328 DISEASES OF THE HOBSB. 



FEACTURE OP THE SESAMOID BONES. 



This lesion has been considered by veterinarians, erroneously, we 

 think, one of rare occurrence. We believe it to be more frequent 

 than has been supposed. Many observations and careful dissections 

 have convinced us that fractures of these little bones have often been 

 mistaken for specific lesions of the numerous ligaments that are 

 implanted upon their superior and inferior parts, and which have 

 been described as a "giving way" or "breaking down" of these 

 ligaments. In my post-mortem examinations I have always noted 

 the fact that when the attachments of the ligaments were torn from 

 their bony connections minute fragments of bony structure were also 

 separated, though we have failed to detect any diseased process of 

 the fibrous tissue composing the ligamentous substance. 



Cause. — From whatever cause this lesion may arise, it can hardly 

 be considered as of a traumatic nature, no external violence having 

 any apparent agency in producing it, and it is our belief that it is 

 due to a peculiar degeneration or softening of the bones themselves, a 

 theory which acquires plausibility from the consideration of the 

 spongy consistency of the sesamoids. The disease is a peculiar one, 

 and the suddenness with which different feet are successively attacked, 

 at short intervals and without any obvious cause, seems to prove the 

 existence of some latent, morbid cause which has been unsuspectedly 

 incubating. It is not peculiar to any particular class of horses, nor 

 to any special season of the year, having fallen under our observation 

 in each of the four seasons. 



Symptoms. — ^The general fact is reported in the history of a 

 majority of cases that it makes its^ appearance without premonition 

 in animals which, after enjoying a considerable period of rest, are 

 first exercised or put to work, though in point of fact it may manifest 

 itseH while the horse is still idle in his stable. A hypothetical case, 

 in illustration, will explain our theory: An animal which has been 

 at rest in his stable is taken out to work, and it will be presently 

 noticed that there is something unusual in his movement. His gait 

 is changed, and he travels with short, mincing steps, without any of 

 his accustomed ease and freedom. This may continue until his return 

 to the stable, and then, after being placed in his stall, he will be 

 noticed shifting his weight from side to side and from one leg to 

 another, continuing the movement until rupture of the bony structure 

 takes place. But it may happen that the lameness in one or more of 

 the extremities, anterior or posterior, suddenly increases, and it 

 becomes evident that the rupture has taken place in consequence of 

 a misstep or a stumble while the horse is at work. Then, upon com- 

 ing to a standstill, he will be found with one or more of his toes 

 turned up ; he is unable to place the affected foot flat oii the ground. 

 The fetlock has dropped and the leg rests upon this part, the skin of 



