In conclusion, then, the doctrine of fever which appears to approximate most nearly to the truth, may be summed up in few words. The immediate cause of fever is a poison, which operates primarily and specifically upon the brain and the spinal cord. The diseased state into which these organs are brought by the operation of this poison, deprives them of the power of communicating to the system that supply of stimulus (nervous and sensorial influence) which is requisite to maintain the functions of the economy in the state of health. The organs, the seats of the functions, deprived of their supply of nervous influence, become deranged, the derangement in each taking place in a fixed order, and in a determinate manner. Subsequently to the nervous and the sensorial, the organs the next to suffer are those of the circulation; then those of respiration; and, ultimately, those which belong to secretion and excretion. The condition of the nervous system which produces this derangement in this circle of organs, occasions further, in that portion of the circulating system which consists of the capillary blood-vessels, that peculiar state which constitutes inflammation: hence inflammation is almost always established in one or more of the organs comprehended in the febrile circle, and sometimes in all of them. The peculiar and primary affection of the nervous system, which is here assigned as the cause of inflammation, does not become identical with inflammation, but superadds the morbid condition of inflammation to its own; does not lapse into or terminate in the inflammatory state, but accompanies it, and by this combination modifies in a peculiar manner the inflammatory process. The great practical conclusion to be deduced from this doctrine of fever is, that while the inflammatory processes that are thus set up in so many important organs, greatly aggravate the severity of the disease, and ought to be constantly kept in the view of the practitioner, both on account of their own peculiar danger, and also because they are perhaps the only real states over which he has any control, yet that these inflammatory processes do not alone constitute fever; that their removal, though essential to the cure, will not complete the cure; that another, a primary, and a most formidable disease, is at the same time to be contended with, and that the presence of this distinct and primary disease requires very important modifications in the treatment of the inflammatory condition. CHAPTER VIII. _Of the Causes of Fever._