larger amount of blood circulating in the part on account of the dilatation of the vessels. The pain is due to stretching of the nerve fibrils or compression of them by the turgid vessels in the swollen tissues. This latter cause is chiefly observed when the tissues are of a very unyielding character; for example, when the inflammation occurs in a bone or under a thick fibrous and unyielding membrane. The swelling, heat and pain may sometimes be relieved by mere change of position altering the flow of blood to the inflamed part. Thus when inflammation occurs in the finger, as in a whitlow, the pain is not only constantly severe, but it is increased by every pulsation of the heart, and thus has a throbbing character. By raising the hand nearly to a level with the head both the constant pain and the severity of the throbs may be relieved, as the blood is not sent with such great force into the arteries and returns more readily through the veins. In other parts of the body the same relief may be obtained by raising the inflamed part as high as possible. Relief is. frequently given also by both heat and cold, and at first sight it seems strange that agents having such an opposite action should each produce a similar effect. The reason probably is that the application of cold causes contraction of the arteries leading to the inflamed part, while heat by dilating the vessels around forms a side channel through which the blood passes, the tension in the seat of inflammation being thus lessened in both cases. When the inflammation occurs in soft parts where the surrounding vessels can be readily dilated, heat often affords more relief to the pain than cold, but when the inflammation is in a bone or in unyielding fibrous tissues, cold generally gives more relief. For example, the pain of a gum-boil is generally relieved more by warmth, because the yielding tissues of the gum, mouth and cheek can be readily relaxed by heat and their vessels dilated; but when the pain is dependent upon inflammation in the hard unyielding socket of a tooth, cold generally gives greater relief. The removal of blood, either by incision or by the application of leeches, sometimes gives considerable relief to the pain and tension of inflamed parts. Blisters applied at some distance from inflamed parts are also sometimes useful; and probably they produce this good effect by causing a reflex contraction of the arteries in the inflamed part, and thus acting like a cold application. Certain drugs have the power of relieving inflammation by slowing the heart and rendering its impulse more feeble. Amongst those are to be classed small doses of aconite and colchicum; the former especially tends to lessen the process of inflammation generally, when it is not too severe. There can be little doubt that the intensity of inflammation frequently depends very much on the condition of the blood, and that by altering the blood inflammation may be lessened. Thus free purgation, and especially purgation by cholagogues and salines, has long been recognized as a useful means of reducing the inflammatory process. For example, a mercurial pill at night, followed by salts and senna in the morning, will often relieve the pain in toothache or gum-boil, and lessen inflammation not only in the mouth, but other parts of the body as well. Such remedies are termed antiphlogistic. Venesection (blood-letting) at one time was highly esteemed as an antiphlogistic measure, and while it is possible that it has now fallen too much into disuse, there can be no doubt that at one time it was very greatly abused, and was carried to such an excess as to kill many patients who would have recovered perfectly had they been let alone. Although the high temperature in an inflamed part is chiefly due to the increased circulation of blood in it, yet the presence of inflammation appears to cause increased formation of heat either in the inflamed part itself or in the body generally, because we rarely find inflammation exist to any extent without the temperature of the body being raised and a febrile condition produced.
Two very old remedies for fever are acetate of ammonia and nitrous ether. These were formerly given empirically, simply because they had been found to do good. Now we can see the reason for their administration, because the nitrous ether, consisting chiefly of ethyl nitrite, dilates the superficial vessels and thus allows greater escape of heat from the surface; while acetate of ammonia, by acting as a diaphoretic and stimulatingFever. the secretion of sweat, increases the loss of heat by evaporation. When a patient is covered with several blankets, loss of heat from the surface both by radiation and evaporation is to a great extent prevented, but if a cradle be placed over him, so as to raise the bedclothes and allow of free circulation of air around his body, both radiation and evaporation will be increased and the temperature consequently lowered. If his body be left uncovered except by the sheet or blanket thrown over the cradle, the loss of heat is still greater, and it may be much increased by sponging the surface with either hot or cold water so as to leave it slightly moist and increase evaporation. The temperature may be still further reduced by placing vessels filled with ice inside the cradle. When the patient is very restless, so that cradling is impossible, a wet pack may be employed, a sheet wrung out of cold water being wrapped round him, and over this a blanket. The pack has the double effect of restraining his movements and thus lessening the production of heat, while at the same time it dilates the vessels of the skin and produces loss of heat. The restraint which it imposes and the equal distribution of heat over the surface frequently cause sleep quickly in patients who have previously been wildly delirious and entirely sleepless. When the temperature continues to rise in spite of wet sponging and cradling, recourse must be had to the cold bath. The bath should be brought to the bedside and the patient, wrapped in a sheet, should be lifted into it by two attendants. The water should be at the temperature of 90 and gradually reduced by the removal of hot water and displacement by cold, until the temperature of the patient as taken in the mouth is reduced to about 9912° or 99°. After this the patient should be taken out and again put into bed. It is inadvisable to lower the temperature quite to the normal while the patient is in the bath, as frequently it falls after his removal, and may fall so far as to induce collapse. In cases where no bath is available a large mackintosh sheet may be spread upon the bed under the patient, the sides and top may be raised by pillows, and cold water may be applied to the surface of the body with large sponges. The mackintosh sheet forms a shallow bath, and the water may afterwards be run off from it at the lower end of the bed. Another way of applying cold is to dip an ordinary sheet into cold water, apply it for three or four minutes to the surface of the body, then remove it and replace it by another sheet while the first one is being dipped in water. By the alternate use of the two sheets, or by the use of one quickly wrung out of cold water as soon as it becomes warm, the patient's temperature may be rapidly reduced.
There are a number of drugs which have a very powerful action in lowering temperature. Most of these belong to the aromatic group of bodies, although one of them, antipyrin, belongs rather to the furfurol group. Carbolic acid has an antipyretic action, but on account of its poisonous properties it cannot be employed as an antipyretic. Salicylic acid has a strong antipyretic action, and is most commonly used in the form of its sodium salt, which is much more soluble than the acid itself. Amongst other antipyretics, the most important are quinine, phenacetin and antifebrin. These probably lessen fever by their action upon the nerve centres which regulate the temperature of the body, and partly by their peripheral action in causing the secretion of sweat. Very high fever in itself will cause death, the fatal temperature in rabbits being 114.6°. Before death occurs the pulse and respiration become exceedingly rapid and weak, and complete unconsciousness sets in. That these symptoms are simply due to heat is shown by the fact that if the temperature be quickly reduced by the application of cold the symptoms at once subside. But the delirium which is common in fever, although it may be partly due to rise of temperature, is very often due to poisons in the blood, for in some cases it occurs with quite a low temperature, 101° or 102°, whereas in others the temperature rises to 104° and 105° with no delirium whatever. The presence of toxins in the blood not only
