THE CAUSE OF FEVER.
The temperature of the body is maintained at a nearly constant level by the action of the nervous system. Heat is always being pro duced in the body, and heat is always being lost from the body. For a detailed considera tion of this subject refer to p. 186, Vol. 11. If the same level of temperature is regularly maintained, it is because the heat production and heat loss are regulated to balance one another, and this is effected by the nervous system. We need not atop to inquire here by what means this balance is effected by the nervous system. Details are given on p. 415, and the others already referred to.
Now in fever something occurs to upset the working of the control of temperature by the nervous system. It may be that the heat production in the body is excited to a rate that cannot be equalled by the heat loss in ordinary circumstances; or it may be that the arrange ments for promoting heat loss are upset, and that while there is a normal production the loss is far below the normal; so that tempera ture increases; or it may be the nerve-regulat ing portion of the mechanism that is disturbed. It may be that all three factors in the mainten ance of an even temperature are upset.
Most cases of fever, however, seem to fall under the first and the third of the possibilities stated. For the chief cause of fever is un doubtedly the introduction into the blood and tissues of the body of living organisms, which multiply enormously and produce the phe nomena of fever either by their vitality or by the substances which, in their multiplica tion, they produce.
Fever can be produced experimentally by the injection into the blood of material in which organisms have been grown, but out of which they have all subsequently been removed by filtration. That is to say, though no organ isms remain in the material, it contains all the waste products or by-products they produced while they were living and multiplying in it. Such material, injected into the blood, will pro duce all the chief phenomena of fever. The morbid material circulating in the blood, and coming into contact with the tissues, sets up an exaggerated tissue change, that is an ab normal heat production. This view of fever explains the great rapidity of exhaustion and the rapid loss of flesh in acute fevers, and also the increased quantity of waste products thrown off from the body. Thus in the urine the quantity of urea, which represents the break ing down of certain kinds of tissue, is increased nearly 50 per cent. The remarkable fact that, in some cases of blood poisoning, the heat of the body has gone on increasing for a time after death, is also explained by this view. It means that though the person has died, the tissues have not all died simultaneously, and the morbid production of heat has continued for a little in some of the tissues.
This explanation of fever would account for the rise of temperature in all cases where the disease is recognized as dependent on an infec tion, on the introduction into the body of a specific organism or an infusion of its products —toxins as they are called.
Thus we have the class of specific fevers, ab they are termed, of which scarlet fever, typhus, and typhoid are types.
The fever of pneumonia, of consumption, of influenza, of sore throat, can readily be ascribed to a similar cause. Indeed, all of these diseases are now ascribed to the operation of one kind of organism or another. All the varieties of blood-poisoning, including child-bed fever, are typical illustrations of the same kind of cause.
But there are cases in which, with an ailment strictly limited to a very restricted area, the temperature runs very high. For instance, a small boil in the ear of a child may produce very high temperature for several days. This, too, is an infection, the boil being due to organ isms, but it seems more likely that in such a case it is the nervous disturbance that is, in the main, responsible for the high fever. In the case noted, the bursting of the abscess in the ear and discharge of the matter is followed almost immediately by the disappearance of all the symptoms. This is not surprising if we suppose the local disease of the narrow ear passage so disturbed the nervous system as to cause the febrile manifestation, but one would hardly expect the fever to disappear so rapidly if it were due to a general overproduction of heat by the tissues, excited by a toxic cause.
We may conclude, then, that fever is in the main due either to an excessive pi oduction of heat in the tissues of the body, acted on by morbid material which has gained entrance to the body, or to disorder of the nervous arrange ments for regulating temperature produced by the ailment, and that L. many cases both of these factors play a part. In cases of the first type the amount of the fever will depend on the quantity or virulence of the morbid ma terial, and to a certain extent will indicate the gravity of the attack. In cases of the second type the height of the fever will depend to a greater extent on the excitability of the nervous system of the individual attacked, and on the situation and sensitiveness of the part which is affected by the ailment. Thus, children, with their uustable nervous system, and women, with their more excitable nervous system, ex hibit a higher degree of fever iu some ailments than men do. In this second type of cases, therefore, the gravity of the disease is not so well gauged by the height of the fever.