GENERAL.

The term Pathology, in its widest signification, comprehends all the knowledge which we possess relative to the state of Disease. For the facility of teaching and of studying, it has been found convenient to make various divisions of this extensive science. By the French, the terms of external and internal pathology have been employed as synonymous with what in this country are denominated the principles and practice of surgery and physic; the purpose of this division obviously being to separate the objects of medical doctrine and practice into two departments, and to assign each of these to a particular class of cultivators and practitioners. Another very important division of pathology which has long been recognised, is that into special and general; the first, or special pathology, being intended to comprehend the consideration of particular diseases, as they occur in nature; and the second, general pathology, to include, in the first place, the more general facts or principles that have been ascertained relative to the primary elements of diseases, as comprehending the causes, phenomena, and effects of the various derangements to which the animal economy is subject; and, in the second place, those more general facts or principles relative to the more obvious analogies of diseases, and the natural groups to which they admit of being referred, which medical men have deduced from the comparison of particular diseases with one another. Unlike the division into internal and external, that into special and general makes no partition of the subjects of pathological inquiry; for both survey the whole of these subjects, though under different aspects. General pathology, though in its investigation obviously resting, as we had formerly occasion to show (see article MEDICINE), upon a knowledge of the special, has, in teaching, been found to form a convenient and appropriate introduction to it; just as, in other sciences, it is convenient to give a general view of the principles which have been established, before entering upon the particular details the knowledge of which has led to the establishment of these principles, but of which details these principles, when once ascertained, very materially facilitate the comprehension and acquisition.

Under whatever point of view we consider the derangements of the human economy, whether, with the clinical physician, we regard them as they present themselves in individual cases, or, with the special pathologist, as constituting particular genera or species of diseases; or whether, with the general pathologist, we endeavour to reduce them to their primary elements; in each case, they offer precisely the same subjects for our investigation. These are, first, the morbid phenomena or symptoms by which we become aware that derangements have actually occurred in the economy; second, the morbid agents, by which derangements of the economy are liable to be produced; third, the more immediate seats of the derangements to which the economy is liable, and the peculiar nature of each of these derangements; and, fourth, the morbid alterations discoverable in the dead body, in those who, during life, had exhibited derangements in the performance of their functions, whether these perceptible alterations stand in the relation of cause or of effect to the derangements of function.

It is in the mode of considering these several subjects, therefore, rather than in the subjects themselves, that the distinction between general and special pathology must be looked for. In special pathology, symptoms, morbid agents, proximate causes, and organic lesions, are respectively considered in those combinations in which they give rise to, or occur in, particular diseases; and attention is directed to them only in as far as they are calculated to elucidate the natural history of the particular disease that may be at the time under consideration. In general pathology, on the other hand, the consideration of symptoms, of morbid agents, of proximate causes, and of organic lesions, or those branches of medical science which have been termed symptomatology or semiotics, etiology, pathogeny, and morbid anatomy, constitute so many separate portions of pathological doctrine, in which the whole of the subjects falling under each department are methodically arranged, and considered in reference to one another.

It may perhaps tend to place the distinction between general and special pathology in a clearer light, if we endeavour to illustrate it by a particular example.

It not unfrequently happens, that an individual exhibits a combination of symptoms of the following kind. He has pain in some part of the chest, his respiration is difficult, and he is subject to cough; and these symptoms, all of them obviously referrible to some derangement in the respiratory organs, are attended with others of a more general character,—with those symptoms which are denominated febrile, that is, with increased frequency of pulse, with increased heat of skin, and with disturbance of several of the other functions of the body. Now the first object of the special pathologist, in respect of this combination of symptoms, is to distinguish it as constituting a particular disease which he terms pneumonia (or inflammation of the lungs), from other combinations of symptoms which may bear a certain degree of resemblance to it,—to establish its diagnosis, or distinction from other analogous diseases. And even in the several cases which present the combination of symptoms that has been mentioned, the special pathologist may be able to detect certain differences of character which will lead him to establish more or fewer divisions of his particular disease; differences, for example, in the condition of the pulse, and in the characters of the pain and of the cough. Thus, of the disease in question, nosologists, or those who treat expressly of the divisions, definitions, nomenclature, and arrangement of diseases, have been led to recognise three principal forms, under the names of peripneumony, pleurisy, and bastard peripneumony. The special pathologist, in his consideration of the symptoms of pneumonia, besides distinguishing it from other diseases, and marking the more probable diversities in which it may present itself, traces its characteristic symptoms throughout the whole course of the disease, and marks the diversities which these assume in its different stages, and the other less distinguishing symptoms with which they are accompanied; in short, he applies his knowledge of the morbid phenomena, or symptoms of this disease, to determining its definition, its diagnosis, and its history.

All of those symptoms which have been mentioned as occurring in and characterizing pneumonia, fall under the consideration of the general as well as of the special pathologist; but the view which the former takes of them is considerably different from that which we have just endeavoured to sketch as being taken by the latter. By the general pathologist, these symptoms fall to be considered, not in the combinations in which they present themselves in nature, but each of them as an abstract existence, and in its relations to the other morbid affections of the organ or function of which it indicates the derangement. Thus the general pathologist has occasion to consider the symptom of quickness of pulse, in the general view that he takes of the different morbid phenomena which result from de- Pathology. arrangements of the function of circulation. An opportunity is thus afforded him of considering this symptom of increased frequency of pulse, not only in relation to the healthy state of this phenomenon, but in relation also to the other morbid states to which it is subject, whether as regards its frequency, its strength, or its regularity. By studying, in this manner, the morbid conditions of the pulse as a general pathological doctrine, medical men are furnished with a body of information of most important practical application in the investigation, not of one particular disease only, but of many different diseases. The morbid phenomenon or symptom of cough, in like manner, is obviously capable of being considered as a particular subject of investigation in reference to the other morbid derangements of function to which the respiratory organs are liable, and particularly in reference to the various modifications which this symptom may itself exhibit.

Secondly, a similar difference may be traced in the manner in which the special and the general pathologist consider the morbid alterations of structure that are discoverable in the body after death. In pneumonia these morbid alterations consist of more or less extensive marks of inflammatory action in the contents of the cavity of the chest. The special pathologist considers these morbid alterations in reference to the particular combination of symptoms that characterize pneumonia, or may accompany its progress. He examines into the condition of the contents of the chest, with a view to throw light on the phenomena which the disease exhibits during life, to trace the correspondence of the morbid appearances with the nature, degree, and progress of the external symptoms. The general pathologist likewise has occasion to direct his attention to those morbid alterations of structure to which we have alluded; but, in the view which he takes of the diseased economy, they present themselves to his attention, not, as they do to the special pathologist, in their connection with a particular disease, but as constituting one of the forms of morbid alteration of structure to which the respiratory organs are liable, the whole of which he passes successively in review, simply as a department of the natural history of the economy in its diseased conditions.

Thirdly, when the special pathologist, in endeavouring to discover the morbid agencies by the operation of which pneumonia has been excited, is led to ascribe its production to the influence of cold, he pays no further regard to that morbid agent, than in its relation to this particular disease; he considers merely the conditions under which cold must be applied to the economy in order to produce pneumonia, the length of time that intervenes between its application and the appearance of the symptoms, and such other points as bear directly upon the agency of the particular cause in producing the particular effect. By the general pathologist, on the other hand, this morbid agent, cold, falls to be considered as a special subject of investigation, along with the various changes that are liable to occur in the different physical conditions, and particularly in the temperature, of the atmosphere; and not as giving rise to one particular combination of symptoms or disease, but, generally, in its injurious operation on the several functions and organs of the body.

Lastly, as regards the consideration of the proximate cause of pneumonia, the special pathologist is led, by a consideration of the symptoms which he has observed during life, of the morbid changes which he has found after death, and of the morbid agent to which he has traced the production of the disease, to conclude that the more immediate seat of derangement is in the substance or in the membranes of the lungs, and that the particular mode in which these parts are affected is that usually termed inflammation. He is contented, therefore, with having detected the proximate cause of pneumonia as being inflammation of the lungs. But the general pathologist, in considering proximate causes as a particular department of inquiry, endeavours to go farther back in the succession of morbid changes, and to ascertain, from an investigation of the circumstances which attend the development of inflammation in different parts of the body, what are the more intimate conditions of the economy to which that morbid state is referrible, in whatever organ or texture it may occur.

There can, we conceive, be little doubt, that a much more complete and satisfactory view must be obtained of each symptom, morbid agent, proximate cause, and organic lesion, when treated of systematically, in connection with other analogous phenomena, than when noticed incidentally in those varying combinations in which they present themselves to the special pathologist, in tracing and in describing the histories of particular diseases. And if we reflect upon the circumstances under which the several subjects of pathological investigation actually present themselves to the attention of the student of pathology, in the consideration of a particular disease,—morbid functions, morbid structures, morbid agents, and proximate causes of disease, all of them combined in one whole, the relations of the several parts of which it is necessary for him, as if intuitively, to comprehend,—it must be obvious, that unless he shall previously have had an opportunity of taking a systematic view of each of these branches of pathological inquiry by itself, such as is afforded in the study of general pathology, he cannot fail to be lost among the multitudinous and imperfectly understood matters which, simultaneously, as it were, press themselves upon his attention.

The pathologist, indeed, is in a great measure in the same situation as the chemist, who meets in nature, for the most part, with objects which consist, not of one, but of several different elements, and which have been produced and are maintained in their combinations by the action, not of one, but of several different forces. To be able to understand the constitution of such a compound object, and the share which each physical and chemical force has had in its production and maintenance, it is necessary that the chemist should be well acquainted with those elements into which compound bodies are found to be reducible. And he must also be acquainted with those few powers or forces which, by their operation on the several elements of matter, enable it to enter into those multitudinous combinations that give rise to the great diversity of substances of which the globe consists. In short, the special pathologist has to do with particular diseases, the general pathologist with the elements of diseases—elements which can be ascertained only by analytical examination, founded on long-continued observation and experience; but a knowledge of which, when once acquired, is of primary importance in those synthetical operations by which the special pathologist endeavours to arrive at the establishment and distinction of particular diseases.

The limits which we are obliged to prescribe to ourselves in the following article render it impossible to be but a satisfactory view of the various subjects which fall under the province of general pathology; and, at the same time, we are unwilling to occupy the pages of this work with a bare enumeration of the topics which, in a systematic consideration of this department of medical science, would properly claim our notice. We shall confine ourselves, therefore, to some general observations relative to the state of disease; the distinctions between this state and that of health; the primary seats of diseased actions or diseased conditions in the animal economy; and the more essential differences existing among those simple pathological states, morbid conditions, or primary elementary derange-

GENERAL.

Pathology. ments in the structure and functions of the different parts of the human economy, on which the series of morbid phenomena constituting particular diseases depend—those states, in short, to which the name of proximate causes of disease has very generally been applied. The topics which we have now enumerated are those the consideration of which is usually included under the branch of general pathology termed Pathogenesis. A slight view of them, we hope, may be rendered both interesting and instructive to general readers; and, at the same time, will prepare the way for a review of the difficulties to which medical men are exposed in endeavouring to determine, in individual cases, the nature of the maladies with which their patients are affected, which we purpose to sketch in the article PHYSIC. PRACTICE OF.

The first duty of the pathologist seems obviously to be, to define that which professedly forms the object of his inquiries and speculations, viz. the state of disease. The definitions of this term, which have been proposed by pathologists, have differed, not only in the precise language in which they have been expressed, but in the general principles on which they have been constructed. Some have been merely what are called verbal definitions, that is, substitutions of synonymous expressions; such, for example, is the definition which represents disease as a change from the natural to a preternatural state, natural and preternatural being nothing more than synonymous expressions for healthy and diseased. It is needless to insist on the obvious fact, that no possible benefit can result to medical science from definitions of this kind.

In others of the definitions that have been given of the term disease, an attempt has been made to found this upon the supposed final cause of the phenomena which that state presents. Thus disease has been said by some pathologists, including the illustrious Sydenham, to be an extraordinary effort undertaken by nature, for the purpose of throwing out from the system, by the motions excited, some morbid or noxious matter, and of thereby averting from it death and corruption. The attempt to establish the final cause of any phenomenon obviously implies a persuasion of our being acquainted, as far as the particular object is concerned, with the views and intentions of the Author of nature, in obedience to whose will the universe is conducted. The ends or purposes of some of His arrangements seem sufficiently obvious to justify us in deducing them; but there are others of these arrangements in which this is far from being the case, and in attempting to establish the final causes of which, we run the risk of substituting some crude conception of our own minds for the wisdom of the Creator. That there is great risk of doing so in respect of disease, might easily be established, by the various and even contradictory views of its end or purpose which have been taken by those who have endeavoured to derive their definition of this state from its final cause.

In a third set of definitions of the term disease, an attempt has been made to explain what has been called its real essence; as when disease has been said to consist in a disproportion of the four humours, or in an excess or deficiency of the principle of excitability. It would be easy to show that the definitions of disease which have been framed upon the principle of explaining its real essence, have varied with the prevailing medical doctrine of the period in which they have been proposed, insomuch as they have necessarily borne a relation to the views entertained by medical men respecting the powers by which the functions of the human economy are carried on in the state of health, in whichever of the various forms of mechanical, chemical, animistic, or vital doctrines, these powers may have been sought for.

How, then, is disease to be defined? Precisely, it is conceived, upon the same principles that every other object which admits of definition ought to be defined. By an enumeration of circumstances obvious to all, and acknowledged by all, to appertain to it; an enumeration not depending for its reception on the speculative opinions of the person to whom it is addressed, but recognised as valid, whatever decision we may come to on certain controverted points of physiological or pathological doctrine; whether, for example, we suppose the functions of the animal economy to be executed conformably to, or in a manner subversive of, the physical and chemical laws of inorganic matter; whether we admit or reject the agency of a rational soul, or that of a peculiar principle of life, in regulating its healthy and morbid phenomena; whether we affirm or deny that dynamical derangement must in all instances be preceded by organic alteration; whether or not we suppose mental derangement to be in all cases dependent on corporeal affection; and whether or not we admit that the fluids may be the primary seats of disease. Health and disease must be defined in reference to one another. It is certainly the occurrence of disease that suggests to the mind the idea of health; but this idea is the rule or standard by which we fix our notions of the state of disease. They are both states of living beings; and the respects in which they differ seem to be, that in the state of health living beings maintain their ordinary structure, and are capable of exercising all their functions with ease, regularity, and harmony; whilst in the state of disease there is an obvious change in the structure or organization of some of the solid parts of which the living beings consist, or in the composition of some of their fluids; or there is a considerable deviation from the easy, regular, and harmonious performance of one or more of their functions.

This definition, it is conceived, is applicable to any being, or class of beings, of which health and disease can be predicated. The structure of living beings is more or less complicated, and the functions they perform are more or less numerous, according to the place they hold in the scale of organized existence. Consequently the number of particulars falling within the two terms, health and disease, must vary. In the human subject these terms must be understood as having reference to the exercise of the mental faculties or functions, as well as of the corporeal; but the definitions above suggested are, we conceive, equally applicable to the simplest and to the most complicated of organized beings. The definition which we have given of disease makes provision also for those slighter diversities in the manner in which different persons, or the same persons under different circumstances, exercise their functions, which, though not consistent with perfect health, are still too inconsiderable to amount to absolute disease; diversities which are usually included by pathologists under the term of the latitude of health.

Having pointed out the principles which should guide us in the definition of the term disease, and the elements of causes of which that definition should consist, we shall now proceed to offer some general observations on what are called the proximate causes of diseases, or, in other words, those morbid states or pathological conditions of the different portions of the economy to which the morbid phenomena or symptoms of diseases are ultimately referrible. As we had formerly occasion to advert to the relations in which symptoms and proximate causes stand to one another, we shall not at present dwell on this subject farther than to remark, that general readers as well as students of pathology are exceedingly liable to be puzzled by the great variety of synonymous terms which have been employed by different pathologists to designate respectively the proximate causes of diseases, and the concourses of symptoms to which they give rise. Thus Professor Sprengel, in his Institutiones Medicae, iv. 19, with the purpose of marking the distinction between these two distinct constituent parts Pathology of disease has proposed to employ the term "morbus," or disease, to denote the internal morbid condition or proximate cause; and the term "affectio," affection or passion, to mark the attendant combination of external symptoms.

"Whatever," he remarks, "is perceptible by the senses of the patient himself, or of his attendants, is to be considered as the passion or affection, but the internal state is the true disease." By others of the German pathologists, and particularly by Gmelin of Tubingen, and by the late Professor Hartmann of Vienna, it has been proposed to mark the same distinction between the internal morbid states and the external symptoms of diseases, by the employment of the terms disease, and form of disease; the term disease being applied by them, as it is by Sprengel, to the morbid or pathological condition or conditions of the economy in which particular diseases essentially consist; whilst, by the term form of disease, they wish to designate the combinations of morbid phenomena occurring in concourse and succession which manifest themselves in the progress of particular diseases, and which Sprengel has included, as we have just seen, under the ambiguous and equivocal term of "affectio."

Besides the terms to which we have alluded, a considerable variety of other appellations have been employed more particularly to designate the internal morbid conditions of the economy considered as the states on the existence of which, singly or in combination, the phenomena or symptoms of particular diseases depend. For in different pathological works these internal morbid conditions are treated of under the various appellations of primary elements of diseases, primary morbid states or pathological conditions, and of simple morbid affections or simple diseases (morbis simplices). Chomel speaks of them as the essences of diseases; they form the internal morbid conditions of Broussais, the simple affections, the internal alterations, and common principles of diseases, of Buffalini; and the "interna indoles morbi" of Friedlander. Some pathologists have denominated them pathological, in contradistinction to nosological diseases; the term nosological being applied in the same sense as the "morbi forma," or form of disease, of the later German writers, to those combinations of morbid phenomena or symptoms occurring in concourse and succession, by which particular diseases are externally manifested and are characterized in our systems of nosology.

In speaking of the proximate cause of any disease, it is necessary to keep in recollection, that under this title may be comprehended everything that goes on in the economy between the application to it, or action upon it, of the morbid agent which disturbs its physiological or healthy condition, and the manifest derangement of function which results. Frequently the change from the healthy to the morbid state does not consist in a single event, but in a succession of events. Thus, when the effect of a blow inflicted upon the head is to induce the concourse of symptoms that are comprehended under the nosological disease apoplexy, the first effect may have been the rupture of an artery within the cranium; as a consequence of this rupture there occurs an extravasation of blood; and, as a consequence of this extravasation, a particular state of the brain, whether or not we may admit it to be of the nature of compression. We may regard all this series of events combined, as constituting the proximate cause of the apoplectic attack; or we may restrict this term either to the last event in the series which we are able to trace as preceding the production of the symptoms, or to the event or change which first succeeds to the operation of the morbid cause.

A curious topic of inquiry relative to those primary morbid states or pathological conditions which constitute the proximate causes of diseases, relates to their seats, or the parts of the economy in which the changes from the healthy to the morbid condition, on which the production of morbid phenomena or symptoms depends, may occur. We formerly noticed the division of proximate causes into the organic or structural, and the dynamic or functional (article Medicine). This is a division as to the propriety of which much disputation has taken place amongst pathologists. If it were to be understood as drawing an absolute line between pathological states arising out of altered conditions of the organic structure of the different textures, systems, and organs of the body, and pathological states arising out of altered conditions of the properties or powers by which the functions are executed, independently of any altered conditions of the organic structure, the distinction would obviously be fallacious. The properties or powers by which the functions of the body at least are performed, have no existence independently of its material organization. And accordingly we cannot conceive any change to occur in the condition of these properties, without its being preceded by a corresponding change in the condition of the material organization. The proper signification to be attached to the terms organic and dynamic proximate causes seems, therefore, to be, that in the former there occurs an apparent alteration in the structure of some part of the frame; whilst in the latter, no alteration of structure is discoverable, the change in the condition of the material organization being of too subtle a nature to be appreciable by the senses.

The next question relative to the seats of the proximate causes of diseases that presents itself for consideration is, and whether, when the mental functions betray evidence of a deranged performance, this is to be considered as having its primary origin in morbid conditions of the mind itself, or in changes, perceptible or imperceptible, in the material organization. It is allowed on all hands, that it is by no means infrequent, in cases of mental derangement, to find marks of organic alteration of structure in the brain, whilst in other cases no such appearances are discoverable. Of these dissimilar, yet to say contradictory results, those who contend for and those who oppose the dependence of mental derangements on morbid conditions of the material organization are equally prepared to give explanations. Those who oppose this dependence aver that when morbid appearances are present, they are to be regarded as concurrent effects of the condition which produces the symptoms of mental aberration, and not as the causes of the mental disturbance; and hold that the independence of mental upon bodily derangements is proved by those cases in which all appearance of organic alteration is wanting. The pathologists who contend for this dependence allege, on the other hand, that whatever may be thought of the morbid appearances observable in the first class of cases, it is quite possible to conceive respecting the second, that changes in the material organization actually exist, although they are of too subtile a nature to be discovered; in short, that mental derangements may be dependent on dynamical and not on structural alterations of the material organization.

Setting aside, then, as inconclusive, the arguments deduced on either side from the results of anatomical investigations, the opposed partisans appeal to the morbid agents by which mental derangements are liable to be induced, and to the means by which their removal is best promoted, for corroboration of their respective views. The advocates for the independence of the mind refer to cases in which mental derangement has been produced or removed by moral or purely mental causes; whilst the advocates for its dependence allege that almost every morbid affection of the mind succeeds to the action of certain physical and vital causes, which can be supposed to operate on the mind only through the intervention of the organization, and particularly of the brain; and they enforce the importance of attention to the state of the corporeal organs in

GENERAL.

The treatment of insanity. This contrariety of opinion obviously rests on the opposite views that have been propounded relative to the connection of the mind and the body in the state of health; a subject into which we feel indisposed here to enter, not from the apprehension that any conclusion at which we could arrive regarding it would be inconsistent with that belief in the future existence of the soul which forms the groundwork of all religion, but from a conviction that it is a question to the solution of which the human faculties are incompetent.

There is still another question relative to the seats of the proximate causes of diseases, which it is necessary for the general pathologist to consider and determine, viz., it being admitted that the different fluids of the body are liable to morbid alterations in their physical and chemical qualities, whether such morbid conditions of the fluids are capable of constituting in themselves real proximate causes of diseases; or, in other words, whether the fluids are ever the seats of those morbid conditions or pathological states on which the external phenomena or symptoms of diseases depend.

Against the supposition of morbid conditions of the fluids ever being the proximate causes of diseases, it has been argued, first, that the morbid alterations to which they are liable depend on previously existing morbid conditions of the solids, and are to be regarded in the light of effects rather than as causes. When, for example, the secretion of the kidneys contains some of its ordinary constituents in undue proportion, or contains an element not usually found in it, this morbid condition of the urine, it is urged, must be supposed to depend on a previous morbid condition of the kidneys. To estimate the force of this argument, it is necessary to consider the fluids of the body as belonging to two classes; first, the blood, and the fluids out of which it is formed, the chyme and chyle; and, second, the fluids formed out of the blood, including the various secretions, as the saliva, the bile, the urine, &c. Now, without any morbid action of the organs of digestion, and merely in consequence of the introduction of unsuitable food into the stomach, we may suppose the chyme and chyle, and consequently the blood into which they are converted, to be vitiated. Again, in passing through the lungs, the blood may be acted on in such a way as to produce important changes in its physical and chemical constitution, by elements contained in the inspired air, and independently of any morbid condition of the solids. The blood being vitiated in either of the ways supposed, or in others that might be mentioned, the fluids secreted from it may be conceived to participate in its noxious qualities likewise, without any previous morbid condition of the solids. But if, on the other hand, the blood be in a healthy state, and the fluids formed from it be diseased, we must suppose this to depend on some morbid condition of the secretory organ, whether of a structural or dynamical character. From this view it appears that morbid states of the fluids, though they in some instances proceed from morbid conditions of the solids, in others occur independently of any such conditions.

But it has been argued, secondly, that when there exists any noxious principle in the fluids, and particularly in the blood, whether preceded or not preceded by morbid conditions of the solids, it is not immediately on the altered state of the blood, but on a change which it induces in the solid parts, that any morbid phenomena or symptoms which manifest themselves depend; that the blood serves merely as a vehicle for bringing certain noxious agents in contact with those parts on which they most readily exert their action; so that the blood, when it has undergone any morbid alteration, ought to be regarded rather in the light of a remote or occasional, than as a proximate cause of disease. Thus, for example, when, in consequence of extirpation or disease of the kidneys, urea accumulates in the blood, this acts as a poison upon the nervous system. Here, it is said, the blood can only be regarded as a vehicle of the urea, which acts as a morbid agent upon the brain; and it is in the brain that the change takes place which constitutes the proximate cause of the comatose affection that succeeds.

In this argument a fact seems to be overlooked, to which we formerly adverted, viz., that between the first action of a morbid agent upon some part of the economy, and the manifestation of those phenomena or symptoms which ultimately result, there usually occurs a succession of morbid changes. Is the term proximate cause to be understood as embracing the whole of these changes, or as being confined to one only? and if to one, does it apply to the first change which we can detect as being produced in the economy, or to the last of the series which we are able to trace, as immediately producing the development of the symptoms? If we include the whole series of changes under the term proximate cause, then morbid states of the fluids must, we conceive, be admitted as forming a constituent element of some proximate causes. Or if we restrict the term to the change in the economy that is first produced, then we must admit that this occurs frequently in the states of the fluids. So that it could only be by restricting the term proximate cause to the last change which we are able to trace in the economy, previously to the manifestation of the symptoms, that we could be supposed justified in denying that morbid conditions of the fluids act occasionally as the proximate causes of diseases.

The question, whether preternatural conditions of the fluids, and of the blood in particular, can be regarded as capable of constituting the proximate causes of diseases, or indeed are themselves entitled to the appellations of morbid or diseased states, has been supposed to depend on the judgment that may be formed relative to the vitality of the fluids, or their possession of life; it being argued, that unless endowed with life, they cannot be subjects of disease. There seems to us to be great fallacy in this argument. We cannot concur in the physiological doctrine which would represent life as a peculiar property, with which certain bodies are endowed; nor are we any more disposed to regard it as a single definite result. The phenomena of the human economy are no more effected by the agency of a single property, power, or force, than are those of a steam-ship; and it would, in our estimation, be as reasonable to suppose that the admission of a principle of propulsion is necessary and sufficient for the explanation of the latter class of phenomena, as that the former can be explained by the assumption of a principle of life. The propulsion in the one case, and the life in the other, are the effects of the conjunct operation of several properties or powers, and do not constitute in themselves either simple powers or simple results. The expression of the life being in the blood, seems to be obviously a metaphorical expression, of the same character as would be a poet's invocation to steam as the principle of propulsion.

We shall now proceed to take a summary view of the different forms of morbid states, pathological conditions or proximate causes, from the existence and operation of which severally, or more or fewer in conjunction, in the different parts of the human economy, the various concourses of symptoms, or nosological diseases, to which that economy is subject, seem to originate. We shall, in the first place, pass in review organic or structural proximate causes, or, in other words, the visible morbid changes that are discoverable in the physical and structural conditions of the different textures, systems, organs, and cavities of the body.

The greater degree of attention that is now bestowed on Organic the examination after death, of the morbid changes which proximate are liable to take place in the structure of the different parts causes. Pathology of the body, must be regarded as one of the circumstances that most strikingly distinguish the medical investigations of the present period from those of former times. Indeed, the result of these investigations has been the creation of an entirely new branch of medical science, designated by the name of pathological anatomy, a branch the knowledge of which is every day becoming more and more important, from the discoveries that are continually making in it, and from the light these discoveries have a tendency to throw upon the phenomena, the nature, the effects, and the treatment of diseases. It may justly, indeed, be said, that it is to the zeal and success with which morbid anatomy has been cultivated during the last half century, that we principally owe the recent rapid progress and advancement of pathological knowledge, and much of all that is most solid and exact in medicine considered as a science.

Pathological anatomy has been said by the late Professor Lobstein, in his work on that subject, to have three objects to accomplish. In the first place, it describes the changes which occur, in regard to the position, form, size, and intimate structure of each organ in the state of disease, and considers every such organ in its relations to the other parts with which it is connected by more or less immediate sympathies. The second object of pathological anatomy is to explain, as far as this may be possible, the morbid changes that occur in different organs; to point out the manner in which these changes are effected; and to ascertain under what influences, and according to what laws, they are produced. These inquiries comprehend all questions relative to the origin, formation, and development, of organic diseases. In the third place, it is the province of pathological anatomy to compare organic alterations with the morbid phenomena or symptoms that manifest themselves during the course of a disease, to analyse these phenomena with care, and to determine to what degree they are dependent on the alterations of structure by which they are accompanied.

It is in the second of these points of view only that we have occasion at present to consider this department of medical science, as elucidating the origin, formation, and development of the various visible structural alterations which occur in the different organs of the body. As the morbid changes of structure that are liable to occur in different parts of the body are all referrible to a certain number of specific elementary forms, which exhibit the same general characters, in whatever textures or organs they may be seated, great advantage is derived from studying these elementary forms of morbid alterations of structure abstractedly, before proceeding to consider them as they are observed to occur in the particular organs of the body. This view of the elementary forms of diseased alterations of structure might, perhaps, without impropriety, be considered as forming a branch of pathogeny, the more peculiar province of morbid anatomy being, as we conceive, to consider, what Professor Lobstein has marked out as its first object, the primary morbid changes as taking place in the structure of each of the different textures, systems, and organs of the body individually.

The morbid changes of structure that occur in the different textures and organs of the body may be temporary, disappearing after a longer or shorter period of time, and leaving the parts which they attack in their original healthy condition. Hence it is that in many diseases not of a fatal nature, it is only from death occurring accidentally during their continuance, or in a short time after their termination, that we have an opportunity of ascertaining the morbid changes of structure by which they are accompanied. In other instances, again, the morbid changes are of a more permanent nature, and when the disease in the course of which they arise does not prove fatal, they may either continue to exist without materially disturbing the economy, or they may prove the cause of new diseases.

The first physical change in the condition of the body to which we shall allude, as giving rise to morbid phenomena or symptoms, is the presence of air in situations in which it does not naturally exist, or its excessive accumulation in situations in which it is usually met with. This occurrence it has been proposed to designate by the name of Pneumatositis. The presence of air in the subcutaneous cellular substance, sometimes occurring as a consequence of injury, and in other instances independently of injury, has been long known to surgeons by the name of emphysema. In the sacs of the pleura, a quantity of air occasionally collects, producing great disturbance of respiration, an occurrence to which the name of pneumo- or pneumothorax has in recent times been applied. It is well known, too, that in some cases of sudden death occurring during surgical operations, air has been found in the cavity of the heart. In the cavity of the alimentary canal there is always present a quantity of air or gas, but under certain circumstances the quantity becomes greatly augmented, giving rise to the state of the abdomen termed by medical men tympanites. It belongs to the general pathologist to ascertain the different seats in which a preternatural accumulation of gases is liable to occur, and their chemical characters in these various situations; and to endeavour to determine the sources from which, in each situation, they may be supposed to have been derived; whether the particular form of pneumatositis under observation has depended on the introduction of atmospheric air by natural or accidental passages; on the putrefactive decomposition of solid or fluid substances; on mechanical obstruction to the free passage of gases in parts which naturally contain them; on the perforation of organs naturally containing gases, and the consequent escape of these into other parts; or whether a gas is ever exhaled from the surface of a cavity or canal in the human body in consequence of diseased action.

A second change that sometimes presents itself to those engaged in tracing the pathological conditions of the body, and one which, according to its particular seat, may give rise to the symptoms of various diseases, is a deficiency of blood either in the vascular system generally (in which case its most obvious indications are to be found in a peculiar paleness of the face, and particularly of the lips and of the gums), or in the vessels of some particular textures or organs. To this state medical men give the name of anaemia, or bloodlessness. It belongs to the general pathologist to inquire into the various situations in which anaemia is liable to be met with; and into the circumstances in which it may be supposed to originate, whether from absolute deficiency, or from vitiated qualities of the nutritious fluid.

A third morbid condition, which gives rise to symptoms of much importance and of considerable variety according to the particular seat which it may occupy, is the reverse of that last mentioned, consisting in a turgescence of the whole, or of particular portions of the vascular system. This is the morbid condition which medical men have denominated congestion, and to which the terms active or passive are affixed, according as it is supposed to depend on an increased propulsion of blood into a particular texture or organ, by the powers which maintain the circulation; or on an obstruction, which prevents the blood that has been sent to a part in due quantity, from being returned with proper freedom to the heart. When the state of vascular turgescence is general, in consequence of an excessive production of blood, the vascular system is said to be in a state of plethora; so that plethora is general congestion, and congestion is partial plethora. When the blood is sent to some particular part of the body in in-

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creased quantity, without the morbid condition of inflammation being produced, or, in other words, when there occurs active local congestion, English pathologists apply to this morbid state the name of determination, and French pathologists that of fluxion. It forms by no means an unimportant object of pathological inquiry, to determine the characters by which local congestion occurring during life may be distinguished, in the examination of dead bodies, from similar appearances originating during the agony of death, or subsequently to that event; principally in obedience to the laws of dead matter.

Another morbid condition, and one nearly allied to congestion, is that in which the contents of the sanguiferous system escape from the vessels in which they circulate, and are discharged either on the surface of a cavity or canal, or into the substance of an organ. This constitutes the state termed hemorrhage. We have examples of hemorrhage occurring on the surface of a cavity or canal in the discharge of blood from the lungs, termed haemoptysis by medical men, or from the stomach in haematemesis; and of hemorrhage occurring into the substance of an organ we have examples in many cases of apoplexy, in which a larger or smaller quantity of blood is discharged into the substance of the brain. Like congestion, hemorrhage may be active or passive, that is to say, it may depend either on the blood being propelled into a particular texture or organ in greater quantity or with more force than is usual, or on some obstruction to its return to the heart. To that state of the sanguiferous system on which active hemorrhage depends, pathologists give the name of the molimen-haemorrhagicum. It belongs to the general pathologist to inquire into the various seats in which hemorrhage is liable to occur; the conditions of the blood, and of the blood-vessels on which it may be supposed to depend; the modes in which the blood escapes from the vessels in cases in which no visible solutions of continuity can be detected; whether this takes place by dilatation of open terminations of blood-vessels, or what is usually called sanguineous exhalation; or whether by dilatation of pores in their coats, a theory of hemorrhage which is intended to be expressed by the terms sanguineous transudation. The changes which extravasated blood produces on the surrounding tissues, and those which it itself undergoes in various situations subsequently to its being extravasated, constitute inquiries of very considerable importance to the pathologist, particularly the question, whether, in any instances, extravasated blood is capable of becoming organized.

In the state of health there occurs an effusion of a watery fluid into the cellular texture lying beneath the skin, or entering into the composition of parenchymatous organs, and into those cavities of the body which are lined by serous membranes; but the removal of this fluid by absorption seems to go on as rapidly as its secretion, so that the quantity never becomes considerable. In disease, however, an accumulation of watery or serous fluid is liable to occur in the various situations that have been mentioned, producing a pathological state which has long been known to pathologists, under the name of dropsy, as a fertile source of morbid phenomena. It has been supposed that an accumulation of serous fluid occurring in disease, might depend either on the secretion being increased without a proportionate increase in the power of absorption, or on a diminished power of absorption not attended with a corresponding diminution in the power of secretion. It is well ascertained, that in a large proportion of the cases in which dropsical effusion occurs, there exists, as in passive congestion, an impediment to the free return of the blood to the heart. Such, for example, seems to be the case in those organic diseases in the course of which dropsy is so apt to supervene, such as the organic diseases of the liver, or of the heart itself. An impediment to the capillary or venous circulation does not however appear to be essential to the production of dropsy. In certain inflammatory conditions of the membranes by which serum is naturally secreted, dropsical effusion is liable to take place, constituting what may be called inflammatory or active dropsy; and it would appear from modern investigations, that in certain diseased conditions of the kidneys, dropsy occurs, without there being any reason to suspect mechanical impediment to the capillary or venous circulation. Under certain circumstances, an effusion of a serous fluid takes place from membranes of a mucous character; but in this case the fluid, instead of accumulating in the body as in serous dropsy, is discharged externally.

There is no morbid state to which the economy is liable, inflammation of greater importance, in respect of the number of diseases of which it serves as the foundation or which it complicates in their progress, or in respect of the severity of these diseases, and the frequency of their occurrence, than that of inflammation. Everything combines to prove that it is in the capillary vessels that this morbid state has its immediate seat; but much diversity of opinion subsists among pathologists as to the precise condition of these vessels, in respect of increased or diminished action, in the state of inflammation. From its frequent occurrence on the surface of the body, as in inflammation of the skin or of the eye, the phenomena of inflammation are more generally known to non-professional readers, than those of any other morbid condition to which the body is subject. But the pathologist is aware that these phenomena undergo very considerable modifications, according to the texture in which the inflammation may happen to occur.

The state of inflammation sometimes disappears entirely from an organ or texture that has been affected by it, leaving in them no trace of its having existed. In this case it is said to undergo resolution. Sometimes, again, it becomes associated with, or leaves behind it, various morbid conditions, which have been denominated the terminations, local effects, or consequences of inflammation. Of these terminations, some manifest themselves in the effusion either of an increased quantity of the fluids that are naturally secreted, or in the formation of preternatural fluids from surfaces, or into the substance of organs. When boiling water, or a blister, is applied to the skin, the scarf-skin, in a longer or shorter time, rises in vesications; and if it be pierced, a quantity of watery fluid exudes. This is an illustration of inflammation terminating in an effusion of serum. If a part of the body be removed by a cutting instrument, and after a short time the surface thus produced be examined, it will be found to be covered by a glutinous fluid. Again, if a fluid be injected into the cavity of the abdomen, the serous membrane which lines that cavity, and covers the intestines, will in no great length of time be found coated with a similar glutinous matter. These are examples of the termination of inflammation in effusion of coagulable lymph; an occurrence, as we shall presently see, of equal importance, whether we regard its salutary or its noxious effects in the economy. Every one knows, more or less, what is meant by an abscess, viz. a collection of what is called purulent matter in some texture or organ of the body. The effusion of purulent matter, whether into the substance of an organ or texture, or on the surface of a membrane, is uniformly preceded by inflammation, and constitutes what is denominated its suppurative process, or termination in suppuration.

In many instances, the state of inflammation is followed by the removal or disappearance of a larger or smaller portion of the substance of the body, in consequence of a morbid absorption. We have illustrations of such a morbid absorption, first, in the formation of ulcers on the surface of the body; this may be called ulcerative absorption; second, Pathology in that process by which an abscess that may be seated at a considerable depth from the surface of the body, gradually approaches towards it, and at last is discharged externally; in which and similar cases, the absorption is said to be progressive: and, third, in the mode in which parts of the body that have become dead are separated from the living, or what has been called disjunctive absorption.

The death of a part is another event which is liable to occur as a termination of inflammation, particularly when very intense in its character. This state has been variously designated. By applying to the whole progress of this consequence of inflammation, from its commencement to its conclusion, the name of mortification, pathologists are enabled to mark out two important stages, the first extending to the period when the mortified part loses its vitality, which stage has been named gangrene; and the second designating the state in which the part is perfectly dead, the stage or state of sphacelus.

As some of the terminations of inflammation are destructive, so others are reparatory. We have already noticed the effusion of coagulable lymph as being frequently of this character. If the two surfaces of an incised wound covered with coagulable lymph be brought into apposition, they will adhere, and in a short time become united by the passage of blood-vessels from one surface to the other. This is called the termination of inflammation in adhesion. But if the surfaces of a wound be not brought into apposition, the layer of coagulable lymph effused upon them will in a short time exhibit a number of granular eminences, which acquire a bright red colour, from their becoming penetrated with blood-vessels. To this process is given the name of granulation. In a longer or shorter time, the granular surface becomes covered with a bluish-white layer, and being considerably diminished in extent by its own contraction and the elongation of the surrounding integuments, it comes to be again skinned over; or, in the language of surgeons, it undergoes cicatrization. Similar processes take place in the interior parts of the body. Should a person on the serous surface of whose bowels an effusion of coagulable lymph has taken place, survive the violence of the inflammatory attack, the lymph, in becoming organized, will produce adhesion of the different folds of intestines to one another, and to the inner surface of the walls of the abdomen; and an ulcer on the inner surface of the stomach or intestinal canal may undergo the processes of granulation and cicatrization, just in the same way as an ulcer on the skin.

In the progress of the various inflammatory processes which we have enumerated, the different textures and organs in which they occur are liable to undergo alterations in their consistence, becoming in some cases harder, and in other instances softer, than natural. There seems reason to believe, however, that these changes of induration and softening sometimes occur in particular organs or textures, independently of any inflammatory action, and simply from morbidly increased interstitial deposition, or morbidly increased interstitial absorption. Much attention, for example, has recently been paid to a state of softening occurring in the brain, in cases in which there is no reason to believe it to have been connected with inflammation. A peculiar softening of the coats of the stomach, first particularly noticed by Mr John Hunter, and attributed by him to the solvent action of the gastric juice after death, has been supposed by some pathologists to be a product of disease, taking place during life, and characterized by a peculiar concourse and succession of symptoms. As softening is a change liable to occur in the putrefactive decomposition which the different parts of the body undergo after death, considerable care is requisite to avoid confounding pseudo-morbid with truly morbid softening of the textures.

The different textures and organs of the body sometimes undergo an alteration in the amount of their natural substance, capable of modifying very considerably the exercise of their functions, and consequently of constituting the approximate causes of diseases. Sometimes the substance of the texture or organ is in excess, in which case it is said to be in a state of hypertrophy. In other instances there occurs a diminution in the amount of substance, or what has been called atrophy, or, more properly, perhaps oligotrophy. Every one is aware how much the bulk of the voluntary muscles depends upon the degree of exercise to which they are subjected. A similar principle is applicable to the involuntary muscles; and accordingly it is found, that when by any cause impeding the free motion of the blood in either circulation, the action of one or other ventricle of the heart requires to be performed with increased vigour, it takes on the state of hypertrophy. The same change is liable to occur in the urinary bladder when there exists a mechanical impediment to the discharge of its contents. Under certain circumstances, one of the kidneys becomes incapable of effecting its natural secretion. In this case, the bulk of the organ very frequently diminishes, or, in other words, the kidney passes into a state of atrophy; whilst its neighbour, taking upon itself, as it were, the duties of both, becomes enlarged in bulk, or passes into a state of hypertrophy. The only explanation we are able to give of the production of this class of organic changes is, that the nutritive vessels of the texture or organ which experiences them act with increased or with diminished vigour.

In a large number of cases of morbid alteration occurring new in the different textures and organs of the body, there is found replacing more or less of their natural substance, or disseminated through it, a substance of a nature entirely foreign to it. Sometimes this new or foreign substance resembles more or less closely one of the natural textures of the body, as when a mass of fat, or portions of cartilage or of bone, are formed in situations which they do not naturally occupy. To such productions of natural textures in preternatural situations the name of homoiplastic formations has been applied. In other instances, the new formations consist of substances altogether foreign to the natural plastic organization of the body, as when masses of hard or of soft cancer (the scirrus and fungus hematodes of pathologists) are developed in one of the various situations in which they may occur. Such formations receive the general denomination of heteroplastic. Various other divisions have been made by pathologists, of the different new growths to which the textures, systems, and organs of the body are subject, according as they are symptomatic or idiopathic, cystic or sarcomatous, &c.; but that which is perhaps of most practical importance is, their division into the mild and the malignant. The latter of these terms is applied to such new growths as manifest more or fewer of the following characters; first, that at no period of their development are they susceptible of resolution, that is, of being removed by natural processes of the economy; second, that they are very apt to appear in different textures and organs of the body simultaneously, or in succession; and, third, that when they are removed by operation, growths of the same character are very apt to recur in the same situation, or to develop themselves in some part not previously affected. It is obvious, that in the production both of the homoiplastic and of the heteroplastic formations, the nutritive vessels of the part must be supposed to secrete a matter different from that which they habitually furnish; with this distinction, that in the first class the secreted matter is analogous to that which the same vessels in the state of health furnish to other textures, whilst in the second, the matters are totally different from those formed in any part of the economy in a healthy condition.

The morbid products that have hitherto been mentioned as occurring in the different parts of the body, are either

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Pathology inorganized, as in the cases of pneumatisis, dropsy, and some of the new growths; or, if organized, it is by a vascular communication with the body in which they exist. But it sometimes happens that separate living beings are met with in different textures and organs, constituting what by naturalists are termed entozoa. The entozoa most familiarly known are intestinal worms, which, as every one is aware, give rise to a great variety of morbid phenomena or symptoms. Sometimes the entozoon, instead of having the general characters of a worm, consists of a nearly transparent bag filled with serous fluid, in which case it is termed an hydatid. The disease occurring in sheep, named the sturdy in some parts of this country, depends on the existence of hydatids in the brain; and entozoa of the same generic character have now been found in the substance of almost every organ and tissue of the human body, and even in the fluids contained in the transparent cavities of the eyeball. Entozoa are different from any species of animals that are found out of living bodies; and nothing is more perplexing to naturalists than to explain the manner in which they are produced and propagated. It has been ascertained that some genera and species of entozoa are confined to particular animals, whilst others are distributed pretty widely over the animal kingdom.

It sometimes happens that a secreted fluid deposits a portion of the solid matter which it contains, and this by accumulation comes to form one or more masses of various dimensions, which may either remain in the situation in which they were first formed, or may make their way into other situations. These masses, of which we have examples in the depositions that occur from the urine, from the bile, from the saliva, and sometimes even from the tears, are called concretions, calculi, or stones, by pathologists. A singular form of concretion is not unfrequently met with in certain veins of the body, particularly the uterine and pelvic, to which, from their position, the name of phlebolites has been given. In these several instances, we may suppose the deposition to have depended either on a deficient quantity of the dissolving menstrum in which the solid matters were contained, or on an excess of the saline, &c., ingredients; or it may in some cases have depended on the presence of a foreign ingredient in the fluid, producing precipitation of some of its natural principles. In the alimentary canal, concretions are occasionally formed by an agglutination of matter introduced along with the food, and the viscid secretions of the mucous surface of the stomach or intestines. Thus it has been found, that in those districts in which oatmeal forms a large portion of the diet of the labouring classes, such concretions are liable to be formed by the inner beards of the oats; and an excessive employment of magnesia as an antacid medicine has been known to produce an analogous result. In horses, alvine concretions, formed chiefly out of their food, sometimes attain a very large size; and in those animals which are in the habit of licking with their tongues their own hides, or those of their young, balls of hair, curiously fashioned, are very frequently met with.

Sometimes the several hollow organs of the body, without any appearance of change in the textures of which they consist, are found to have undergone an alteration in their capacity, which may either extend over a considerable portion, or be limited to a single point. In some instances the cavities or canals referred to are more capacious than natural, or in a state of dilatation; in other instances they are less capacious than natural, or in a state of contraction; and sometimes contraction occurring in the course of a canal may approach, if not amount, to obliteration. Contraction, as occurring in a canal, constitutes simple organic stricture. It not unfrequently happens that the states of contraction and dilatation are met with in different parts of the same organ; for if a portion of the alimentary canal, for example, become contracted, so as to retard the passage of its contents through it, the portion above the contraction will be very liable to become dilated by distention. The arteries are liable to undergo two different forms of dilatation, the one consisting in a preternatural and permanent enlargement of the whole circle of the canal, the other in a partial or lateral distention of its coats. To a dilatation of the second kind the name of an aneurismal sac is given by pathologists, and much controversy has existed as to the conditions of the coats of the vessels in which it is formed. Permanent dilatation of the veins, produced by the accumulation of blood in their cavities, constitutes what has been called varix. In some instances contraction at a particular portion of a canal, or stricture, seems to be congenital. Of this there is a curious illustration in a contraction that has been repeatedly met with in the aorta, or great artery of the systemic circulation, at a very short distance from its origin in the heart. Congenital stricture, sometimes amounting to obliteration, is not unfrequently met with at the lower extremity of the intestinal canal.

Very serious morbid phenomena occasionally result from alterations in the relative position of the parts constituting a joint, viz., the socket, and the lever which moves upon it as a fulcrum; surgeons, as is well known, give the name of dislocations.

Lastly, morbid phenomena are found to be referrible, in some cases, not to any structural alterations occurring in the progress of life, but to imperfections in the original organization of the individual,—to what are called malformations or monstrosities. These imperfections or malformations seem sometimes to consist in the absence or incomplete development of a particular organ or set of organs, as if the natural process of development had been arrested or retarded during the early stages of the growth of the fetus. In other instances they consist in reduplication of one or more of the parts of the body; and in others, again, the process of development seems to have taken a perverted or vicious direction, so as to produce anomalies not referrible to either of the two heads that have just been mentioned. Of malformations compatible with life, but laying a foundation for disease, we have examples in certain conditions of the heart, and large vessels immediately connected with it, which allow a portion of the blood to pass from the right side of the heart to the left, without passing through the lungs, and consequently without undergoing that depuratory process which it is the purpose of respiration to effect. In this case the extremities of the fingers, the lips, and other external parts of the body, have more or less of a blue colour, giving rise to the affection denominated cyanosis, or blue disease.

Such seem to be the principal sensible alterations that are liable to occur in the animal frame, and which, as giving origin to various combinations of morbid phenomena or symptoms, we regard as proximate causes of diseases. We have, in the next place, to consider those proximate causes of disease, pathological states, or morbid conditions, which are not attended with any sensible alterations in the textures or organs of the body, recognisable during life or after death; and the occurrence of which is inferred solely from the disturbance that takes place in the exercise of particular functions. Thus, under certain circumstances, the action of the heart may become irregular, and yet after a time resume its wonted regularity, showing that no organic alteration had occurred in it; or this fact may be still more decidedly established, in case of accidental death, by the actual inspection of the parts. The secretion of the kidneys may, in like manner, be very materially altered in respect of its quantity or composition, without these organs having undergone any discoverable change in their anatomical constitution. In our inability to refer such derangements of function to perceptible organic changes, we attribute them to changes or alterations in the peculiar powers, forces, or principles, with which the parts are endowed, that enter into the composition of the texture or organ the function of which is deranged; and it is in this respect that these derangements are properly termed dynamical.

In judging of the structural changes which disease is liable to induce in the several textures, systems, and organs of the body, it is obviously of primary importance that we should be well acquainted with their healthy structure and appearances, and with the changes which these are liable to undergo subsequently to death, from putrefactive decomposition, and other causes. The more extensive and accurate our knowledge of these matters becomes, the better must we be qualified to recognise the presence of structural alterations, and to determine in what they actually consist. In like manner, in considering the dynamical derangements which are liable to occur in the human economy, it is essential to have determined what powers are concerned in the production of its various healthy phenomena. The full consideration of this subject obviously falls under the province of the physiologist; but as it is one respecting which considerable confusion of ideas seems to us to prevail, and the correct determination of which is not less important to the pathologist than to the physiologist, we shall venture to offer a few remarks with regard to it.

In entering on this inquiry, it is necessary to keep in mind, that all the phenomena of the human economy, as far as they are corporeal, are produced by the reciprocal action of certain external agents, and of the different parts of the organized frame, upon one another. It is necessary also to keep in mind, that all which is meant by ascribing to any substance the possession of a particular property, is, that when a certain other substance is present, a particular change will take place in the condition of one or other, or of both of them. In stricter language, we substitute the term susceptibility for that of property, in those cases in which the change is most obvious in the substance to which we ascribe the property; and we use the term power in those cases in which the change is most obvious in the substance that is brought into relation with that to which we ascribe the property. It is equally a property of water to be solidified by a certain degree of cold, and to dissolve salt; but, in accurate expression, susceptibility is applicable to water in respect of the former, and power in respect of the latter, of these phenomena. When the pathologist, therefore, speaks of derangements or diseased conditions of the powers or properties of the human economy, as contrasted with morbid conditions of the structure of the body, he does not mean to allege that changes have taken place in certain mysterious agencies or spirits lurking in certain textures of the body; but he means that changes not recognisable by our senses have occurred in these textures, in consequence of which they differently affect, or are differently affected by, external agents, from what is habitual to them. It is of these differences in the mode of affecting and of being affected that we, by observation, obtain a knowledge; and it is by reasoning back from these that we infer the occurrence of those changes in the conditions of the particular textures of the animal frame, of which, in the application to them of the term dynamical, we avow that we cannot obtain any more direct information.

Understanding the term power in this signification, we may remark, that it is not peculiar to organic textures to undergo changes in their powers or properties, without any perceptible change of their interior physical conditions. When a bar of iron, on being struck with a hammer, is rendered magnetic, or deprived of its magnetic power, according to the direction in which it is previously placed (see the article MAGNETISM), no change can be detected in the characters of the mass, or of the particles of which it consists. The only knowledge we obtain of any change having taken place in the bar of iron, is derived from its evincing or not evincing magnetic properties.

What, then, are the properties concerned in the production of the various phenomena of the human economy, so far as these are of a corporeal nature?

The learned and the unlearned all concur in recognizing a particular class of beings under the title of living or organized, and in distinguishing this from another class of beings, which they designate as inorganized, lifeless, or dead. There is likewise a pretty general concurrence in acknowledging that the prominent characters or outstanding phenomena by which living beings are distinguished from those that are dead, are, first, the conversion of foreign matters into their own substance, which is continually going on within them; and, second, their invariably taking their origin from a part which had previously belonged to another being of exactly the same nature with themselves. For accomplishing these two ends (the processes of assimilation and reproduction, as they are termed), it is found that certain determinate series of phenomena are executed by living beings, to which the name of vital or organic functions is assigned, such as the functions of circulation, of respiration, of secretion, &c. The question, therefore, as to the properties concerned in producing the various corporeal phenomena of the human economy, resolves itself into the inquiry, what powers or agencies are concerned in the execution of each of these vital functions? Are the phenomena of which each of them consists, and which, as has been said, result from the reciprocal action of external agents, and of the different parts of the body, on one another, when analysed and separately examined, of the same nature as the phenomena observed to occur in the inorganized world; or are they of a nature specifically distinct from these; or is there a correspondence in some and a diversity in others? It is on the determination of these questions, obviously, that our judgment must be founded, how far it is necessary to attribute to the different parts of the body powers, principles, or properties, distinct from those of inorganized matter, or, shortly speaking, vital or organic properties, since such properties, if recognised, can be considered only as general expressions for determinate groups of phenomena, identical in themselves, and different from any which can be observed to occur in the inorganized world.

And here we may remark, that, in modern times particularly, there has very generally prevailed among physiologists a great disinclination to admit an identity in the various phenomena of living beings and resembling phenomena of inorganic matter; or, in other words, to admit the operation, in the production of the phenomena of living beings, of those physical and chemical properties to which the various mutations that dead matter is liable to

GENERAL.

The advocates of the third doctrine recognise the important influence of those physical and chemical powers to which the phenomena of inorganic matter are attributed, in producing the phenomena of the several functions of the animal economy, so far as these are corporeal. But an analysis of these functions leads them to believe that, besides the inorganic powers, there must be others concerned in their production, seeing that some of their phenomena are of a nature specifically distinct from those exhibited by any form of dead matter. They do not content themselves with the general conclusion that the function of digestion, for example, is totally different from any process which occurs in inorganic beings, and that it is consequently incumbent upon us to admit the existence of a peculiar vital principle of digestion; but analysing, as far as they are able, the various phenomena which, in combination and succession, constitute this function,—tracing the series of antecedents and consequents by which it is effected,—they endeavour to determine what are the precise phenomena which do, and what are those which do not, admit of being referred to the ordinary properties of inorganic matter, and are thus led to judge what phenomena, from not being referrible to these properties, require the recognition of powers peculiar to living beings in general, or to the animal economy in particular.

There are obviously two sources of error in the judgments which may be formed on these points. 1st, Our imperfect knowledge of the phenomena respecting which we are called on to judge; our inability to trace the successive series of changes by which the obvious result is ultimately effected. How much of the knowledge requisite for enabling us to refer the phenomena of digestion, to resume our former example, to their respective causes, is of very recent attainment? how much perhaps still remains to be acquired? But, 2d, our knowledge of the laws which preside over the physical and chemical changes of inorganic matter is likewise still very imperfect. There are doubtless very many phenomena going on in the inorganic world, which have not even been observed, far less generalized. These may have their resembling phenomena in the economy of living beings; and, from our ignorance of the one, we may fail to observe the other; or, in observing them, we may erroneously suppose them to depend on principles or properties peculiar to the economy in which they present themselves to our notice. The observations and experiments of Mr Brown respecting the motions of molecular particles, those of Dutrochet relative to Endosmosis and Exosmosis, and those of Professor Graham relative to the transmission of gases, have brought to light in our own days a number of phenomena occurring in the inorganic world, which may very possibly have their resemblances in the economy of organized beings; and other sources of motion and change in inorganic matter may yet remain to be discovered. And even in respect of those physical and chemical agencies, with the operation of which, in the inorganic kingdom, we are more or less familiar, it is quite possible that they may be taking a share in producing the phenomena of organized beings, though we do not recognise their operation. Thus a very strong belief has been entertained by many physiologists that electricity or galvanism exerts a very important influence in the performance of several of the functions of the animal economy; and that, in like manner, as this economy possesses within itself the power of generating heat, so it is provided with an apparatus capable of evolving electricity or galvanism. It is not necessary to enter here into a consideration of the circumstances which have led to the belief that the brain is such an apparatus, and the nerves the conductors of the electrical or galvanic fluid. But we may suggest, that if this opinion could be proved to be correct, many of those phenomena which seem at present irreconcilable... Pathology, with the ordinary properties of inorganic matter, and consequently to require the recognition of peculiar vital powers, might find their explanation in the agency of this powerful source of physical and chemical changes.

If these views relative to the powers concerned in producing the phenomena of living economies be correct, it follows, that it is the duty of the pathologist, in tracing the dynamical derangements to which the different parts of the animal frame are subject, to keep in mind the variations which may occur in the ordinary physical and chemical properties of the solids and fluids of which that frame consists, as well as in those properties which are peculiar to itself; seeing that modifications of these inorganic principles must necessarily have great influence in inducing pathological phenomena.

With this caution we shall now proceed to consider what are the ultimate or simple phenomena occurring in the animal economy, which seem to be specifically different from phenomena observable in the inorganic kingdom, and to require the recognition of peculiar vital properties, and to what pathological conditions these properties seem to be subject. The vital properties most usually recognised by physiologists and pathologists seem to be Irritability, Tonicity, Sensibility, Nervous Energy or Innervation, Sympathy, and Vital Affinity.

Muscular irritability. Whatever differences may exist in the views which physiologists entertain respecting the other agencies by which the various functions of the animal economy are executed, they universally agree in admitting muscular irritability, or the power which muscular fibres possess of shortening on the application of certain agents, which physiologists term stimuli, as a property of great influence in the production of the physical motions observable in the economy, and as one to which nothing strictly analogous, so far as is known, has been discovered in any other portions of nature's works. There are few, indeed, if any, of the corporeal functions of the animal economy, natural, vital, or animal, in the exercise of which muscular fibres, and the principle of irritability with which they have been endowed, are not more or less immediately concerned. And, consequently, the dynamical morbid conditions of these fibres, or the morbid conditions of the principle of irritability, enter largely into the explanations which the pathologist endeavours to give of the derangements to which the different organs of the body are liable in the exercise of their functions.

Its morbid conditions. The deviations from healthy action to which the principle of irritability is subject, seem referrible to three principal heads, viz., first, increased, second, diminished, and third, perverted or vitiated action.

In respect of irritability, physiologists distinguish between the facility and the force with which muscular fibres contract, or the mobility and vigour; and the same distinction must be kept sight of in pathology. Irritability may be excessive in facility, or, in other words, muscular fibres may be excessively mobile, a slight stimulus producing a contraction to which it would have been quite inadequate in health; or irritability may be deficient in facility, or muscular fibres preternaturally immobile or torpid, a stimulus which would have called a muscle into action in the state of health being now insufficient to effect this. Of preternatural mobility of muscular fibres we have an example in the readiness with which, in particular states of disease, the muscular coats of certain canals, as the gullet and urethra, are excited to contraction by the introduction into these canals of foreign bodies which, in their healthy state, would pass through them without exciting any perceptible muscular contraction. Of preternatural immobility or torpidity, throughout all its possible degrees, we have examples in the state of palsy, both in the voluntary muscles and in involuntary muscular organs.

Again, irritability may be excessive in force, a given amount of stimulus producing a more forcible contraction than in health; as frequently happens to the voluntary muscles in cases of mania, when the patient manifests a degree of physical strength greatly beyond his natural powers; and as seems to occur in respect of the action of the vascular system on the circulating blood, in what is called the phlogistic or inflammatory diathesis. Irritability may likewise be deficient in force, as is well known to happen to the voluntary muscular system in some diseases, as fevers at a very early stage of their progress, and as happens in all diseases, sooner or later, in the course of their progress. Of deficient force of irritability in involuntary muscular organs, we have an example in the action of the sanguiferous system in the state of collapse, or sinking.

It may be remarked, that the states of diminished force or vigour, and increased facility or mobility of contraction, are frequently combined in the same muscles or muscular organs; so that although a small amount of stimulus is sufficient to call them into action, their action is not powerful. This fact is often exemplified in the contractions of the heart, which may be very frequent in number, and at the same time very feeble in force.

Besides increased and diminished force and facility of action, there are other morbid conditions to which the power of muscular irritability is liable, that may be referred to the head of altered or vitiated action. In the ordinary circumstances of the economy, the contraction of a muscle, succeeding to the application of a stimulus, is speedily followed by a state of relaxation, and this even though the stimulus which produced the contraction continues to be applied. But there is a morbid state of the contraction of muscles that is not disposed spontaneously to alternate with relaxation, and in which, too, the fibres do not easily yield to any extending powers that may be applied. Such a state of contraction, which may occur either in voluntary muscles, or in involuntary muscular organs, is called a state of spasm. Most persons have had experience of those local spasms which, under various circumstances, occur in the muscles of the extremities, particularly of the calves of the legs, and to which the name of cramps is familiarly given. That singular affection which has been termed catalepsy, in which a part of the body retains for a great length of time the position in which it may be placed, however disagreeable or fatiguing it might be to the person when in health, furnishes us with an example of a tendency to spasmodic contraction pervading the whole of the voluntary system of muscles. The various muscular canals, as the gullet, the intestines, the gall-ducts, the urethra, &c. are frequently the seat of spasmodic affection, producing an inorganic form of stricture.

A second morbid condition of irritability that may be referred to the head of vitiated or altered action, is that in which muscles and muscular organs are excited to contraction by preternatural causes, and are contracted with unusual velocity and force, and in which, especially, the contractions alternating with relaxation are frequently and preternaturally repeated. Contractions of this kind are observable in the greater part of the muscles of voluntary motion, in the fits or paroxysms of the disease termed epilepsy; and to the same class belong the agitated motions observable in different parts of the body in chorea, or St Vitus's dance, and in hysteria. These contractions have sometimes been called clonic spasms, whilst the epithet of tonic spasms has been applied to contractions not alternated with relaxations. But the terms tonic and clonic spasms are now very generally laid aside by pathologists, and the two different kinds of muscular contraction formerly designated by them are now usually distinguished from one another by the simple names of spasms and convulsions. Though

GENERAL.

Pathology spasms and convulsion be in themselves distinct phenomena; it would be easy, by a reference to particular diseases, to illustrate the truth of Dr Cullen's remark, that "many, and indeed most, of the diseases considered as spasmodic affections, are, in respect of tonic and clonic contractions, of a mixed kind." (Sect. 1753.)

A wide difference of opinion has subsisted among physiologists as to the nature of the power by which the relaxation of a muscle succeeding to its contraction, consequent on the application of a stimulus, is effected; some conceiving that a sufficient explanation of this phenomenon is to be found in the simple elasticity of muscular substance, whilst others maintain that it can be accounted for only by recognizing in muscles an active power of expansion as well as of contraction. Nor is it muscular tissue only which has been supposed to be endowed with an active principle of expansion or dilatation. By many the expansion which is liable to occur under peculiar circumstances, in what has been called the erectile tissue, is supposed to have its primary origin in an active distention of that tissue itself, and not in its mere passive dilatation by fluids propelled into it from behind, or accumulating in it in consequence of obstruction to their further course (Chaussier, Adelon, Stieglitz, &c.); whilst by others it is conceived, that to explain the state of orgasm, as it is called, we must pre-suppose the existence of an increased vital affinity between the blood and the tissue of the organ which is capable of distention (Müller). The phenomena in question are certainly highly deserving of investigation; but we confess we are not at present prepared to acknowledge the necessity of admitting a peculiar vital property as being concerned in their production.

Many physiologists have admitted the existence in the animal economy of another form of contractile power besides irritability, distinct from any observable in inorganic matter, to which they have given the name of tonicity. There has been great vagueness, however, in the attempts which have been made to define the peculiar characters of this property, so as to distinguish it from the elasticity of inorganic matter on the one hand, and from muscular irritability on the other, as well as to determine by what textures it is possessed.

Many phenomena seem to prove, that in living and healthy animals, the muscular fibres, both of the voluntary muscles, and of involuntary muscular organs, have a constant tendency to become shorter, and, but for counterbalancing powers, such as antagonist muscles or distending liquids, would actually become so. Thus, if any joint be bent by external force, the flexor muscles contract spontaneously without any exertion of the will. If a muscle be divided transversely by the knife of the surgeon, a considerable degree of retraction takes place in the separated portions, and the antagonist muscle also contracts. That the retraction in this latter case is not attributable to the stimulus of the knife, appears from the fact, that "the separate portions which have been retracted," as Mr Mayo remarks, "if excited, shorten further, and then again become elongated to their last dimension." Besides, when the tendon of a living muscle is cut across, the muscle instantly contracts, and continues of its diminished length. In fracture of the patella, the rectus muscle of the thigh contracts sometimes to a very great extent; and in most cases of fracture there occurs similar retraction, which, though it may be in part explicable by the irritation of splintered pieces of bone, cannot be wholly attributed to that cause. It is found, also, that the arteries are always nearly accommodated to the quantity of blood contained in them. When a ligature is placed upon an artery of a living animal, the part of the artery beyond the ligature becomes gradually smaller, and is emptied to a certain degree, if not completely, of the blood it contained. It has been observed, too, that some hours after death the arteries are much diminished in size, and this occasionally to such an extent as to be rendered impervious.

By some physiologists it has been imagined that these phenomena may be explained on the principle of simple elasticity, it being conceived that in the living body muscles are stretched out or extended beyond their natural state as dead elastic substances. "To the elastic nature of the muscles generally," says Dr Bostock (Elem. Syst. of Physiology, i. 160-1), "consisting of a compound of fibre and membrane, I should refer the natural contraction of Whytt; those actions which Cullen, and many physiologists since his time, have called tone or tonicity, and which Bichat has classed under the head of contractility from texture, in which, after a part has been distended by any cause, when the distending force is withdrawn, it gradually recovers its natural form and dimensions." But the supposition that muscles are stretched, in the living body, beyond their natural elasticity, is opposed by the fact, that when a dead muscle is cut out of the body, before it has begun to putrefy it will be found to extend farther than from its origin to its insertion, as is particularly evident in a long muscle, such as the sartorius.

There are other circumstances, too, which seem to show that this constant tendency of muscular fibres to contract depends on their connection with the nervous system, on a constant and regular action of the nervous system on the muscular, a fact which does not seem reconcilable with the notion of its being simple elasticity. When the portio dura (or muscular nerve) of one side of the face is divided, the muscles of the opposite side of the face contract to such a degree as to draw the cheek of the affected side over to it; and the same thing is liable to occur as a consequence of cerebral apoplexy. It is usual to explain this phenomenon by saying that the muscles of the affected cheek, having lost their tonicity, no longer counterbalance those of the sound side, which, in consequence, being left to the uncontrolled influence of their own tonicity, undergo contraction; nor does there appear to be any mode of accounting for it, either on the hypothesis of simple elasticity or of irritability. We may perhaps also regard the pathological condition of relaxation of the sphincter muscles occurring in particular states of the nervous system, as evidence of the dependence of tonicity upon that system. It is proper, however, to keep in mind a fact which seems to have been ascertained by Bichat, viz. that when a muscle is transversely divided, the retraction is equally prompt and energetic, whether the nerves of the part have been previously cut through or not.

If, then, we recognize irritable contractility and tonic contractility, or irritability and tonicity, as two distinct vital properties, the following seem to be the characters by which they must be distinguished from one another:

First, tonicity is the tendency which certain parts of the animal frame have to contract, independently of the agency of stimuli; irritability is the tendency of muscular fibres to contract in consequence of the agency of stimuli; secondly, the contractions dependent on irritability are alternated with relaxation; those dependent on tonicity are not so alternated. As a third distinctive character, it has been alleged that while the contractions of irritability are instantaneous, those arising from tonicity are very gradual and slow.

While the existence of tonicity as a separate power has been a matter of considerable doubt and discussion, to pathologists who would seem to imply that they were fully persuaded of its existence and very extensive operation in the animal economy; for there is no explanation of morbid phenomena more familiarly in use with the learned or the unlearned, than that of ascribing them to loss of tone, or the state of Pathology. Atony. And, certainly, no class of remedies enjoys a higher degree of popularity than those which, under the designation of tonics, are supposed to possess the power of restoring or increasing the tone of the several organs of the economy, and particularly of the digestive. In examining these expressions with any degree of accuracy, however, we shall find that all which is in general meant to be implied by the use of the term tone, whether applied to the economy generally, or to particular parts of it, is merely vigour of action, without any consideration being paid to the question, whether this depends on a single and peculiar power, or is the result of the combined operation of several distinct powers.

Even in regard of the voluntary muscles, it may be a matter of no small difficulty to decide, when a particular class of muscles are in a state of preternatural contraction, whether this depends on what we have called spasmodic irritable contraction of their own fibres, overcoming the resistance of their antagonists, or on their tonic contraction, consequent on a loss of tone on the part of their antagonists. In wry-neck, for example, is the primary affection, so far as the muscles are concerned, in those on the side towards which, or in those on the side from which, the head is turned? or may it in some instances depend on one of these causes, and in other instances upon the other cause, affording what Dr Good has designated the two varieties of loxia irritata, or spasmodic wry-neck, from excess of muscular action on the contracted side; and loxia atonica, or atonic wry-neck, from direct atony of the muscles on the yielding side?

In involuntary muscular organs, however, it must be a matter of infinitely greater difficulty to trace the influence of pathological conditions of the property of tonicity, in consequence of the more concealed and more limited field of its operations. One of the pathological phenomena occurring in an organic function which seems most to favour the hypothesis of tonicity as a distinct power from irritability, is the state of the arteries in inflammation. Notwithstanding the increased velocity with which, in some cases at least, the small or capillary arteries of an inflamed part propel their contents, they are in a state of distention. Dr Thomson, in his experiments on the effects produced by applying various substances to the web of the frog's foot, found that the state of the capillary vessels thus excited that bore the greatest resemblance, in outward appearance, to the state of inflammation, was that which occurred on the application of a saturated solution of common salt. In this case, the arteries, instead of being contracted, as he found to happen when ammonia is applied, were actually and sensibly dilated. "The part of the web to which the salt was applied became of a red colour, and this redness, which was visible to the naked eye, lasted in general for a period of from three to five or more minutes. It was impossible to view with the naked eye the part to which the salt had been applied, without conceiving it to be inflamed." As in some cases, the application of the salt produced an increased velocity in the circulation through the dilated larger and smaller arteries and capillary vessels to which it was more immediately applied, the vascular distention, obviously, could not be attributable to mechanical obstruction.

Whether the distended state of the capillary arteries in inflammation, a state which, it thus appears, can be so readily imitated, if not induced, by the action of salt upon the web of the frog's foot, be attributable to a loss of tone in their parietes, seems a question fairly open for the consideration of pathologists. The idea seems to receive countenance from an interesting observation of Dr Alison's, who found that when, subsequently to death, an artery going to an inflamed limb is compared with the corresponding artery going to an uninflamed limb, it is of larger calibre, and possesses less power of re-acting upon a distending fluid. (Edin. Med. and Surg. Journ. xiv. 98.)

On the whole, it may, we believe, without injustice be affirmed that, to determine the propriety of recognising such a peculiar vital property as tonicity at all, and, in the event of its recognition being found necessary, to ascertain the particular phenomena, physiological and pathological, which ought to be referred to its agency, would require a much more precise method of analytical investigation than has ever yet been brought to bear on the elucidation of this subject.

The next vital property which we have to mention as generally recognised by physiologists, is sensibility. As voluntary motion consists of an affection of the mind succeeded by an affection of certain parts of the organic frame, viz. the voluntary muscles; so sensation consists of an affection of certain parts of the organic frame, viz. the organs of sense, succeeded by an affection of the mind. In both cases we have reason to believe that the nerves are the media of communication between the brain as the organ of the mind and the other parts of the body. In speaking of sensibility as a vital property, it is necessary to keep in mind the twofold character of sensation, as a corporeal and as a mental phenomenon. We presume that those agents the application of which to certain parts of the body is ultimately followed by those states of mind which we designate sensations, produce some change in the state of the nervous extremities, and that some corresponding changes subsequently ensue in the nervous cords, and ultimately in the brain; just as we presume that, in voluntary motion, the affection of the mind acts in some way on the brain, and that the change induced in this organ is propagated along the nerves to the muscular fibres.

Although the property of irritability is liable to be called into play in a large class of muscles, by the particular state of mind termed the will or volition, yet, in the assistance which it gives in effecting a number of the functions of the animal economy the mind has no share, these functions being purely corporeal. Different names have been given to the irritability of muscular fibres, according as it is called into operation by one or other of these causes, viz. the will or material stimuli, and amongst these the names of animal and organic contractility. Some physiologists have conceived that a similar distinction may be established in respect of sensibility; that, besides what is called animal sensibility, or that property of the nervous system in virtue of which impressions produced on particular parts of the body by external agents, or by peculiar conditions of its own textures, are communicated through the brain to the mind, there is an organic sensibility, in virtue of which the different textures themselves become sensible of the action upon them of external agents; "la faculté," says M. Cailliot, "qu'ont les parties des corps animés de recevoir des impressions quelconques, qui produisent des changements proportionnés à ces impressions." So completely independent of mind did Bichat, the great advocate of organic sensibility, consider this property to be, that he ascribes it to vegetables. "Nature," says he, "has endowed each portion of a vegetable with the faculty of feeling the impression of the fluids with which the fibres are in contact." (Anat. Génér. i. xli.) But if this application of the term sensibility be legitimate, we do not see how it can be confined to the phenomena of organic beings. A piece of marble may with equal propriety be said to be sensible of the impression of the acid which resolves it into its constituent elements; and a detonating powder sensible of the impression of the blow which occasions its explosion. The word sensibility, which is intended to denote a peculiar form of susceptibility, a form the essential peculiarity of which consists in its terminating in the production of a particular state of mind, would in this way be rendered synonymous.

GENERAL.

It is probable that the idea of an organic sensibility may arise in part from the belief entertained by physiologists, that, in many instances, external agents, in acting upon our corporeal organs, do not act upon them directly, but through the intervention of the nerves, the same channels by which sensible impressions are conveyed to the brain as the organ of the mind. But even this point of analogy, if fully established, would not warrant us in connecting the name of sensibility with a phenomenon with which the mind is in no way related.

In respect of sensibility, we know that, independently of any perceptible alterations in the organization of the several parts concerned in the exercise of that function (from that part upon which the impression is primarily made, to that by which it is transferred as it were to the mind, so as to become an object of consciousness), morbid variations are liable to occur, both as regards the intensity of the sensations produced by a given amount of impression, and as regards the qualities of the sensations. Under a variety of circumstances more or less perfectly understood by us, our sensations (both those depending on the impression of external objects, and those which result from processes going on within the body, or our sensations of impression and of consciousness, according to the distinction recognised by Dr Cullen) are liable to become more intense than they are in the state of health. In other circumstances, these sensations, particularly those of impression, become less distinct than natural, or are not at all produced; a state variously designated by nosologists, according to the seat which it may occupy, but which, from its frequent coincidence with diminished muscular irritability, has often been improperly included under the term of paralysis or palsy.

The various morbid conditions of sensibility which cannot be referred to the two heads of increased and diminished, and which are therefore included under that of vitiated or perverted, seem referrible to the three following:

1st, The perception of objects that do not exist, as when those appearances which have been called muscae volitantes are seen floating in the air like dark or luminous spots, lucid ribbons, &c.; 2d, the perception of external objects otherwise than they really are or appear to others, whether as respects their number, form, size, colour, or state of motion or rest; and, 3d, the perception of the qualities of bodies different from what is usual to us, as when those substances which in health are agreeable to us, become disagreeable, or the reverse.

When these various conditions of sensibility occur as dynamical affections, it is by no means easy for the pathologist in all instances to ascertain in what portion of the nervous system the dynamical affection has its more immediate seat; whether in the extremities of the nerves on which the impression is first received, or in the nervous cords by which it is conducted to the brain, or in the brain itself, in which we presume that some change must be produced previously to the affection of the mind which completes the function of sensation. When, for example, the sense of sight is lost, as in amaurosis, and no perceptible change of structure can be discovered capable of explaining the morbid phenomenon, are we to seek for the seat of the dynamical affection in the retina, in the optic nerve, or in the part of the cerebral mass with which that nerve is more immediately connected?

Before passing from the consideration of the properties of irritability and sensibility, we may observe, that nothing can mark more strongly the extreme difficulty which exists in obtaining the general recognition of the clearest and best established truths of science, than the frequent proposals that have been made, since the differences in the characters of these two vital, or, more correctly speaking, animal properties, irritability and sensibility, were fully demonstrated by Haller, to re-unite them as one property under a common denomination, such as that of excitability, &c. That there is a coincidence in some of their laws, may be admitted; so is there in some of the laws of heat and light, which, too, frequently occur in combination. But the physiologist has no stronger reason for alleging identity in the one case, than the natural philosopher for alleging it in the other; and nothing, we are persuaded, can be conceived more calculated than this confusion to retard the progress of medical science. It has frequently, indeed, been argued in favour of this identity, that irritability implies sensibility; that everything which is irritable must be sensible, in order that it may perceive the stimulus which calls it into action. But, as has been already shown in speaking of organic sensibility, we might as well say that every thing which is inflammable must be sensible, in order that it may perceive the impression of heat; that gunpowder must be sensible of the spark which inflames it.

A strong belief has existed among medical men that the nervous organs of the body are greatly dependent, for the energy suitable exercise of their functions, on an influence or energy communicated to them by the different parts of the nervous system; some organs being supposed to be more immediately under the control of its cerebro-spinal, and others under that of its ganglionic portion.

This belief has had its origin in the interruption to the exercise of the different functions which has been found to be occasioned by division of the nerves of their respective organs, or by the removal or destruction of particular portions of the nervous system, as well as in the functional derangements that are observed to occur under the influence of diseases of that system, or under the operation of certain agents, such as opium, upon it.

But though the facts that have been alluded to seem to warrant the general inference that the central portions of the nervous system exercise, through the medium of the nervous cords, an important influence on the performance of the several organic functions, as well as of those in which consciousness is involved, it must be confessed that we are still unable, from the results of physiological experiments, numerous as these have been, or of pathological observations, to say in what particular manner this influence is brought to bear upon the organic functions, and in what manner it operates. Those who recognise the operation, in the animal economy, of a peculiar principle, to which, from its source, the name of innervation has been given, are not able to say whether it produces or concurs in producing phenomena of a physical or of a chemical character; whether its mode of operation be the same in all the different functions, as the notion of its being a special agent or principle would lead us to conclude, or peculiar in each. Thus, for example, physiologists have very generally concurred in admitting that an influence derived from the nervous system is essential to the performance of the function of digestion, seeing that the division of the par vagum, or the destruction of particular portions of the brain or spinal marrow, put a stop to its continuance. But there is very far from being a like concurrence of opinion as to the particular process or part in the performance of this function, with which that nervous influence is more immediately connected, and the interruption of which causes the discontinuance of the whole function; whether the nervous influence be essential to the conveyance of blood to those secreting organs by which the fluids of the stomach are elaborated; or whether it assists these secreting organs in the performance of their task; or whether it aids in those reciprocal chemical actions which take place between the gastric fluids and the food introduced into the stomach; or whether, by maintaining the peristaltic motion of the stomach, it contributes to the physical removal of the portion of food that has been acted Pathology, on by the gastric juices, and to the bringing of a new surface of the food in contact with them; or, lastly, whether it may not be that several or all of these successive phenomena of the function of digestion depend on the influence which the stomach derives from the central portions of the nervous system, the ganglionic as well as the cerebro-spinal, through the nerves which ramify in its parietes.

At one time there seemed reason to believe that physiologists had ascertained the nature of the influence communicated by the nervous system to the several organs of the body—and were thus put in a fair train for ascertaining its mode of operation. When it was found that the interruption to the process of digestion, occasioned by the division of the par vagum, could be obviated by connecting the lower extremity of the nerve with a galvanic battery, or even by allowing its divided extremities to approach within a small distance of one another, it was scarcely possible to resist the conclusion, that galvanism was the active principle essential to the exercise of digestion, of which the division of its nerves deprived the stomach. More recent observations, however, have suggested doubts as to the correctness of this conclusion, and threaten to deprive us of the simple solution of the problem of innervation which it seemed to afford.

Some physiologists, indeed, doubt altogether the production in the central portion of the nervous system, and propagation along the nervous cords, of an energetic power or principle aiding the several organs in the exercise of their particular functional phenomena; and conceive, that in respect of the organic functions the nervous system acts as a medium of communication between their organs and the stimuli or impressions by which they are called into action. According to this hypothesis the food introduced into the stomach produces a particular impression on the extremities of the gastric nerves, which is propagated along the nervous cords to the nervous centres, and the nervous centres being in some way affected by the impression, react, through the same medium of communication, upon the organs in which a change is to be produced; as, for example, upon those which secrete the gastric fluids, or upon those which effect the peristaltic motion of the stomach. If this can be proved to be the correct explanation of the manner in which the nervous system operates in promoting the performance of the organic functions, it may be right to employ some appropriate term to designate it; but, for the reasons already assigned, we must avoid giving to this intervention of the nerves the denomination of sensibility, even with such a qualifying appellation as organic.

With the physiological doctrine of innervation in a state of so much embarrassment and uncertainty, it cannot be expected that in pathology it should be possible to make any very precise or extensive application of it to the explanation of morbid phenomena. It is obvious, however, that many of the facts on which the doctrine of innervation rests are of a pathological nature. And it is by availing himself of the experiments which nature as it were performs to his hand,—by noting, in cases of organic diseases of the different portions of the nervous system, the changes which occur in the action of the several organs,—that the pathologist may hope to contribute his share to the elucidation of this difficult subject.

In recognising variations in the condition of this vital power, as a probable source of morbid derangements in the exercise of the functions, the pathologist must be careful not to give to this source of morbid actions an overwhelming preponderance, to the exclusion of variations in the other powers, inorganic or organic, that are concerned in the production of the various phenomena of the animal economy. With some pathologists, dynamical derangement of function and innervatory derangement seem to be regarded as synonymous expressions, as if, whenever an organ, in which no structural alteration is discoverable, performs its function in an irregular manner, this must depend on some disturbance of its innervatory influence. But this is by no means the case. Of the three conditions of the economy, for example, described by M. Andral, in which palpitation of the heart is liable to occur, independently of organic lesion, viz. a state of plethora, a state of anaemia, and a state unattended with either of these conditions of the vascular system, it is in the last only, in which we conclude that the nervous centres are themselves affected, that we are entitled to attribute the palpitation of the heart to a lesion of innervation.

From the nature of the connection which subsists between the nervous system and the several organs of the body, it follows that a dynamical affection of an organ,—that is to say, a morbid exercise of its function, unattended with any perceptible alteration in its own structure,—may depend on an organic affection of some distant part of the nervous system; and it is particularly by tracing such dependencies that pathological anatomists have diminished or sought to diminish the number of diseases previously regarded as ultimately dynamical.

There is still another form of nervous conduction to which, under the name of sympathy, pathologists frequently refer in their explanations of morbid phenomena, and which, without being in itself a new source of such phenomena, occasionally modifies in a very important manner the relations between proximate causes of disease and the symptoms by which they manifest their existence.

There are, perhaps, few terms under which a greater diversity of phenomena have been sought to be comprehended than that of sympathy, owing in a great measure to the very imperfect analyses with which medical inquirers too frequently content themselves, of the succession of events by which an obvious result is preceded. To us it appears, that in medical language the term sympathy ought strictly to be confined to denote the arising of sensations, motions, or other vital changes, in the animal economy, suddenly and without the intervention of the will, from external or internal impressions made upon, or irritations excited in parts distinct or at a distance from, those in which these sensations, motions, or changes, actually occur; and in pathology more particularly to denote a certain co-suffering or condolence of different parts, in consequence of which, when one part is morbidly affected, either all the other parts of the body, or some particular and different part, is simultaneously affected, either in the same or in some different but obvious manner. When the sympathetic morbid affection extends to all parts of the body, as when the state of fever is produced by a wound, it is said to depend on the general sympathy of the economy. When, again, the sympathetic affection is limited to some particular part, as when the presence of stone in the bladder gives rise to itchiness and pain at the extremity of the urethra, it is said to depend upon a particular sympathy.

The great variety of pathological phenomena which have been regarded as sympathetic, may perhaps be referred to two general classes, sympathetic sensations and sympathetic motions. According to the general definition that has been given of pathological sympathetic phenomena, it obviously follows that sympathetic sensations are those which we experience in a part distinct from that to which the exciting cause is applied; as when the sensation of itchiness of the nose is occasioned in children by the presence of worms in the intestines. Sympathetic motions, in like manner, are those that occur in particular muscles or muscular organs, in consequence of the application of a physical stimulus to a part distinct from that to which they immediately belong, and with which they cannot be shown to have a render an explanation of many of the chemical processes occurring in organized bodies; secondly, that in living systems, chemical combinations are effected, or organic compounds are formed, to which nothing analogous is met with in dead matter, and which the chemist is unable to imitate; and, thirdly, that elements remain combined in living systems, which, under the ordinary laws of chemical affinity, would speedily separate from one another, so as to produce decomposition of their compound products. Notwithstanding the confidence with which these arguments have been urged, and the assent which they have very generally received, to us, we confess, it appears that if there really exist in living economies any principle or principles capable of producing chemical combinations and decompositions different from those of inorganic chemistry, both its general character, and the particular phenomena which depend upon its agency, remain yet to be discovered.

It is no way impossible that nature may employ in living economies a peculiar principle of chemical action, just as, in the case of irritability at least, she employs in the animal kingdom a peculiar principle of physical action. But, supposing this to be the case, from the harmony which we find to prevail through all parts of nature's works, we may be assured that this chemic-vital principle, if it actually exists, must be supplementary and additional to, and not inconsistent with or subversive of, those other principles which regulate the phenomena of chemical combination and decomposition.

In regard to the first argument which we have mentioned in favour of the existence of a particular principle of vital affinity, it would not, we believe, be difficult to show that our inability to render an explanation of many of the chemical processes that go on in the animal economy, is owing to our ignorance of the phenomena as they actually occur—to our seeing the results only, and not the means by which they are brought about; that, so far as we are acquainted with the chemical phenomena of the animal economy, they do not exhibit anything inconsistent or irreconcilable with the ordinary laws of chemical affinity as manifested in the inorganic world; and that the better we become acquainted with the circumstances under which chemical actions take place in living bodies, the more are we enabled to explain them conformably with these laws.

In regard to the second argument, it might, we conceive, be shown, that it is not universally true that organic compounds cannot be imitated exterior to living economies, as is shown by the preparation of oxalic acid, of sugar, of camphor, of allantoic acid, and of urea, in the laboratory of the chemist; and that even though the chemist were unable to imitate organic chemical products, this would not be a conclusive argument in favour of the existence of a distinct vital chemical principle, unless we could show that the means employed by him in his attempts to effect this were, in every other essential, analogous to those which nature employs in the living economy.

The third argument which we have mentioned, is that upon which the supporters of a principle of vital chemical affinity have most confidently relied. They appeal triumphantly to the changes which an organized body undergoes subsequently to death, as exhibiting the natural tendencies of the elements of which its several parts consist, under the ordinary laws of chemical affinity; and represent the prevention of these during life as the effect and the evidence of a peculiar chemic-vital principle. But it is strange that they should overlook how materially any one portion of an organized body, which they may mark as undergoing putrefaction subsequently to death, is altered in its circumstances from its condition during life, by the cessation of the processes of absorption, nutrition, exhalation, &c. And it is, perhaps, still more strange, that they