CHAPTER IX, 
THE EXTREMITIES. 
FORMATION OF JOINTS. 
OINTS are formed of bones which fit each other on uneven surfaces, 
the cavities and elevations mutually corresponding, with an interven- 
‘J ing smooth, elastic substance, called cartzlage, which prevents fric- 
“RX, tion of the surfaces, and relieves the jar that would otherwise occur 
from walking on hard roads. This cartilage is covered with a fine “ syno- 
vial” membrane which secretes an albuminous and oily fluid that acts as 
oil to prevent friction. Strong flexible substances, fibrous in texture, called 
ligaments, are the chief bonds to hold the parts of the joints together. 
Some joints are further strengthened with tendons and muscles. Small 
closed sacs, called “ bursz mucose,” situated between the surfaces of the 
joints, secrete a fluid similar to that furnished by the synovial membrane 
named above, to which membrane they are similar in structure. 
SYNOVITIS. 
Synovitis is an inflammation of the synovial membranes. The in- 
flamed membranes do not exceed a certain size,do not burst, and do not he- 
come well without treatment, but may remain in the same condition for 
years. It affects the knee, fetlock (then called “wind galls,’ which see), 
but generally the hock (then called “ bog spavin” and “ thorough-pin,” 
which see). Among its causes are exposure to cold and heat; sprains; 
friction of joints from quick work on hard roads; rheumatic fever. 
Symptoms.—Lameness immediately followed by swelling of some 
joints (not of the surrounding fibrous texture, as in rheumatism); a fluid 
exudes from the joint, at first usually serous, without the marked fever 
which attends the beginning of muscular rheumatism; later, lymph es- 
capes and the joint is permanently enlarged, or less frequently the joint 
becomes stiff and immobile, baffling all treatment. 
TREATMENT.—Aconite is the most effectual remedy, both internally 
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