NEURALGIA - the term neuralgia is one which only serves to remind us of the limited range of our knowledge : had we attained to a perfect pathology, it would find no place in a systematic classification of disease, except as a symptom. In itself a mere sensation dependent on a variety of causes, we are yet forced very often to rest satis fied with the knowledge of its existence, without being able to trace it backward to its true source in the causality of disease ; and at the same time its very vagueness too often serves as a cloak for ignorance, or furnishes a ground for deception. It is exposed to all the difficulties in investigation which are insepara ble from merely subjective phenomena, and there are few indica tions by which we can correct an opinion we are driven to form merely upon the patient's own statement. Even when convinced that there is no exaggeration or deception, we are still so ignorant of the changes in nervous structure, that when able to prove by post-mortem evidence that there has been no traceable cause for the pain, we must rest satisfied with the fact that it has been felt, and with the expression that it was neuralgia.
One point is perhaps not sufficiently attended to in the employ ment of the term, that while in truth all pain is perceived by the nerves, and in that sense is seated in the nerve, yet all pain ought not to be called neuralgia. The true distinction between the two is that in the one instance the sensation is produced by some irri tation acting locally on the terminal filaments of the nerves which are the normal recipients of it while in the other it is caused by something affecting the trunk of the nerve, that bundle of fibres, large or small, lying within the neurilemma, which in a state of health does not receive but transmit the sensation : consequently, neuralgia properly so-called affects all the sensitive branches uniting to form the trunk on which the irritation acts, and pain is felt sometimes distinctly to the terminal filaments, sometimes vaguely in the course of the ramifying fibres. As in paralysis, a knowledge of the parts over which pain is distributed, and of the anatomical relations of the nerves, will best assist us in dis tinguishing between neuralgia and local pain. When two dia tinct parts of the body, having no nervous communication with each other, are both in the seat of pain, the presumption is very strong that they are not simultaneously affected with neuralgia; when all the structures supplied by one nerve are painful, it is highly improbable that each should be influenced by a local cause ; when one form of structure only is affected, we are led to suspect that there must be some change in that to account for the suffer ing, rather than an affection of the nerve: these rules are well exemplified in the diagnosis between rheumatism and neuralgia.
At the risk of repetition, I must again remark that if there be a distinction between pain and neuralgia, it is still greater between all sorts of pain and inflammation. Pain is the expression of irritation of nerve matter, and nothing more ; in different individuals it has a very different signification ; some are intolerant of pain, and generally use big-sounding words to express it—it is terrible. dreadful, intense—when, in reality, there is little derangement ; some are callous and indifferent, and will scarcely admit that they suffer pain, when such disorder is present as can scarcely exist without it. Perhaps the best criterion of the reality and amount of pain experienced by the patient, is when it produces an expression of anxiety and pinching of the features ; this is something quite different from the eyebrows being knitted together in a frown, and is equally distinct from the sadness and tear-shedding aspect of hysteria; it is one of the points in the physiognomy of disease which has to be learned by the student.
It may be stated generally that pain accompanying inflammatory action is less noticed by the patient than that attending nervous disorders, whether functional or neuralgic. The pain of inflammation is described as acute, darting, or stabbing. in opposition to dull, aching pain ; and that of suppura tien as a throbbing pain : but the whole vital functions are so deranged that the attention is less engrossed by it, and it less frequently forms the chief subject of complaint : perhaps, too, it is not so constant ; and as it is aggra vated by pressure, it is also in some measure dependent on movement, and is therefore less felt in perfect quietude. Inflammations of various organs differ very materially in the amount of pain they cause ; the hones, joints, and liga ments, the skin, and the scrolls membranes, become the seat of much greater pain when inflamed than the mucous membranes and the viscera. For ex ample, in peritonitis, acute rheumatism, gout, carbuncle, the pain is generally a prominent symptom ; in inflammations of the liver, the bowels, and the bladder, it is much less noticeable: again, a dyspeptic headache is much more complained of than the pain of the most intense meningitis ; in acute pleurisy, the patient dare not cough or draw a deep breath ; and yet, till his attention be drawn to it, the pain may be the last thing he speaks of. Corroding cancer affords an example of pain without inflammation. which is very severe and lancinating, and yet patients occasionally present themselves who suffer very little while laboring under that dreadful malady.