POSTERIOR ANTIBRACHIAL GROUP. 



229 



capsule of the navicular bone, termed the navicular sheath, forms 

 two cid-de-sacs, one stretching upwards almost to the inferior 

 cul-de-saG of the sesamoid sheath, the other being situated under 

 the inferior navicular ligament. A broad strengthening sheath of 

 fibrous tissue covers the plantar aponeurosis and blends with it 

 inferiorly, being attached above by two bands to the sides of 

 the first phalanx. 



Action — It flexes the joints below the carpus, and assists in 

 flexing the latter. 



Fig. S-:. 



Longitudinal section through the digit of a Horse. 

 1, The slsiu ; 2, Extensor pedis tendon ; 3, Synovial cap- 

 sule of pastern joint ; 4, Metacarpus ; 5, Perforatus 

 tendon ; 6 (omitted in cut), Perforaus tendon ; 7, Synovial 

 sheath; 8, Projecting synovial cul-de-sac; 9, Inner aspect 

 of sesamoid bone; 10, The fetlock; 11, The y-ligament; 

 12, The v-Hsanieut ; 13, Proximal phalanx ; 14, Terminal 

 portion of extensor tendon ; 15, Median phalanx ; 16, 

 Third sesamoid or navicular bone ; 17, The sensitive frog ; 

 18, Distal phalanx ; 19, The hoof ; 20, Sensitive laminae. 



ULNARIS ACCESSORIUS. 



(Flexor Accessorlus StMhnis.) 



(Fig. 81. c".) 



Situated on the posterior part of the fore-arm, between the 

 external and middle flexors of the metacarpus, it is triangular, 



