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tents, and these last become often of the most continued kind. In all these cases, the fever has its paroxysms protracted longer than usual, before it changes into a type of more frequent repetition.

32. From all this a presumption arises, that every fever consists of repeated paroxysms, differing from others chiefly in the circumstances and repetition of the paroxysms; and, therefore, that it was allowable for us to take the paroxysm of a pure intermittent as an example and model of the whole,

CHAP. II.

OF THE PROXIMATE CAUSE OF FEVER.

33. The proximate cause of fever seems hitherto to have eluded the research of physicians; and I shall not pretend to ascertain it in a manner that may remove every difficulty; but I shall endeavour to make an approach towards it, and such as I hope may be of use in conducting the practice in this disease : while, at the same time, I hope to avoid several errors which have formerly prevailed on this subject.

34. As the hot stage of fever is so constantly preceded by a cald stage, we presume that the latter is the cause of the former; and, therefore, that the cause of the cold stage is the cause of all that follows in the course of the paroxysm. See Boerh. aph. 756.

35. To discover the cause of the cold stage of fevers, we may observe, that it is always preceded by strong marks of general debility prevailing in the system. The smallness and weakness of the pulse, the paleness and coldness of the extreme parts, with the shrinking of the whole body, sufficiently shew, that the action of the heart and larger arteries is, for the time, extremely weaken. ed. Together with this, the languor, inactivity, and debility of the animal motions, the imperfect sensations, the feeling of cold, while the body is truly warm, and some other symptoms, all shew that the energy of the brain is, on this occasion, greatly weakened; and I presume, that, as the weakness of the action of the heart can hardly be imputed to any other cause, this weakness also is a proof of the diminished energy of the brain,

36. I shall hereafter endeavour to shew, that the most noted of the remote causes of fever, as contagion, miasmata, cold, and fear, are of a sedative nature, and therefore render it probable that a debility is induced. Likewise, when the pa. roxysms of a fever have ceased to be repeated, they may again be renewed, and are most commonly renewed by the application of debilitating powers. And further, the debility which subsists in the animal motions and other functions, through the whole of the fever, renders it pretty certain, that sedative or debilitating powers have been ap: plied to the body,

37. It is therefore evident, that there are three states which always take place in a fever; a state of debility, a state of cold, and a state of heat ; and as these three states regularly and constantly succeed each other in the order we have mention. ed them, it is presumed that they are in the series of cause and effect with respect to one another. This we would hold as a matter of fact, even although we should not be able to explain in what manner, or by what mechanical means, these states severally produce each other.

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38. How the state of debility produces some of the symptoms of the cold stage, may perhaps be readily explained; but how it produces all of them, I cannot explain otherwise than by referring the matter to a general law of the animal economy, whereby it happens, that powers which have a tendency to hurt and destroy the system, often excite such motions as are suited to obviate the ef. fects of the noxious power. This is the vis Mes DICATRIX NATURÆ, so famous in the schools of physic ; and it seems probable, that many of the motions excited in fever are the effects of this power.

39. That the increased action of the heart and arteries, which takes place in the hot stages of fevers, is to be considered as an effort of the vis medicatrix naturæ, has been long a common opinion among physicians; and I am disposed to as. sert, that some part of the cold stage may be imputed to the same power. I judge so, because the cold stage appears to be universally a means of producing the hot; because cold externally applied has very often similar effects, and more certainly still, because it seems to be in proportion to the degree of tremor in the cold stage, that the hot stage proceeds more or less quickly to a termination of the paroxysm, and to a more complete som lution and longer intermission. See 30.

40. It is to be particularly observed, that, during the cold stage of fever, there seems to be a spasm induced everywhere on the extremities of the arteries, and more especially of those upon the surface of the body. This appears from the supression of all excretions, and from the shrinking of the external parts: and although this may perhaps be imputed, in part, to the weaker action of the heart, in propelling the blood into the extreme vessels'; yet, as these symptoms often continue af

ter the action of the heart is restored, there is rea. son to believe, that a spasmodic constriction has taken place; that it subsists for some time, and supports the hot stage; for this stage ceases with the flowing of the sweat, and the return of other excretions, which are marks of the relaxation of vessels formerly constricted. Hoffman. med. rat. system. tom. 4, p. 1, sect. 1, cap. 1, art. 4.

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41. The idea of fever, then, may be, that a. spasm of the extreme vessels, however induced, proves an irritation to the heart and arteries ; and that this continues till the spasm is relaxed or overcome. There are many appearances which support this opinion; and there is little doubt that a spasm does take place, which proves an irritation to the heart, and therefore may be considered as a principal part in the proximate cause of fever. It will still, however, remain a question, what is the cause of this spasm ; whether it be directly produced by the remote causes of fever, or if it be only a part of the operation of the vis medicatrix maturæ.

42. I am disposed to be of the latter opinion, because, in the first place, while it remains still certain that a debility lays the foundation of fever, it is not obvious in what manner the debility produces the spasm, and, what seems to be its effect, the increased action of the heart and arteries; and,

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