332 DISEASES OF THE HOKSE. 



synovial sacs. A large articular sac contributes to the lubrication of 

 the shank bone (the tibia) and one of the bones of the hock (the astrag- 

 alus). The tendinous sac lies back of the articulation itself and 

 extends upward and downward in the groove of that joint through 

 which the flexor tendons slide. The dilatation of this articular syno- 

 vial sac is what is denominated bog spavin, the term thoroughpin 

 being applied to the dilatation of the tendinous capsule. 



The bog spavin is a round, smooth, well-defined, fluctuating tumor 

 situated in front and a little inward of the hock. On pressure it 

 disappears at this point to reappear on the outside and just behind the 

 hock. If pressed to the front from the outside it will- then apjDear 

 on the inside of the hock. On its outer surface it presents a vein 

 which is quite prominent, running from below upward, and it is to 

 the preternatural dilatation of this blood vessel that the term blood 

 spavin is applied. 



The thoroughi^in is found at the back and on the top of the hock 

 in that part known as the " hollows," immediately behind the shank 

 bone. It is round and smooth, but not so regularly formed as the 

 bog sjjavin, and is most apparent when viewed from behind. The 

 swelling is usually on both sides and a little in front of the so-called 

 liamstring, but may be more noticeable on the inside or on the outside. 



In their general characteristics bog spavins and thoroughpins are 

 similar to windgalls, and one description of the origin, symptoms, 

 pathological changes, and treatment will serve for all equally, except 

 that it is possible for a bog spavin to cause lameness, and thus to 

 involve a verdict of unsoundness in the patient, a circumstance which 

 will, of course, justify its classification b}^ itself as a severer form of a 

 single type of disease. 



We have already referred to the subject of treatment and the means 

 employed — i'est, of course — with liniments, blisters, etc., and what 

 we esteem as the most active and beneficial of any, ea7'ly, deep, and 

 well-performed cauterization. There are, besides, commendatory 

 reports of a form of treatment by the application of pressure pads 

 and peculiar bandages upon the hocks, and it is claimed that the 

 removal of the tumors has been effected by their use. But our expe- 

 rience with this apparatus has not been accompanied by such 

 favorable results as would justify our indorsement of the flattering 

 representations which have sometimes appeared in its behalf. 



OPEN JOINTS, BROKEN KNEES, SYNOVITIS, AND ARTHRITIS. 



The close relationship which exists among these several affections, 

 their apparently possible connection as successive developments of a 

 similar, if not an essentially identical, origin, together with the 

 advantage gained by avoiding frequent repetitions in the details of 

 symptoms, treatment, etc., are our reasons for treating under a single 

 head the ailments we have grouped together in the present section. 



