414 DISEASES OF THE HORSE’S FOOT 
example, that of rheumatism) circulating in the blood- 
stream. 
Pathology.—Uncomplicated acute synovitis never causes 
death. The pathological changes in connection with it have 
therefore been studied in cases purposely induced, and the 
animal afterwards slaughtered. It is then found that, as 
in inflammation elsewhere, the synovial membrane is show- 
ing the usual inflammatory phenomena—that it is thick 
and swollen as a result of the inflammatory hyperemia and 
commencing exudation. Later, the synovial fluid becomes 
increased in quantity, is thin and serous, and after a time 
is seen to be mixed with the inflammatory exudation poured 
into it. We then find that it has lost its clear appearance, 
has become thick and muddy, and has floating in it flakes 
of fibrin. 
If the case progresses favourably these materials are soon 
absorbed and resolution occurs. In rarer cases the thicken- 
ing and congestion of the membrane increases, and the 
articular capsule becomes so distended with the increased 
synovia and accumulated inflammatory discharges that a 
kind of chemosis occurs. In other words, there oozes 
through, without actual rupture of the membrane, a thin, 
blood-stained, and purulent-looking discharge. 
It is an important point to note that in cases of synovitis 
the fringes of the synovial membrane become swollen and 
blood-injected, forming noticeable red elevations at the 
margins of the cartilages. It is then that the diseased 
condition soon spreads and runs into arthritis. 
Further, it is important, especially with regard to the 
question of the degree of pain and lameness likely to be 
caused, to note that often granulations are thrown out upon 
the looser folds of the membrane. As these increase in 
size they come to form fringed and villous membranous 
projections inserting themselves between the bones forming 
the articulation. In such cases there is no doubt that the 
intense pain sometimes observed in these cases is due to 
pinching of these prolongations of the synovial membrane 
by the opposing bones of the joint. 
