The essentials of pathology

Front matter

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NATIONAL LIBRARY OF MEDICINE

NATIONAL LIBRARY OF MEDICINE Washington

Preface

The object of this little book is to unfold to the beginner the fundamentals of pathology in a plain, practical way, and by bringing them within easy comprehension to increase his interest in the study of the subject. It is not, therefore, intended to supplant more pretentious works by allaying, but rather to lead up to them by kindling, a thirst for pathologi¬ cal investigation. Some departures from the ordinary have been made in the arrangement of the work, but it is believed that they will conduce to a more thorough and easy under¬ standing of the subjects treated. I have, in great measure, purposely avoided the discussion of unsettled questions, and have occasionally stated dogmatically that which admits of question. This has been done with a view to prevent con¬ fusion in the mind of the student, and to impart clear-cut conceptions of the generally accepted doctrines of to-day. For the same reason I have avoided the slight detractions incident to bibliographical references, though, I fear, with questionable propriety. A very considerable experience in teaching, extending through some years past, leads me to hope that this effort will not prove barren of some good results.

D. Tod Gilliam.

42 North Fourth St., Columbus, O., July, 1883.

Chapter I. General Considerations Of D

Pathology treats of disease; its nature, termination, etc. Diseases are divided into general and special. A general disease bears the same relation to a special disease as, with the naturalist, the species does to the individ¬ ual. All the members of a species have certain marks in common by which they may be recognized as belonging to the same family, and yet each individual has certain peculiar¬ ities by which he may be distinguished from every other. So it is with diseases—there are general or family diseases, and special or individual diseases. Fever is a general disease, as also are inflammation, cancer, tuberculosis, scrofula, etc. Now, all fevers have certain points in common by which they are recognized as belonging to the same family, and yet there are many special forms of fever by which they are differ¬ entiated one from another. Thus, we have typhoid fever, intermittent fever, remittent fever, etc., each of which con¬ stitutes a special disease. A treatise on general diseases is called general pathology —a treatise on special diseases, special pathology. Special pathology is taught in works on the prac¬ tice of medicine.

Many attempts have been made to define disease, health, and life, as they are all correlated, but no perfect definition has ever been devised. We know, practically, what is meant by these terms, and it is more important for us to understand the relationship subsisting between them than to be able to 2 9

THE ESSENTIALS OF PATHOLOGY.

frame a definition. Health and disease are not opposites, as is generally supposed, but are closely related. A diseased organ has essentially the same structure, and works essentially the same way, as does the healthy organ. There is no sub¬ stance created in disease, no force or function evolved, that does not exist in health. Take, for instance, a morbid growth —cancer. We are wont to look upon this as something for¬ eign to the body; something that has no counterpart in the natural tissues, and that is not amenable to the natural laws. Place a section under the microscope, and it is found to con¬ sist of epithelial cells impacted in the meshes of a connective tissue network. Epithelial cells and connective tissue are two of the most widely distributed of the histological con¬ stituents of the body. Observe the process of growth ; the cells divide and subdivide, as do the cells of normal tissue ; they depend for their sustenance on the materials furnished by the blood, as do the normal tissues, and like the latter, die when this is withdrawn. Now, as to function ; this is also the same in kind as that of health, though deviating from the healthy standard. The diseased brain evolves thought; the diseased glandular organ, if it does anything, secretes; muscles contract, and so on, through the whole cate¬ gory. So we might continue to illustrate, and it would be found that disease processes are the same in kind as the pro¬ cesses of health. Hence, pathology and physiology are closely related. Pathology has indeed been defined as the physiology of disease. It is of the utmost importance that the student should charge his mind with the intimate rela¬ tion between health and disease, or he will not be able to obtain an intelligent conception of the teachings of path¬ ology.

The healthy as the type of the morbid. It will be

seen from the foregoing that every disease process copies after the healthy—endeavors, as it were, to reproduce the healthy.

GENERAL CONSIDERATIONS OF DISEASE.

We say, therefore, that all morbid states have their types in the normal. Thus, if we find a morbid growth, we submit it to inspection to ascertain to which one or more of the healthy tissues it is related; and having ascertained, we assign it to its proper place. We find in every instance that it belongs to one or the other—that it partakes of the nature of muscle, nerve, bone, cartilage, common connective, epithelial, or some of the other tissues, structures or organs of the body. So it is with function; the processes of disease imitate and aspire to the healthy. Virchow considers disease processes as being healthy processes occurring at the wrong time or at the wrong place. Thus, a hemorrhage from the uterus at the menstrual period would be physiological—it would be at the right time and at the right place. Occurring from any other organ, or from the uterus at any other time, it would be pathological. Disease processes are usually characterized by an excess or deficiency, as compared with the normal. We may conclude by saying that disease is a deviation from health, and that this deviation consists, for the most part, in an excess or deficiency, or a perversion as to time or place.

Extension of Disease. Most diseases are local at the onset, as the causes of disease do not usually operate upon the whole organism at once. Ordinarily, one or more foci of disease are established, from which the disease extends.

The methods of extension are by continuity or contiguity; by the blood and lymph ; by migrating cells, and by similar¬ ity of structure and function.

By Continuity or Contiguity. When a disease extends along the same structure in an unbroken line, as, for instance, along the skin, the mucous membrane, or through the substance of an organ, it is said to extend by continuity. When it passes over from one structure to another which touch, but are not united to each other, it is said to extend by contig¬ uity. Thus an inflammation of the pleura covering the lung

THE ESSENTIALS OF PATHOLOGY.

may be communicated to the costal pleura by mere contact of the opposing surfaces. The extension by contiguity is frequently more apparent than real, as a continuity ot tissue—connective tissue, for instance—often may be traced from structure to structure, that are apparently distinct and separate.

By the Blood and Lymph. The materies morbi, or germs of disease, may be conveyed from place to place on the blood or lymph currents, and thus establish new foci of disease.

By Migrating Cells. Cells which move about from place to place, both within and outside the vascular channels, and known as mobile or migrating corpuscles, may also prove the medium of extension.

By Similarity of Structure and Function. It is a matter of common observation that organs of similar structure and futfction are prone to become “sympathetically ” diseased, from each other. As, for instance, if one eye be affected the other is liable to become affected also, and so with other bilateral organs, and organs remote from each other, but of analogous structure. Many of the so-called metastatic dis¬ eases belong to this category—the inflammation of the testes in mumps, etc. Why such is the case does not admit of ready explanation. Possibly in some instances it is due to the similarity of vascular and nervous endowment, and in others to the increased functional activity imposed on the well organ by the disablement of its fellow; or possibly to a peculiar susceptibility of certain kinds of structure to special morbific influences.

Organic and Functional Diseases. Authors have been in the habit of dividing diseases into organic and func¬ tional. By the former is meant a disease attended by struc¬ tural changes in the tissues or organs; by the latter a disease unaccompanied by such changes. As we advance in our researches we find the number of functional diseases con-

GENERAL CONSIDERATIONS OF DISEASE.

stantly diminishing—structural changes being found where they were not supposed to exist.

It is very probable that all diseases are attended by such changes, therefore are organic diseases; nevertheless, the dis¬ tinction is for the present convenient, as indicating such as have, and such as have not, been found to be so attended.

Diseases are furthermore divided into idiopathic and symp¬ tomatic, according to the absence or presence of an obvious cause. Typhoid fever is an idiopathic disease, because we are unable to demonstrate the presence of that which gives rise to it. The fever which follows an injury, however, or one which depends upon some other evident disease, is symptomatic— the cause being apparent. In other words, a symptomatic disease is one of the symptoms of an obvious disturbing agency, whether that be another disease or not.

An acute disease is one which runs a rapid course ; a chronic disease one that pursues a lingering course. Acute diseases are usually characterized by intensity of morbid action; chronic diseases by the opposite. There is no definite time when a disease ceases to be acute and becomes chronic. The terms are relative, and are used with much latitude. A regu¬ lar disease is one which runs a methodical course, in which the phenomena follow each other in regular order. An irreg¬ ular disease is one in which this order of succession is not observed. The term regular has reference solely to the order in which the phenomena occur, and does not take into account the duration of these, or the intervals between them. Thus, ague is a regular disease, because it invariably presents, first, a cold stage; second, a hot stage; and third, a sweating stage, in the order named. Each stage, however, may be of long or short duration, mild or severe, or present other pecu¬ liarities without affecting its title as a regular disease. Most diseases run a regular course. Regular diseases are, for the sake of convenience, divided into stages. These are usually

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three in number: the stage of invasion, an intermediate stage, and the stage of decline.

A continuous disease is one which pursues an even course with slight variations of intensity. A remittent disease is one characterized by very pronounced variations in intensity. An intermittent disease is one which comes and goes at intervals. Remittent and intermittent diseases are usually periodical — that is, they recur at stated intervals.

The tendency of diseases to periodicity is more common than generally supposed. Many diseases of the nervous sys¬ tem; neuralgia, epilepsy, insanity; of the circulatory system; congestions, anaemias, hemorrhages; syphilis, gout, rheuma¬ tism, erysipelas, and many other diseases, are often distinctly periodical. The underlying cause of this tendency to period¬ icity is not known. We know that many of the processes of health are periodical, and as disease is, for the most part, an excess or deficiency of health processes, the clue may lie here. The rhythmical action of the heart and of respira¬ tion, the periods of activity and repose of mind and muscle, of secretion and excretion, and the diurnal variations of temperature, are suggestive examples.

Terminations of Disease. Diseases terminate in re¬ covery, partial recovery, in other diseases, or in death. A disease seldom leaves one in all respects as it found him. An impression has been left which entails an increased or a diminished susceptibility to the same or other diseases. This is sometimes to the benefit of the individual, as when an attack of smallpox, measles, scarlatina or whooping cough secures immunity from subsequent attacks of the same disease. Oftener, however, it is otherwise, and one attack predisposes to subsequent attacks of the same or other diseases. As has been intimated, many, if not all, diseases are attended by structural changes in some one or more of the tissues. These changes consist either in the loss of substance, or in the addi-

GENERAL CONSIDERATIONS OF DISEASE.

tion of new material. In the first instance repair is effected by restitution, in the latter by resolution. Both may co-exist. The time devoted to the reparative process is called the period of convalescence.

Not infrequently the recovery from disease is only partial, and a permanent disability remains. Sometimes disturbances occur in the course of, or as the result of, a disease, which give rise to other diseases, as, for instance, the bronchitis or pneumonia occurring in typhoid fever, the heart complications in rheumatism, the strictured urethra as the result of gonor¬ rhoea.

Causes of Disease. The causes of disease may be ex¬ ternal or internal, predisposing or exciting. An internal cause is one originating within the system ; an external cause one that assails it from without.

Some of the internal causes are of a mechanical nature, as strictures, dilatations, contractions, retractions, displace¬ ments, etc.; some of a chemical nature, as the effete and excrementitious matters which have been retained in the .sys¬ tem. Many of the internal causes are the result of previous disease.

The external causes are to be sought in the food and drink, their quantity and quality; the atmosphere, its composition, temperature, humidity and density ; the clothing, bedding, and habitation ; the soil and the various emanations there¬ from ; and the atoms that infest the air, the water and the food.

A predisposing cause is one which creates or develops a tendency to a disease; an exciting cause one which directly produces a disease.

Predisposing causes frequently operate by impairing the general health and by diminishing the resisting power of the organism, thus increasing its liability to all kinds of disease. At other times they conduce to the development of a special

THE ESSENTIALS OF PATHOLOGY.

disease. Thus, by exposure, privations, long continued re¬ sidence in a vitiated atmosphere, etc., the vital energies may be so reduced that the individual falls an easy prey to any disease. On the other hand, the predisposing cause may lay the foundation for a scrofulous, tuberculous or cancerous out¬ break—one or the other, as the case may be. Predisposing causes are occasionally inherited, as when they descend from generation to generation. These give rise to the so-called inherited diseases. The number of inherited diseases is not great, but the subjects of such are extremely numerous. Syphilis, scrofula, cancer, epilepsy, insanity, rheumatism, and above all, consumption, cast their baneful shadows over suc¬ cessive generations. Hereditary diseases do not always descend in a right line from parent to child; they sometimes skip members of a family, or even a whole generation. The healthy children of a blighted family sometimes bring forth diseased offspring, or, conversely, the diseased may bring forth healthy offspring.

An hereditary disease does not always assume the same form in the progeny as in the parent. This is especially true of diseases of the nervous system. Thus, a parent suffering from epilepsy may entail upon his offspring the same disease, or in lieu of it, an asthma, insanity, or obstinate neuralgia. These are allied forms of an underlying morbid condition. Children are sometimes born with disease. These congenital diseases are acquired in utero. They may be inherited, as in the case of syphilis, or acquired otherwise. The foetus in utero is subject to many ailments, and their blight¬ ing influence does not always end with the intra-uterine sojourn. In this way arise malformations, deficiencies and monstrosities. Children have been born in the eruptive stage of the exanthemata.

Age, sex, idiosyncracy, occupation, habits of life, etc., pre¬ dispose to disease in various ways, according to the anatom-

GENERAL CONSIDERATIONS OF DISEASE.

ical and physiological peculiarities of the individual, or the modifying influences by which his system is affected. In infancy and childhood the first and second dentitions, to¬ gether with the many anatomical and physiological changes occurring at the same time, predispose to gastro-intestinal and nervous disorders. Thus, convulsions, epilepsy, chorea, true asthma, and spasmodic croup are the special heritage of this period. Scrofula, true croup, intestinal worms also manifest at this time. At the period of adolescence the sex¬ ual system is unfolding, accompanied by the most striking changes in the physical, moral and mental constitution of the individual. These predispose to erotic and religious manias, moral perversions, etc. With the decline of life come retrograde changes of all kinds, among which may be enumerated changes in the brain substance, leading to child¬ ishness, imbecility, fatuity; brittleness of the vessels, leading to dropsies and hemorrhages-} non-specific diseases of the genito-urinary apparatus, etc. Paralysis and cancer are more common at this period. Of the two sexes, males are more prone to diseases resulting from exposure and hardship, as pneumonia, heart disease, rheumatism, paralysis, etc. ; fanales to the functional and reflex ailments, such as hysteria and spinal irritation. Many of the ailments of females may be traced to confinement, sedentary habits, ungratified sexual desires, but, also, many to conditions arising from her con¬ stitutional peculiarities and the relations of maternity.

The Germ Theory. The cause of contagious and in¬ fectious diseases deserves more than a passing notice. The contagious or infectious principle, unlike all other causes of disease, accumulates after it enters the system. We can ac¬ count for this accumulation in no other way than that it is a living, growing germ, capable of reproducing itself. A drop of matter taken from the pustule of a smallpox patient, and introduced into the body of another, produces smallpox.

THE ESSENTIALS OF PATHOLOGY.

Here, again, are multiplied hundreds of pustules, each of which contains many drops of matter identical with that first introduced. That it has not lost any of its virulence or potency is evidenced by the fact that it will produce the disease in a third person as surely and quickly as the original drop did in the second. From the first drop there has been a prodigious increase in quantity, together with an unchanged quality; and thus it has been throughout the ages. No other cause, whether it be animal, mineral, or vegetable in its nature, if not endowed with life and the power of procreation, will perpetuate a disease of unabated intensity through suc¬ cessive individuals. Strychnine given to an animal will produce its characteristic effects, but these effects cannot be maintained by transmission from one animal to another. So it is with the mineral poisons, and with the non-contagious animal poisons. The experiment has often been made of submitting a fowl to be bitten by a venomous reptile, and establishing therefrom a series of inoculations. The fowl bitten speedily succumbs to the virulence of the poison intro¬ duced into its system. A second one, inoculated from the blood of this, may also die, but less speedily. A third inoc¬ ulated from the second is much less profoundly affected, and so on continually, the poison losing its strength as it becomes diluted by dissemination through different bodies, until it finally becomes practically inert. So it is with all other known substances, except such as consist of living elements.

Every contagious disease has its own special contagium, which differs from that of all others, and which imparts to the disease its distinguishing characters. Thus, the contagium of smallpox differs from that of scarlet fever, cholera, or any other contagious disease, and always produces smallpox. So it is with the other contagia; each produces its kind and nothing else.

The ordinary parasites of the body are the grosser representatives of the minute organisms which we call contagia. Fleas, lice and tics infest the surface of the body; they grow and multiply, pass from individual to individual, and pro¬ duce their characteristic effects on each. They are contagious. The same may be said of the intestinal worms; and by the aid of the microscope numerous other parasites are revealed. These are too small to be detected by the naked eye, yet none the less certainly the producers of disease.

As familiar examples, we may mention the itch mite, the trichina spiralis, and the filaria medinensis, each of which gives rise to its characteristic disease. Lowly organisms have been found in most of the contagious and infectious diseases; notably in cholera, typhoid fever, diphtheria, smallpox, ery¬ sipelas, relapsing fever and the septic diseases.

It can hardly be claimed that for the present the specific contagium for either of the above has been affixed beyond question, though the field is being cleared for subsequent investigations. Beale believes the contagious principle to consist of cells belonging to the body which have acquired specific properties under the stimulus of inflammation or otherwise. This accords to it life, but not an extraneous origin.

Chapter II. Normal Histology

Constituents of the Organism. All living organisms consist of living and lifeless elements. The living elements have * received various names, such as protoplasm, bioplasm, germ¬ inal matter, etc. The lifeless elements consist of mineral, earthy and inert animal or vegetable matters, which have been placed there through the agency of the living elements.

Protoplasm or germinal matter is an albuminous substance, which is colorless, transparent and viscid. Its primitive form in a state of rest is globular; as found in the tissues, however, it is of every conceivable shape, and varies greatly in its physical characters as regards color, consistence, etc. These little masses of protoplasm are called cells.

Cells. There are three principal varieties of cells; (i) cells consisting of a small clump of homogeneous or granular protoplasm ; (2) cells containing a dark spot in their interior —the nucleus ; and (3) cells with a nucleus and also an in¬ vesting membrane. Cells of the first class are not common in the human organism. Those of the second class are called emb 7 yonic, or germinal cells, and those of the third class typi¬ cal nucleated cells. The nucleus also consists of protoplasm.

It represents the protoplasm in its pristine condition, and is in all respects similar to the fresh and youthful protoplasm as it exists in the non-nucleated cells. Inside the nucleus may frequently be seen another differentiated spot—the nucleolus , and, at times, yet another within this. As the nucleus grows and expands its outer margin undergoes a change, and constitutes the body of the cell, while the nucle¬ olus in its interior develops into the nucleus. Thus, by suc¬ cessive changes from centre to circumference the cell is made

NORMAL HISTOLOGY.

up, the freshest protoplasm always occupying the centre. The investing membrane is the oldest and most hardened part of the cell. The vitality of the cell diminishes from the centre toward the circumference.

Structure of the Cell. Until within a recent period the cell has been supposed to be structureless. The higher powers of the microscope, however, reveal the fact that the cell, in¬ cluding the nucleus, consists of a network of extremely fine threads, filled in with a structureless material.

The network can be more easily demonstrated in the nucleus than in the surrounding substance, but the threads are con¬ tinuous from one into the other. Although the entire cell consists of protoplasm in various stages of senescence, it is customary to speak of it as consisting of a nucleus, proto¬ plasm and an investing membrane,—the protoplasm here having reference to the intervening substance between the nucleus and the investing membrane.

Physical Properties of the Cell. Cells vary greatly in size and form. In size they may range all the way from the one hun¬ dred thousandth to the one hundredth of an inch in diameter. In form they are round, oval, fusiform, spindle-shaped, stellate or irregular.

Functions of the Cell. The functions of the cell pertain to the maintenance of itself, the perpetuation of its kind, and other functions of a special character, by which it sub¬ serves the general economy. The cell is a living organism in miniature. As such it feeds, grows and multiplies. This implies the selection of proper food, its assimilation and the casting off of effete and excrementitious matters. This is the nutritive function of the cell. It receives its food from the blood and from the nutritive fluids that escape therefrom. It discharges its excreta into the blood and lymph.

Reproduction of Cells. A cell is always the offspring of a preexisting cell. Commencing with the primary germ cell,

THE ESSENTIALS OF PATHOLOGY.

which is itself derived from the mother cell, the work of repro¬ duction goes on and on, to the evolution of a new organism. It does not cease here; for the maintenance of the organism depends on the ever recurring birth and death of cells.

Cells are reproduced in three ways : —

1. By simple division , in which the cell divides into halves, each of which constitutes a new cell. These again may divide in like manner, and so on indefinitely.

2. By vacuolation, in which a brood of young cells form inside the mother cell—they are supposed to be formed from the substance of the mother cell. They make their escape

Fig. i.

through natural openings in the cell wall or by the bursting of the latter. This is called the endogenous method of cell formation.

3. By gemmation, in which a portion of the cell projects at the periphery, becomes constricted at the base, and separates, forming a new cell. In all these instances, a certain amount of substance becomes separated from the parent cell and forms a new cell. A portion of the nucleus is almost invariably included in the separated part, and on this account it has been

NORMAL HISTOLOGY.

supposed that the power of reproduction was vested in the nucleus. This, however, is not the case, as the non-nucleated cells have been known to divide ; and as we recognize in the nucleus nothing more nor less than a fresh and vigorous pro¬ toplasm, it may be seen that it is not indispensable to the reproductive act. Occasionally there is a nuclear division without a corresponding division of the cell substance. The cell enlarges, however, in the same ratio of growth, and as a consequence there results a larger mass of protoplasm, con¬ taining many nuclei. This is known as the myeloid of giant cell.

Special Function. Aside from the nutritive functions, the cells have a special function, by which they subserve the gen¬ eral economy. These special functions are as varied as the varied processes of the economy, of which, indeed, they are the authors. Secretion, excretion, muscular contraction, nerve and brain force, are examples of the special function of cells.

Amoeboid Movement. Young cells that are not fixed in the tissues, are endowed with the property of changing their form, by which they throw out processes and by flowing into the same change their locality. This is called the amoeboid movement. By flowing around substances in their course they sometimes become filled with particles of extraneous matter.

Differentiation of Cells. All cells at birth resemble each other, and are not to be distinguished by any points of differ¬ ence capable of recognition. In the process of development they assume widely different properties and functions. Thus one becomes a secreting, another a nerve, another a connect¬ ive tissue cell, and so on until all the varied types of cell are evolved. This is called the differentiation of cells. Just how it is effected is one of the mysteries of life. In some in¬ stances, as will be seen further on, it would seem that cells of a certain kind when brought in contact with new-formed cells

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have the power of converting them into their own kind. This will not apply, however, to the differentiation as it occurs in the original formation. The progeny of certain cells of the higher order, as those of the muscular and nervous sys¬ tems, do not differentiate.

Intercellular Substance. The intercellular substance is the substance occupying the spaces between the different cells. It is for the most part lifeless and inert, and is placed there through the agency of the cells. It is sometimes fluid, as in the blood; at others solid or semi-solid, as in the solid tissues. In some situations it consists largely of earthy mat¬ ter, as in bone; in others of animal matter, as in common connective tissue. Just how the intercellular substance is formed is not definitely known.

By some it is regarded as a secretion from the cell, by others as the outgrowth of the cell, and others still are of the opinion that its formation is coeval with that of the cell. Lifeless cells are frequently seen scattered throughout the intercellular substance, and constituting a part of the same.

Sometimes a tissue is composed of a network of cells, the meshes of which are filled with other cells. In such cases each acts in the capacity of an intercellular substance to the other. Several of the higher order of tissues are thus com¬ posed.

Tissues. Tissues are formed of cells and intercellular substance, variously arranged and combined. From these tissues are formed all the organs and structures of the body. The number of different tissues is not as great as might at first seem. Many of them, though entirely dissimilar in their outward appearance, belong to the same class. Thus bone, cartilage, tendon, areolar tissue and the soft, jelly-like sub¬ stance that constitutes the vitreous body of the eye, are of one class.