THE SUSPENSORY LIGAMENTS. 273 



At the back of the shank just below the knee, and in the space between the two 

 splint-bones, is found an important ligament, admirably adapted to obviate concus- 

 sion. It orio-inates from the head of the shank-bone, and also from the heads of the 

 splint-bones ; then, descending down the leg, it fills the groove between the splint- 

 bones, but is not attached to either of them. A little lower down it expands on either 

 side, and, approaching the pasterns, bifurcates, and the branches are inserted into two 

 little bones found at the back of the upper pastern, one on each side, called the sessa- 

 moid bones. (See page 272, and in this cut which represents the pastern and foot, 

 sawn through the centre.) The bones form a kind of joint both with the lower head 

 of the shank-bone and the upper pastern-bone, to both of which they are united by 

 ligaments (t and g), but much more closely tied to the pastern than to the shank. 

 The flexor tendons pass down between them through a large mucous 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 sessamoids, and afterwards obliquely 

 forward over the pastern to unite with the long extensor 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 suspensory 

 ligam.ent, why splints placed backward on the leg are more likely to produce lame- 

 ness than those which are found on the side of it. They may interfere with the motion 

 of this ligament, or, if they are large, may bruise and wound it. 



The principal action of these ligaments is with the sessamoid bones, which they 

 seem to suspend in their places, and they are therefore called the suspensory liga- 

 ments. The pasterns (see cut p. 272) are united to the shank in an oblique direction, 

 differing in degree in the different breed of horses, and in each adapted to the pur- 

 pose 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 

 weiorht must be communicated to the sessamoids. Much concussion is saved by the 

 yielding of the pasterns, in consequence of their oblique direction ; and the concus 

 sion which would be produced by that portion of weight which falls on the sessa- 

 moid 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 

 lengthening, materially lessening, or generally preventing, all painful or dangerous 

 concussion. 



If the ligament lengthens, the sessamoid bones must descend when the weight is 

 thrown on them, and it would appear that they do so. If 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. This, 

 however, is from the combined action of the fetlock and pastern-joints, and the sessa- 

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

 turn over. The strong ligament by which they are attached to the pastern-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 be- 

 comes lower. How is it raised ag-ain ? This ligament, strangely 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 

 f(5rre is removed, its elastic power is exerted, and it regains its former dimensions, 

 and the sessamoid-bono springs back into its place, and by that forcible return assists 

 in raising the limb.* 



It may be supposed that Mgaments of this character, and discharging such functions, 



* Mr. Percivall very clearly describes this : " Furthermore it seems to us that these elastic 

 parts assist in the elevation of the feot from the ground in those paces in which they are called 

 into sudden and forcible action. The suspensory licrament. by its reaction, instantaneously 

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

 activity and c.\p'^di:ion 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 

 .1exor muscles are duly prepared ; the latter, wo should say catch, as it were, and then direct 

 the limb fitst snatched from the ground by the powers of elasticity." — Percivall's Tiecturea 

 oij the Veterinary Art, vol. i. p. 334. 



