The same cause, when it acts upon the extremities of the blood-vessels, produces coldness and chills. This is obvious to any person, under the first impression of the miasmata which bring on fevers, also under the influence of fatigue, and debilitating passions of the mind. The absence of chills indicates the sensibility of the external parts of the body to be suspended or destroyed, as well as their irritability; hence when death occurs in the fit of an intermittent, there is no chill. A chilly fit, for the same reason, seldom occurs in the most malignant cases of fever. It is sometimes excited by blood-letting, only because it weakens those fevers to such a degree, as to carry the blood-vessels back to the grade of depression. Coldness and chills are likewise removed by blood-letting, only because it enables the arteries to re-act in such a manner as to overcome the depression that induced it. It has been remarked, that the chilly fit, in common fevers, seldom appears in its full force until the patient approaches a fire, or lies down on a warm bed; for in these situations sensibility is restored by the stimulus of the heat acting upon the extremities of the blood-vessels. The first impressions of the rays of the sun, in like manner, often produce coldness and chills in the torpid bodies of old and weakly people.
Tremors are the natural consequence of the abstraction of that support which the muscles receive from the fulness and tension of the blood-vessels. It is from this retreat of the blood towards the viscera, that the capillary arteries lose their fulness and tension; hence they contract like other soft tubes that are emptied of their contents. This contraction has been called a spasm, and has improperly been supposed to be the proximate cause of fever. From the explanation that has been given of its cause, it appears, like the coldness and chills, to be nothing but an accidental concomitant, or effect of a paroxysm of fever.
The local pains in the head, breast, and bones in fever, appear to be the effects of the irregular determination of the blood to those parts, and to morbid action being thereby induced in them.
The want of appetite and costiveness are the consequences of a defect of secretion of the gastric juice, and the abstraction of excitement or natural action from the stomach and bowels.
The inability to rise out of bed, and to walk, is the effect of the abstraction of excitement from the muscles of the lower limbs.
The dry skin or partial sweats appear to depend upon diminished or partial action in the vessels which terminate on the surface of the body.
The high-coloured and pale urine are occasioned by an excess or a deficiency of excitement in the secretory vessels of the kidneys.
The suppression of the urine seems to arise from what Dr. Clark calls an engorgement, or choaking of the vessels of the kidneys. It occurs most frequently in malignant fevers.
Thirst is probably the effect of a preternatural excitement of the vessels of the fauces. It is by no means a uniform symptom of fever. We sometimes observe it, in the highest degree, in the last stage of diseases, induced by the retreat of the last remains of excitement from every part of the body, to the throat.