DISSECTION OF THE ANTERIOR LIMB. 51 



suspensory ligament is a muscle which, in the evolution of the horse, 

 has undergone retrogi-essive changes, and lost its original function.* 



The Inferior Sesamoidean Ligaments. These are three in number, 

 and may be distinguished as superficial, middle, and deep. The super- 

 ficial ligament is fixed below to the glenoidal fibro-cartilage developed 

 behind the superior articular surface of the second phalanx. It ascends 

 as a flattened band behind the os suffraginis, where it is placed between 

 the middle ligament and the tendon of the deep flexor ; and, widening a 

 little, it is inserted into the base of the sesamoids and the intersesamoid 

 ligament. By cutting the ligament about its middle, and i-eflecting it 

 upwards and downwards, the middle ligament will be brought into view. 

 The middle ligament consists of a median and two lateral bands. Each 

 is fixed to the back of the os suffi-aginis, and ascends to be inserted into 

 the base of the sesamoids. This should be cut and reflected like the 

 preceding ligament, in order to expose the next. The deep ligament 

 consists of a few short fibres disposed like the letter X, and fixed, on the 

 one hand, to the upper part of the posterior surface of the os suffraginis, 

 and, on the other, into the base of the sesamoid bones. This ligament 

 supports the synovial membrane of the joint. 



The Lateral Ligaments of the fetlock-joint. Each comprises (1) a 

 superficial fasciculus connecting the lower extremity of the large 

 metacarpal bone to the upper extremity of the first phalanx ; and (2) a 

 deep fasciculus attached, on the one hand, to the large metacarpal 

 beneath the preceding, and, on the other, to the sesamoid and upper 

 extremity of the first phalanx. 



The Anterior Ligament has a membranous, four-sided form. It 

 covers the joint in front, and supports the synovial membrane by its 

 deep face ; while the extensor pedis tendon passes over its superficial 

 aspect, a synovial bursa being interposed. It is fixed above to the 

 large metacarpal, below to the first phalanx, and on each side to the 

 lateral ligament. 



Directions.- — On one side of the joint the lateral ligament and the 

 slip sent from the suspensory ligament to the extensor tendon must be 

 removed to expose the next ligament. 



The Lateral Sesamoidean Ligaments. These are not to be con- 

 founded with the lateral ligaments of the joint, by which they are 

 partly covered. Each fixes the sesamoid of its own side to the upper 

 extremity of the first phalanx. 



The Intersesamoid Ligambmt is the name given to the fibro-cartila- 

 ginous tissue which unites the two sesamoids, and with them forms 

 a pulley-like surface for the passage of the deep flexor tendon. 



The Synovial Membrane is supported in front by the anterior 



* According to Professor D. J. Cunningham (RrporU of the Challenger Expedition, Vol. V.), the 

 ligament is the altered flexor brevis of the middle digit, the corresponding muscle in the human 

 subject being tlie 1st plantar interosseous muscle. 



