is sometimes the first thing
to draw attention to the condition.

As pain across the small of the back and along the course of the
sciatic nerve may be among the early symptoms of sacro-iliac disease,
the condition is liable to be mistaken for lumbago or for sciatica.
From hip disease it is recognisable by noting that the movements of
the hip-joint are not restricted. It is not always possible without
the aid of skiagrams to differentiate sacro-iliac disease from disease
of the lumbar spine, and the two conditions sometimes coexist.

The _prognosis_ is unfavourable, particularly in cases complicated by
extensive disease of the ilium with abscess formation and mixed
infection.

_Treatment._--In early cases the patient should use crutches and wear
a patten on the foot of the sound side; in more advanced cases he must
be confined to bed, and have absolute rest to the joint secured by
means of extension applied to both legs, or by other apparatus. In
children a double Thomas' splint or Stiles' abduction frame is a
convenient appliance. Counter-irritation by blisters or the actual
cautery may be had recourse to in dry cases in which pain is a
prominent feature. If operative treatment becomes necessary, as it
may, for removal of a sequestrum, access to the seat of disease is
obtained by removing the posterior portion of the iliac bone. Cold
abscess is treated on the usual lines.

#Syphilitic Disease of the Vertebrae.#--All the clinical features of
Pott's disease may be simulated by gummatous disease of the vertebrae.
This is usually met with in adults who have suffered from acquired
syphilis; it is most common in the upper cervical vertebrae, and begins
on the anterior surface of the bodies. The onset is more sudden than
that of tuberculous caries, and the progress more rapid. The bone is
early and extensively destroyed, but abscess formation is rare. Severe
nocturnal pains are complained of, and some degree of angular
deformity may develop. In almost all cases other evidence of tertiary
syphilis is present, and this, together with the history and the
effects of anti-syphilitic treatment, aids in diagnosis. The local
treatment is carried out on the same lines as for tuberculous disease.

#Malignant Disease of the Vertebrae.#--_Sarcoma_ is the most important
of the primary tumours met with in the vertebral column. It gives rise
to symptoms which are liable to be mistaken for those of Pott's
disease or of arthritis defor