k 



STRUCTURE AND DISEASES OF THE HOCK JOINT. 285 



from inflammation, and the notch, though denuded of cartilage, 

 is generally covered by a thin synovial membrane. 



These diseased appcai*ances of both the upper and lower arti- 

 culations of the hock, appearing as they often do, without any 

 enlargement or external inflammation, go far to account for the 

 existence of so many cases of obscure lameness of the hind 

 extremity. 



The only treatment for these incurable cases is the excision 

 of the nerve a few inches above the hock, on the inside onlv : 

 it has been performed successfully several times by Professor 

 Spooner, and and also by Mr. Stanley. — Ed.] 



Bog Spavin. 



Bog spavin is a disease very common among young horses, 

 and occui's chiefly at the time of breaking : it is, of course, more 

 likely to happen when they are broke at too early an age. The 

 hock, it has been before observed, is an important joint, and 

 designed for very extensive motion ; but the motion which takes 

 place in a state of nature in this joint, or during reasonable 

 labour of any kind, is very different from that which is pro- 

 duced in throwing the animal upon his haunches, as it is called, 

 in pulling him up from a gallop suddenly with a powerful bit, 

 or in taking high or wide leaps. These violent motions of this 

 joint in particular are, it may well be supposed, likely to pro- 

 duce this disorder. Bog spavin, then is a distension of the 

 capsular ligament, by an accumulation of synovia, formed in 

 consequence of the violent exertions I have just described, and 

 appearing in a swelling on the inside, towards the bend of the 

 hock. 



[When bog spavins appear suddenly, they are usuaHy accom- 

 panied by stiffness, and even lameness, and then treatment should 

 be had recourse to ; but generally, they come on gi-adually, and 

 are productive of no injury or inconvenience. 



There has been much diflference of opinion on the subject of 

 these bursal enlargements. The following appears to the editor 

 to be their true nature. The seat of bog spavin is the upper 

 articulation between the tibia and astragalus, and it appears in 

 that part of the joint where there is nothing but the capsular 

 lio-ament and the skin to protect the joint. The capsular liga- 

 ment is bound down by membrane to the neighbouring parts. 

 In the action of the joint, when there is an abundant supply of 

 synovia, this fluid is pressed with some degree of force against 

 the capsular ligament, and raptures some of the fibres of the 

 membrane which confines it. The consequence of this is an 

 actual enlargement of the cavity of the joint itself; it is capable 

 of containing more than it did before ; and it is soon supplied 



