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FEVER (Lat. febris, connected with fe...

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Originally appearing in Volume V10, Page 306 of the 1911 Encyclopedia Britannica.
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FEVER (See also:Lat. febris, connected with fervere, to See also:burn) , a See also:term generally used to include all conditions in which the normal temperature of the See also:animal See also:body is markedly exceeded for any length of See also:time. When the temperature reaches as high a point as 1o6° F. the term hyperpyrexia (excessive fever) is applied, and is regarded as indicating a See also:condition of danger; while, if it exceeds 107° or io8° for any length of time, See also:death almost always results. The diseases which are called specific fevers, because of its being a predominant See also:factor in them, are discussed separately under their See also:ordinary names. Occasionally in certain specific fevers and febrile diseases the temperature may attain the See also:elevation of 110°-112° See also:prior to the fatal issue. For the treatment of fever in See also:general, see See also:THERAPEUTICS. See also:Pathology.—Every rise of temperature is due to a disturbance in the See also:heat-regulating mechanism, the See also:chief variable in which is the See also:action of the skin in eliminating heat (see ANIMAL HEAT). Although for all See also:practical purposes this mechanism See also:works satisfactorily, it is not by any means perfect, and many physiological conditions cause a transient rise of temperature; e.g. severe See also:muscular exercise, in which the cutaneous eliminating mechanism is unable at once to dispose of the increased amount of heat produced in the muscles. Pathologically, the heat-regulating mechanism may be disturbed in three different ways: 1st, by See also:mechanical interference with the See also:nervous See also:system; 2nd, by interference with heat elimination; 3rd, by the action of various poisons. 1. In the human subject, fever the result of mechanical interference with the nervous system rarely occurs,, but it can readily be produced in the See also:lower animals by stimulating certain parts of the See also:great See also:brain, e.g. the anterior portion of the corpus striatum. This leads to a rise of temperature with increased heat See also:production. The high temperature seems to cause distintegration of See also:cell See also:protoplasm and increased See also:excretion of See also:nitrogen and of carbonic See also:acid.

Possibly some of the' cases of high temperature recorded after injuries to the nervous system may be caused in this way; but some may also be due to stimulation of vaso-constrictor See also:

fibres to the cutaneous vessels diminishing heat elimination. So far the pathology of this condition has not been studied with the same care that has been devoted to the investigation of the third type of fever. 2. Fever may readily be produced by interference with heat elimination. This has been done by submitting See also:dogs to a temperature slightly below that of the rectum, and it is seen in See also:man in See also:Sunstroke. The typical nervous symptoms of fever are thus produced, and the See also:rate of chemical See also:change in the tissues is accelerated, as is shown by the increased excretion of carbonic acid. The protoplasm is also injured and the proteids are broken down, and thus an increased excretion of nitrogen is produced and the cells undergo degenerative changes. 3. The products of various micro-organisms have a toxic action on the protoplasm of a large number of animals, and among the symptoms of this toxic action one of the most frequent is a rise in temperature. While this is by no means a necessary See also:accompaniment, its occurrence is so general that the term Fever has been applied to the general reaction of the organism to the microbial See also:poison. Toxins which cause a marked rise of temperature in men may cause a fall in other animals. It is not the alteration of temperature which is the great See also:index of the severity of the struggle between the See also:host and the See also:parasite, but the death and removal to a greater or lesser extent of the protoplasm of the host.

In this respect fever resembles poisoning with phosphbrus and See also:

arsenic and other similar substances. The true measure of the intensity of a fever is the extent of disintegration of protoplasm, and this may be estimated by the amount of nitrogen excreted in the urine. The increased disintegration of protoplasm is also indicated by the rise in the excretion of See also:sulphur and See also:phosphorus and by the See also:appearance in the urine of See also:acetone, aceto-acetic and R-oxybutyric acids (see See also:NUTRITION). Since the temperature is generally proportionate to the intensity of the toxic action, its height is usually proportionate to the excretion of nitrogen. But sometimes the rise of temperature is not marked, while the excretion of nitrogen is very decidedly increased. When the temperature is sufficiently elevated, the heat has of itself an injurious action on the protoplasm, and tends to increase disintegration just as when heat elimination is experimentally retarded. But the increase due to rise of temperature is small compared to that produced by the destructive action of the microbial products. In the beginning of a fever the activity of the See also:metabolism is not increased to any marked extent, and any increase is necessarily largely due to the greater activity of the muscles of the See also:heart and See also:respiratory mechanism, and to the muscular contractions which produce the initial rigors. Thus the excretion of See also:carbon dioxide—the great measure of the activity of metabolism—is not usually increased, and there is no See also:evidence of an increased See also:combustion. In the later stages the increased temperature may bring about an See also:acceleration in the rate of chemical change; but this is comparatively slight, less in fact than the increase observed on taking muscular exercise after See also:rest. The rise of temperature is primarily due to diminished heat elimination. This diminished giving off of heat was demonstrated by means of the calorimeter by I.

See also:

Rosenthal, while E. Maragliano showed that the cutaneous vessels are contracted. Even in the later stages, until defervescence occurs, heat elimination is inadequate to get rid of the heat produced. The toxic action is manifested not only by the increased disintegration of protoplasm, but also by disturbances in the functions of the various See also:organs. The activity of the See also:digestive glands is diminished and appetite is lost. See also:Food is therefore not taken, although when taken it appears to be absorbed in undiminished quantities. As a result of this the patient suffers from inanition, and lives largely on his own fats and proteids, and for this See also:reason rapidly emaciates. The functions of the See also:liver are also diminished in activity. Glycogen is not stored in the cells, and the bile secretion is modified, the essential constituents disappearing almost entirely in some cases. Theproduction of See also:urea is also interfered with, and the proportion of nitrogen in the urine not in the urea increases. This is in See also:part due to the increased disintegration of proteids setting See also:free sulphur and phosphorus, which, oxidized into sulphuric and phosphoric acids, combine with the See also:ammonia which would other-See also:wise have been changed to urea. Thus the proportion of ammonia in the urine is increased.

Concurrently with these alterations in the functions of the liver-cells, a condition of granular degeneration and probably a See also:

state of fatty degeneration makes its appearance. That the functional activity of the kidneys is modified, is shown by the frequent appearance of proteoses or of albumen and globulin in the urine. Frequently the toxin acts very markedly on the protoplasm of the See also:kidney epithelium, and causes a shedding of the cells and sometimes inflammatory reaction. The muscles are weakened, but so far no satisfactory study has been made of the See also:influence of microbial poisons on muscular contraction. A granular and fatty degeneration supervenes, and the fibres See also:waste. The nervous structures, especially the See also:nerve-cells, are acted upon, and not only is their functional activity modified, but they also undergo structural changes of a chromatolytic nature. The See also:blood shows two important changes—first, a fall in the alkalinity due to the products of disintegration of protoplasm; and, secondly, an increase in the number of leucocytes, and chiefly in the polymorpho-nuclear variety. This is best marked in See also:pneumonia, where the normal number is often increased twofold and sometimes more than tenfold, while it is altogether absent in enteric fever. An interesting general modification in the metabolism is the enormous fall in the excretion of See also:chlorine, a fall far in excess of what could be accounted for by inanition, and out of all proportion to the fall in the See also:sodium and See also:potassium with which the chlorine is usually combined in the urine. The fevered animal in fact stores chlorine in its tissues, though in what manner and for what reason is not at See also:present known.

End of Article: FEVER (Lat. febris, connected with fervere, to burn)

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