376 LESIONS OF THE SUSPENSORY LIGAMENT. 



pastern-bone, to both, of wliicli they are united by ligaments (i and g\ 

 but much more closely tied to the pastern than to the shank. The flexor 

 tendons pass down between them through a large synovial bag, to relieve 

 them from the friction to which, in so confined a situation, they would be 

 exposed. The suspensory ligament is continued over the sesamoids, and 

 afterwards obliquely forward over the pastem to unite with the long ex- 

 tensor tendon, and downward to the perforated tendon, which it surrounds 

 and fixes in its place, and also to the smaller pastern-bone. 



It will be easy to perceive, from this description of the situation of the 

 suspensoiy ligament, why splints placed backward on the leg are more 

 likely to produce lameness than those which are found on the side of it. 

 They may interfere with the function of this ligament, or, if they are 

 large, may bruise and wound it. 



The principal action of these ligaments is "with the sesamoid-bones. 

 which they seem to suspend in their places, and they are therefore called 

 the suspensory ligaments. The pasterns (see cut, p. 360) are united to thS 

 shank in an oblique direction, difiFering in degree in the different breeds 

 of horses, and in each adapted to tho purpose for which that breed was 

 designed. The weight falls upon the pastern in the direction of the 

 shank-bone, and the pastern being set on obliquely, a portion of that 

 weight must be commimic^ted to the sesamoids. Much concussion is 

 saved by the yielding of the pasterns, in consequence of their obHque 

 direction ; and the concussion which would be produced by that portion 

 of weight vsrhich falls on the sesamoid-bones is completely destroyed, for 

 there is no bone underneath to receive it. They are suspended by this 

 ligament — an elastic ligament, which gradually yields to, and is lengthened 

 by, the force impressed upon it, and in this gradual yielding and lengthen- 

 ing, materially lessening, or generally preventing, all painfal or dangerous 

 concussion. 



If the ligament lengthens, the sesamoid-bones must descend when the 

 weight is thro^wn on them, and it would appear that they do so. K the 

 thorough-bred horse with his long pasterns is carefully observed as he 

 stands, the tuft at the fetlock will be some inches from the turf; but 

 when he is in rapid motion, and the weight is thrown violently on this 

 joint, the tuft descends and sweeps the very ground. Tliis, however, is 

 from the combined action of the fetlock and pastern-joints, and the sesa- 

 moid-bones. The sesamoids do not actually descend ; but they revolve, 

 they partly turn over. The strong ligament by which they are attached 

 to tlae pastcrn-bone acts as a hinge, and the projecting part of the bone, to 

 which the suspensory ligament is united, turns round with the pressure of 

 the weight ; so that part of the bone becomes lower. How is it raised 

 again ? This ligament, exceptionally constructed as a ligament, is elastic. 

 It yields to the force impressed upon it and lengthens ; but as soon as the 

 foot is lifted from the ground, and the weight no longer presses, and the 

 force is removed, its elastic power is exerted, and it regains its former 

 dimensions, and the sesamoid-bone springs back into its place, and by 

 ihat forcible return assists in raising the limb. 



Mr. Percivall very clearly describes this in his Lectures : ' Furthermore, 

 it seems to us that these elastic parts assist in the elevation of the feet 

 from the ground in those places in which they are called into sudden and 

 forcible action. The suspensory Hgamcnt, by its reaction, instantaneously 

 after its extension, aids the flexor muscles in bending the pastern-joints. 

 The astonishing activity and expedition displayed in the movements of the 

 race-horse at speed, seem to be referable, in part, to the promptitude with 

 which the suspensory ligament can act before the flexor muscles are duly 



