The pathology of the solids in fever, derived from inspection of the fatal cases after death, has already acquired, as we have seen, a high degree of perfection. The pathology of the fluids is scarcely at all known, and the difficulty of arriving at exact and certain results is great. Why the investigation of the morbid changes that take place in the fluids should be a much more arduous task than that of tracing the changes produced in the structure of the organs, is too obvious to need to be pointed out; but those only who have actually engaged in researches of this nature can form a just conception of the number of repetitions that are requisite of the same analysis, of the care required in conducting each, and consequently, of the labour and time it is necessary to devote to the investigation, before satisfactory results can be obtained. The analysis of the animal fluids in their healthy state is far from being perfect; yet their composition in the state of health must be ascertained, as far as it can be ascertained, as a preliminary step: and, in order to discover the morbid changes that take place in the blood, in the urine, in the products of respiration, and in those of transpiration, and still further to determine the nature and extent of such changes in the different types and stages of fever, it is obviously necessary to examine the respective fluids and gases in a great number of cases, and to vary the experiments in a great variety of modes. Experiments of this kind, on an extensive scale, have been undertaken by my friend Mr. Cooper; and, when this work was commenced, they had already advanced so far that there appeared to be a prospect that, before its completion, they would be sufficiently matured to justify us in laying the results before the reader. And that deviations from the state of health, and some of them of great importance, do take place in these fluids, and especially in the blood and the urine, is ascertained. What they are, with what degree of constancy they occur, how far they are respectively connected with the cerebral, the thoracic, the abdominal, and the mixed affections, with different degrees of intensity in these affections, and with different stages of their progress, we hope, at no distant period, to be able to lay fully before the public.