Writers on fever in general have confined their account of the phenomena of this disease to an explanation of the relation between the cold and the hot fits. Were their success in establishing that relation as complete as it is defective, they would still have done little or nothing, by a view so incomprehensive, towards establishing the theory of fever. Both the cold and the hot fits, about the exposition of which such a theory is alone concerned, are themselves accidents, since in the most formidable and dangerous forms of fever, the supposed relation between these phenomena is not only constantly disturbed, but often the phenomena themselves do not occur, it being one of the very characters of some of the intensest fevers, that the temperature is little changed, and that the diminished temperature which may be, or which may have been present, is never succeeded by any increase of heat. The true theory of this, as of every other disease, must be sought in the study of its pathology, and can be found only by comparing the pathology of the organs ascertained to be affected with their physiology. The cold stage of fever, when it exists, is produced by a disturbance of the functions of the circulation and of the respiration, and these functions are disturbed, because the organs in which they have their seat no longer receive their accustomed and their requisite supply of nervous influence from the nervous system. The hot stage, when it exists, arises from a disturbance of the same functions: and the reason why we cannot assign with precision why the same cause produces in the one case a diminished, and in the other an increased temperature, or why the temperature is disturbed at all, is because we do not know with precision on what circumstances in the animal economy the generation of heat depends: when the physiologist has clearly and completely ascertained all the circumstances upon which this process depends, the pathologist will probably have but little difficulty in tracing with equal clearness and completeness the connexion between the disturbance of that process, and the commencement of the febrile state.