Fever in general is characterized by a combination of disturbances in the physiological processes of the body. Such processes are those concerned in the production and dissipation of heat, in respiration and circulation, digestion and secretion, and in mental, motor, and other sensorial action. Such disturbances are manifested by a persistent elevation of temperature, an increased destruction of tissue, a quickened and modified pulse, accelerated breathing, increased thirst, diminished appetite, and diminished quantity and altered quality of the secretions. The sensorial disturbances include wakefulness and stupor, headache, delirium, twitchings, cramps, and other symptoms indicative of functional impairment of the nervous system. Of all these manifold evidences of fever, the elevation of temperature is the one whose cause, range, and results have been most carefully and critically investigated. No record of a case in which fever is present is regarded as complete without the chart of the daily variations in temperature, respiration, and circulation. The practical value of such records is thus admitted, and in the experiments relating to the origin of animal heat the observations of temperature are as essential as the chemical analyses, each of which supplements the other. The more accurate determination of the heat produced in the body is obtained either by the use of the calorimeter (an apparatus for measuring the collected heat liberated from the body) or by estimating the quantity of heat produced in the destruction of the constituents of the body from quantitative analyses of the discharged carbonic acid and urea. The results of such investigations are regarded by Rosenthal[5] as possessing only a relative value, but justify the conclusion that most of the heat produced in the organism results from the oxidation of its constituents. [Footnote 5: _Hermann's Handbuch der Physiologie_, Leipzig, 1882, iv. 2, 375.] For the preservation of health it is essential that this heat should be removed from the body in such quantity that the temperature of the latter shall not vary to any considerable extent, for any considerable time, from 37.2° C. (98.4° F.). The removal of the heat is mainly accomplished by its radiation or conduction into a surrounding cooler medium, and by the evaporation of moisture from the surface of the body. Too great a removal of heat results in death from freezing, while too great an accumulation of heat terminates fatally from the effects of an unduly elevated temperature. To ensure the normal range of temperature, constantly changing relations must exist between the production of heat and its dissipation. The cooler the surroundings, the more must heat be produced, or the less must heat be evolved from the body.