This subject, it is my intention to take up, and to discuss fully in a future publication, in which will also be investigated some inquiries, which it has been found impossible to include in the present volume; such as whether the vegetable and animal poison we have been considering, be the only true exciting cause of fever; by what means its general diffusion is effected; on what conditions its propagation depends; by what measures its extension may be checked, and its power diminished or destroyed; what circumstances in the modes of life, in the habits of society, in the structure of houses, in the condition of the public streets and the common sewers, in the state of the soil over large districts of the country, as influenced by the mode of agriculture, drainage, and so on, favour or check the origin and propagation of this great curse of civilized, no less than of uncivilized man. It is obvious that these inquiries will include the investigation of several exceedingly curious and important statistical questions; and the object of these researches will be accomplished should they lead to the establishment of any useful principles of extensive application.[34] II. OF THE REMOTE OR PREDISPOSING CAUSES OF FEVER. The remote or the predisposing causes of fever have been stated to be those circumstances which bring the body into a condition capable of being affected by the immediate or the exciting cause. Whatever diminishes the vigorous action of the organs, impairs their functions, and so weakens the general strength of the system, is capable of becoming a predisposing cause of fever; and every predisposing cause acts in one or other of these modes, and becomes a predisposing cause only and in proportion as it lessens the energy of the system, or disturbs the balance of its actions, which in fact is to render some portion of it weak. During a state of vigorous health the body is endowed with the power of resisting the influence of noxious agents, which in a less perfect state of health are capable of producing intense and fatal disease; and the action of all predisposing causes is to lessen this resisting power, or to weaken the energies of life. Of all predisposing causes, the most powerful is the continued presence and the slow operation of the immediate or the exciting cause. It is a matter of constant observation, that the febrile poison may be present in sufficient intensity to affect the health, without being sufficiently potent to produce fever. In this case the energy of the action of the organs is diminished, their functions are languidly performed, the entire system is weakened, and this increases, until at length the power of resistance is less than the power of the poison. Whenever this happens, fever is induced; not that the power of the poison may be at all increased; but the condition of the system is changed, in consequence of which, it is capable of offering to the noxious agent that assails it less resistance.