sheaths for the index, 

 middle, and ring fingers are distinct from the great palmar 

 synovial membrane. That for the little finger reaches up 

 to it and may connect with it. See Diag. 18. 



The great palmar synovial membrane envelopes the 

 tendons of the flexor sublimis and profundus digitorum 

 from the middle of the palm to an inch above the annular 

 ligament of the wrist. This is distinct from the synovial 

 membranes for the fingers, excepting that the sheath for 

 the little finger may open into it. 



The flexor longus pollicis is surrounded by a similar 

 synovial sheath that reaches from the insertion of the 

 tendon to a like distance above the annular ligament. 

 This sac lies in contact with, and often communicates with, 

 the above sheath for the flexors of the fingers. 



