PAIN is an undefinable sensation, of the nature of which all persons are conscious It resides exclusively in the nervous system, but may originate from various SMUT:VS. Irritation, or excessive excitement of the nervous system may produce it; it frequently precedes and accompanies inflammation; while it sometimes occurs in, nail seems to he favored by a state of positive depression, as is seen in the intense pain which is often experienced in a limb benumbed with cold, in the pain which not unfrequeutiy accom panies palsy, and in the well-known fact, that neuralgia is a common result of general debility. Hence, pain must on no account be regarded as a certain indication of inflam mation, although it rarely happens that pain is not felt at sonic period or other in inflam matory diseases. Moreover, the pain that belongs to inflammation differs very much, according to the organ or tissue affected; the pain, for example, in inflammation of the lungs, differs altogether in character from that which occurs in inflammation of the bowels, and both these pains from that occurring in inflammation of the kidneys.
Pain differs not only in its character, which may be dull, sharp, aching, tearing, gnawing, stabbing, etc., but in its mode of occurrence; for example, it may be flying or persistent, intermittent, remittent, or continued. It is not always that the pain is felt in the spot where the cause of it exists. Thus, inflammation of the liver or diaphragm may cause pain in the right shoulder, the irritation caused by stone in the bladder pro duces pain at the outlet of the urinary passage; disease of the hip-joint occasions pain in the knee, disease of the heart is often accompanied with pain in the left arm, and irrita tion of the stomach often gives rise to headache. Pain is differently felt by persons of
different constitutions and temperaments, some persons being little sensitive to painful impressions of any kind, while others suffer 'greatly from slight causes. There even seem to be national differences in this respect; and before the introduction of chloroform it was a matter of common observation that Irishmen were always more troublesome subjects for surgical operations than either Englishmen or Scotchmen; and the negro is probably less sensitive to pain than any of the white races.
Although in most cases we are to regard pain merely as a symptom to be removed only by means which remove the lesion which occasions it, there are cases in which, although it is only a symptom, it constitutes a chief element of disease, and one against which remedies must be specially directed. As examples of these cases, may be men tioned neuralgia, gastralgia, colic, dysmcnorrhma, and perforation of the intestines; and in .'less degree, the stitch of pleurisy, which, if not relieved, impedes the respiration, and the pain of tenesmns, which often causes such efforts to empty the lower bowel, as seriously to disturb the functions of the intestine, and to exlmust the strength.
For the inepiods of relieving pain, the reader is referred to the articles ou the different diseases in which it specially occurs (as COLIC, NEURALGIA, PLEURISY, etc.), and to those on CimonoFouNr, Emma, INDIAN HEMP, MORPHIA, NARCOTICS, OP/IDI, etc.