Fever is a condition of increased bodily temperature, due to increased production or to decreased loss of heat. As a rule, in all fevers the metabolic changes in the body are increased. Hence the patient becomes emaciated in a long fever. The frequent increase in the amount of urea during fever shows an increase in protein metabolism. The temperature in fevers rises as high as 106° and in sunstroke sometimes to 110°. Except in sunstroke a higher temperature than 106° generally means death. Subnormal temperature is due to a decrease in the bodily metabolism and so to lessened heat production. As a rule, if the functions are all active, especially that of the sweat glands, a person can be exposed to severe heat without the temperature being affected, though sometimes on a hot summer day it may be up half to one degree. The cause of heat-stroke with its high fever is unknown, but probably it is due to some effect on the heat center in the brain. Heat prostration is also due to prolonged exposure to heat, but is generally accompanied by a subnormal temperature. The effect of cold, as in freezing, is to diminish all the metabolic activities of the body. The temperature can be artificially regulated more or less by variations of food, varying amounts of exercise, by drugs, etc.
Sense of Touch.—Before passing on to a discussion of the individual parts, a few words might well be said of the sense of touch, since that is general and resides largely in the skin, whose other functions have just been described. It may be regarded as the form from which all the other special senses have developed, certain portions of the body having become more sensitive than others to certain vibrations, as the eye to those of light. The internal organs probably have little sense of touch.
Figs. 13, 14.—Meissner’s corpuscle from man; ×750.
(Böhm, Davidoff, and Huber.)
Touch is useful only within arm’s reach but there gives one a sense of space that sight does not give. It is practically determined by the [touch corpuscles], which are found in the skin over almost the entire body, though they are more numerous in some places than in others, the distribution of the corpuscles determining the sensitiveness of the skin. These touch corpuscles are protoplasmic bodies containing nuclei, about which are entwined filaments from the cutaneous nerves. Where the corpuscles are absent the filaments of the cutaneous nerves themselves play an important part. The finger tips have a very delicate sense of touch and the tip of the tongue is the most sensitive part of the body. Hence spaces in the mouth seem larger than elsewhere. By the transmission of sensations of touch to the brain the sensation is localized and the tactile sensation becomes a tactile perception.
There are three main divisions of the sense of touch: 1. sensations of touch proper or tactile sensation; 2. sensations of temperature, and 3. sensations of pain. The temperature sense is the transmission by the skin of sensations not so much of a certain degree of heat or cold as of the difference between the temperature of an object and that of the skin. The longer an object is in contact with the skin, the less conscious the person is of it, not only because it becomes of the same temperature, but also because he becomes accustomed to it. There also seem to be in the skin, besides the touch corpuscles, two other terminal organs with separate nerve fibers, the one for detecting heat, the other cold; for there are places on the body where heat can be detected and cold cannot, and vice versa.
Sensations of pain may be merely an exaggeration of tactile sensation, as in too hard pressure or too great heat, but there seems to be also a sensation of pain in the skin. All organs are said to have common sensibility to pain and any exaggeration of this sensibility causes a sensation of pain. All the special senses require a certain amount of judgment in the interpretation of the sensations they convey.