be thin and
pointed, and project straight out from the transverse process
terminating in a free end, in which case, as it passes above the
subclavian artery and the brachial plexus, it gives rise to no
trouble. In other cases it arches downwards and forwards, and is
attached by dense fibrous tissue to the first thoracic rib about the
level of the scalene tubercle, or to the sternum by cartilage like an
ordinary rib. When it encroaches upon the posterior triangle the
scalene muscles are attached to it, and the subclavian artery and the
lower trunk and medial cord of the brachial plexus pass over it in a
groove behind the scalenus anterior. The pleura may reach as high as
the medial border of the rib.

_Clinical Features._--The condition, which is more common in women
than in men, is seldom recognised before the age of twenty, and is
often discovered accidentally, for example after some emaciating
illness, or by a tight collar causing pain. The diagnosis is
established by the X-rays.

[Illustration: FIG. 269.--Bilateral Cervical Ribs; the left one is the
better developed.]

When symptoms arise, they may be referable either to pressure on the
artery or on the nerve roots. When the subclavian artery is displaced
upwards it may be recognisable as a prominent pulsatile swelling, and
as the part of the vessel distal to the rib is sometimes dilated and
yields a systolic bruit, it may simulate an aneurysm (Sir William
Turner). The pulse beyond is weakened while the arm hangs by the side,
but may be restored by raising the hand above the head. Gangrene of
the tips of the fingers has been observed in rare instances, but it is
probably nervous rather than vascular in origin.

Symptoms referable to pressure on the nerve roots usually affect the
right arm, and may be either neuralgic or paralytic in character (Wm.
Thorburn). In the neuralgic group there is tingling pain, a feeling of
numbness, and sensations of cold in the limb, most marked along the
ulnar border of the forearm; the arm is weak, and susceptible to cold.
This condition may be mistaken for brachial neuritis; it is relieved,
however, by holding the arm above the head, for example, during sleep.

In the paralytic group, the pressure symptoms are referred to the
first dorsal, or first dorsal and eighth cervical roots. The paralysis
is most marked in the muscles of the thumb, and becomes less towards
the ulnar side; the affected muscles atrophy, especially those for