bones: diseases and accidents. 281 



metically sealing the cavities of the articulation. This structure and 

 the articular surface of the bone is covered by a thin, delicate mem- 

 brane, known as the "synovial membrane," which secretes the joint 

 oil (synovia). This fluid is viscid and colorless, or slightly yellow, 

 and although it does not possess a large amount of fat, its character 

 somewhat resembles oil, and it serves the same purpose in lubri- 

 cating the joints that oil does to the friction surfaces of an engine. 

 Although the tissues of the joint when used in a natural way are able 

 to withstand the effect of great exertion, when unnaturally used, as 

 they are very delicate and complex, they are liable to inflammatory 

 and other changes of a very serious nature. The synovial membrane, 

 and in fact the whole structure of the joint, is susceptible to injury 

 and serious inflammatory derangement, and the capsular ligament is 

 liable to be distended from excessive secretion of synovia. The lat- 

 ter process may be almost noninflammatory, and attended with little 

 inconvenience or importance other than a blemish to the animal, 

 which in cattle is not serious. It may occur on the back part of. the 

 leg above the fetlock or on the inner and fore part of the hock, cor- 

 responding in its location to windgalls and bog spavin of the horse. 

 Continuous support by bandages will generally force reabsorption, 

 and as the limb is not subjected to violent action, as in the case of the 

 horse, the affection is not so liable to recur. 



SPAVIN. 



Occasionally working oxen that are used in the lumber woods and 

 made to pull heavily, with bad footing, are afflicted with this condi- 

 tion. "When it occurs lameness is the first symptom. During the 

 early stages of the disease the lameness is most severe in the morning 

 and disappears after the animal is exercised; it gradually becomes 

 more severe as the disease advances, so that when the disease is well 

 established the animal is lame continuously. Shortly after the lame- 

 ness appears a bunch (exostosis) will be noticed on the inner and fore 

 part of the affected joint. This bunch differs from bog spavin in that 

 it is hard, while bog spavin is soft. It increases in size as the disease 

 advances till the animal is too lame to be used for labor. As the dis- 

 ease is always attended with considerable pain there is more or less 

 loss of flesh. In the most advanced stage the animal will step with 

 difficulty, frequently holding the foot from the ground, or, if forced 

 to take a few steps, stands with it elevated, twitching with pain. In 

 the earlier stage of the disease only a small portion of the fore part 

 of the lower, or second, articulation is involved, but the inflammatory 

 process gradually extends over the whole surface of the lower joints 

 of the hock. The structures of the joint are broken down and the 

 bones are united (anchylosis). This process may include any or all 

 of the three lower joints of the hock. The joint of motion which is 

 situated on the lower end of the leg bone is seldom involved. 



