290 DISEASES OF CATTLE. 



lage, shaped to fit the other surfaces with which it comes in contact 

 (articular). This layer is thickest toward its center when covering 

 bony eminences, and is elastic, of a pearly whiteness, and resisting, 

 though soft enough to be easily cut. The bones forming an articula- 

 tion are bound together by numerous ligaments attached to bony 

 prominences. The whole joint is sealed in by a band or ribbon-like 

 ligament (capsular ligament) extending around the joint and at- 

 tached at the outer edge of the articular surface, uniting the bones 

 and hermetically sealing the cavities of the articulation. This struc- 

 ture and the articular surface of the bone is covered by a thin, deli- 

 cate membrane, 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 lubricating 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 un- 

 naturally 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 secre- 

 tion of synovia. The latter 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, corresponding 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. 



Occasionally working oxen that are used in the lumber woods and 

 made to pull heavily, with bad footing, are aiflicted with this con- 

 dition. T\Tien 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 



