These periods are of uncertain duration except the reactive stage of the self-limited "diseases." Maladies such as rheumatism, neuralgia, neuritis, appendicitis, etc., present a wide range of difference.

The periods of reaction and termination often present more or less distinct changes or stages during their continuance. Thus in smallpox there are the stages of eruption, lasting from the appearance of the papillae to the distension of the vesicles: of suppuration, when the fluid in the vesicles is becoming purulent; and desiccation, when the pustules are drying into scabs. In pneumonia there are the stages of engorgement, when biogony is advancing; red hepatization when the cells are occluded with stagnant or exuded blood; and of gray hepatization, when the softening of the exudation advances.

Fever is almost if not always preceded by a chill in the cold stage--in which there is increased sensitiveness with chilliness when a current of air passes over the surface or perhaps the chilliness persists despite several blankets. In a short time this reaches a distinct sense of shivering, beginning usually in the back and extending over the limbs and body. This stage may be light and transient, but is usually strong enough to be marked to the feelings of the patient and is sometimes sufficiently violent to produce decided and visible rigors.

This chilliness may develop abruptly, without the patient noticing any premonitory symptoms, but the usual course is for the lassitude of the developing stage to slowly merge into the cold stage. The cold stage may last but a few minutes, or recur at intervals through several hours, or even over a space of several days.

During this stage aches and pains are present in the back, limbs, loins and perhaps in the head. Pains are most likely to be sharp or even violent in the back and groins, causing suffering and "nervousness."

The circulation, previously languid, now becomes depressed, the pulse is weak and "small," often irregular, and with varying frequency.

Peripherial circulation is feeble, perhaps lending a dusky-red or even purplish hue to the nails, and mottled appearance to the hands and feet. Paleness and perhaps contraction of the features, increased respiration, drowsiness and mental dullness accompany this stage. The temperature of the surface is lowered, although not always to a degree corresponding to the feelings. Internal temperature is commonly increased, though rarely reduced. The chilliness, which may exist despite summer temperature, is obviously a nervous sensation, as are many of the other symptoms of this stage.

This stage suspends skin radiation, suppresses sweating and withdraws the blood from the surface, to the point of injury. The chill has the effect of stimulating the thermogenic center and thus results in increased heat production.

The hot stage is the stage of fever (pyrexia) proper. Body temperature rises, due to suspended skin radiation, and the pulse rate is accelerated as is also respiration. This represents a vital reaction and may appear suddenly and be of short duration; but commonly develops gradually and continues many days; or even weeks, before subsiding.

External temperature is increased, the skin is dry, general secretions are diminished, heart action increases, sometimes ranging from 90 to 100, or even from 120 to 140 or more pulsations a minute, and internal temperature rises to 102, 103, 104, or even to 108 degrees.

As a general rule the frequency of heart action at this time is inversely proportioned to the energy of the organism; so that it is most frequent in fevers in feeble cases and less frequent when the person is strong and vigorous. In the first case the pulse will be rapid and weak, in the second case, it will be slower, and firm and strong.

Respiration is more or less hurried, corresponding in general with the rate of the circulation, the face is flushed, the head painful, sleep disturbed, the tongue coated, the breath fetid, the mouth and tongue dry, the secretions are altered and the body rapidly wastes due to the preponderance of katabolism over anabolism. The patient is weak, even prostrated and forced to rest.

So great are the nervous changes in fever, that Vircow declared that the essential phenomena of fever must have their immediate cause in this system. Let us glance at a few of these phenomena. The mental and bodily languor, the apathy and chilliness at the beginning of aggressive biogony belong to the nervous system. To this system also belongs the fact that the patient is sometimes so depressed during the cold stage as never to react from it, but dies in a few hours with profound prostration, a very rapid, feeble and failing pulse, and almost panting respiration.

When the temperature rises the restlessness, wakefulness, sensitiveness and tendency to slight nocturnal delirium seen in one class of biogonies are nervous manifestations, as are low delirium, somnolence, stupor, tremor, subsultus tendinum, and convulsions seen in another class of biogonies.

Defervescence is the term applied to the decline of the febrile process. The change is marked by increased activity of one or several of the excretory functions, a free perspiration being most common, accompanied with or soon followed by copious discharges from the kidneys and bowels. The resumption of sweating marks the resumption of skin radiation and this lowers temperature. Saliva and mucous are more abundant, moistening the mouth and tongue, the pulse rate decreases, and the head and general nervous system are relieved. The transition is sometimes quite sudden, there being no period of gradual recovery, or convalesence. This is more frequently seen in nervous affections. More commonly, however, there is a period of convalescence, in which the patient feels much exhausted after the unusual effort and losses incident to biogony, and regains strength by degrees.

When defervescence begins suddenly with discharges and a rapid lowering of temperature, it is said to end by crisis. If the temperature subsides slowly and regularly for some days and the secretions return gradually, without the development of critical discharges the "disease" is said to end by lysis. In some cases there is a combination of crisis and lysis--a crisis being followed by a gradual completion of the return to healthy action.

How is a crisis brought about at one time in one case and at another time in another case? How account for the retention of so much water during fever? I do not pretend to be able to explain these things. But we know that the more vigorous are the vital activities in biogony the greater is their likelihood of success and the less the danger of a fatal ending. I believe that the suspension or diminution of any function, particularly the excreting functions, is purposive and not a mere mechanical necessity. We know that these functions may be increased by a number of means so that we may be sure that their reduction serves some urgent need.

Occasionally defervescence is very irregular in its progress. It may advance and recede with strange uncertainty. In a few cases the temperature falls below the normal standard and the vital functions are markedly lowered, or seem to cease, so great is the need for rest.

I am aware that this presentation of the progress of fever is somewhat antiquated and is not strictly in harmony with the prevailing fashions. In our opinion) too much attention is given to themometric observations; for, however much thermometry may be able to disclose, it cannot picture the whole of the fever to us.

On the other hand, I do not like the method of describing certain forms or types of biogony as fevers. For, after all, increased temperature is but one incident in the symptom-complex presented by the patient. It would be just as logical to name these conditions after the vascular acceleration or the respiratory increase, etc., as after the increase in temperature.

Analysis of Fever History. The history of biogony should include the period of incubation, the cold stage, the hot stage and defervescence.

One of the most prominent phenomena of biogony is the retention of water in the body. The patient with fever has more than usual thirst, in some instances demanding enormous quantities of water. Accompanying this increased consumption of water is the characteristic fact that much less water is excreted from the body than in a state of health. The skin is dry due to the suspension of sweating. There is less moisture in the breath, saliva is diminished in quantity, the bucal mucous membrane becomes dry early in the biogony. The gastric and intestinal secretions are reduced, the feces, except in rare cases, are dry, while the quantity of urine passed is greatly reduced, actually becoming scantiest when the skin is driest. So uniform is the reduction of the urine that its concentration is almost as good an index to the amount of fever as is the thermometer.

Another marked clinical phenomena is the reduction of the amount of excreta. Despite the great and rapid wasting of the body the excretions are diminished. There may be an increase in one or the other processes of elimination, the urine, for instance, may contain increased amounts of urea, uric acid, phosphoric acid, sulphuric acid, etc., there may be diarrhea, even great diarrhea; or in exceptional instances there may be sweating; but these occurrences do not militate against the general fact that excretion is diminished during '"fevers." The diminuition of excretion begins before the fever sets in and continues till defervescence.

Although there is a diminished output from the body, the tissues themselves often seem to literally melt away. The fat disappears, the muscles are reduced and the bones may even become lighter. In the blood there may be a decrease of the red cells, an increase in white cells, a diminution of serum albumen, an increase in water, a reduction of alkalinity and a decrease of the alkaline salts. Products of tissue decomposition--uric or lactic acid, etc.--also find their way into the blood.

When finally the work of biogony is accomplished, and the patient makes a decided change healthward, excretions and secretions are resumed--there is free perspiration, increased urination, free bowel movements, a return of salivary and gastric secretions, and of suppressed menstruation, the temperature falls, pulse frequency becomes less and the pulse is stronger and the nervous system gives evidence of relief in great quietude or actual sleep. Appetite and the power to digest food slowly returns, nutrition improves, the wasted tissues are soon repaired, the body is renewed and should have better health than before the biogony.

A relapse is a resumption of the biogony after the patient is apparently convalescing. In relapses, the vital energies are prostrated from the original efforts; hence the system is not so active but the danger is much greater.

Convalescence is the period of recuperation following a successful biogony. It may proceed uninterruptedly, strength gradually recovering, the secretions becoming normal, the circulation steadily regaining its regular force, the nervous system recovering its accustomed equilibrium, feebleness and emaciation steadily disappearing.

This happy progress is subject to numerous interruptions, consequent upon extrinsic conditions unfavorable to health--such slight causes as too much food, undue excitement, over-exertion, exposure, etc., may sufficiently weaken the organism to result in a relapse.

Internal weakness--feeble digestion, nervousness, impaired kidneys, damaged lungs, etc.--may delay recovery for a time. But in due time these are likely to disappear and the rebound may even carry the body beyond the previous healthy standard--increased vigor, improved digestion, increased weight resulting.

Sometimes convalescence is somewhat protracted, lasting months and even years. An acute affection may subside into a chronic malady, as when acute bronchitis becomes chronic bronchitis; parts once affected are often subject to the same affection upon the slightest provocation for a long time thereafter; one form of "disease" often follows another, almost as if engrafted upon it, as when tuberculosis of the lungs follows pneumonia or an exanthem; or anemia or dropsy, follow an acute "disease," may still further impede recovery.