256 DISEASES OF BONE. 



lame in them. Young horses often have enlarged hocks which fine 

 down as they grow older. 



OCCULT SPAVIN is a term used to signify that condition of 

 the hock in which no external sign of disease can be observed ; 

 although the lameness due to pain in the part may be of a most 

 inveterate form. Here there is ulceration of the surfaces of 

 the bones which form the gliding joints without bone being 

 deposited between or about them. In health, the different bones 

 of a joint never touch each other ; as they are separated by 

 articular cartilage. In ordinary bone spavin, this cartilage 

 becomes ulcerated as the result of inflammation extending from the 

 bones, and is finally absorbed ; the exudation thrown out from the 

 blood-vessels of the bones being converted into bony material, 

 which causes bony union and consequent destruction of the joint. 

 Here is a reparative process with cessation of inflammation. In 

 occult spavin, on the contrary, the process stops short at ulcera- 

 tion, and no reparative action takes place; hence, the serious and 

 intractable nature of this form of the disease. Occult spavin is 

 naturally much more common in old, than in yoimg horses ; for, 

 in the latter, repair is much more active than in the former. 

 As the inflammation, and not the deposit, constitutes the disease, 

 bone and occult spavin must be regarded as one and the same 

 complaint. 



SYMPTOMS. — The lameness of spavin is characterised by want 

 of freedom in bending the hock, which causes the horse to '" drag 

 his toe " and to wear the hoof at that part (Fig. 1) ; and by the 

 lameness getting better as he " warms up " at exercise. In severe 

 cases, and especially in occult spavin, the lameness consists in a 

 sort of spasmodic catching up of the spavined limb the moment 

 the heel of the foot comes down upon the ground, something 

 after the manner of stringhalt. At times,- the stiffness can be 

 observed only when the animal is pushed over from one side to 

 the other in his stall. A spavin may often be detected when riding 

 a horse down a steep hill, from the fact of his " dragging the toe." 

 The time of all others when a spavined horse will be apt to mani- 

 fest his lameness will be the day following after a hard day's 

 work; and when he makes his first egress from the stable in the 

 morning is the critical period for examination. Therefore, be 

 prepared to judge quickly in these cases ; for the longer the animal 

 is trotted up and down the less lame will he generally become. At 

 the end of each trot past, he should be turned a different way ; for 

 instance, first to the left about, then to the right about, so as tq 

 see on which hind leg he turns best. If there still be a doubt, the 



