exteiul the third 



DISSKCTION OF THE ANTERIOR LIMI!. 33 



The tendon is tinully inserted into the pyramidal process of the os 

 pedis. 



Arti,>n.~-T\iQ first action of the muscle is t( 

 phalanx on the second, and then 

 the second on the first. When con- 

 traction is continned, it produces 

 successively extension of tlie fet- 

 lock and of the carpus. 



Directions. — The tendons on the 

 back of the metacarpus and diyit 

 must next be dissected ; and as " ' 

 a preliminary step, the carpal,, 

 and metacarpo-phalangeal sheaths 

 formed in connection with these 

 tendons should be examined. 



The Carpal Sheath (Fig. 1) is the 

 tubular passage through which the 

 flexors of the digit are transmitted 

 behind the carpus. It is formed 

 in front by the back of the carpus 

 covered by the posterior common 

 ligament of that joint. Behind it 

 is bounded in its outer third bv 

 the pisiform bone, and in its inner' 

 t\YO-thirds by a strong fibrous liand 

 representing the anterior annti/ar 

 ligament of the human wrist. This 

 baud stretches like an arch from 

 the pisiform bone to the inner side 

 of the carpus. It is continuous 

 above with the deep fascia on the 

 liack of the fore-arm, of which it 

 may )ie considered a thickened 

 portion ; and below it becomes 

 thinner, and is continued as the 

 fascia on the back of the ineta- 

 carjjus {palmar fascia of man). 

 The carpal sheath is provided with 



Dl.SSECTION OF THE jVlETACARPrs AND DtGIT-, .SHOWING THE TeNDONS AND THEIR 8yK0\-1AL 



Sheaths (Chauveau). 

 1. Synovial bursa of the extensor metacarpi magniis ; 2. Superior ciU-de-sac, or pouch, of the 

 synovial membrane of the carpal sheath ; '2\ :^\ Inferior part of the same ; 3. Pouch of the radio- 

 Cixrpal synovial membrane, appearing as a hernia between the posterior common ligament and the 

 outermost radio-carpal ligament ; 4. Synovial bursa of the extensor pedis ; 5. Protrusion of the 

 synovial membrane of the fetlock-joint ; U, 7, S. Sui)erior, middle,- and inferior pouches of the 

 synovial membrane of the metacarpo-phalangeal sheath ; 9. Inferior extremity of the same, exposed 

 by the removal of the reinforcing sheath of the perforans tendon ; E. S. E.xtensor sufFraginis ; S. L. 

 Bubcarpal ligament ; E. P. Extensor pedis ; S. S. Superior sesamoidean (suspensory) ligament ; F. 

 Pa. Flexor perforans ; F. Pt. Flexor perforatus. 



D 



Fig. 1 



