(See Articui.atio and Articulus.) We have resumed the consideration of this subject, to reduce into one view the diseases of the cavities of the joints: these are either effused fluids, or loose cartilaginous or bony bodies. The fluids effused are either blood, pus, synovia, or water. Any fluid is ascertained to exist in these cavities by a swelling felt on every side, and yielding on pressure; while accumulations in the bursas mucosae are partial, and will not pass, on pressure, to the opposite side. When the disease arises from a violent bruise, the fluid is probably bloody; the accumulation which follows rheumatism, watery; but when it is the consequence of a strain, which has been followed by violent inflammation, the matter is usually pus mixed with synovia. When dis-cutients, with gradual pressure from a bandage, fail, and the fluid must be evacuated, a very small trochar should be employed; the skin drawn up, so that immediately on emptying the cavity it may be again drawn down, to cover the aperture in the ligament. A sticking plaster must be immediately applied, the joint firmly swathed with a flannel bandage,and some blood taken from the arm to prevent inflammation.

These precautions are peculiarly necessary, as the air stimulates the cavities of joints, and excites an unconquerable inflammation, which nature sometimes relieves by forming an anchylosis, but in which art usually fails.

The extraneous bodies in the capsular ligaments are generally found in the knee; but of the treatment necessary in these cases we have already spoken. See Genu.