764 DISEASES AND THEIE TKEATMENT. 



EXOSTOSIS, OR BONY ENLARGEMENT. 



Exostosis is, in general, the consequence of periostitis, or in- 

 flammation of the vascular membrane 

 covering the bone, though it doubtless 

 also arises from other causes. It some- 

 times comes on without having attracted 

 the least attention, or produced the least 

 apparent disturbance to the animal, and 

 may appear on any bone in the body, or 

 on any part of a bone, sometimes so small 



as to escape observation altogether, and 



, . r . , FIG. 641. An 



. 640-Ex- sometimes is very large. It may be exostosig) or 



ostosis. caused by external injury, or it may be bony eniarge- 

 1. Splint; 2 3 the result of constitutional disturbance, ment below 

 Enlargements more commonly the former. Its nature, the knee> 

 caused by in- ca uses, symptoms, and treatment will be better un- 

 ^ ury * derstood by taking the most common example of 

 splint, spavin, and ringbone. 



SPLINT, OR SPLENT. 



Splint is a hard, bony tumor occurring on the inside of the 

 shank or cannon-bone of the fore leg, usually well up near the 

 knee, which is well represented by Fig. 642. It is situated partly 

 on the splint-bone (from which it takes its name), and partly 

 on the cannon. Young horses are most subject to splints. The 

 periosteum in them being more vascular than in old animals, it 

 is more liable to inflammation, which is very readily induced in 

 the unsolidified bones of the young horse when exposed to con- 

 cussion or external violence. It occurs in the inside, because the 

 center of gravity falls through that part; when there is splint or 

 enlargement on the outside, it is usually caused by an injury. 

 Sometimes the opposite foot striking the part will cause so much 

 inflammation as to produce considerable soreness and lameness, 

 followed by thickening and enlargement of the part. 



Symptoms. At the start there may be no enlargement, nor 

 anything to indicate the seat of trouble. The horse appears all 

 right on a walk or on soft ground ; but if moving rapidly on a 

 hard road, and especially down hill, considerable lameness will be 



