NATURE OF SPRAIN. 23 



NATURE OF SPRAIN. — Ligaments, as well as tendons, may break right 

 across ; or they may tear, especially small portions of them, here and there, 

 so that the whole thickness is not broken across at any one spot ; but they 

 will not stretch. It is true that under certain conditions they do become 

 elongated, but this only happens when the strain is continuous, and lasts for 

 some considerable time. A slight degree of inflammation sets in then, and 

 under its influence the fibrils soften, until they yield. Sometimes ligaments 

 give way in the middle, but it is more common for them to separate from 

 the bone, or to wrench from it a small thin scale corresponding to their 

 attachment. This is due in part to the arrangement of their fibres. In the 

 centre they are woven strongly together, and form a rounded bundle of 

 great strength. At the end they spread out like a fan, so as to secure a 

 wider attachment. A ligament that can resist successfully a straight pull of 

 great violence, yields at once to a twisting force of much less severity ; 

 because this pulls on the fibres unequally, one by one, and tears them from 

 their attachment. The fibres of muscles may also become more or less torn 

 from a sprain. 



In a sprained tissue, there is not only an inflammatory exudation (p. 14) as 

 a result of the injury ; but there is also, as a rule, extravasated blood, that is, 

 blood which has escaped from vessels that were ruptured at the same time 

 as the broken fibres. ' In human practice, discoloration of the affected tissues 

 in the case, say, of a badly sprained ankle, often proves the presence in 

 them of extravasated blood, which is visible on account of the thinness and 

 translucency of the skin. As a rule, the horse's skin is too thick and too full 

 of pigment to allow of the discoloration in question to be seen through it. 



HOW SPRAINS OCCUR.— Lameness from an acutely swollen 

 fetlock, may be cited as a good example of sprain of ligament. 

 This is caused mainly by fast work on hard ground, and is generally 

 found in horses with comparatively straight pasterns. It is brought 

 on by tie continued and excessive pressure of fluid present in the 

 part affected, which induces the swelling. Here concussion appears 

 to be the exciting cause. 



In many cases sprains are due to accident, such as a sudden 

 twist at a moment when the muscles are unable to act quickly 

 enough to save the part, or again when they have become so 

 fatigued that they are powerless to preserve its stability. The 

 practical inferences are obvious. 



Experienced horsemen will agree that sprained tendons and 

 ligaments of the fore legs — the most common accidents to which 

 horses employed in fast work are liable^ — come on gradually, as a 

 rule, from the injured structures having become abnormally weak. 

 The history of the case is usually as follows : — 



On previous occasions heat and tenderness were observed in the 

 part after exercise. These symptoms subsided more or less after 

 rest, and the aid of the ordinary remedies, the horse being thus 

 enabled to continue work, off and on, until the final accident 

 occutred. In other words, until the presence of continued in- 

 flammation, or tension, rendered the part too weak to stand the 

 strain of ordinary work, or of work well within its power in a 

 healthy condition. When out of work, horses^ are much more liable 

 to sprain than when " fit and well." For the more a healthy part 



