990 DISEASES OF THE HOCK. 



the tibia, below to the astragalus, scaphoid, and large cuneiform 

 bones, and on either side to the lateral ligaments of the joint. Bog 

 spavin varies considerably in size, but in well-marked cases the 

 distension is associated with two smaller dilatations (articular 

 thoroughpin) on the lateral surfaces of the hock, as may be proved 

 by applying pressure to the bog spavin. Compression of the anterior 

 distension increases the lateral dilatations, and vice versa. In some 

 instances distension of the tarsal sheath of the perforans tendon 

 (tendinous thoroughpin) co-exists with bog spavin, but as a rule 

 there is no communication between the joint and the tendon sheath. 



Bog spavin is commonest in young horses with straight or upright 

 hocks, but it is also frequent in aged stallions and breeding mares. 

 It is due to chronic synovitis, brought about by wear, hard work, 

 debilitating disease, or accident ; occasionally it follows acute 

 synovitis. It is often regarded as indicating inherited weakness of 

 the hock -joint. 



The most noticeable symptom is the presence of a fluctuating 

 swelling on the antero-internal aspect of the hock. Lameness is 

 exceptional, though sometimes owing to large size of the distension 

 there is stiffness or restricted hock action. If bruised or injured, 

 bog spavin may cause serious symptoms, acute synovitis may ensue, 

 the joint may burst, and the patient's life may be endangered. Acute 

 (closed) synovitis is distinguished by great lameness, fever, sweating, 

 inappetence, and intense suffering ; and locally by tense, hot, very 

 painful swelling of the hock. (See also " Acute Inflammation of the 

 Hock Joint.") 



Treatment must follow general principles. Recent swellings are 

 treated by cold applications, and later by blistering. As firing only 

 diminishes the swelling, and always leaves visible scars, it merely 

 substitutes one blemish for another ; nevertheless, Stockfleth recom- 

 mends it. In young horses, with moderately developed bog-spavin, 

 repeated painting with tincture of iodine or massage may diminish 

 swelling, but seldom removes it completely. In foals treatment is 

 rarely of permanent value, and relapses often occur. Spring trusses 

 are often applied, and occasionally succeed in reducing the distension, 

 which, however, is apt to recur when treatment by spring or elastic 

 pressure has been discontinued. 



Caution is required in operating surgically. Removal of contents 

 by Pravaz's syringe or a slender trocar is occasionally followed by 

 benefit, and injection of iodine may be tried. In most cases the 

 operation must be repeated several times, at intervals of four to 

 six weeks, to be of service. Evacuation by Pravaz's syringe, washing 



