There is a special cause of cervico-brachial neuralgias which is of more importance than, till quite lately, has ever been recognized, namely, reflex irritation from diseased teeth. The subject of these reflex affections from carious teeth has been specially brought forward by Mr. James Salter, in a very able and interesting paper in the "Guy's Hospital Reports" for 1867; and Mr. Salter informs me that he has been surprised by the number of cases of reflex affections, both paralytic and neuralgic, of the cervico-brachial nerves, produced by this kind of irritation, and that he agrees with me in thinking that a peculiar organization or disposition of the spinal centres of these nerves must be assumed in order to account for the fact. The liability of particular nerves in the upper extremity to neuralgia from external injuries requires a few words. The nerve which is probably most exposed to this is the ulnar. Blows on what is vulgarly called the funny-bone are not uncommon exciting causes of neuralgia in predisposed persons, and cutting wounds of the ulnar a little above the wrist are rather frequent causes. The deltoid branches of the circumflex and the humeral cutaneous branches of the musculo-spiral are much exposed to bruises and to cutting wounds. So far as I know, it is only when a nerve trunk of some size has been wounded that neuralgia is a probable result. Wounds of the small nervous branches in the fingers, for instance, are very seldom followed by neuralgia. I have no statistics to guide me as to the effect of long-continued irritation applied to one of these small peripheral branches, but it is probable that that might be more capable of inducing neuralgia. As far as my own experience goes, however, it would appear that a more common result is convulsion of some kind, from reflex irritation of the cord. (_d_) _Dorso-intercostal Neuralgia._--This is one of the commonest varieties of neuralgia, and yet it is very likely to be confounded with other affections not neuralgic in their nature. The disorder with which it is especially liable to be confounded is myalgia, which will be fully described in another chapter, and which, when developed in the region of the body to which we are now referring, is commonly spoken of as pleurodynia, or lumbago (according as it affects the muscles of the back or of the side), or muscular rheumatism. It must be owned that the severer forms of this affection can scarcely be distinguished from true intercostal neuralgia by anything in the character or situation of the pains. It will be seen, hereafter, however, that myalgia has its own specific history, which is very characteristic; at present, it is sufficient to remember that it is often extremely like neuralgia when situated in the dorso-intercostal region.