anied by marked symptoms or deformity. The
diagnosis, therefore, is often difficult, unless good skiagrams are
available. The disease may be associated with pain in the distribution
of the sciatic nerve, which is liable to be mistaken for sciatica.
Single or double _iliac abscess_ frequently forms without the patient
showing any characteristic signs of spinal disease. When the disease
begins in childhood it may induce a permanent deformity of the
pelvis, the conjugate diameter at the brim being increased, while the
transverse diameter at the outlet is diminished--kyphotic pelvis, and,
in females, this may lead to complications in parturition.

#Tuberculous Disease of the Sacro-iliac Joint.#--This condition may
occur as a primary affection, but is much more frequently secondary to
disease in the ilium, sacrum, or lower lumbar vertebrae, and is most
common in adolescents and young adults of the male sex. It is attended
with pain in the lumbar region, and sometimes in the buttock and along
the course of the sciatic nerve. The pain is aggravated by movements,
especially such as involve sudden and violent contraction of the
lumbar and abdominal muscles, for example, coughing, sneezing, or
straining during defecation. Tenderness is elicited on making pressure
over the joint, on pressing together the iliac bones, or on attempting
to abduct the limb while the pelvis is fixed. The muscles of the
buttock and thigh are wasted. As any attempt to bear weight on the
affected limb causes pain, the patient walks with a limp, and to save
the joint he assumes an attitude which is characteristic: he throws
his weight on the sound limb, leans forward, using a stick for
support, tilts the affected side of the pelvis downwards, and flexes
the hip and knee-joints of the diseased limb. The anterior superior
spine is unduly prominent on the affected side, and the limb appears
to be lengthened. Sooner or later, in most cases, an abscess forms,
and the pus may reach the surface over the posterior aspect of the
joint. When the pus forms in front of the joint, it may spread
laterally in the iliac fossa as an _iliac abscess_ or may gravitate
downwards in the hollow of the sacrum and emerge on the buttock
through the sacro-sciatic foramen--_sub-gluteal abscess_. Sometimes it
passes into the ischio-rectal fossa or into the perineum. The presence
of an abscess in the pelvis may sometimes be recognised on rectal
examination. The appearance of an abscess