As the fever patient eats less than a healthy person, the excessive production of heat takes place, to a large extent, by the combustion of the tissues. Hence, as the fever progresses, there is great Wasting of the tissues, both of the adipose tissue and the proper nitrogenous tissues. The consumption of the nitrogenous tissues is expressed by the appearance in the urine of an excess of urea, which is the chief ultimate product of the metabolism of the nitrogenous principles in the body.

Under ordinary circumstances the amount of urea and other nitrogenous substances in the urine bears a close relation to the diet, being greatly diminished during fasting; hence the excretion of urea in fever can only be appreciated by comparing it with that of a healthy person on the same diet. A young healthy man on ordinary febrile diet will excrete 16 to 18 grammes (245 to 275 grains) of urea, while a similar person in fever will excrete 40 to 45 and even 50 grammes. The excess of urea has been stated by Unruh at 50 per cent., by Liebermeister at 70, and by Senator at 100.

It is a point of great interest that the increase of urea begins in some cases before the rise of temperature (Sidney Einger and others). This has been observed chiefly in relapsing fever, and indicates a period in which the fever is latent. There is also usually an excess of urea for the first two days or so of convalescence, the " epicritical" excess. This is, in some cases, due to a retention of urea, whose amount sometimes shows a diminution towards the crisis of the fever, especially in cases characterized by the so-called ' typhoid state.'

Besides the increase of urea, there is an increase of the so-called extractives, which are nitrogenous principles of various kinds. The colouring matter is greatly increased. The salts of soda, and more particularly the chloride, are diminished, while those of potash are much increased. The phosphates and sulphates are increased.

The State of the skin during the fastigium is worthy of special attention, especially as it forms an important item in the means of regulating the temperature of the body in health. The conditions vary considerably in different fevers, and even in the same case, from time to time. In a few forms (chiefly acute rheumatism) there is usually profuse perspiration, but as a general rule the skin is, considering the temperature, remarkably dry. Even apart from this,' however, the condition of the skin in regard to blood supply varies greatly, and its temperature also varies. Hence the temperature of the skin does not bear a close relationship to that of internal organs.

The Termination of fever is often by a more or less abrupt Crisis. It is as if the regulation of the temperature had been re-established in its normal condition, and the temperature rapidly falls to the normal This is often accompanied by an attack of sweating, this part of the apparatus for regulating the temperature, which we have seen to be disordered, being restored to action. The other secretions are also restored at the crisis, the salivary, gastric, etc. It is remarkable how a temperature which has been for days or weeks persistently above normal, will suddenly and definitely fall, and with this all the symptoms at once improve. Sometimes, however, there is a more gradual fall of temperature, and instead of a crisis we have a Lysis.

Theories Of Pyrexia

The very striking phenomena described above have been somewhat variously explained. In order that the different theories may be understood, let us remember the principal facts in regard to the phenomena. The rise in temperature is due directly to an abnormal combustion in the tissues, but the actual amount of heat-production is not greater than what frequently obtains in health without any rise in the temperature. The mode of heat-production is usually abnormal, implying a pathological metabolism in the tissues, but there is something abnormal also in the regulation of the temperature, as the body does not dispose of an amount of heat which it is capable of disposing of under normal circumstances.

It is acknowledged in all modern theories of fever that the abnormal heat-production is in the tissues, and is the result of increased tissue-change, and it is agreed that the regulating process by the nervous system is altered, but opinions differ in regard to the exact place which the nervous system takes in the matter. According to one view pyrexia is essentially due to the action of the nervous system, alterations in the heat-centre inducing the increased tissue-change, and at the same time changing the regulatory process. The view opposed to this is that the increased heat-production is due'directly to the action of the contaminated blood on the tissues, the abnormal constituents in the former inducing increased chemical change in the latter. The altered regulation is also regarded as related to the state of the blood.

The Nervous Theories Of Fever

The various theories which trace pyrexia to a nervous origin are chiefly based on the facts already indicated, that injuries to the brain, whether produced experimentally in animals or accidentally in man, have been known to cause a rise in temperature, sometimes to a very high degree.

The view of Liebermeister, adopted in this country by Hilton Fagge, is that in fever the high temperature depends on a change in the normal function of heat-regulation, according to which the balance of heat production and discharge is so arranged that the temperature is maintained at a higher level. The regulatory apparatus is at work, but it has pitched its normal at a higher level. The object of this change is a curative one. The high temperature has an influence in freeing the blood of the abnormal constituents which we have seen to be present in fever.

The view of Wood, Hale White, D. Macalister, and others is almost the converse of this. According to them the heat centre is paralyzed by the fever-producing agent. This centre when in normal action, as we have seen, is supposed to restrain or inhibit the production of heat, and when paralyzed it allows of an over-production.