carpa's triangle, the
two sacs communicating with each other through a narrow neck beneath
Poupart's ligament.

So long as the skin is intact, the abscess is unattended with
symptoms, and may escape notice. If it bursts externally, pyogenic
infection is almost inevitable, and the patient gradually passes into
the condition of hectic fever or chronic toxaemia; he loses ground from
day to day, may become the subject of waxy disease in the viscera, or
may die of exhaustion, tuberculous meningitis, or general
tuberculosis.

#Dislocation# is a rare complication of hip disease, and is most
likely to occur during the stage of adduction with inversion. It has
been known to take place during sleep, apparently from spasmodic
contraction of muscles. In the dorsal dislocation, which is the most
common form, adduction and inversion are exaggerated, the trochanter
projects above and behind Nelaton's line, and the head of the bone may
be felt on the dorsum ilii. It is a striking fact that after
dislocation has occurred there is less complaint of pain or of
startings than before, and passive movements may be carried out which
were previously impossible.

#Diagnosis of Hip Disease.#--The diagnosis is to be made not only from
other affections of the joint, but also from morbid conditions in the
vicinity of the hip, as in any of these the patient may seek advice on
account of pain and a limp in walking. The patient should be stripped,
and if able to walk, his gait should be observed. He is then examined
lying on his back, and attention is directed to the comparative length
of the limbs, to the attitude of the limbs and pelvis, and to the
movements at the hip-joint, especially those of rotation. When there
is any doubt as to the diagnosis, the examination should be repeated
at intervals of a few days. In children, there are three non-febrile
conditions attended with a limp and with shortening of the limb, which
may be mistaken for hip disease,--_congenital dislocation_, _coxa
vara_, and _paralysis following poliomyelitis_--but in all of these
the movements are not nearly so restricted as they are in disease of
the joint.

In tuberculous disease of the _sacro-iliac joint_, while the pelvis
may be tilted, and the limb apparently lengthened, the movements at
the hip are retained. In tuberculous disease of the _great
trochanter_, or of either of the _bursae_ over it, while there may be
abduction, eversion, impairment of mobility, and swe