The normal temperature of the body depends upon the balance maintained between heat-production and heat-expenditure. This balance is maintained through a complicated nerve mechanism consisting of various nidi in thalamus, medulla, spinal cord and sympathetic ganglia, and a network of communicating axons of both the cerebro-spinal and sympathetic systems, controlling the amount of blood passing through any given body area at a given time, the secretion of the perspiratory glands, the internal metabolic processes, etc. Most important are the vaso-motor nerves, directly, but not originally, derived from the sympathetic, and governing the size and caliber of all blood-vessels so as to control the amount of blood flowing to and through the surface capillaries on the one hand, or the deep-seated, heat-making organs on the other. More than seventy per cent of the body’s heat expenditure is through the skin by evaporation, radiation, and direct conduction. The major portion of the heat production is in the muscles and the parenchymatous viscera, such as liver, spleen, etc., where metabolism is active. This mechanism is so delicately adjusted that when the outside temperature is lowered the amount of blood passing to the skin is reflexly lessened while internal heat production is increased and the bodily temperature retained at normal. Conversely, the body perspires freely and the surface is flushed with blood in a high temperature, so that heat production is lessened and its discharge accelerated, again tending to maintain an even and normal temperature. The nervous mechanism is responsive to many and various forms of stimuli--thermic, emotional, mechanical, physiologic need, toxic. Poisons in circulation may affect the bulbar center and produce general fever. A number of centers in the spinal gray may be stimulated with like result. Or there may be purely local irritation which results in local hyperaemia and inflammation. It will always be found that the primary cause of any permanent derangement of the mechanism lies in vertebral subluxation impinging some of the nerves and thus throwing the mechanism out of its natural balance and poise. Other forms of disturbance are transient and the very nature of the mechanism makes it normally capable of adjusting itself to thermic, mechanic, or emotional stimuli in a short time. Only the subluxation produces permanent elevation of temperature. When such elevation does occur there are many associated changes, increased katabolism, lessening of secretions, anorexia, sometimes mental changes, such as delirium or coma. Fevers vary according to the part of the nerve mechanism affected and the action of any secondary causes.