In regard to the Morbid Poisons, which excite diseases often of the most virulent and appalling character, but confined to certain seasons or localities, there has been much and often violent discussion within the last forty years; during which time the contagious nature of the fever of this climate, of yellow fever, of plague, of purulent ophthalmia, of erysipelas, dysentery, and malignant cholera has been successively and freely agitated; the laws of the origin and diffusion of the malaria producing intermittent and remittent fevers have been investigated; and the extraordinary protection against small-pox afforded by vaccination has been first established as a general law by the observations of Jenner, confirmed by others in all parts of the world, and afterwards ascertained to be subject to limitations, the exact amount of which is still doubtful.

Perhaps the most important results of the labours bestowed on these important subjects are the following:

1. The contagious nature of the common continued fever of this country has been firmly established; at the same time the truth of the representations of the older authors, as to the variations to which this disease is liable at different times and places, in duration, in symptoms, in the effects of different remedies upon it, and the extent to which these can be borne, and in the degree of its contagious property, has been fully and repeatedly demonstrated.

2. The influence of the most important auxiliary causes which favour the extension of this disease, the cold weather of this climate, imperfect nourishment, and mental depression,- has been fully exemplified and repeatedly observed, particularly in the disastrous history of various military enterprises, and in the equally melancholic civil history of one unfortunate portion of the British dominions:* whether these circumstances of predisposition ever suffice for the generation of the disease, without the aid of a specific contagion, is perhaps still doubtful.

3. It has been well ascertained, particularly by the researches of Dr. Bancroft, that neither the accumulation of human effluvia from healthy persons, nor the effluvia from putrid animal and vegetable matters, (however injurious to the strength, and in various ways to the health, of the human body,) are a sufficient cause for the production of contagious fever.

4. Several of the conditions which appear chief

*It is gratifying to be able to state that the members of the medical profession in Ireland cannot be charged either with want of zeal to alleviate the distresses of their countrymen, or with want of judgment and intelligence, in attempting to draw from these distresses, themselves, lessons of the highest importance to posterity.

malaria, which is the other great cause of fever, have been sufficiently investigated, perhaps more successfully by Dr. Ferguson, (Edinb. Philosophical Transactions, vol. ix.) than any other author. It appears certain that the stagnation, and subsequent evaporation of water on the earth's surface are essential to the development of this poison, and that the higher the temperature at which this evaporation takes place, the more violent is the poison generated. It is very doubtful whether any putrescent matter is necessarily connected with its formation; but it must be admitted that there is some condition necessary to that process, which is still unknown, and that we must still be guided in a great measure by experience, in judging of the situations where it is chiefly to be apprehended. [From all the writer's observations, it would not seem to be either of animal or vegetable origin, but to be geological, or connected with locality.]

5. It has been clearly ascertained that the contagious fever of this climate, which usually abates during the summer, is seldom or never met with in the tropical climates; and this fact seems to be illustrated by the important observations of Dr. Henry, by which it appears that the contagious effluvia of the exanthemata, as well as of typhus, loses all its efficacy at the temperature of 140° or even 120°. On the other hand, it is certain, that the fever from malaria is greatly aggravated in these climates, and takes, occasionally, quite the form of the most malignant Yellow Fever. [Yet there would seem to be a marked difference between yellow fever and those fevers that are commonly regarded as malarious-intermittent and remittent, for example.] It has been ascertained, also, that the worst epidemics of that kind, which have so frequently appeared in certain localities in the hot climates, are generally to be ascribed to certain local causes, and are confined within certain limits or boundaries; so that among those who keep beyond these limits the disease hardly ever spreads, whatever the intercourse of persons already affected with others may be; as has been repeatedly exemplified at Gibraltar, New York, &c.; but it is still doubtful whether, within these limits, and at these times, the worst form of the yellow fever does not spread by contagion.

6. It has been equally demonstrated that the Plague spreads by contagion chiefly, if not exclusively, although with very various rapidity on different occasions; and that precautions to prevent the intercourse of the sick with the healthy are more certainly efficacious in checking the ravages of that than any other epidemic disease; as has been repeatedly found in the experience of the British colonies in the Mediterranean, as well as of the army in Egypt. [Still, many observers deny its contagious nature].

7. It has been shown, to the satisfaction of the greater number of medical men who have seen the diseases prevailing epidemically, particularly in civil life, that the purulent ophthalmia is a con, tagious disorder; and that erysipelas and dysentery do also occasionally spread by contagion; but it has also distinctly appeared that completely isolated cases of the two last diseases, occur so much more frequently in some seasons and countries

than in others, that there must be some cause, not yet understood, corresponding to the idea usually affixed to the term "epidemic or atmospheric influence," which aids in determining many attacks of these diseases.

8. The numberless observations which have been made, in so many different quarters of the globe, on the diffusion of the malignant cholera, have still left such an obscurity on that point as clearly to indicate that the mode of extension of that "nova pestis" must be very peculiar. The present writer has no difficulty in expressing his own conviction that the disease has a contagious property; which conviction is founded simply on the repeated observation of persons who had intercourse with those ill of the disease, becoming themselves affected in a proportion infinitely greater than those, similarly circumstanced in other respects, who avoided such intercourse. But, on the other hand, it is equally certain that in various instances, where it has prevailed epidemically, this superior liability of those holding intercourse with the sick has not been observed; it has affected so many, in whom no such intercourse could be ascertained, or appeared possible, and has left unaffected so many others, whose intercourse with the sick had been frequent and close, that we can hardly suppose contagion the only mode in which it can diffuse itself.

It may be added, that whatever be the true origin of the poison which generates the cholera, it certainly possesses in an extraordinary degree the properties, which all other morbid poisons possess in some degree, of lying latent for a length of time,-in certain localities, or in the constitutions of individuals, or in both,-and afterwards resuming its activity and rapidly extending itself, without any assignable cause.

The additions which have been made to our knowledge of the nature and proper treatment of diseases during the time under review, may be traced, for the most part, to the extent and minuteness with which the study of morbid anatomy has been cultivated. The example of Baillie, in London; the lectures of the late Dr. Gregory, in Edinburgh, (who, although not deeply learned in morbid anatomy, was keenly interested in the subject, and took every opportunity of inculcating its importance ;) the laborious researches of Abercrombie and others, have had much influence in extending this study among British practitioners; but we must admit that it is to the zeal of the profession in France, and to the opportunities afforded by the French hospitals, that we are chiefly indebted for the increased extent and precision of our knowledge of the changes of structure effected in the human body by disease.

This study has, indeed, engaged so much attention of late years, that the term pathology has very often been used as synonymous with morbid anatomy; as if there were no other sources, from which we could draw our knowledge of the changes in the living body, constituting disease, than the changes in the dead body which disease leaves behind it. This, however, is a manifest error in science. These alterations in structure produced by disease are only one of the elements of our reasoning on the nature of diseased actions themselves; and there are many other facts, as to

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the external causes of diseases, the nature of their leading symptoms, their consequences, local and general, in the living body, and the juvantia and lædentia affecting them, which likewise furnish the proper elements of inductive reasoning, for the determination of those laws of the animal economy, which it is the object of the science of pathology to establish.

It is also an important practical error to fix the attention, particularly of students of the profession, too much on those characters of disease which are drawn from changes of structure al ready effected, and to trust too exclusively to these as the diagnostics of different diseases; because in many instances these characters are not clearly perceptible until the latest and least remediable stages of diseases; the very object of the most important practice in many cases is to prevent the occurrence of the changes on which they depend; and after they are established, the cases are very often hopeless, or admit only of palliative treatment. In those diseases in which most can be done by art, our practice must always be guided in part by conjecture, because, if we wait for certainty, we very often wait until the time for successful practice is past; and therefore, although an accurate knowledge of the whole history of each disease is essential to its proper treatment, yet in a practical view the most important part of its history is the assemblage of symptoms, by which its nature at least, if not its precise seat, may often be known, before any decided lesion of structure has occurred. Accordingly, when this department of pathology is too exclusively cultivated, the attention of students is often found to be fixed on the lesions to be expected after death, much more than on the power and application of remedies, either to control the diseased actions, or relieve the symptoms, during life.

But although in this, as in other instances, there has been an admixture of error, if not in our scientific acquisitions themselves, at least in our estimate of their value, and our judgment of the uses to which they may be applied, yet it is evident that the department of morbid anatomy is that in which the grand improvement of medical science has lately been effected; and that it is from judicious reasoning on the more intimate knowledge thus acquired of the nature of diseases, that any material improvement in the precision of our practical rules has resulted.

These observations apply particularly to the case of inflammatory diseases, those in which remedies avail the most, and with the history of which, therefore, it is most important to be familiar.

The characteristic effects of inflammation, adhesion, suppuration, ulceration, and gangrene, have been investigated with great acuteness and success by Mr. Hunter and his followers, among whom Dr. Thomson, of Edinburgh, [Professor Alison himself, Dr. Macartney, of Dublin, and Dr. C. J. B. Williams,] may be particularly noticed; and the provisions of nature for the favourable terminations of all these processes are now well understood. The nature of the process of inflammation itself has been carefully scrutinized, in so far as microscopical observations avail in the re

search, by Drs. Wilson Philip, Thomson, Hastings, and Black; and more lately by Andral, Gendrin, Kaltenbrunner, [Magendie, Gulliver, W. Addison,] and others. It may be confidently asserted that these observations have proved the inadequacy of any explanation of the process, which turns merely on the changes in the contractile power of the vessels concerned. It was, indeed, clearly perceived by Mr. Hunter, that changes in the vital properties of the blood itself must necessarily be taken into account, in attempting any explanation of inflammation and its consequences: and the inquiries of the three last-mentioned continental authors, of Schröeder van der Kolk, Pring, Rogerson, and others, have opened a prospect of some more definite information being acquired as to the nature of the essential changes which these vital properties undergo during these processes. [See a Report on the Present State of Knowledge of the Nature of Inflammation, by Mr. T. Wharton Jones, in Brit. and For. Med. Rev. for April, 1844, p. 567.]

But the most important recent additions to our knowledge of inflammatory diseases have been the accurate observations made on the varieties of inflammation, and consequently increased precision of our views as to the different modes of fatal termination to be apprehended in different inflammatory diseases; and these may be considered under several distinct heads.

1. Much has been done in regard to the different course and effects of inflammation, as it affects different textures of the body; and the fact has been established, that even in its acute, and still more in its chronic form, inflammation frequently spreads extensively, lasts long, and produces decided lesions in one texture, without in the slightest degree affecting others in its immediate neighbourhood. Repeated observations on the bodies of those who have died of pleurisy, of bronchitis, of peritonitis, and of dysentery, as well as of more external inflammations, leave no room for doubt on this point. Formerly the diagnosis of different inflammatory diseases seldom extended farther than the organs chiefly affected, and the functions of which were deranged; but we now consider the texture primarily affected to be one of the most important objects of inquiry, and to be frequently within the reach of careful scrutiny. The variety in the course and effects of inflammation to be expected in different textures,-in the cellular, serous, fibrous, and mucous membranes, in the different parenchymatous viscera, the muscles, bones, &c. was first pointed out as a particular object of attention by Bichat in France and Dr. Carmichael Smyth in England; its importance was strongly inculcated by Dr. Gregory in his lectures; and our knowledge of these varicties in the different parts of the body, and of the symptoms by which the attacks of inflammation in the different textures may, in general, be first distinguished, has been greatly extended and improved by many other authors,-by Thomson, Abercrombie, Pemberton, Brodie, Travers, Hastings, and others in this country; and by Pinel, Corvisart, Bayle, Laennec, Rostan, Lallemand, Andral, Louis, &c. in France. The distinction of the different species of inflammation attacking the eye, and the accurate anticipation of the dan

ger of each by all the recent writers on the eye, furnish a beautiful example of the increased precision which the attention to variety of textures has given to pathology.

Farther, not only the effects to be expected from inflammation in the various textures have been ascertained by dissections, but characteristic symptoms resulting during life from these consequences of inflammation in several parts of the body, not open to ocular inspection, have been clearly pointed out by recent authors.

This is remarkably the case in regard to inflammations within the chest. The lesions resulting from these, as well as other organic changes in that part of the body, may certainly be very frequently ascertained by manual examination, and by auscul tation and percussion, according to the methods of Laennec, with a precision formerly unknown. The usual effects of the inflammation of the pleura, and of the bronchiæ, may almost always be recognised and distinguished by percussion and auscultation; and there are many instances of these diseases occurring without any complication, which might formerly have been confounded under the general term pneumonia, and which it is not only satisfactory, but practically important, even in their later stages, to distinguish, because they admit of relief from different modes of treatment. There is, in general, more difficulty in forming a judgment as to the existence or extent of inflammation in the substance of the lungs; for this inflammation is very frequently combined with others within the chest; and although the «râle crepitant" and the "peripneumonic sputa” are occasionally well marked and characteristic symptoms, yet they are by no means to be depended on as constant symptoms. The effects of inflammation, either of the external or internal surface of the heart, frequently show themselves unequivocally, on auscultation and percussion, and by the increased action and obvious enlargement of the heart resulting from them; but there are cases, particularly of the former, where much injury may be done, without such indications clearly presenting themselves, even to the most experienced observer.

One important result of the recent observations on the effects of inflammation within the chest is, the ascertained rarity of circumscribed collections of pus in the substance of the lungs, and the frequeney of such collections exterior to the pleura; the established easy diagnosis of the two kinds of Empyema, the one with and the other without pneumothorax, from fistulous communication with the bronchiæ; and the distinction of the former class of cases of empyema, according as the communication has been opened from without inwards, in consequence of ulceration of the diseased pleura, or from within outwards, in consequence of tubercular disease and ulceration of the lungs; the former of these two cases admitting sometimes of gradual cure, the latter being only an accident in the course of incurable phthisis.

Another important addition to our knowledge of thoracic disease is the discovery of the frequency, and explanation of the nature, of the change called Emphysema of the Lungs, as a consequence of long-continued Bronchitis, particularly when combined with spasmodic Asthma.

All these improvements, as well as the original discovery of the application of the sounds heard in the chest to the diagnosis of its diseases, are to be ascribed chiefly to the industry and acuteness of Laennec.

The occurrence of inflammation of the Larynx and glottis in adults, tending to a fatal termination, by mere thickening of the membrane, by effusion of pus behind it, or by the oedema glottidis, without the formation of the false membrane of croup, is an important fact ascertained by the observations of Baillie, Farre, Lawrence, and many others; and the diagnosis of the cases of the kind in which the bronchi are unaffected, and an operation promises relief, is another advantage which the new methods of examining the chest afford.

The existence of inflammation of the Mucous Membrane of the great Intestines in all cases of dysentery, and of inflammation of the same membrane of the small intestines in a certain class of cases of diarrhoea, the diagnosis of inflammations of this membrane from those of the peritoneum, its remarkable tendency to ulceration, its frequent (though by no means uniform) combination with inflammation of the liver, particularly in the hot climates, and with continued fever in this climate, and the indications of its degree, and of its stage, to be drawn from examination of the stools, are important additions to our knowledge of abdominal inflammations, which we owe to the labours of Somers, Ballingall, Johnson, Robertson, and many other military and naval practitioners,-of Abercrombie, Cheyne, Harty, and others in this country, and of Petit and Serres, Broussais, Andral, Chomel, Billard, &c., in France. The instantaneous change of symptoms, violent pain, and rapid sinking, which succeed the perforation of intestine by an ulcer beginning in the mucous membrane, and effusion of feculent matter on the peritoneum; the correspondence of this accident to the perforation of the pleura in phthisis, and the evidence, thence resulting, of variety of endowment of the serous and mucous membranes, are striking illustrations of the increased precision of our pathological information.

The varieties of inflammation within the Head, and of its results, have likewise attracted particular attention, chiefly since the publication of the writings of Lallemand and Rostan on the softening of the brain, certainly one of the effects frequently produced by inflammation there. The inflammation of the membranes may often be distinguished, by the acuteness of the symptoms, in its earlier stages, from that of the substance of the brain. Much more minute diagnostic marks have been proposed by the authors just named; by Bouillaud and others; but subsequent observations have shown that on these no great reliance can be placed; and in fact, as the only symptoms which can yet be relied on, as indications either of inflammatory effusion or disorganization within the cranium, are affections of sensation or voluntary power, and as these result only from changes at the base of the brain, therefore generally in parts at some distance from the actual seat of disease, and the affection of which may be said to be accidental, it is evident that there may be great variety in the symptoms, independent of varieties

in the diseased states themselves; and accordingly, we cannot with any certainty anticipate either the nature or the exact seat of the effects of inflammation within the head, from any symptoms or combinations of symptoms;-all that we can pretend to distinguish (and that not with absolute certainty) is the period of the disease when the symptoms no longer depend on the inflammatory action itself, but chiefly on effusions or disorganizations consequent upon it, and continuing after it has subsided.

2. The distinctions of inflammatory diseases according either to the organs or textures affected, and the usual effects produced in these, are not the only distinctions of practical importance in that class of diseases which have been elucidated by modern pathologists. A very important class of their observations relates to cases which, although running the usual course, and often with even more than the usual rapidity, are concealed or rendered latent by peculiarity of constitution, and can only be recognised with certainty by such unequivocal local indications of effusion or disorganization, consequent on inflammation, as those to which allusion has just been made. The circumstances in which these latent inflammations are most to be apprehended (which are in general those in which the system is much weakened, the quantity of blood lessened, and the sensibility blunted, as in the last stage of fever or of some of the febrile exanthemata,) are very important to be known, because, in some such cases, if the practitioner is on his guard, he may detect their existence while it is yet time to apply remedies.

Again, many important observations made by modern pathologists have given precision and authority to the statements of older writers, as to inflammations occurring and producing exactly their characteristic effects in various parts of the body, but running their course so slowly, as to take the form of chronic instead of acute disease; as in the case of cold or chronic abscess on the surface of the body; chronic pleurisy leading to extensive empyema, without either acute pain or inflammatory fever; partial inflammatory induration of the brain, or hepatization of the lungs confined to individual lobules, &c. The knowledge of this form of inflammation is obviously important, as suggesting and justifying a corresponding modification in the use of the usual antiphlogistic remedies.

The term Sub-Acute Inflammation has also been properly applied by Dr. Armstrong and others to a form of truly inflammatory diseases of various textures, where not only the symptoms, general and local, are milder, but the local consequences which show themselves much less extensive than in the more decided and acute cases, and the amount of depletion necessary to avert danger is much less, while at the same time there is no such extension of the period of the disease as to justify the use of the term chronic.

3. What makes it peculiarly important to attend to these varieties in the intensity and duration of strictly inflammatory disease, even in the same parts of the body in different individuals, or at different times in the same, is the obvious application of this principle to other cases, where the symptoms are in the first instance those of

inflammation, but the ultimate result is the establishment of other forms of disease, which have been often regarded as quite distinct from, or even incompatible with inflammation. Of this the most striking example is in the case of Dropsy, or serous effusion in various parts of the body, the connection of which with inflammation has lately been the subject of much inquiry.

The lectures of the late Dr. Gregory, and the writings of Rush, of Cheyne, of Abercrombie, [of D. Davis,] and others, have satisfied the great majority of practitioners in this country, that the acute Hydrocephalus of Cullen is to be regarded in general as an inflammatory disease, although in many fatal cases no other effect of the inflammatory action can be found than the serous effusion into the ventricles; and the cases recorded by Blackall, by Abercrombie, by Crampton, and many others, have also shown that there are many cases of general dropsy, beginning, or repeatedly renewed, by inflammatory attacks, and admitting of great relief from a certain extent of bloodletting, generally premised to, or combined with, the purgative or diuretic medicines. This practice, which had been repeatedly adopted by various practitioners, and again fallen into disuse, has been put on the proper footing by numerous dissections, which have shown the very frequent complication of dropsical effusion with repeated inflammatory attacks, (often of the sub-acute or chronic character, but known by their usual products,) in the heart, lungs, liver, or kidneys; while, at the same time, these observations sufficiently demonstrate that any great extent of dropsical effusion is hardly ever the effect of inflammation alone; that some more permanent lesion of these parts is usually likewise present; and that even when partly or chiefly dependent on inflammation in its origin, the effusion is very generally persistent long after this cause has disappeared.

Nor is dropsical effusion the only form of disease, usually regarded as chronic, to which we may confidently assert, (trusting to the information acquired by recent pathologists,) that inflammation may give rise, or into which it may graduate. Attentive observation shows that many of those organic changes of structure which are commonly called Obstructions in the more important viscera, whether combined with dropsical effusion or not, appear frequently to originate from the causes of inflammation, to be attended with some of the first symptoms of inflammation, and to combine themselves with, or graduate by insensible degrees into, the acknowledged effects of inflammation. It is true that in many other cases their invasion is quite gradual and insidious, and there is no evidence of more than mere "perversion of nutrition" in their development; and that such organic alterations of texture likewise differ essentially from the simple effects of inflammation, in being hardly at all liable to absorption, to which the simply inflammatory effusions are peculiarly prone; it is clear, therefore, that in every case there must be some condition, independent of inflammation, necessary to their production; yet the inference from the former class of facts is still a fair one, that an inflammatory action, generally of the sub-acute or chronic kind, is, in

many cases, one of the conditions on which their growth depends. These points have been keenly discussed of late years by the French pathologists, particularly Broussais, Laennec, and Andral; the first of these authors certainly attributes too much to the "phlegmasies chroniques" as the cause of all chronic diseases; the second probably too little; and the conclusion now stated seems to agree very nearly with the opinion of the last, who is generally thought in this country the best informed and most judicious of the present French pathologists.

[Of late, however, by many pathologists, as by Papavoine, Fabre and Constant, Gerhard and Rufz, Piet, Barthez and Rilliet, and others, the acute hydrocephalus of authors has been regarded as tubercular meningitis, the tubercular matter being deposited in the meshes of the pia mater; and many of the cases classed under hydrocepha lus are, unquestionably, of this character.]

Of those cases of visceral organic disease, often connected with dropsy, and often originating in inflammatory action, there is one, the frequency of which was not suspected, and the indications of which were not understood, until very lately,viz. the granulated or tuberculated state of the secreting portion of the Kidneys, first ascertained by Dr. Bright to be the almost inseparable concomitant of the albuminous state of the urine, which had been previously noticed by Dr. Wells, Dr. Blackall, and others, in many cases of dropsy, but which exists also, not unfrequently, without any dropsical symptom.

This discovery is the more important, as the effect of the diseased condition of the kidneys is to alter the nature and diminish the quantity of one of the great excretions from the body; from which results, as the experiments of Dr. Christison and Dr. Bostock, Rayer, Martin Solon and others,] have shown, a palpably diseased condition of the blood, and an undoubted example, there fore, of the kind of morbid changes to be apprehended from such a cause. All that has yet been ascertained on this point is this, that when the urine is albuminous, and its specific gravity low, and the serosity of the blood therefore unnaturally loaded with urea, or extractive matter resembling urea, the health is always precarious, inflammatory diseases of different parts are apt to occur, and organic disease, particularly of the lungs or brain, frequently supervenes; and that in the last stage of such disease, when the secretion is almost suppressed, slight febrile symptoms rapidly advancing to coma, as in the true ischuria renalis, have been repeatedly observed.

Again, the tendency of inflammation, when it occurs in particular constitutions, to pass into, or give origin to, organic disease, is thought by many pathologists to be remarkably exemplified in the case of scrofulous Tubercles, and to be one of the principles, regarding the origin of that very frequent and fatal form of organic disease, which it is most incumbent on the practitioner, with a view to the prevention of such diseases, to have constantly before his eyes. On this point likewise there has been lately a difference of opinion both among French and English pathologists; and it is evident that tubercles frequently originate without either the causes or the indications of inflam