260 OPERATIONS ON BONES. 



cause, seems to prove the existence of some latent morbid cause 

 which has been unsuspectedly iacubatiag. It is not peculiar to 

 any particular class of horses, nor to any special season of the 

 year, having fallen under our observation ia each of the four 

 seasons. The general fact is reported ia the history of a majority 

 of cases that it makes its appearance without premonition ia 

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

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

 manifest itself whUe the horse is stUl 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 wlU be presently noticed that there is something un- 



FlG. 885.— Fracture of Os SesamoldB. 



usual in his movement. His gait is changed, and he travels with 

 short, mincing steps, without any of his accustomed ease and free- 

 dom. This may continue until his return to the stable, and then, 

 after being placed in his stall, he wiU be noticed shifting his 

 weight from side to side and from one leg to another, continuing 

 the movement untU rupture of the bony structure takes place. 

 But it may happen that the lameness in one or more of the ex- 

 tremities, anterior or posterior, suddenly increases, and it be- 

 comes evident that the rupture has taken place in consequence of 

 a misstep or a stumble while the horse was at work. Then, upon 

 coming to a standstill, he wUl be found with one or more of his 



