It may be considered then as established, that the primary morbid condition of the body, in fever, consists of an affection of the nervous system, which there is reason to believe is of a peculiar and specific nature, although that nature be at present wholly unknown. This specific derangement of the nervous system having continued for some time, the vascular system becomes disturbed. How the nervous system so influences the vascular as to bring it into the morbid condition into which it passes, is as unknown to us as the peculiar affection of the nervous system itself. That there is the most close and intimate connexion between these two systems, and that they exert over each other the most important influence both in the state of health and of disease, are in the present state of our knowledge ultimate facts. With two apparent exceptions, (whether these two cases form real exceptions may still admit of doubt) the vascular derangement connected with, and dependant upon nervous derangement, passes sooner or later into true inflammation. Of this we have the most complete and indubitable evidence—evidence derived both from changes, the known results of inflammatory action, produced in the structure of organs; and from the generation of new products, such as are formed by no other known process but that of inflammation. Almost every change of organic structure which inflammation is ascertained to be capable of producing, is found to take place in fever: almost every product which inflammation is ascertained to be capable of forming, is observed to be generated in fever: it is not possible to doubt, therefore, that the morbid condition into which the vascular system is brought in the progress of fever, is that of inflammation. In what circle of organs inflammation is peculiarly liable to be excited in this disease, by what particular character febrile inflammation is distinguished, and what remarkable differences it exhibits in intensity and extent, have been fully illustrated. It follows, then, that the second event that takes place in the morbid series constituting fever, is inflammation.