shable from the thickened and enlarged bursa so commonly
present in this situation in the condition known as bunion.

[Illustration: FIG. 61.--Ganglion on lateral aspect of Knee in a young
woman.]

Ganglionic cysts are met with in other situations than those mentioned,
but they are so rare as not to require separate description.

Ganglia are to be diagnosed by their situation and physical characters;
enlarged bursae, synovial cysts, and new-growths are the swellings most
likely to be mistaken for them. The diagnosis is sometimes only cleared
up by withdrawing the clear, jelly-like contents through a hollow
needle.

_Pathological Anatomy._--The wall of the cyst is composed of fibrous
tissue closely adherent to or fused with the surrounding tissues, so
that it cannot be shelled out. There is no endothelial lining, and the
fibrous tissue of the wall is in immediate contact with the colloid
material in the interior, which appears to be derived by a process of
degeneration from the surrounding connective tissue. In the region of
the knee the ganglion is usually multilocular, and consists of a
meshwork of fibrous tissue, the meshes of which are occupied by colloid
material.

It is often stated that a ganglion originates from a hernial protrusion
of the synovial membrane of a joint or tendon sheath. We have not been
able to demonstrate any communication between the cavity of the cyst
and that of an adjacent tendon sheath or joint. It is possible, however,
that the cyst may originate from a minute portion of synovial membrane
being protruded and strangulated so that it becomes disconnected from
that to which it originally belonged; it may then degenerate and give
rise to colloid material, which accumulates and forms a cyst. Ledderhose
and others regard ganglia as entirely new formations in the
peri-articular tissues, resulting from colloid degeneration of the
fibrous tissue of the capsular ligament, occurring at first in numerous
small areas which later coalesce. Ganglia are probably, therefore, of
the nature of degeneration cysts arising in the capsule of joints, in
tendons, and in their sheaths.

_Treatment._--A ganglion can usually be got rid of by a modification of
the old-fashioned seton. The skin and cyst wall are transfixed by a
stout needle carrying a double thread of silkworm gut; some of the
colourless jelly escapes from the punctures; the ends of the thread are
tied and cut short, and a dressing is applied. A