Thus febrile diseases are commonly divided into idiopathic and symptomatic—a division which is liable to the fundamental objection that the diseases included under the second section are not fevers but inflammations. There are no fevers but idiopathic fevers. It has been shewn that fever differs from inflammation both in the individual phenomena forming the train that constitutes the disease, and in the order in which the several phenomena succeed each other. There are, it is true, individual phenomena common to both; but since the series as well as the order in which the several phenomena stand in the series are different, to call both by the same name can only produce confusion and misconception.
Of true or idiopathic fevers two great divisions are made; one comprehending intermittent and the other continued fevers: a division founded on the occurrence of the trains of the phenomena in an interrupted or in an uninterrupted series. Intermittent fever is further divided into intermittent and remittent, the interruption in the series being said to be complete in the one and incomplete in the other. In continued fever, on the other hand, the trains of phenomena are supposed to proceed in a perfectly uninterrupted series, whence the name continued. The single fact suggested to the mind of the practitioner by this classification is in the highest degree trivial.
Of the particular groups of symptoms which have been brought together under the great class, continued fever, it is impossible to discover any kind of principle which has led to the formation of the distinct assemblages that have been made, or to their nomenclature when thus collected. Synocha, typhus, synochus, are the three genera which modern nosology, in the power and pride of its strength, has put forth as at once distinctive and exhaustive of this class of disease. The aggregate phenomena constituting synocha, form just that particular series which is common to some forms of fever and to all acute inflammations: namely, “Calor plurimum auctus, pulsus frequens, validus, et durus, urina rubra, sensorii functiones parum turbatæ.” The train of symptoms thus brought together do not alone form any variety of fever. The second group of symptoms forming typhus—“morbus contagiosus, calor parum auctus, pulsus parvus, debilis, plerumque frequens, urina parum mutata, sensorii functiones plurimum turbatæ, vires multum imminutæ:” and the third, forming synochus,—“morbus contagiosus, febris ex synocha et typho composita; initio synocha, progressu, et versus finem, typhus,” independently of their being brought together and named according to no known or even assigned principle, are liable to the further and the fatal objection, that they do not even occur in nature.
Even Dr. Wilson Philip, who labours to reconcile to nature and to improve in accuracy and comprehensiveness these classifications and definitions, expressly admits that a simple synocha or typhus is a fever which we rarely, if ever meet with: for that however high the inflammatory symptoms at an early period may be, those of typhus always, at least in this country, sooner or later supervene; and that however well marked the symptoms of typhus may be in the progress of fever, in almost every case, the first symptoms are more or less inflammatory; that the fevers mentioned by authors, under the names synochus and typhus, are in fact no other than varieties of the synochus; that when the symptoms of debility predominate, the fever has been termed typhus; that when, on the contrary, the inflammatory symptoms are most remarkable, and present through the greater part of the disease, it has been called synocha.[[19]]
Again, while according to this received arrangement a train of symptoms, every one of which is found in acute inflammation, is made a distinct genus of fever, numerous diseases, each forming an exquisite specimen of fever, are totally excluded from the order, and placed at a considerable distance in the nosology. Because scarlatina is a fever attended with a peculiar eruption on the skin; because rubeola is a fever attended with an eruption on the skin also peculiar; because variola is a fever attended with another peculiar eruption, and urticaria with another, these diseases are not made varieties of fever, but, designated by the term exanthemata, are formed into a separate order: while, on the other hand, fevers attended with petechiæ, with papulæ, with aphthæ, with vesicles, are accounted fevers, and accordingly are termed petechial, miliary, aphthous, erysipelatous, vesicular fevers; whence synochus petechialis, synochus miliaris, synochus aphthosus, &c.
Without doubt is right that these varieties of disease should be discriminated and named; but this mode of classifying them has a necessary tendency to divert the mind from dwelling on those essential circumstances which make all of them mere varieties of one great disease; and to fix it upon those comparatively unimportant though obvious circumstances which simply modify the malady without in the least affecting its identity.
It has already been stated that the grouping of the symptoms, or, in other words, the formation of the species of fever cannot be scientifically or usefully accomplished until we have arrived at a perfect knowledge of the condition of the organs upon which the trains depend; and that our knowledge of these conditions is so imperfect, especially with regard to many of the species, that this classification cannot possibly be made at present. It is not even known whether the condition of the organs in intermittent be the same as it is in continued fever. The mere periodicity in the recurrence of the febrile paroxysms by which this class of disease is at present characterised, is an exceedingly unsatisfactory principle of distinction, unless we at the same time knew the state of the system upon which that periodicity depends. The alternate transition of intermittent into remittent and continued, and of continued and remittent into intermittent fever, of which the history of epidemics affords so many striking examples, and of which Sydenham, Pringle, and all the older writers have recorded so many interesting accounts, as events which they themselves daily witnessed, seems to shew that there can be nothing amounting to a generic difference between these several diseases. The type, as far as we have the means of judging, appears to be determined entirely by the intensity of the disease. An intermittent increasing in violence and malignity changes into a remittent or a continued fever, and a continued or remittent, diminishing in violence and malignity, often assumes the form of intermittent. Speaking of the epidemic constitution of the years from 1661 to 1664, Sydenham states that, in the year 1661, the autumnal intermittents which had prevailed for some years broke forth afresh, especially obstinate tertians; that increasing daily until August, at which time they raged fiercely and became extremely mortal, in many places seizing whole families, and destroying great numbers, decreased by degrees until October; and, disappearing at the approach of Winter, were succeeded by a continued fever, which differed from the Autumnal intermittent only in being continued, while the former returned in paroxysms: that both invaded almost alike; that those who violently laboured of either vomited; that in both the skin was dry; the tongue black, the thirst urgent, and that, at their declination, the morbific matter in both was readily exterminated by sweats. “It was manifest,” he adds, “that this fever belonged to the family of intermittents, because it rarely appeared in the Spring: it was a sort of compendium of the intermittents; and, on the contrary, every fit of the intermittent seemed to be a compendium of this fever; so that the difference chiefly consists in this, namely, that the continued fever once begun, perfects its effervescence with the same degree of heat; but the intermittents perform their business by parts, and at several times.”[[20]]
In like manner, Pringle, among many other examples of the fact, which, indeed, he states to be of constant occurrence, gives an account of an epidemic that prevailed in the army of the Netherlands, and which in its worst form assumed the appearance of an ardent fever. He states that the men were suddenly seized with violent head-ache, and frequently with delirium: that, if sensible, they complained also of grievous pain in the back and loins; intense thirst; burning heat; great sickness and oppression at the stomach, sometimes with vomiting of bile, sometimes with evacuation of bile by stool, accompanied with tenesmus and pains in the back: that this fever generally remitted from the beginning upon bleeding and purging: that if these precautions were omitted, the fever went on in almost a continued form, and that its tendency to putrefaction was so great, that while many had spots and blotches, some had mortifications, which were almost always fatal: that this fever continued to rage throughout August; that it began to abate with the heat in the middle of September; that from this period its violence diminished, and the number attacked gradually decreased; and that now “the remissions became more free, so that insensibly, with the coolness of the weather, this raging fever dwindled into a regular intermittent, and entirely ceased upon the approach of Winter.”[[21]]
What that condition of the system is, which, in forms of fever that are thus mutually convertible, causes one to persist in an uninterrupted series, another to remit, and another, after disappearing for a time, to recur in distinct and regular paroxysms, is wholly unknown. Sydenham, indeed, cuts the knot and removes the difficulty at once. Speaking of the return of the fits in intermittent, he replies to the inquirer into their cause,—“I would fain know why a horse comes to his growth in seven years and a man at twenty-one; or why some plants flower in May and some in June. I am persuaded that the progress of nature is as certain and regular in this case as in any other, and that the matter of a quartan and tertian ague is subject to Nature’s laws and governed by them, as well as any other bodies whatever.” The regularity of nature in the production of disease, no less than in the maintenance of health, cannot be doubted: but the point in question is not clearly one of those ultimate facts, into the reason of which it is wholly vain for the human mind to inquire.
Hitherto, however, no one appears to have hazarded even a conjecture as to the cause of this striking difference between these two forms of disease; and pathology, as has just been observed, has afforded no clear light to enable us to determine whether the febrile circle of organs is similarly affected in both. Examinations of fatal cases have been made; but none on that large scale and with that accuracy which alone can render them of any value. I have endeavoured to ascertain the morbid appearances in the spinal cord and the brain, and in the mucous membrane of the respiratory and digestive apparatus, from those who have been long engaged in extensive practice in districts in which ague prevails: but I have been able to obtain no satisfactory answer, excepting that intermittent does not kill! Greatly as the severity of intermittent is without doubt diminished, in the present age, yet we cannot receive such an account without blessing the bark of the seventeenth and the skill of the nineteenth century!