Fevers, Or Pyrexiae, diseases characterized by a morbid increase of animal heat not referable to any local affection; that is, diseases in which the febrile state is idiopathic or essential. (See Fever.) A fever lasting but a single day in some cases, or continuing for a few days in other cases, is called ephemeral fever or a febricula. It is without danger, as a rule, and calls for only palliative treatment. Exclusive of this form of fever, the different fevers are classified as follows: 1. Fevers characterized by periodical intermissions or marked remissions. This class is distinguished as periodical, or, from their causation, malarial fevers. Intermittent fever and remittent fever are embraced under these names, and yellow fever is generally included in this class. 2. Fevers which, in contrast with the foregoing, are characterized by a continuous febrile state, are called continued fevers. The fevers so classified are typhus and typhoid fever, relapsing fever, and erysipelatous fever. 3. Fevers in which an eruption on the skin is a prominent and a pretty constant feature are distinguished as eruptive fevers, namely, smallpox, chicken pox, scarlet fever, and measles. To this list may be added the disease known as the plague.

Other diseases which are essentially fevers are not always nosologically so classified. Examples of this kind are insolation or sunstroke, cerebro-spinal meningitis, influenza, and diphtheria. I. Periodical Fevers.-1. Intermittent and Remittent Fevers. The periodical fevers of malarial origin manifest this remarkable peculiarity: Intermissions or remissions recur at regular intervals, following a law of periodicity. This is especially marked in intermittent fever, called also fever and ague, chills and fever, and various other names. This law of periodicity varies, giving rise to what are known as the different types of an intermittent fever. The regular or simple types are as follows: a, the quotidian type, in which a paroxysm of fever recurs on each successive day; b, the tertian type, in which the paroxysms recur on every other or every third day; c, the quartan type, in which two days elapse between the paroxysms, that is, in which they recur on the fourth day, dating from the commencement of one to the commencement of the next paroxysm.

Compound types, as they are termed, are the' double quotidian, two paroxysms occurring daily; the double tertian, a paroxysm occurring daily, the paroxysms differing in certain respects on two successive days, but corresponding on alternate days; a double quartan, in which a paroxysm occurs on two successive days, and on the third day there is no paroxysm. Extremely rare varieties of type are a quintan, sextan, heptan, and octan; these names expressing the length of the intervals. The facts thus exemplifying a law of periodicity are, with our existing knowledge, inexplicable. A paroxysm of an intermittent fever, when complete, consists of three periods or stages, called generally the cold, the hot, and the sweating stage. These different stages are of variable duration, the length of the paroxysm in different cases varying from three to eight hours. The cold stage is sometimes characterized by shaking, that is, mus- cular tremor or rigor, and sometimes only by a sense of chilliness. This stage is sometimes wanting. The intensity of the fever varies much in different cases in the hot stage, and ' so the amount and continuance of the sweating; which follows.

If not arrested by remedies, intermittent fever tends to continue indefinite- ly, and is apt to induce notable anaemia or impoverishment of the blood (see Chlorosis), and sometimes general dropsy. Enlargement of the spleen is an occasional result of the disease. There are certain remedies which possess the power of arresting the parox- ysms, and these remedies are therefore called antiperiodics. The drugs which especially have this power are the salts of quinia or quinine. (See Cinchona.) In the vast majority of the cases of intermittent fever, the disease is promptly cured by quinine, which, given judiciously, does no harm. This drug also has a prophylactic power; that is, it pre- vents the occurrence of intermittent fever, and protects against relapses. Other remedies which are efficacious, but in a less degree, are salacine, bebeerine, ferrocyanide of iron or Prussian blue, strychnia, and arsenic. Remit- tent fever is also often controlled by uinia and other periodics.-In general, intermittent and remittent fevers are not immediately dangerous to life, even if they be allowed to continue; but they are sometimes attended' with great danger, and they may cause death within a few hours. In these cases the disease is distinguished as pernicious intermittent or remittent fever.

In some portions of this country it is called congestive chill. Patients affected with this fatal form may fall quickly into unconsciousness (coma), from which they do not emerge; some cases are characterized by delirium, and sometimes vomiting and purging occur, followed by a state of collapse resembling that in epidemic cholera. Pernicious intermittent or remittent fever is more apt to occur in tropical than in cold and temperate climates. Cases are more likely to occur at certain seasons than at others; and whenever their occurrence is observed, it is immensely important to arrest the disease in every instance as speedily as possible, lest succeeding paroxysms may prove to be pernicious. If a patient pass through one paroxysm in which the symptoms threatened danger, the treatment which succeeded in preventing another paroxysm may be the means of saving life. Quinine should be given promptly and boldly under such circumstances. -The nature of the special cause of intermittent and remittent fever is unknown. Whether it be a chemical product or a living entity (animal or vegetable) is as yet a question which can only be met with reasoning and speculations. The cause is endemic in certain situations, and therefore it is of telluric origin.