III. Pathological Relations

The mechanism concerned in the regulation of the body-heat is liable to disorder, when heat-forming or heat-losing organs are diseased. Elevation of the body temperature, or pyrexia, most commonly called fever, is very rarely absent in illness of any consequence. An abnormal fall is seen as an effect of extreme cold or of exhausting diseases, but being comparatively insignificant does not require to be discussed here.

Pyrexia.-The temperature of the body may be abnormally raised in several ways. Thus we meet with excessive pyrexia in injury or disease of the heat-centre or tracts, especially injury of the cervical and dorsal regions of the spinal cord. Exposure to excessive heat induces "heat-fever," a variety of sunstroke which is common in India. More familiar to us is fever brought on by interference with the refrigerating function of the skin, as the effect of exposure to cold or damp. This is known as a "chill." A powerful impression of cold on the afferent nerves of temperature appears to throw the regulating mechanism into disorder; perspiration is arrested; the cutaneous vessels are spasmodically contracted; rigors, shivers, or chilly feelings ensue; and the heat thus retained in the blood quickly raises the temperature.

Increased production of heat at one focus, such as an inflamed part, contributes in an insignificant degree to the accompanying fever.

The increased production of heat in the tissues generally which is probably present in all kinds of fever, whatever its cause, is no doubt the principal origin of the pyrexia. The increased activity of metabolism is proved by the rapid wasting of the tissues, by the increase of urea and other excretions, and by the pyrexia as tested by the thermometer-all obvious phenomena in every case attended by fever.

In the specific fevers there is at work, however, another cause of oxydation of the tissues, which furnishes an extraneous addition to the body heat. We now believe that many diseases, such as typhoid fever, small-pox, and septicaemia, are associated with the presence of organisms in the tissues, if not actually caused by them. The life of such organisms, the processes of fermentation with which they are associated, and the destruction of the tissues which they produce, must all be a considerable source of heat within the body, in a way perfectly foreign to the normal processes, though closely resembling some of them.

A combination of several of the preceding causes is commonly at work in fever. Thus, when a patient has a local wound which acts as a focus of heat, the pus may decompose, i.e. become infected by organisms; these are absorbed into and flourish in the blood; fresh foci of disease are set up in the tissues; and the natural refrigeration of the blood is reduced by the disturbances of the skin, lungs, and circulation, which always accompany serious illness.

Disorders of perspiration.-Only two disorders of perspiration concern us here, viz. (1) excessive sweating, and (2) deficient sweating.

1. Excessive sweating, hidrosis, hyperidrosis, is found in a great variety of morbid conditions. In some kinds of fever, such as rheumatism, its pathology is bound up with the pathology of the fever as a whole. In disorders of respiration, as we have seen, dyspnoeal sweats are due to stimulation of the sweat-centres by venous blood. The "cold" sweats of wasting diseases such as phthisis, especially during sleep, appear to be due to the same cause, associated with anaemia and coldness of the skin, which prevent evaporation and "insensible perspiration," and thus give rise to a profuse collection of visible sweat as well as great depression of the bodily strength from interference with the cutaneous excretion. "Critical" sweats are referred to sudden changes in the disturbance of the vaso-motor system of the skin present in fever. Toxic sweating, as is seen in alcoholism and gout, may obviously be variously induced.

2. Deficient sweating : anhidrosis. -Dryness of the skin occurs at the beginning of most fevers, and throughout the course of most of them more or less interruptedly. It is also marked in some diseases and disorders of the urinary functions, such as Blight's disease and diabetes; in certain diseases of the skin itself; and as the result of poisoning by atropia (belladonna), etc. Manifestly different parts of the nervo-glandular apparatus are disordered in the different cases.

IV. Natural Recovery

Disorders of the body heat being disturbances of a regulating mechanism, that is, of one means of natural recovery, we can hardly expect to find at work in fever those very provisions which have been interfered with. For the same reason, the temperature of the body generally returns to the normal on the cessation of the cause of the fever, either spontaneously or with the artificial assistance of the therapeutist. Occasionally the temperature rises beyond all control-to 107°, 110°, and even higher, and the subject dies of the effects of excessive heat or hyperpyrexia. In most instances of death from fever, however, the fatal result is due to one of the other factors of fever, especially the body waste.

V. Therapeutics

A great part of our knowledge of the body heat, its regulation and its disturbances, has been derived from careful observation of the results of treatment; and the use of measures to control fever-antipyretics or febrifuges (febris, fever, and fugo, I drive away,) is one of the most successful, as well as rational, of therapeutical proceedings.

1. Preventive Treatment: Antiperiodics.-The periodical return of fever may be prevented by means of antiperiodics. The most powerful of these is Cinchona, with its constituents, especially Quinia; Salicin, Salicylic Acid, and Chinolin, are not so powerful; less important are Nectandra and its alkaloid Beberia.

2. Immediate Treatment

Immediate Treatment. With the abundant means at our command which we have discussed in the second section, the immediate treatment of pyrexia is very easy, inasmuch as we can lower the temperature of the surface of the body to any degree we please; for instance, by the cold bath. But we soon discover that it is one thing to reduce pyrexia, and another thing to treat fever. We can readily assist the refrigerating mechanism of the body, and we can even so far reduce the metabolic activity of the tissues, but our remedies can rarely reach the actual cause of the disorder, and the temperature rises again. As far as possible, however, we are bound to begin by discovering and attacking the causes; and if we fail in this, we must then combat the fever itself, so as to prevent its injurious effects on the system.