Neuralgia (Gr. vevpov, nerve, and alyoq, pain), an affection of which pain is the essential and characteristic feature, without visible alteration of the tissues or organs in which it is seated, and which depends on some disease affecting the structure or function of the nerves or of their centres. The varieties of neuralgia are very numerous. Some are distinguished according to the nerve affected; as neuralgia of the trifacial nerve, commonly called tic douloureux; sciatica, or neuralgia of the sciatic nerve; intercostal neuralgia, affecting the intercostal nerves, etc. Other varieties are described according to the locality which is the seat of pain; as gastralgia, or pain in the region of the stomach; nephralgia, or pain in the region of the kidneys, etc. Other varieties again are indicated by the causes which produce them; as miasmatic neuralgia, the neuralgia caused by marsh miasm; saturnine neuralgia, the neuralgia produced by the poison of lead, etc. The causes of neuralgia may be classified as constitutional and local.

The principal constitutional causes are: 1, an impoverished condition of the blood, resulting either from haemorrhage or the exhausting effects of disease, such as fevers, chlorosis, etc.; 2, the miasm of paludal regions; 3, the materies morbi of rheumatism; 4, the virus of syphilis; 5, the circulation in the blood of poisonous secretions, such as urea and bile; 6, the poisonous effects of lead, and probably of some of the other metals; 7, the functional derangement of the nervous system in the disease known as hysteria. The local causes are: 1, inflammation of the delicate fibrous sheath which envelopes the nerves, called the neurilemma; 2, the development of tumors near the origin, or along the course, or amid the ramifications of the nerves, as neuromata, fibrous tumors growing from the nerve sheath, and cancerous, aneurismal, cartilaginous, or bony tumors, so situated as to stretch or press upon the nerves; 3, the bulbous expansion of the extremities of divided nerves, oc-curring after amputation, and causing painful stumps; 4, the pinching of nerves in the cicatrices or scars of lacerated wounds. - The successful treatment of a neuralgia depends of course on a correct appreciation of the causes that produce it.

Where it arises from constitutional causes, it is generally amenable to treatment. The neuralgia that depends on an impoverished state of the blood yields almost invariably to iron tonics, good diet, and outdoor exercise; that which arises from the effects of paludial poison disappears rapidly under the use of quinine; neuralgia of rheumatic origin is ordinarily controlled by the preparations of col-chicum, the alkalis, alkaline and sulphur baths, & '..: while the neuralgia caused by lead poison has its specific antidote in the iodide of potassium, a remedy which is useful also in the neuralgia of syphilitic origin. The neuralgia which occurs in hysteria yields, like most of the protean phenomena of that disease, to the mineral tonics, electricity, shower baths, and exercise. Before speaking of the treatment of the forms of neuralgia caused by local disease, it is to be remarked that the seat of pain in these cases does not always correspond with the location of the cause of irritation. For instance, a tumor within the cranium may produce pain at the extremity of the sensitive nerves, near the origin of which it is located; or pressure in the course of a nerve may cause pain in its ultimate ramifications.

Where neuralgia is caused by irritation near the origin of the nerves, in the brain or spinal cord, its radical cure is generally impracticable; where it depends on the pressure of tumors that can be removed, the pain will generally disappear with the removal of the cause. In inflammation of the nerve sheath, local counter-irritation, by cups, blisters, issues, setons, etc, usually gives relief, and generally effects a cure. The neuralgia of painful stumps and scars, and of obstinate cases of inflammation of the neurilemma, requires surgical interference, such as reamputation, removal of the cicatrix, or ex-Section of a portion of the diseased nerve. Temporary relief may be given in all forms of neuralgia by the administration of powerful anodynes. Those most commonly used are morphine, the active principle of opium, and aconitine. the active principle of the aconitum aapellus or monkshood. These maybe used internally or externally. A solution of morphine injected into the areolar tissue beneath the skin. near the seat of the neuralgia, gives more prompt relief than when given by the stomach. Aconitine is generally used externally, in the form of an ointment, rubbed upon the affected part.

In most cases it rapidly relieves the neuralgic pain.