164 



THE STRUCTURE OF THE HORSE 



(see fig. 25, 10, p. 179). The obvious mechanical use of 

 this ligament (as it has now become) is to prevent 

 over-extension of the fetlock-joint. If it is ruptured or 

 stretched the animal becomes what is termed in veteri- 

 nary language 'broken down' — i.e., the fetlock-joint 

 sinks down, and the hoof has a tendency to tilt forwards 

 and upwards. 



1 The most interesting point, however, in connec- 

 tion with this structure is that it bears its history on 

 its face. Almost invariably two thin streaks of stri- 

 ated muscular fibre are to be found on its superficial 

 surface, leading down to its two inferior divisions. 

 Again, on examining its deep surface, two very distinct 

 strands of pink fleshy tissue are always observed ex- 

 tending throughout the entire length of the ligament. 

 These consist in each case of short, oblique, striated 

 fibres converging towards the middle line of the liga- 

 ment. They represent those muscular fibres of the two 

 heads of the flexor brevis which have not yet been con- 

 verted into fibrous tissue. On making a thin micro- 

 scopic transverse section the muscular fibres are seen 

 to sink deeply into its substance, but it is altogether 

 so small in amount in comparison with the bulk of 

 the ligament that it can exercise no function what- 

 ever.' 1 



1 D. J. Cunningham, Zoology of the Voyage of H.M.S. Challenger, 

 Part XVI. Report on the Marsupialia, p. 95. 



