Principles of medical pathology

Front matter

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Contents

CHAPTER PAOS

Translator's preface iii

Author's preface v

Chapter I Intbodtjctoiiy Bemabks

Definition of the words medicine, health, disease — Disease and affection— The causes of diseases : division, according to the nature of the pathogenic agent, into mechanical, chemical, and animate causes; division, according to the action on the organism, into eflB.cient, accessory, predisposing causes — Object of the various branches of pathology — The bases of therapeutics.

Medicine is sometimes considered as a science, sometimes as an art. Both conceptions are correct ; all depends upon the view point at which we place ourselves. Medicine is a science hy its means of study; it is an art by its applications. We are thus led to the following two definitions :

The object of medical science is the study of disease. The aim of medical art is to restore and maintain health.

That part of medical science which studies disease is called pathology (Trddos, suffering, ailment). The teaching of the medical art, as it is done at the sick bed, constitutes climes (kXivikos, from Kkuvrj, bed).

Pathology comprises the following chapters : Etiology (atrta, cause), which investigates the morbific causes; pathogeny, which explains by what mechanism these causes act on the living organism to disturb its state of health or abolish its existence; pathological physiology, which shows how the organism reacts (morbid reactions) under the influence of pathogenic causes ; pathological anatomy, which unveils the structural modifications resulting from the morbid actions and reactions; symptomatology, which gives an account of the disturbances and lesions appreciable during life; nosology, which describes and classifies diseases. To these different branches, which constitute the medical science, should be added two others concerning rather the medical art — namely, the technical side (rexyrj, art) of medicine; I refer to diagnosis and prognosis. Diagnosis (discrimination, from Sio, through, and yiyv<a<TK€iv, to know) determines the place which the disease occupies in nosology; prognosis (from Trpo, before, and ytyvwo-Kctv, to know) tries to foretell the evolution of the disease.

The indispensable complement of pathology is therapeutics, with surgery, prophylaxis, and dietetics. Therapeutics {OepoTrevciv, to take care) is that part of the medical art which, profiting by the scientific data furnished by materia medica and pharmacology, endeavours to relieve the sick and to modify favourably the evolution of the disease. Surgery is that branch of therapeutics which proposes to cure by means of manual procedure (xeipovpyCoy from x«p> hand, and epyov, work). Prophylaxis ( 7r/oo<^vXao-o-€tv, to watch) whose principal part is represented by hygiene (vyteta, health), dictates the precepts to be followed for avoiding disease. Dietetics (SiatTo, regime) indicates the diet conducive to the restoration or preservation of health.

Pathology embraces, then, nearly all of medicine. There is a manifest disproportion between its vastness and the limitations of the human mind; hence the necessity of dividing its study into several distinct branches. The following divisions are generally admitted: Special or descriptive pathology, which makes an analytical study of diseases and comprises internal or medical pathology and external or surgical pathology; comparative pathology, which takes into consideration diseases in man, in animals, and even in vegetables ; experimental pathology, which proposes to modify the evolution of spontaneous diseases and to reproduce, with a view of explaining and combating them better, the disturbances, lesions, and diseases with which we have been acquainted through observation; finally, general pathology, which defines the terms and fixes their meaning, determines the laws of morbid phenomena, investigates the causes, processes, and symptoms, and classifies them. It outlines the rules of nosology, and prepares the frames in which special pathology will place its descriptions. Although general pathology is often considered as the synthesis, that is, the loftiest part of medical science, and often rises to sublime conceptions well calculated to seduce and captivate the mind, it may well be contented with more modest views ; it may be elementary and furnish the beginners with rules to guide in their studies of diseases. When we know which are the morbific causes most frequently intervening, when we are sure of their mode of action and have understood the mechanism of morbid reactions, derangements, symptoms, and lesions, we are prepared to understand and appreciate particular cases.

We have repeatedly made use of the words health and disease. These two words are currently employed ; but, while there is a universal agreement as to their meaning, there arises considerable difficulty when an inquiry is made into the precise nature of phenomena designated by these terms. The same is true of all abstract ideas : only those subjects are well defined whose limits can be comprehended by the mind. Health and disease (or hygid state and morbid state) are connected by a multitude of disturbances more or less well characterized; it is therefore very difficult, not to say impossible, to draw a sharp line between these two states, which, absolutely different in their highest expressions, approach and unite with each other in their attenuated manifestations. The difficulty is rendered greater by the fact that perfect health does not exist; living organisms are always in a state of unstable equilibrium, which finds its explanation and cause in the very conditions of life.

It is known, in fact, that living matter is the seat of a series of acts which do not depend, as was once believed, upon a vital force animating matter, but should be considered as reactions produced by the variations of external agents.

Let us suppose for a moment that no modification whatever is produced in the cosmic forces, no change at all in the relations of a being with the objects that environ it: equilibrium will soon be established between this being and the surrounding world. Of course, life is not annihilated under these conditions ; but it remains latent, as was once said, or, to speak more correctly, remains in a static state. But the moment an external variation occurs, the equilibrium is broken; the living organism, to adapt itself to the new conditions, presents a series of reactions making life again apparent — ^that is, causing it to pass into the dynamic state. Now, in reality, the cosmic forces constantly vary, the objects are displaced and modified; the world we live in changes, and, life being but an adaptation to medium, living matter is incessantly agitated by reactionary oscillations calculated to counterbalance the influence of the external agencies. Thus is explained the unstable state just referred to.

If neighbouring variations are slight and slow, adjustment is readily made and health preserved. Should they be intense and sudden, compensation becomes more difficult, often resulting in indisposition, sickness, or death. Let us suppose, for example, a man placed in a room with a fixed temperature of 20° C. ; the organism of this man is regulated so that the production and dissipation of heat maintain his organic temperature at 37° C. As the medium is supposed to be constant, heat production will be managed also in an invariable way. Suppose, now, that the temperature of the room rises or falls one degree; the equilibrium is disturbed and thermogenesis modified. In order that his temperature may always remain at 37° C, he must either produce more heat or expend less. When the variation is light and progressive, adjustment is made easily and unconsciously; the organic modifications are not perceived and do not cause any trouble. But if the temperature of the room should suddenly rise from 20° to 80° C, or fall to — 40° C, this change of 60° in plus or minus would completely upset the thermogenic equilibrium of the organism and provoke a series of disorders resulting in disease or a fatal termination.

What we say about heat can be repeated with regard to other physical agents. Barometric variations, imperceptible when slight, give rise to indisposition when intense. If it is a question of considerable change of pressure — for instance, when making a balloon ascent, or when one is submitted to the action of compressed air, and especially when one is caught in a gas explosion— the accidents may prove very serious, or even fatal.

Physical variations are not the only ones capable of impressing the organism ; all modifications occurring in our relations with surrounding objects and beings may produce the same effect. It is therefore possible to transport into medicine the classical data of the physical and natural sciences and divide the pathogenic agents simply into four groups : Mechanical agents; physical agents; chemical agents, including the caustics and the toxics; animate agents, subdivided into parasitic and infectious (the latter including most of the pathogenic bacteria). This enumeration shows that diseases are not provoked by new, special, mysterious causes, but by the ordinary cosmic agents — ^by the objects and beings that surround us. When impressed by these various agents, the organism, as above noted, does not remain indifferent; it responds by reactions, whose purpose, if not the effect, is to bring the economy to a state compatible with life. Therefore two orders of phenomena are to be noticed in every disease : those due directly to the cause and those referable to the reaction of the organism. The latter are far more important than the former. In a good definition, however, we must, following Dr. Bouchard, take into account both series of morbid manifestations. We are thus led to the following definition :

" Disease is the ensemble of the phenomena which are produced in an organism undergoing the action of a morbific cause and reacting against it."

We have thus far supposed this morbific cause to be exogenous — i. e., outside of the organism. But authors often attribute disease to internal or endogenous causes — that is, causes taking origin within the organism. We have excluded this etiological group for the reason that it is no longer acceptable ; all diseases, indeed, proceed from an external cause. The opposite view is due to a persistent confusion of disease with affection.

Take, for instance, a man suffering from typhoid fever. The disease being over, the organism is restored to health. But the restoration is only apparently perfect ; modifications persist which, too slight to be perceived, follow nevertheless their progressive evolution. Ten, fifteen.

twenty years later, new manifestations break out — ^for example, some disturbances due to heart lesion. By that time the disease is almost forgotten, and, as no intermediate bond connects the actual manifestations with the disease left far behind, considerable difficulty is experienced in tracing the succession — some sort of repugnance to connect this cardiopathy with the long expired typhoid fever. In another case the subject will have been through a number of different diseases, and the physician will be at a loss as to which of them to attribute the new visceral disorder.

From a philosophical point of view it is essential to reascend to the first disease. From a practical standpoint this inquiry is often useless. Whatever the etiological conditions may have been, the effect is the same. Organic affections are simply cicatrices; disengaged from the initial cause, they become autonomous and develop on their own account.

Let us take up the example above referred to. Suppose a man suffering with a cardiac affection. Whatever the starting point of the cardiopathy may have been, whether rheumatism, typhoid fever, or any other disease, the effects are identical. The new morbid manifestations derive no particular character from their origin. The etiological notion is of no practical importance, but is indispensable to the nosologist who will even refuse to consider the affections of the organs as diseases.

What is true of the heart is true of all the viscera. Their affections take origin from some antecedent cause. For a long time this very simple truth has not been understood because the initial disease is not always easily found out ; the visceral derangement may be the first outward manifestation, leading to the belief that it is making its appearance spontaneously.

To those who should wonder how a visceral lesion is capable of developing silently for twenty or thirty years without giving rise to any symptom, we can answer by the well-known example of gonorrhoea. A man has a urethral discharge at the age of twenty ; he recovers in a few months, and seems to be completely cured. Toward the age of forty or fifty micturition grows difficult, and a urethral stricture is discovered, which nobody hesitates to connect with the former attack of gonorrhoea. It is a remnant of the infectious process, a cicatrix that has shrunken little by little. Why, then, should we regard as doubtful in the case of the viscera and organs that which is so readily admitted to be true as regards the urethra ? The process is alike in both cases ; it is one of cicatricial evolution, slow and progressive.

We can therefore, in the presence of these tardy manifestations, sequelae of diseases, isolate the exciting cause ; but on condition of being

6 INTRODtJCTOEY REMARKS

mindful of the fact that the actual disorders are due to an anterior cause which voluntarily we disregard.

When the actual morbid process is considered without taking into account its initial cause, the name disease can not be applied to it. It is preferable to employ the term affection. We shall define, therefore: ^^ Disease is the morbid process considered in its entire evolution, from its initial cause to its final consequences; affection is a morbid process considered in its actual manifestations, apart from its cause."

It is improper to speak of diseases of organs ; affection is the proper term. Some authors use, in this sense, the term pathy as a sufifix following the name of the organ. The word thus created indicates an affection of this organ, without prejudging the disease. This procedure, strongly advocated by Dr. Landouzy, is perfectly rational. The words cardiopathy, pneumopathy, etc., have the advantage of being both well constructed and very suggestive ; " cardiopathy " is simpler than ^^ cardiac affection" and more exact than "heart disease." This nomenclature would put an end to the confusion that has been established and maintained between disease and affection.

Another condition further complicating the problem is the fact that the modifications produced by diseases and affections may influence the descendants. Thus is created morbid heredity, which may be transmitted through a great number of generations, and may explain the development of pathological families. Variously tainted children are brought into the world, presenting a defective nutrition and predisposition to certain diseases. In this event the disturbances of health are autogenous so far as the sufferers themselves are considered, but in reality they are exogenous in that they are the result of external influences exerted upon their parents. In pathology, as in biology, the successive series of livings beings must be considered as a single being eternally existent.

We shall consider at length, in a later chapter, the role of heredity, which explains a group of causes which, at first sight, seem to form an exception and to depend upon an internal origin. I refer to psychical causes. Psychical phenomena, the highest manifestations of life, appear to be independent of the external medium. In reality, though more complex, they do not differ essentially from bodily phenomena; they are equally dependent upon external agents which have acted upon the person himself or his ancestors.

These considerations amply authorize us to reject absolutely the division of morbific causes into internal and external. The initial causes are always to be looked for outside the organism. In view of their nature they may, as we have said, be classified into four groups:

INTRODUCTORY REMARKS f

Mechanical, physical, chemical, and animate causes. In view of their action upon the organism, it is possible to divide them into efficient and predisposing causes.

The efficient causes are always necessary; at times they are sufficient by themselves. Let us take, for example, the anthrax bacillus, which is one of the microbes best studied by experimenters. Let us introduce it beneath the skin of a guinea pig. The animal contracts the disease and dies within three or four days. In this case the efficient cause has proved sufficient. Let us make the same inoculation into a more resistant animal, the white rat. No disorder will be produced. But let us submit this white rat to some fatiguing exertion, or inject into it some toxic substance. The intervention of such an accessory cause will favour the action of the efficient cause: the anthrax will develop. The more we study pathology and get an insight into the history of infections, the better we understand the importance of auxiliary causes. There are certain microbes which develop as soon as they are deposited on a wound or even a healthy mucous membrane, but they are exceptions. In most instances various causes must come to their assistance. This is especially true of the microbes inhabiting our normal bodies. Our integuments and mucous membranes swarm with innumerable pathogenic agents, which vegetate as simple innocent parasites until the day when an auxiliary or, as some still say, a determining cause permits them to overcome our resistance and exercise their noxious influence ; then appear a series of acts ending in indisposition and disease. Pneumonia, for example, is an infection induced by a microbe frequently present in the mouth of healthy persons ; so long, however, as the organism is in a normal state the microbe can not develop. But let some common cause — fatigue, cold, or inhalation of irritating vapours — reduce the resisting power; the microbe, until then harmless, becomes pathogenic. This well-known example proves that the co-operation of the two orders of causes is indispensable. Let us not fall into the error of the first bacteriologists, who thought the microbe was sufficient to explain all; an error less excusable than that of the ancient authorities, who, having no idea of the role of animate agents, explained morbid phenomena by the intervention of auxiliary causes alone ; and hence they believed also in morbid spontaneity. They believed in it also because they did not understand the nature and mechanism of predisposing causes. They assigned to predisposition an internal origin instead of seeing in it the resultant of impressions made upon the subject or his progenitors by external causes having acted antecedently. Predisposing causes are antecedent causes with respect to present disorders; efficient and auxiliary causes are present

causes.

Each pathogenic agent may play alternately the part of efficient cause and of auxiliary cause ; heat and cold, for instance, in mortifying a tissue, act as efficient causes, but they fall into the order of auxiliary causes when they favour the development of a microbe. Likewise a microbe or a poison may produce a disease or aid another pathogenic agent. We should never lose sight of the possibility of these etiological associations, these morbid synergies which play a part extremely important in pathology.

According to the mode and extent of their action, the pathogenic causes are often divided into local causes and general causes. The former act on a limited point of the organism, the others act on the entire economy, or rather on numerous points thereof. The same pathogenic agent may enter into either of these groups. For example, streptococcus, a kind of microbe, when inoculated subcutaneously, produces a local lesion — erysipelas ; when injected into the veins, it gives rise to a general infection — i. e., septicaemia.

Every local lesion presents to study two orders of phenomena: those occurring at the point of application of the cause and those produced in distant parts.

At the point where the agent acts, the cellular elements are irritated, altered, or destroyed. These first disturbances, provoked directly by the pathogenic agents, give rise secondarily to responsive phenomena in the elements that remain alive. These manifestations constitute what Dr. Bouchard calls primitive autonomous elementary dystrophies.

But the organism is so constituted that a lesion can by no means remain local; it soon arouses a series of secondary manifestations, of which some are due to nervous reactions, others are caused by the absorption and penetration of anomalous substances produced at the primary focus. These secondary morbid manifestations represent pathogenic processes of a second order. They result in the formation of new lesions and the production of new disturbances, which become themselves the starting point of manifestations of a third order, and so on. The pathological process is thus liable to become extremely complicated. These successive manifestations are of course of an internal order; only the starting point (the primum movens) of the morbid series has been an external cause.

The study of morbid reactions, of which we have outlined the mechanism, constitutes physiological pathology. It is not to be supposed, however, that these reactions are essentially different from those observed in a physiological state. Biological laws are the same in both morbid and normal phenomena. It would be an error to believe that the living being is able to dispose of different manifestations, some of them intended for normal conditions, others for pathological conditions. The mode of reaction is ever the same; the results vary only in their intensity, but they are directed toward the same end — i. e., they always tend to counterbalance the action of external forces. In other words, health is organic reaction in fixed and pre-established conditions; disease is represented by reactions of the same nature, but produced in variable and new conditions. While the causes vary, the reactions may remain the same in their essence, notwithstanding the dissimilarity of their manifestations. Pathological physiology must not, therefore, be opposed to, but simply considered as the consequence of, normal physiology.

The morbid actions and reactions express themselves by functional modifications and structural lesions, which may be recognised during life or discovered only after death. The structural lesions, the study of which constitutes pathological anatomy, must be considered as the result of functional disturbances; as we are taught in general biology that it is the function that creates the organ, so in pathology it is proved that the disturbance of the function is responsible for the organic lesion.

Disturbances and lesions may, as above stated, be disclosed during life; they then constitute the symptoms and signs of the disease, and, according as they are perceived by the patient or recognised only by the observer, are divided into subjective phenomena and objective phenomena. In order to study them, we usually begin by interrogating the patient and making a list of his subjective symptoms ; next we proceed to observe the objective signs by passing systematically in review all the apparatus and all the organs. Then comes the task of resolving the final problem: the symptoms presented by the patient being given, to recognise the disease. A difficult problem, indeed, because error may be owing to a bad determination of symptoms as well as to faulty interpretation of their relative value. Doubtless there are certain cases in which the recognition of a single phenomenon suffices to settle the diagnosis ; the symptom is then called pathognomonic. But this is exceptional. The relative significance of the different symptoms must be determined, or, as is sometimes said, their semiological value established. When we are through with the methodical analysis of the patient, we must make the synthesis of the disease, connecting each trouble with its immediate cause, determining the nature and mechanism of the latter, and thus ascending the entire scale of successive manifestations until we reach the affection or disease which has been the point of departure of the morbid series.

Let us take an example : A man is complaining of pain in the side. This subjective phenomenon leads to an examination of the respiratory organs. On auscultation, rales are heard at the base of the lung, indicating congestion. But pulmonary congestion is not a disease; the cause of the trouble is to be looked for. So, pursuing the examination, we find out that this man has a cardiac lesion and that the pulmonary manifestations are due to the insufficiency of the heart. If we had seen no more than the congestion of the lung we might, by treating this organ, have done some good to the patient, but we would not have cured him. Having recognised that all depends upon the heart, we may act upon the cause of the disturbances and obtain far better results. By making the diagnosis of cardiopathy, the clinician has thus far done enough for practice, but the nosologist has not completed his task. He knows there is no organic disease ; he must, therefore, discover the cause of the cardiac lesion. Questioning the patient brings to light the fact that he has once suffered from an infectious disease, typhoid fever or acute articular rheumatism, which has given rise to endocarditis ; this explains all. We have discovered the primary disease, of which the present affection is but the sequel. So far, however, as treatment is concerned, this disease is of no importance; the patient is not suffering from typhoid fever or rheumatism, but from a cardiopathy, and the medication will be the same, no matter what may have been the cause of the affection.

It is not to be supposed, however, that it is useless to inquire into the causes. Here is a man who has lost the faculty of speech; he is attacked with aphasia. Now, aphasia is dependent upon a lesion of the third frontal circonvolution of the left side. Taking our stand upon antecedent or concomitant troubles, we diagnosticate a tumour pressing upon the cortical centre of speech. If we stop there in our diagnosis, we shall have recognised a cerebral affection, and might tell the patient there is no efficacious treatment for it. But, pushing farther our analysis, we discover on the skin old cicatrices revealing the existence of an ancient syphilis. At this point our diagnosis is complete, and leads us to institute the specific treatment which will cure the patient. In this case inquiry into the causative disease has led to the etiological therapeutics which alone could be successful. The determination of an exact and complete diagnosis is attended by that satisfaction which is always experienced when a difficult problem is solved; but, what is of greater consequence, it furnishes the precise indications of treatment. Unfortunately, in practice, the physician is not appreciated according to his skill in determining the nature of a sickness. What the patient and his friends, require of him is prognosis ; they are, of course, unable to verify his diagnosis, but they witness the course and termination of the sickness, and according as his predictions are realized or not they conclude that the doctor was right or mistaken.

INTRODUCTORY REMARKS H

In a great number of instances prognosis and diagnosis are connected. A child, for example, presents certain symptoms which lead ns to diagnosticate tubercular meningitis ; the prognosis is then well-nigh fatal. On a more careful examination, some rather odd phenomena might be discovered, and, auscultating more attentively, there might be heard a tubal murmur in the thorax. It was not, therefore, a question of meningitis, but simply meningeal accidents dependent upon pneumonia. The termination will be altogether different — the patient will recover. In this case the error of prognosis is connected with the error in diagnosis. ,

Prognosis is not always deducible from diagnosis. Besides diseases with a well-nigh fixed prognosis, there are others in which prognosis totally varies with the forms, the epidemics, the concomitant phenomena, and the previous state of the subject. On all these questions there can be given some general notions that may materially help, but for the matter of prognosis, as well as of diagnosis, books and lectures are inadequate. The medical art may be learned only by practice. It is only by seeing many patients and comparing different cases that one acquires the habit of weighing the value of signs which lead to correct diagnosis and prognosis.

In establishing the prognosis, the expected influence of the treatment should also be taken into account. The therapeutic indications are derived from the study of symptoms, causation, pathogenic process, and pathological physiology. We may, then, according to the indications which serve as our basis of treatment, admit a symptomatic, an etiological, a pathogenical, and a physiological therapeutics.

Symptomatic therapeutics aims to relieve painful symptoms, functional disorders, and to combat immediate accidents; it appeases and assuages, but seldom cures.

Etiological therapeutics fights the very cause of the evil ; it furnishes antidotes, vermifuges, antiseptics. The method of treatment is etiological when specific remedies, such as mercury for syphilis, quinine for intermittent fever, and salicylate of sodium for rheumatism are prescribed.

The morbific cause is often beyond our reach, either because we are unable to touch it by our present procedures or because its action has been transitory ; we must therefore act on the mechanism set in action by the cause or on the reactions presented by the organism. This would be pathogenical or physiological medication. This is what is realized when an attempt is made to restore to the normal rate nutrition disturbed by various causes, or to modify nervous reactions, or to neutralize the effects of microbic toxines.

The therapeutic ideal is to realize these rational medications. But at present, while it is easy to lay down general indications, it is oftentimes impossible to fulfil them ; the physician must content himself with symptomatic treatment, at times even with empiricism. He must still resort to statistics, whose data are indispensable in reassuring him as to the value of treatments; he thus secures some tentative results, which he will abandon as soon as the advance of science enables him to substitute rational for empirical medication.

We conclude, therefore, that the interest of the study of general pathology is not merely a speculative one. It alone can supply guiding ideas which will serve as the basis of the medical art.

CHAPTEK II MECHANICAL AGENTS