In the mean time, it is of some importance to bear in mind the true place which the results of such experiments, be those results what they may, and be they established with all the clearness and certainty that can be desired, must always hold. Changes in the fluids can only be second in the series of morbid events; they can never hold the first place in that series; they can never be primary antecedents or first causes, but merely sequents or effects. To assign the reason of what must be so obvious to every one who is acquainted with the elements of physiology, would be entirely out of place here, because it would suppose the reader to be wholly ignorant of the functions of the animal economy. Our knowledge of the pathology of fever can never be complete, until we know the morbid changes that take place in the fluids as perfectly as we are acquainted with the alterations of structure that are produced in the solids, and we ought, therefore, to spare no labour to render our knowledge of the former as exact and certain as it is of the latter. But, as far as we can at present see, when this is accomplished, we shall have acquired little that is of practical utility. There is but slight, if there be any ground to hope that, when the humoral pathology shall have arrived at the greatest possible degree of perfection, it will furnish us with any additional means of preventing, curing, or even mitigating the severity of the disease. With that disorder of the system over which we have some control, with those morbid actions which we possess some means of subduing or changing, we are already well acquainted. In our knowledge of the invariable tendency there is to the production of certain changes in the structure of certain organs; in our knowledge of the vascular action by which those alterations are effected, we may be said, in a practical point of view, to be already in possession of the most important part of knowledge which we can ever hope to acquire, unless, indeed, we may indulge the expectation, of which it would be truly melancholy to be deprived, that we may discover a more sure and effectual mode of preventing these organic changes, or of restoring to a sound state the organs that may become diseased. It is this part of the pathology of fever alone that can afford a clear and steady light to conduct us to the safe and effectual treatment of the malady. Every step we take without this invaluable guide must be taken in the dark, and will be, therefore, not only likely to be false, but very likely to be fatal. When, on the contrary, we undertake the management of fever under the direction of this faithful guide, in every measure we venture to adopt we, at least, know at what we aim: we propose to ourselves a definite object which we endeavour to accomplish by an instrumentality with the powers of which we are in some degree acquainted: we may not succeed, but we fail because we want the means to do what we clearly see requires to be done: