66 THE SURGICAL ANATOMY OF THE HORSE 



moidean ligament. Posteriorly it is smooth, and in the recent state is 

 covered by fibro-cartilage on which the tendon of the perforans muscle 

 plays. 



The outer surface is roughened and presents a depression. This 

 surface affords attachment to one of the divisions of the lateral ligament 

 of the fetlock joint, to the lateral sesamoidean ligament, and to a slip 

 from the great suspensory ligament. 



The base of the bone is roughened, and to it the several divisions ot 

 the inferior sesamoidean ligament are attached. 



Each sesamoid bone ossifies from a single centre. 



The sesamoid bones are not infrequently fractured. The cause of 

 the fracture is somewhat obscure. Cadiot maintains that fracture of the 

 sesamoid bones of the fore limbs may be due to their being struck 

 during progression by the shoes of the corresponding hind feet. 

 Williams and others have frequently found the bones to be fractured 

 after galloping in deep sand. Small pieces of the bones are often found 

 to be broken off near the insertions of the ligaments, in which cases the 

 bones have usually been found to be very brittle, so that when undue 

 strain has been thrown upon the ligaments the bones have proved to be 

 less resistant than the ligaments, and portions have consequently broken 

 off. 



Occasionally the bones split transversely below the insertions of the 

 slips from the suspensory ligament. In these cases the fetlock sinks, 

 and an interval may be readily felt between the fractured pieces if the 

 case be seen soon after injury. 



If it is decided to treat (as is frequently necessary in animals re- 

 quired for breeding purposes), the animal should be placed in slings 

 immediately, and a dry bandage applied. The joint is then enclosed in 

 a plaster case, which should remain on for about twelve weeks. After 

 its removal the joint is blistered. Treatment, however, is rarely success- 

 ful in rendering the patient fit for work, and, as a rule, permanent 

 lameness and stiffness of the fetlock remain. 



