and finally appear in the thigh.

#Clinical Features.#--The insidious development of the tuberculous
abscess is one of its characteristic features. The swelling may attain a
considerable size without the patient being aware of its existence, and,
as a matter of fact, it is often discovered accidentally. The absence of
toxaemia is to be associated with the incapacity of the wall of the
abscess to permit of absorption; this is shown also by the fact that
when even a large quantity of iodoform is inserted into the cavity of
the abscess, there are no symptoms of poisoning. The abscess varies in
size from a small cherry to a cavity containing several pints of pus.
Its shape also varies; it is usually that of a flattened sphere, but it
may present pockets or burrows running in various directions. Sometimes
it is hour-glass or dumb-bell shaped, as is well illustrated in the
region of the groin in disease of the spine or pelvis, where there may
be a large sac occupying the venter ilii, and a smaller one in the
thigh, the two communicating by a narrow channel under Poupart's
ligament. By pressing with the fingers the pus may be displaced from one
compartment to the other. The usual course of events is that the abscess
progresses slowly, and finally reaches a free surface--generally the
skin. As it does so there may be some pain, redness, and local elevation
of temperature. Fluctuation becomes evident and superficial, and the
skin becomes livid and finally gives way. If the case is left to nature,
the discharge of pus continues, and the track opening on the skin
remains as a _sinus_. The persistence of suppuration is due to the
presence in the wall of the abscess and of the sinus, of tuberculous
granulation tissue, which, so long as it remains, continues to furnish
discharge, and so prevents healing. Sooner or later pyogenic organisms
gain access to the sinus, and through it to the wall of the abscess.
They tend further to depress the resisting power of the tissues, and
thereby aggravate and perpetuate the tuberculous disease. This
superadded infection with pyogenic organisms exposes the patient to the
further risks of septic intoxication, especially in the form of hectic
fever and septicaemia, and increases the liability to general
tuberculosis, and to waxy degeneration of the internal organs. The mixed
infection is chiefly responsible for the pyrexia, sweating, and
emaciation which the laity associate with consumptive disease. A