Varieties of Fever. Common Phenomena. Importance of this Analysis. Results of the Analysis. Organs always diseased in Fever: Functions always deranged in Fever. Fever not Inflammation: Distinction between these two States of Disease. Common Phenomena of Fever exemplified in Plague, in Yellow Fever, in the Varieties of the Fever of our own Country. Different Varieties produced by different Intensities of the same Affections. Received Classification and Nomenclature defective. What is really meant by Genera and Species of Fever. True Principle of Arrangement.

Fever is a genus consisting of several species, and each species presents many varieties. The external characters of these varieties and the internal states upon which they depend, are so opposite, that no two diseases in any two parts of the catalogue of nosology present a more diversified appearance, or require a more varied treatment, than may be the case with two different types of fever. The fever of one country is not the same as the fever of any other country; in the same country, the fever of one season is not the same as the fever of any other season; and even the fever of the same season is not the same in any two individuals. Many of the circumstances which constitute these varieties in the fevers of different seasons and of individual persons, are slight and trivial; but some of them are of the greatest possible importance, and those diversities, especially, which distinguish the fevers of different climates, are intimately connected with the causes, whatever they be, which render the disease mild or severe, and, consequently, comparatively innoxious or fearfully mortal.

Something there is, however, which, amidst this astonishing diversity, preserves the identity of the disease so completely and so obviously, that there never has existed any dispute about that identity, under any aspect which it has hitherto been observed to assume; so that all physicians, without exception, unhesitatingly accord the name of fever to the mildest form of the common fever of this country, to the yellow fever of the West Indies, and to the plague of Constantinople and of Egypt. Bring three persons, each exhibiting an exquisite specimen of one of these several forms of the disease into the same ward of an hospital, the external aspect presented by each would be so different, that an unprofessional observer would probably be able to discover in these modifications of the same malady no common property: yet there is no physician who would not, in each case, instantly pronounce the disease to be fever. There must, therefore, be something that establishes the identity of the disease under this diversity of aspect. What is that something? Whatever it be, it must be common to all the varieties of fever. Thus we are led at once to the second inquiry which we proposed to keep before us in this investigation, namely, what are the particular phenomena which are common to all the varieties and combinations of the disease?

The importance of making this analysis has been felt by every person who has directed his attention to this subject from the remotest antiquity down to the present time. That it is not as easy to be made as the necessity of it is plainly to be perceived is abundantly attested by the want of success which has hitherto attended the efforts to perform it of the acutest minds, and the acutest minds, the pride and boast of our science have applied themselves to the task. Notwithstanding their labours however, the analysis made by Hippocrates has been received through succeeding ages with little variation, and continues to be received even in modern times with only slight modification. And yet that reflecting men of every age have not been satisfied with resolving all the essential phenomena of fever into heat, although they have all consented to designate the disease by some term expressive of that property,^[17] is attested by proofs no less striking than instructive. We are informed by Van Swieten, that Boerhaave collected with much labour from a great variety of authors all the symptoms which they had observed in different fevers: that from these he threw out such as did not appear in all fevers, and that finding himself obliged to exclude one after another, he was at length greatly surprised to find the catalogue so short; it being ultimately reduced to three; namely shivering, frequent pulse, heat.

This is a sufficient and an interesting proof that this illustrious physician saw the importance of making the analysis in question; it shews also, that his ingenuity suggested probably the best mode of conducting it which a philosopher sitting in his study could devise; and the only proper mode of conducting it the circumstances of his age and country did not place within his reach. Accordingly his success did not equal his labour: for out of the three phenomena which he fixes upon as those that are common to all the varieties of the disease there is not one which is invariably found in any type of it; while in innumerable cases the combination of the three is not found. Shivering does not occur in some of the worst forms of the malady; and where it does, it is confined to the commencement of the attack, or to that of its exacerbations. The pulse, instead of being always more frequent than natural, in some of the most formidable aspects assumed by the disease, has been observed to be as low as forty or even thirty in the minute, and, from the beginning to the termination of the attack, the heat in some cases is below the natural standard, as it generally is in the commencement of the cold stage.

To the catalogue of Boerhaave, Cullen makes the following additions:—“languor, lassitude and other signs of debility, together with derangement of the functions, particularly a want of vigor in the limbs without any primary local affection.” This extension of the catalogue adds in no respect to the excellence of the generalization. It has all the vices which a definition can possess. The characters are not present in all cases; the very opposite are strikingly prominent in many, while the last, “without any primary local affection,” has so direct a tendency to mislead the mind, and positively to prevent it from observing the real phenomena of the disease, that it may well be questioned, whether the introduction of this single phrase into the definition of fever, has not been the occasion of far more practical mischief than has been compensated by any good that has been accomplished, or ever can be accomplished by all the rest of the nosology.

In the last attempt to improve the definition of fever with which I am acquainted, Dr. Wilson Philip says, “If we lay aside Dr. Cullen’s term pyrexia, (which it must be borne in mind is precisely Boerhaave’s brief catalogue) we shall considerably lessen the difficulty of giving such a definition of idiopathic fevers as shall apply to all cases. They may be defined as follows. Languor, lassitude, and other signs of debility, followed by a frequent pulse, and increased heat, without any primary local affection.”^[18] Inasmuch as this definition contains fewer words than that proposed by Cullen, it may be liable to fewer objections, but it is less faulty only because it is shorter.

This total failure of men, all of them of unquestionable acuteness, and some of them of splendid genius, in their attempts to discover the common phenomena of fever, affords a strong presumption that they have not pursued their object in the right path. Without doubt, before it is possible to succeed in any scientific investigation, it is necessary to form a distinct conception of the object of inquiry. Fever is not an entity, not a being possessing a peculiar nature; and the object of investigating it, is not to discover in what such nature consists, or what it is that constitutes its essence: but fever is a series of events, and the object of inquiry is to discover what the events are; what the events are that invariably concur in the series; and in what order they constantly succeed each other. When we have discovered this, we have ascertained all that we can ever know of what is termed the nature of fever, as it is this, and only this, that we can ever know of any object or process. Every natural object consists either of one single substance, or of several substances united; and our knowledge of that object is complete when we have ascertained what that single substance is; or what all the separate substances are that combine to form it. Every natural process consists of a number of events, and our knowledge of that process is complete when we have ascertained the events themselves, the order of their succession, and the events to which they give occasion. We can make no real progress in knowledge unless we keep steadily in view the kind of information which it is possible to acquire, and which it is to our purpose to seek; and dispossess our minds of the phantoms which have so long enthralled and abused them.

In relation to our present subject then, the first object of enquiry is, what are the events which invariably concur in fever?

Where shall we look for the events? Not in the symptoms. Symptoms are not events: they are only indications of events: symptoms depend upon states of organs: they are the external and visible signs of internal, and, for the most part, as long as life continues, invisible conditions. It is then to the state of the organs that we must look for the events of which we are in search.

Are there any states of any organs that always exist in fever? Are the states constant? Are the organs affected constant; and can both be ascertained? If this can be truly answered in the affirmative; if it can be proved that there are certain conditions of certain organs which invariably exist in fever, in every type, in every degree, in every stage of it, we shall have arrived at a satisfactory conclusion relative to the first part of our inquiry.

The evidence is as complete as observation during life and inspection after death can make it, that a morbid change does take place in a certain number of organs in every case of fever, from the most trivial intermittent to the most alarming continued fever, from the mildest plague to the most malignant typhus: that at the two extremes of this scale, and at all the intermediate gradations of it, there are certain organs which are always affected, and that the affection in all is similar.

The identity of the organs is inferred from the indications they give of disordered function during life: the identity of the affection is inferred from the similarity of morbid appearances which they exhibit on examination after death.

The organs affected are those which constitute the nervous system; those which constitute the circulating system, and those which constitute the systems of secretion and excretion. The spinal cord and the brain; the heart and the arteries, especially their capillary extremities; the secreting and the excreting organs, which in fact are composed, essentially, of the capillary extremities of the arteries; the secreting and the excreting extremities of these arteries, especially as they terminate in the external skin, and in the mucous membranes, which form the internal skin, this is the chain of diseased organs: derangement in the nervous and sensorial functions: derangement in the circulating function: derangement in the secretory and excretory functions, this is the circle of morbid actions.

There never was a case of fever in which all these organs and affections were not more or less in a morbid state: there never was a concurrence of this morbid state, in this complete circle of organs, without fever. The events which invariably concur in fever, then, are a certain deviation from the healthy state in the nervous and the sensorial functions; a certain deviation from the healthy state in the circulating function; a certain deviation from the healthy state in the functions of secretion and excretion. A deviation from the healthy state in one circle of actions will not present the phenomena of fever; a deviation from the healthy state in two circles of action will not present the phenomena of fever: there must be a deviation in the three circles before fever can exist. Such then are the common phenomena of fever.

For obvious reasons the detail of the proof that these several events really and invariably take place, must be postponed until the phenomena themselves have been stated, or what is termed the history of the disease has been given.

But it is not the invariable concurrence of a particular number of events that is alone sufficient to constitute fever: to this must be added invariableness of concurrence in a particular order. As will be shewn in the proper place, there is complete and irresistible evidence that these events do occur in one invariable order. Derangement in the functions of secretion and excretion never comes first in the series: derangement in the nervous and sensorial functions never comes last in the series: derangement in the function of the circulation never comes either the first or the last in the series, but is always the second in succession.

The order of events then is first, derangement in the nervous and sensorial functions; this is the invariable antecedent: secondly, derangement in the circulating function; this is the invariable sequent: and thirdly, derangement in the secreting and excreting functions; this is the last result in the succession of morbid changes.

Supposing the matter of fact to be as is here stated, and the proof that it is so will be adduced hereafter, it is clear that we are in possession of the true characters of fever. We know the events: we know the order in which they occur: we know therefore what it is that constitutes the disease, and we know consequently what it is by which it is distinguished from every other malady. No other disease exhibits the same train of phenomena in the same order of succession. In inflammation some of the phenomena are the same: but the order in which they concur is not the same; and this affords a clear and universally applicable mark of distinction between fever and inflammation. In inflammation there is similar derangement in the secreting and excreting functions: there is also sometimes similar derangement in the circulating function: but the derangement in the nervous and sensorial functions is seldom if ever similar: the derangement that does take place in these latter functions, while it is apparently different in kind, is certainly and invariably different in the order of its occurrence. In pneumonia, in enteritis, in hepatitis, the spinal cord and the brain are never the organs in which the first indications of disease appear: the earliest indications of disease that can be discovered have their seat in the affected organ itself: it is only after the disease has made some progress that other organs and functions are involved; and apparently, the last to be involved, and certainly the least to suffer, is the nervous system.

We can now then answer the questions so often asked—are fever and inflammation the same? and if not the same in what do they differ? Fever and inflammation are not the same, because the term fever is appropriated to the designation of a certain number of events which occur in a certain series: the term inflammation, on the other hand, expresses another series of events, each event composing this train, succeeding each other in a different order: and the difference between the two series of events is precisely this difference in their individual phenomena and in their order of succession. What the physical and the physiological condition of the organs is, as contrasted with their condition in the state of health, has not yet been made out with regard either to fever or to inflammation: in the present state of our knowledge, therefore, we can neither affirm nor deny any thing respecting either the identity or the difference of that physical and physiological condition of the organs in these two classes of disease. What inflammation is beyond the series of events we are able to observe we do not know: what fever is beyond the series of events we are able to observe we do not know: we compare the events and we see that they differ: and since the use of names is to mark and to express differences, it is right to distinguish these different events by different terms. But though in the present state of our knowledge we are not justified in considering fever and inflammation to be the same, yet the close, perhaps the constant connexion between them, is a fact of the utmost importance to be known, and requires to be incessantly before the view of the practitioner. And of this we shall have but too abundant evidence in the sequel.

Supposing the proofs hereafter to be adduced to be conclusive, that the events in fever and their order really are what has now been stated, how clearly and beautifully does this view of the disease enable us to recognize one and the same malady through all the modifications it undergoes, and therefore through the countless aspects it assumes. Out of the system of organs that are always affected in fever some may be more and some may be less diseased; and it is easy to see how, from this diversity alone, the utmost variety may arise in the external characters of the disease. Thus, at one time, the spinal cord and the brain may be intensely affected: consequently the patient may be seized with violent pains in the limbs; with ferocious head-ache; with early delirium, which may rapidly increase to such a degree of violence as to require restraint: or, on the contrary, all the muscles of voluntary motion may be seized instantaneously with such a loss of energy that they may truly be said to be paralyzed: at the same time the sensorial faculties may be overwhelmed almost as completely as they are in apoplexy: thus may be formed one type of fever: and such a concourse of symptoms is actually found to exist: it ushers in the plague when it first stalks into a devoted city to sweep away its thousands and its tens of thousands.

At another time the disease may seize with peculiar violence upon the organs of secretion, and especially upon those which belong to the digestive apparatus: hence the liver may suddenly pour forth an immense flow of bile, so vitiated in quality as to irritate and inflame whatever it touches, and so abundant in quantity as rapidly to diffuse itself over every part of the body, and to tinge almost every tissue and every fluid: at the same time the stomach and intestines may be involved in such acute disease that the powers of life may be exhausted in a few hours by incessant vomiting and unconquerable purging: thus may be formed another type of fever, and such a concourse of symptoms actually occurs in the yellow fever of the West Indies.

Now we may witness a severe though a less violent affection of the spinal cord and the brain than occurs in plague. There may be present great pain in the back and limbs; intense head-ache; early and violent delirium; a burning skin; a quick and strong pulse; urgent thirst, and constipated bowels: or, on the contrary, there may be not pain of the head, but giddiness; not delirium, but stupor; not a burning hot, but a moderately warm or a cool skin; not a frequent and strong, but a frequent and feeble pulse. In either case we have a fair specimen of the common fever of our own country, the first forming the variety which may be termed acute, the second subacute cerebral.

Now again we may witness a concurrence of symptoms very similar to the latter in the commencement of the attack, only that there is from the beginning greater prostration of strength; and a rapid increase in the derangement of the nervous and sensorial functions: together with a brown and dry tongue; a tender abdomen, and dark and offensive stools: thus may be formed another type of fever to which is commonly assigned the name of typhus.

In each of these cases the most urgent symptoms have their seat only in one set of the organs that compose the circle which we have said to be involved; but in every case all the other organs included in that circle are as really, though not as intensely diseased. When the spinal cord and the brain are so violently affected that the patient appears to be struck with paralysis or apoplexy, the attention is not strongly drawn to the state of the mucous membrane of the digestive apparatus; to the nature of the secretions and excretions of which it is the source; to the temperature of the system, or to the condition of the circulation: because the affection of the nervous system being overwhelming, and all the other affections being comparatively trifling, it is natural that the former should, in a manner, absorb the mind of the observer; yet, if the skin, the pulse, the tongue, the evacuations are examined, all will be found to be in a morbid state, and that morbid state will bear a certain proportion to the affection of the nervous system.

In like manner when the organs of the digestive apparatus form the strong hold of the disease, the morbid condition of the spinal cord and brain, and the altered action of the heart and arteries, may attract less notice; but that morbid condition will be not the less real, and will contribute its portion of disease to the general derangement of the system, not the less certainly because the indications of its existence may be less obtrusive.

And in the milder forms which the fever of our own country presents, in the most intense cerebral affection with which we ever meet, there will always be present unequivocal indications of deranged function both in the heart and arteries, and in the organs of secretion and excretion: while in cases in which the brain may be tolerably clear; in which there may be little or no headache; little or no pain in the limbs; no delirium; in which the disease may be chiefly seated in the mucous membrane of the stomach and intestines, and the prominent symptoms be, pain of the epigastrium, tenderness on pressure over the whole abdomen, a red tongue, and frequent stools, still if we examine the state of the pulse, if we look at the quality and the distribution of the nervous influence, if we observe the operations of the sensorial faculties, we shall find these functions to be as truly, though not as intensely deranged as if the full force of the disease were spent upon the organs in which these functions have their seat.

Thus, although all these organs are invariably affected in every case of fever, yet in no two cases are all these organs affected in the same degree. Sometimes one system is more affected than another; sometimes one organ of one system, and these different degrees of affection, in these different systems, are variously combined and modified. How great then must necessarily be the diversity of symptoms presented by the different forms of fever! How incalculable are the varieties that result from difference of intensity alone. One degree of affection of the brain, for example, will occasion violent headache, constant watchfulness, great restlessness, a peculiar expression of the eye, and intolerance of light; in another there will be no headache, or none of which the patient will complain; there will be sleep though it be disturbed and unrefreshing; there will be no peculiar expression of the eye, and no intolerance of light. By one degree of affection the sensibility will be rendered preternaturally intense; by another it will be totally obliterated: one will produce violent delirium, another, only slight wandering, or unrefreshing slumber: one, violence requiring restraint; another, profound coma. In the circulating system the symptoms will alike vary. One degree will produce a quick, strong and hard pulse; another, a quick, small and feeble pulse; another, a slow and intermittent pulse. A similar diversity will be found in the temperature of the body: in one, the heat will be little changed; in another, it will be below the natural standard; in a third, it will be intense, and the organs of secretion and excretion will equally vary in the extent of their morbid changes.

Thus, from one and the same affection of one and the same organ, not only different but opposite symptoms will be produced in all the organs involved in what we may call the febrile circle. When to this variety are added diversities occasioned by various stages of the diseased processes that are going on in the system; by the previous state of the organs affected; by the reaction of the affected organs one upon another, producing innumerable and ever varying combinations of different intensities of affection, in different sets of organs; and by the treatment to which the whole have been subjected, we cannot wonder if the symptoms of fever appear to be countless.

That no two cases of fever can ever be precisely the same, and that it must be vain to seek for the common phenomena of the disease in the external symptoms, must now be obvious: and why success can never attend the search after these common phenomena in such symptoms as “shivering, frequent pulse, heat,” must be equally manifest. These as well as all other symptoms depend upon the state of the organs. But we have seen that in one degree of the same affection of the same series of organs there may be shivering; excited pulse; burning heat; while in another degree there may be no shivering, a slow pulse and a cold skin: so that from one and the same affection, differing only in the degree of its intensity, the symptoms may not only vary but be directly opposite. The proper object of pursuit in all these enquiries, therefore, is the real nature of the affection, and the symptoms are of consequence only as they are indications of the existence of that affection. Symptoms are not the thing in which observation should terminate, but signs of the thing without the knowledge of which, in every individual case that may come under his care, the practitioner ought never to be at rest, and to the discovery of which they serve as guides.

It is then in the organs alone that we can find a perfect uniformity: but their condition is as fixed and invariable as the return of day and night. All the operations of nature are uniform. When, in any case, we have succeeded in discovering what the operation is, we see that it never varies. The same causes, under the same circumstances, always produce the same effects. The causes of fever, whatever they be, under the same circumstances, always produce the same conditions of the organs. In proportion as we ascertain with clearness and precision what these conditions are, we observe that they recur in all cases with the most undeviating regularity, and when our knowledge of them shall have become complete, it is probable that we shall find that they are as constant in their return as that of the sun after its setting, and that they no more change in their nature or progress than the sun deviates from its path.

The all important thing for the practitioner to know, then, it can never be too often repeated, is what these conditions are. It is greatly to be regretted that we do not know with precision the condition of the most important organs in the intense fevers of other climates. The condition of the most important organs in the various types of fever as they occur in our own country, we do now know with precision, and the main object of the present work is to give an account of these conditions, and of the signs which denote them.

It is found that particular conditions of particular sets of organs give rise to certain groups of symptoms: these groups of symptoms have been supposed to form different genera and species, and have received specific names. Were the nomenclature of these genera and species of fever perfect, the name would in each case be expressive of the condition of the organs upon which the assemblage of symptoms it denotes depends, and perhaps in some greatly advanced state of our science, when these conditions have been perfectly ascertained and have become perfectly familiar, an approximation to this desirable classification and naming may be attempted with success. The state of our knowledge, however, enables no one to undertake the task at present, and in the mean time the slightest glance at the divisions which have been attempted of this class of diseases, is but too sufficient to shew the total absence of that kind of information, which, if there be any truth in the preceding observations, it is alone of value to possess.

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!

A similar want of knowledge exists relative to the condition of the organs in most of the Exanthemata. To supply that want in regard to the various forms of fever that prevail in this metropolis, which, there is good reason to believe, differ but little from the types that appear in other parts of the country, is one of the chief objects for which this work is undertaken.

It is not the object of the present volume to treat of intermittent or of remittent fever, but only of that class which, in ordinary medical language, is termed continued. Of the apparently endless varieties of disease comprehended under the term continued fever, it is found that certain forms occur in this country with great constancy. Each particular assemblage of symptoms occurring in these different forms is said, in ordinary language, to constitute a type or species. Each type or species depends on a particular condition of the circle of organs that has been described. The causes that concur to produce this particular condition of this series of organs, will be treated of in their proper place. But these assemblages of symptoms never occur without being accompanied by these particular conditions of the organs; and these conditions of the organs are never found without having been connected with these assemblages of symptoms. In all the forms of fever hitherto observed this condition of the organs is found to be absolutely the same: it never differs in any thing but intensity; of this the evidence is complete and irresistible: the direct and legitimate inference is, that all these different forms of fever differ in nothing excepting in the intensity of the affection. Were the terms genera, species, variety, merely used as short expressions to denote this fact; to point out and to name different degrees of the same malady, degrees which it is important to discriminate, because they require material modifications of treatment, a clear and precise meaning would be affixed to these words: in nature there would be foundation for the distinction they imply: in practice there might be convenience in their use. But the nosological distinctions at present inseparably associated with these terms, appear to me to be either so vague and unmeaning, or when they cease to be indistinct, to excite notions so false and pernicious, that I think it right to abandon the use of them altogether. The more we investigate the subject, the more satisfied we shall become that continued fever is one disease and only one, however varied, or even opposite, the aspect it may present; but that it differs in intensity in every different case, and that this and this alone is the cause of the different forms it assumes. Many of these diversities it would be frivolous to distinguish: some of them, on the other hand, it is of the highest importance to discriminate. For all useful and practical purposes, it is necessary only to arrange the different assemblages of symptoms into two great classes, the one comprehending the mild and the other the severe forms of the disease. All the forms that continued fever can assume, and all the individual cases that can occur under either, must be mild or severe, and, therefore, must readily find its place under one or other of these divisions. The only real difference in the disease being a difference in degree, it is proper that the principle of the division, by which the varieties it presents are classified, should be founded on this, the only true distinction of which it admits.

It is difficult to frame, and still more difficult to bring into use, new terms; and there is nearly equal inconvenience in using old terms in a new sense: but if the new meaning affixed to an old term be clearly intimated and rigidly adhered to, it is, perhaps, upon the whole, productive of less evil to adopt the old, thus determining and limiting the signification, than to propose a nomenclature entirely novel. For this reason, and only for this reason, I propose to adopt two words, borrowed from the nosology of Cullen, and in common use. These words are here employed merely to express differences of degree relative to one and the same disease. The mild degree may be denoted by the term synochus: throughout this work, this term will be used to express the milder form of fever; that is, its ordinary or common form, or that which it is found most frequently to present in this metropolis, and, I may add, in this country. The severer form, on the other hand, may be designated by the term typhus. Each will be found to present a distinct assemblage of symptoms; each will be found to depend upon a particular condition of certain organs; each will be found to require a peculiar treatment.

For the purpose of distinguishing further important differences, that is, differences which bear an important relation to practice, it will be convenient to divide each of these two great classes into two minor sections. Thus, synochus may be divided into synochus mitior and synochus gravior; and typhus into typhus mitior and typhus gravior. This will afford convenient and ample means of throwing into distinct groups all the varieties of fever that occur in this country, which it can be of any practical importance to distinguish.

This mode of viewing fever as one great and extensive malady never differing in nature, but in every two cases differing in intensity, and giving rise by these differences in intensity to various forms of disease, thus affords a principle of arrangement applicable to all those various forms, which, while it is at once simple and comprehensive, is at the same time in the highest degree practical. It directly leads the mind to the observation of the real, the important differences that exist or that may arise; those differences which must influence and guide the treatment, if it be not altogether blind, and in the worst sense of the term empirical. This principle might easily be extended, and I think with advantage, so as to comprehend the exanthemata, and all the forms of fever which have hitherto been known to exist, or which can arise. Scarlet fever, for example, is continued fever attended with a peculiar eruption upon the skin: at one time it occurs in a mild, at another in an exceedingly severe form: the assemblage of symptoms in the first are precisely those which it is intended to comprehend under the term synochus: the assemblage of symptoms in the second are those which are designated by the term typhus: thus scarlet fever exhibits at one time the synochoid, and at another the typhoid type; the first being what is commonly termed scarlatina benigna, the second scarlatina maligna; and each type is capable of existing in two degrees of severity, one of which may be conveniently distinguished by the term mitior, and the other by that of gravior.

In like manner small-pox is a fever attended with a peculiar eruption upon the skin, which eruption modifies the disease in a very remarkable manner, and gives it a history and progress peculiarly its own; but it is as much a genuine fever as typhus, and ought no more to be taken out of this class on account of the eruption upon the skin, than scarlatina, which likewise modifies, in a very considerable degree, the whole train of febrile symptoms, and is attended with a peculiar condition of some exceedingly important internal organs. Small-pox, like all the diseases of this class, occurs in two widely different forms; the one mild, the other intensely severe: in the first the concourse of symptoms are precisely those of the synochoid, in the second of the typhoid type.^[22] And the same I am satisfied is true of the plague, of the yellow fever, and of all the different forms which this great disease, of many aspects and names, but of one uniform and unchanging nature, presents.

These distinctions and names then, though it were easy to raise objections against them, may serve for all useful and practical purposes. They tend to impress upon the mind the great fact that all the modifications of the disease are still only modifications, and do not affect the identity of its nature; and they afford convenient sections under which to detail the symptoms that attend and discriminate the important diversities in degree as they present themselves in practice; to exhibit the condition of the organs upon which those diversities depend, and to explain the treatment which experience teaches to be appropriate to these several states.

The present work will be restricted to the consideration of the modifications of fever which we have proposed to designate by the terms synochus, typhus, and scarlatina.