Neuralgia may be defined as a disease of the nervous system, manifesting itself by pains which, in the great majority of cases, are unilateral, and which appear to follow accurately the course of particular nerves, and ramify, sometimes into a few, sometimes into all, the terminal branches of those nerves. These pains are usually sudden in their onset, and of a darting, stabbing, boring, or burning character; they are at first unattended with any local change, or any general febrile excitement. They are always markedly intermittent, at any rate at first; the intermissions are sometimes regular, and sometimes irregular; the attacks commonly go on increasing in severity on each successive occasion. The intermissions are distinguished by complete, or almost complete, freedom from suffering, and in recent cases the patient appears to be quite well at these times; except that, for some short time after the attack, the parts through which the painful nerves ramify remain sore, and tender to the touch. In old-standing cases, however, persistent tenderness, and other signs of local mischief, are apt to be developed in the tissues around the peripheral twigs. Severe neuralgias are usually complicated with secondary affections of other nerves which are intimately connected with those that are the original seat of pain; and in this way congestions of blood vessels, hypersecretion or arrested secretion from glands, inflammation and ulceration of tissues, etc., are sometimes brought about. The above is a general description of neuralgia which will identify the disease sufficiently for the purpose of introducing it the attention of the reader. We must now proceed to give a more accurate account of its _Clinical History and Symptoms._--These vary so greatly in different kinds of neuralgia that it will be necessary to discuss the greater part of this subject under the headings of the special varieties of the disease. There are certain common features, however, in all true neuralgias.