I2 4 



THE UPPER EXTREMITY 



phalangeal joints. Each fibrous sheath consists of a number 

 of parts of which the two strongest, the digital vaginal 

 ligaments, lie opposite the bodies and are attached to the 

 margins of the first and second phalanges. Such strong bands 

 placed opposite the metacarpo-phalangeal and interphalangeal 

 joints would seriously interfere with their movements, therefore, 

 in these regions weaker transverse bands, the annular liga- 

 ments, are formed. In addition cruciate bands the cruciate 



ligaments are often found, 

 intervening between the 

 annular ligaments and the 

 stronger portions of the 

 sheaths. The fibrous sheath, 

 together with the phalanges 

 and the volar accessory liga- 

 ments of the metacarpo- 

 phalangeal and interphalan- 

 geal joints, forms, in each 

 finger, an osteo-fibrous canal, 

 in which are enclosed the 

 tendons of the flexor digi- 

 torum sublimis and of the 

 flexor digitorum profundus 

 together with their surround- 

 ing mucous sheath. 



The fibrous sheaths in 

 front of one or more of the 

 fingers may now be opened. 

 FIG. 49. Diagram to illustrate the ar- They will be seen to be lined 



rangement of the Synovial Sheaths of b a mucous s heath, which is 

 the Flexor Tendons. J 



reflected over the enclosed 



tendons so as to give each a separate investment. The mucous 

 sheath of the little finger has been seen to be a direct pro- 

 longation from the common mucous sheath of the flexor 

 tendons ; the other three are distinct from this, and are 

 carried proximally into the palm. They envelop the tendons 

 of the ring, index, and middle fingers, as far as a line drawn 

 across the palm immediately proximal to the heads of the 

 metacarpal bones. 



If the flexor tendons be raised from the phalanges certain 

 mucous folds will be noticed connecting them to the bones. 

 These are termed the vincula tendina. Of these we dis- 



