257 
ON THOliOUGH-PIN, WINDGALL, &c. 
inflammation of the synovial membranes, and others to a dis- 
tention of the envelopes of the synovial cavities. I am of the 
latter opinion. I think that the disturbance in the absorbent 
and secretory functions of the synovial membranes, and conse- 
quently the inflammation of those membranes, are almost always 
preceded by distention of the capsules of the sheaths, or the 
various fibrous textures which surround the articulations or the 
tendons. It often happens that the inflammation, which is re- 
garded as the first and principal cause, does not manifest itself 
outwardly by any symptom belonging to that state of the organs 
which can be properly called inflammation, with the exception 
of the swelling; and that symptom exists only in appearance, 
for no one would maintain that the tumour which is found on 
the hock on which a thorough-pin exists, is owing to tumefac- 
tion of the synovial membranes, or the secretory texture which 
they contain. 
I may observe, in confirmation of this opinion, 1st, that, in 
almost every case, thorough-pins and windgalls are produced by 
the violent and repeated extension to which the fibrous tissues 
that bind together the articulations are subject. 2d, That in- 
flammation of the synovial membrane, excited by a wound pene- 
trating into the joint, is not followed by the development of a 
thorough-pin or a windgall. 3d, That in some cases these en- 
largements immediately follow the distention of the parts, 
without the appearance of any manifest inflammation of the 
tissues in which the thorough-pin or the windgall is seated. 
That which is most to be feared, with regard to the thorough- 
pin and the windgall, is the distention of the tissues which sur- 
round the capsules ; and it is to combat that distention that the 
efforts of the veterinarian should be directed. As I have said, 
I do not deny the lesion, said to be inflammatory, of the syno- 
vial membranes. These membranes undergo many well-marked 
changes, as I have often observed in the carcasses of those that 
had thorough-pins, or varices*, or windgalls, or dropsies of the 
tendinous sheaths, and which have not yet received any appro- 
priate name. I have seen these membranes lose their transpa- 
rency ; I have seen them assume different degrees of cloudiness : 
in the same articulation some portions have been of a vermilion 
redness, others of a cherry colour, others of a deep red, and some 
were yellow, and others black. I have often found gelatiniform 
* Those which I have often heard called varices are not, as one would be 
right in supposing, a dilatation of the saphena, but dropsy of the articular 
capsule of the inferior, anterior, and internal part of the tarso-metatarsian 
articulation. It is a true thorough-pin, of very common occurrence, and 
often resists the most energetic treatment. 
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