296 DISEASES OP CATTLE. 



treatment of a fracture. In order to clearly understand the reason for 

 this a few words are necessary in relation to the structure of joints. 



The different pieces constituting the skeleton of the animal body are 

 united in such a manner as to admit of more or less motion one upon 

 another. In some of the more simple joints the bones fitting one into 

 another are held together by the dense structures around them, admit- 

 ting of very little or no movement at all, as the bones of the head. In 

 other joints the bones are bound together by dense cartilaginous struc- 

 tures, admitting of only limited motion, such as the union of the small 

 bones at the back part of the knee and hock (metaearpal and metatar- 

 sal). In the more perfect form of joint, the power of motion becomes 

 complete and the structures are more complex. The substance of the 

 bone on its articular surface is not covered with periosteum, but is 

 sheathed in a dense thin layer of cartilage, shaped to fit the other sur- 

 faces with which it conies in contact (articular). This layer is thickest 

 towards 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 articulation 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 attached at the outer edge of the articular surface, unit- 

 ing the bones and hermetically sealing the cavities of the articulation. 

 This structure and the articular surface of the bone is covered by a 

 thin, delicate membrane, known as the synovia! 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 joints 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 inflam- 

 matory derangement, and the capsular ligament is liable to be distended 

 from excessive secretion 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 gen- 

 erally 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. When it occurs lameness is the first symptom. During the early 

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



