82 THE ANATOMY OF THE HOESB. 



the tendon and the anterior ligament of the fetlock, but at the front of 

 the interphalangeal joints the ligament supports directly the articular 

 synovial membranes. At the middle of the first phalanx the tendon 

 is joined on each side by a strong band that descends from the sus- 

 pensory ligament. 



Action. — It extends in succession from below upwards the interphalan- 

 geal joints and the fetlock, and finally it flexes the hock. 



The Pbeoneus (Plate 19). The tendon of this muscle emerges from 

 the thecal canal in the external lateral ligament of the tarsus, and joins 

 the tendon of the last-described muscle about the middle of the meta- 

 tarsus. 



Action. — The same as the preceding muscle. 



The Superficial Flexor (flexor pedis perforatus) (Plate 19). The 

 tendon of this muscle, after playing over the os calcis, descends on the 

 middle line of the limb to the back of the fetlf/Sc:, where it forms a 

 remarkable ring for the passage of the tendon of\ the deep flexor. Be- 

 yond this point the tendon bifurcates, and each half is inserted into the 

 upper extremity of the second phalanx, on its lateral aspect. In con- 

 nection with the tendon of this and the next muscle there is developed 

 an extensive synovial apparatus, termed the metatarso-phalangeal sheath, 

 which exactly resembles the metacarpophalangeal sheath of the fore limb 

 described at page 34. 



Action. — It flexes successively the pastern and fetlock joints ; and, 

 by its insertion into the os calcis, it is also an extensor of the hock- 

 joint. It also mechanically maintains the hock in a state of extension 

 as long as the hip and stifle joints are kept extended by their proper 

 muscles. 



The Deep Flexoe (flexor perforans) (Plate 19). The tendon of this 

 muscle, after its passage through the tarsal sheath, descends between the 

 suspensory ligament and the superficial flexor. At the fetlock it passes 

 through the ring of the last-named muscle, descends behind the digit, 

 plays over the navicular bone, and finally becomes inserted into the solar 

 surface of the os pedis {see page 42). At the upper part of the meta- 

 tarsus it receives the check band, or subtarsal ligament, which is 

 analogous to the suboarpal ligament of the fore limb, but not so strong. 

 Like the analogous structure in the fore limb, it is involved in sprain of 

 the back tendons. A little lower the deep flexor is joined on its outer 

 side by the tendon of the flexor accessorius. 



Action. — It flexes successively from below upwards the interphalangeal 

 joints and the fetlock. 



Directiotis.— For the description of the foot, which is identical in 

 the fore and hind limbs, turn to page 35. If the student has already 

 dissected the foot in a fore limb, he may proceed at once to the 

 articulations. 



