The consideration of the diseased states of the other systems and functions that take place in fever, need not detain us long. The respiratory appears to be the next function that becomes deranged. The intimate and inseparable connexion which physiology teaches us subsists between the respiratory and the circulating systems, might lead us to anticipate the fact which pathology demonstrates. We know that the respiratory system is constructed for the circulating: that the form, the extent, the complication of the respiratory apparatus depend entirely upon the quantity of blood that is to be regenerated, and the degree of perfection with which that regeneration is to be accomplished. It is therefore impossible that any considerable derangement in the function of one of these systems should continue long, without being accompanied with a proportionate derangement in the other. The function of respiration cannot be materially deranged, without producing a morbid condition of the blood, that vital fluid which it is the specific object of the process to purify and regenerate. The function of secretion depends upon the quality of the blood conveyed to the secreting organ, upon the action of the capillary vessels of that organ, and upon the supply of nervous influence received by those vessels; it follows, that in a disordered state of the nervous, the circulating and the respiratory organs must be attended with a derangement in the process of secretion; while the excreting being necessarily connected with the secreting processes, the vitiation of the one cannot fail to occasion a corresponding deterioration of the other. Thus we see that the organs and functions deranged in fever are closely and inseparably connected: that no continued disorder can take place in the one, without producing a proportionate disorder in all the others: that a peculiar and specific affection of the first, according to the established laws of the vital economy, invariably produces a peculiar and specific affection of the second, and the second, a third, and so on throughout the circle. And now we see why a certain number of organs are invariably affected in fever; why these organs invariably become affected in a certain order; why the nature of their affection is invariably the same; and why, finally, the ultimate condition of the system, the general result of these individual morbid changes, never varies.