d adductor muscles of the thigh in
disease of the knee, and in the deltoid in disease of the shoulder. The
muscles become soft and flaccid, they exhibit tremors on attempted
movement, and their excitability to the faradic current is diminished.
The muscular tissue may be largely replaced by fat.

_Impairment of the normal movements_ is one of the most valuable
diagnostic signs, particularly in deeply seated joints such as the
shoulder, hip, and spine. It is due to a protective contraction of the
muscles around the joint, designed to prevent movement. This muscular
fixation disappears under anaesthesia.

_Abnormal attitudes of the limb_ occur earlier, and are more pronounced
in cases in which pain and other irritative symptoms of articular
disease are well marked, and are best illustrated by the attitudes
assumed in disease of the hip. They are due to reflex or involuntary
contraction of the muscles acting on the joint, with the object of
placing it in the attitude of greatest ease; they also disappear under
anaesthesia. With the lapse of time they not only become exaggerated, but
may become permanent from ankylosis or from contracture of the soft
parts round the joint.

_Startings at night_ are to be regarded as an indication that there is
progressive disease involving the articular surfaces.

_The formation of extra-articular abscess_ may take place early, or it
may not occur till long after the disease has subsided. The abscess may
develop so insidiously that it does not attract attention until it has
attained considerable size, especially when associated with disease of
the spine, pelvis, or hip. The position of the abscess in relation to
different joints is fairly constant and is determined by the anatomical
relationships of the capsule and synovial membrane to the surrounding
tissues. The bursae and tendon sheaths in the vicinity may influence the
direction of spread of the abscess and the situation of resulting
sinuses. When the abscess is allowed to burst, or is opened and becomes
infected with pyogenic bacteria, there is not only the risk of
aggravation of the disease and persistent suppuration, but there is a
greater liability to general tuberculosis.

The sinuses may be so tortuous that a probe cannot be passed to the
primary focus of disease, and their course and disposition can only be
demonstrated by injecting the sinuses with an emulsion of bismuth and
taking X-ray photographs.

Tuberculous infectio