DISEASES OF THE MUSCLES AND TENDONS. 19'i 



larger and more numerous than elsewhere, as here exists 

 greater liabilitj to friction than in any other joint in the 

 whole body. Such we find to be the case. 



Violent exercise, unusual strains, and blows are liable to 

 injure these sacks and cause them to enlarge. More fre- 

 quently, however, they are ruptured, when their contents es- 

 cape and form a putfy swelling under the skin and cellular 

 tissues. To such accidents, those surrounding the hock-joint 

 are peculiarlj^ exposed; and, from their number and size at 

 this spot, the consequences are at once more noticeable, and 

 really much more serious than when the same things occur 

 in other places. 



The oily, mucous secretions continue as before ; or, rather, 

 they are increased in quantity, from the effort which ITature 

 makes to repair damages and supply the deficiency in the lu- 

 bricating material furnished the joint. But in this case ITa- 

 ture fails ; for the oil-sacks never heal. There is a constant 

 accumulation of the synovial fluid, and as constant a discharge 

 into the spavin-bag, as it may be termed, under the skin. 

 The enlargement increases to an extent and with a rapidity 

 proportioned to the size and number of the oil-sacks which 

 have been ruptured. Sometimes the swelling makes surpris- 

 ingly rapid progress, and in a short time encircles the entire 

 joint. It always disfigures the horse very much, and has 

 been known to grow as large as a man^s head. In such cases 

 the joint becomes so stiff' as to be nearly useless,*the play of 

 tendons and muscles being prevented almost entirely. 



"When a small vein is broken, and the blood mingles with 

 the contents of the spavin-sack, the enlargement is called 

 blood spavin. This is the only point in which this disease 

 differs from ordinary bog spavin. 



Lameness is not always a consequence of these kinds of 

 spavin, and especially when the swelling is small, except 

 in cases where the horse is very hard worked; and while 

 they unquestionably constitute a form of unsoundness, a 

 horse thus afflicted may do very well for ordinary service. 

 He may work before the plow, or be hitched to a wagon or 

 13 • 



