(_c_) _Cervico-brachial Neuralgia._--This group includes all the neuralgias which occur in nerves originating from the brachial plexus, or from the posterior branches of the four lower cervical nerves. The most important characteristic of the neuralgias of the upper extremity is the frequency, indeed almost constancy, with which they invade, simultaneously or successively, several of the nerves which are derived from the lower cervical pairs. The neuralgic affections of the small posterior branches (distributed to the skin of the lower and back part of the neck) are comparatively of small importance. But the "solidarite," which Valleix so well remarked, between the various branches of the brachial plexus, causes the neuralgias of the shoulder, arm, forearm, and hand to be extremely troublesome and severe, owing to the numerous foci of pain which usually exist. Perhaps Valleix's description of these foci is somewhat over-fanciful and minute; but the following among them which he mentions I have repeatedly identified; (1) An axillary point, corresponding to the brachial plexus itself; (2) a scapular point, corresponding to the angle of the scapula. (It is difficult to identify the peccant nerve here; the one to which it apparently corresponds, and to which Valleix refers it, is the subscapular; but we are accustomed to think of this as a motor nerve. Still, it is certain that pressure on a painful point existing here will often cause acute pain in the nerves of the arm and forearm.); (3) A shoulder point, which corresponds to the emergence, through the deltoid muscle, of the cutaneous filets of the circumflex; (4) a median-cephalic point, at the bend of the elbow, where a branch of the musculo-cutaneous nerve lies immediately behind the median-cephalic vein; (5) an external humeral point, about three inches above the elbow, on the outer side, corresponding to the emergence of the cutaneous branches which the musculo-spiral nerve gives off as it lies in the groove of the humerus; (6) a superior ulnar point, corresponding to the course of the ulnar nerve between the olecranon and the epitrochlea; (7) an inferior ulnar point, where the ulnar nerve passes in front of the annular ligament of the wrist; (8) a radial point, marking the place where the radial nerve becomes superficial, at the lower and external aspect of the forearm. Besides these foci, there are sometimes, but more rarely, painful points developed by the side of the lower cervical vertebræ, corresponding to the posterior branches of the lower cervical pairs.