298 THE HORSE. 



but the most ordinary cause is the over-stimulus of hard work. 

 Heavy horses are more prone to exostosis than Hght ones, partly 

 from the weight of their bodies and their high lumbering action 

 jarring their limbs in a greater degree, but also from the more 

 spongy and open texture of their bones, which admit of the pres- 

 sure of large blood-vessels within them, and are thus more liable 

 to congestion, and consequent morbid secretion. Exostosis is shown 

 in the form of splints, ring and sidebone, and ossified lateral car- 

 tilages, as well as in the growths which occur occasionally in other 

 parts of the body which have received no distinguishing name. 

 The vitality of the new growth in exostosis is less than that of 

 healthy bone, and as a consequence, when excessive inflammation is 

 set up in the part, it will often die and be separated by absorption. 



Caries (ulceration) occurs as a consequence of inflammation, and 

 in the horse either results from external injury, as in poll evil and 

 fistulous withers, or from mismanagement, as in navicular disease, 

 which latter aff"ection will be considered under the diseases of the 

 foot. It is always attended with pain, and in severe cases with the 

 formation of sufficient matter to require an outlet, but in very re- 

 stricted ulcerations, such as occur in navicular disease, the pus 

 passes into the joint, and is reabsorbed with the synovia. 



Anchylosis, when it is the result of caries in the two adjacent 

 surfaces of a joint, produces union between them, but in the horse 

 it is generally of a secondary kind, the result of bony growths 

 (exostosis), thrown out from the surfaces of the two bones near 

 the joint, which coalescing, unite into one mass, and thus destroy 

 all motion. 



SPLINTS. 



The strict definition of this disease is " an exostosis from 

 the lower part of the small metacarpal bone, connecting it by bony 

 union with the large metacarpal bone," but among horsemen, any 

 bony growth from the cannon bone is considered a splint, and the 

 latter is almost as common as the former. The regular splint rarely 

 attacks the outer small metacarpal bone alone, but sometimes in 

 very bad cases both are implicated in the disease. It is difiicult 

 to give a valid reason for this greater frequency of splint on the 

 inside than on the out, but it is commonly said that the inner 

 splint bone receives more of the weight of the body than the outer 

 one, and that it is more under the centre of gravity, but as it is 

 merely suspended from the carpus, and is not supported from below 

 (in any way, mediately or directly), this can produce no injurious 

 efi'ect upon it. The fact is so, however, whatever may be the cause. 



The !>i/mptomn of splint are generally a greater or less degree of 

 lameness during its formation, but sometimes it may go on to attain 

 a large size without any such result, especially if its growth is slow 



