Histology and pathology : a manual for students and practitioners

Front matter

22101450559

Kimpton’s Series

OF

Preface

It is the purpose of this work to present all the essential facts relating to the normal histology and the pathological anatomy and histology of man in a systematic and concise way. In subjects so well established as these, originality of data is little to be expected, and the chief object to be aimed at is arrangement and treatment of the subject in a manner convenient and clear to students and practitioners of medicine, for whom this treatise is intended. It is attempted to present the subject up to the most recent discoveries and developments, avoiding points unsettled and in doubt.

The part on normal histology is written entirely bv l)r. Nichols, that on pathology entirely by Dr. Yale. Each is fully responsible for the statements in his own part, and for those only.

J. B. NICHOLS.

FRANK P. VALE.

Washington, D. C.

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Introduction

Histology (from the Greek \a roc, tissue, and Aoyo-, discourse) is a branch of anatomy treating of the minute or microscopical structure of living organisms. In its full significance it relates to the entire organic kingdom, all plants and animals alike. Within large classes of animals or plants the structure of the tissues is quite uniform ; hut on comparing one large group of organic types with another, differences in the structure appear, although there are a fundamental unity and similarity throughout.

The histologic structure of man , with which the present treatise deals, is substantially the same as that of all the mammalia, the points of variation being few and slight ; hence human histology and mammalian histology are almost identical. In passing to the classes of birds and reptiles, however, marked differences begin to appear, as nj the forms of the red blood-corpuscles, while the general structure remains similar.

Analysis of histologic structures: In analyzing the organism into its anatomic and histologic elements we find that they are arranged in an ascending series of aggregations. flic ultimate elements of all are the atoms and molecules ; as the scope of histologic science does not extend beyond the limits of microscopic vision, the atomic and molecular structure of tissues and cells does not come within its field, but is covered by organic chemistry and physics, with different methods of investigation.

The smallest elements with which histology deals are masses :

INTRODUCTION.

hence chemistry and physics cover the atomic and molecular structure ; histology, the minute molar structure of organisms.

The ultimate and smallest perceptible histologic elements of distinct individual character may be divided into two classes, cells and non-cellular or extracellular elements. By the union of these elements tissues are formed, as fibrous tissue, muscular tissue ; by the union of tissues organs are formed ; a combination of organs all working together for the accomplishment of some general function constitutes a system or tract, as the reproductive system, the alimentary tract ; while all the systems together make up the complete organism.

The ascending grades of aggregation in organic structure are, then, after atoms and molecules, cells and extracellular elements, tissues, organs, systems, the organism.

The subject will here be elaborated in the order corresponding to this analysis, beginning with the fundamental elements, cells, etc., then taking up their aggregations in tissues, and finally studying the structure of the organs making up the various systems of organic activity.

Histologic technique : The histologic examination of tissues is carried out entirely by microscopic methods. To gain an adequate idea of histology, actual examination of the tissues under the microscope is necessary. The use of the microscope and the preparation of specimens of tissues for microscopic examination involve numerous delicate procedures, the mastery of which requires much special study and experience. Objects cannot be examined in bulk under the microscope, but require special treatment before their structure can be made visible. For one thing they have to be very thin, so thin as to be transparent ; hence, solid tissues have to be cut into thin slices, or sections , about y^th millimetre thick. In their natural state most tissues are colorless, so that the details of the structure cannot well be made out. To make the details more visible it is customary to stain the sections with certain dyes, of which a considerable number are available for various purposes. Some stains have an affinity for some parts ot the tissues, other stains for other parts; thus by the employment of various materials and methods different structures can be brought plainly into view and differentiated. The nuclear

HISTOLOGIC TECHNIQUE.

dyes, for instance, such as hematoxylin, carmine, methylene-blue, constitute a class of stains very much used, which impart to the cell-nuclei a deep color, while they leave the bodies of the cells uncolored ; the general stains, as eosin, on the contrary, stain the cell-protoplasm, but not the nuclei. There are numerous other processes to be carried out ; but the limits of this work do not permit the consideration of practical methods, for which reference mav be made to the numerous special works on that subject.

Chapter II. Cells And Extracellular Elements

Elements of tissues : The ultimate elements of which tissues are composed are cells and extracellular (or intercellular ) substances. Of these the cells comprise by far the bulk of the tissues and play the chief part in the phenomena of life. The body protoplasm, which is the seat and source of all vital phenomena, is located in the cells.

The non-cellular elements , produced by the vital activities of the cells, provide a connection, support, and framework for the cells, which, composed as they are of semifluid protoplasm, have little consistency of their own and are scarcely capable of self-support. The cells are alive and the seat of life ; the function of the extracellular elements is merelv mechanical, and they do not possess any real vitality of their own.

The cell : A cell is the smallest perceptible organization of protoplasm having a definite and complete individuality, structure, and vitality of its own. It manifests in miniature all the characteristics of life exhibited by the entire organism. It is a unit of organic structure and organic activity. It is the source and the seat of vital manifestations.

The name “cell” literally means a small inclosed space. This meaning does not express a correct conception of the nature of cells. The term arose from the fact that vegetable cells, with their prominent walls and their transparent though vital contents, appear like a mass of cavities separated by partitions. The term “corpuscle,” often used synonymously with cell, better expresses the idea.

Classes of cells: All cells have a fundamental similarity in origin, structure, and nature; but as they actually occur they vary much in form and function in different situations. I wo classes, in general, can be distinguished :

1. Generalized or undifferentiated , independent , free-living

STRUCTURE OF CELLS .

cells, each endowed with all the attributes of vitality and capable of complete existence singly and by itself. rI hey are typical cells. Of this kind are (ft) the sinc/le cells of which some of the lowest (unicellular) forms of living beings consist, as the bacteria, desmids, and diatoms among plants ; and the protozoa — amoebae, foraminifera, infusoria among animals; (6) the ova and spores from which all the higher organisms develop, each being an independent and undifferentiated cell, and derived from the union of two other free though not typical cells, the female ovule and the male sperm-cell ; (c) certain actively vital cells living free in the fluids and tissues of the highest organisms, exemplified by the white blood-corpuscle, or leukocyte.

2. Differentiated or specialized cells. In unicellular animals and plants the single cell carries on all the operations of life. In the forms that through evolution have become more highly developed, instead of a single cell the organism is composed of many cells ; and instead of each cell in the multicellular organism carrying on all the functions of life, those operations are divided among different sets of cells, some serving one purpose, some another. This is differentiation, or specialization ; it is a true division or organization of labor, and by it a maximum result is accomplished with the minimum and most economical expenditure of energy. In such a differentiated organism the cells in various situations and devoted to various purposes vary accordingly in form, structure, and function. Each great class of plant and animal forms has its own characteristic types of cells.

The specialized fixed, cells of mammalian tissues may be in general divided into four classes : epithelial cells, connective-tissue cells, nerve-cells, and muscle-cells.

It is worthy of note that the young or embryonal forms of cells that are specialized when mature often partake of the more generalized character, thus exemplifying the principle that the different phases through which an organism passes in the course of its genesis and development are indicative of the different forms through which its species passed in the course of its evolution.

Structure of cells : All cells have a body of protoplasm, which in most cases contains a nucleus (Fig. 1). The centro-

CELLS AND EXTRACELLULAR ELEMENTS.

Fig. 1.

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Diagrammatic representation of an amoeboid cell, showing the nucleus, nuclear reticulum, nucleolus, the centrosome and attraction-sphere, the spongioplasm, hyaloplasm, and pseudopodia.

some is an important feature of most cells. Many cells are surrounded by a cell-wall, while some have processes and other special features.

1 he cell-body, or cytosome : As a general thing, the body or

main (non-nuclear) portion of cells is composed of typical and active protoplasm. The protoplasm of cell-bodies is often called cytoplasm. In typical cells, like the leukocyte, two parts can be distinguished in the protoplasm : the hyaloplasm, a clear, semifluid, motile portion similar in appearance to the white of an egg ; and the granuloplasm, or spongioplasm , which in the living cell presents a granular appearance, but is supposed by many to be made up of fibres or a sponge-like reticulum. The granular portion usually occupies the central portion of the cell, when it is called the endoplasm, or endosarc ; the hyaline portion then forms the outer part of the cell, and is called the ectoplasm, or eetosarc.

Sometimes the protoplasm contains granules , as of pigment, or foreign particles which have been taken into the soft substance of the cell from without, as bacteria and other bodies absorbed by leukocytes, or food- particles taken in by the small unicellular organisms. Some cells contain vacuoles, minute rounded cavities or spaces ; in some of the protozoa these are contractile, being alternately distended with fluid and then emptied by the contraction of the surrounding protopi asm, thus accomplishing some sort of circulatory process; certain human cells are vacuolated. Cells often contain substances elaborated by their own activity and stored up in their bodies in granules or small masses. One of the commonest of these is fat ; cells, as in the liver, secreting mammary gland, the vitellus of the ovum, often contain small fatty globules. In some cases, as in adipose tissue, this process is carried to an extreme degree and the cell becomes com-

CELL-GRANULES.

pletely filled and distended with a solid mass of fat, the original protoplasm remaining only as a thin atrophied shell. In plant-cells the body of the cell is largely occupied by sap, starch-granules, and the like. In some cases the protoplasm becomes transformed, so that little vitality is left to the cell ; as in the horny layer of the skin, in which the cells have been converted into a tough horny substance well adapted to purposes of protection.

Cell-granules: The granules which occur in the bodies of many cells are of various kinds. Some are particles of pigment produced by the action of the cell or absorbed from without. Some are produced artificially by the reagents employed in the preparation of the specimen, not occurring in the natural state ; even water will cause the appearance of granules in some cells. Other granules, which are colorless, appear to be specializations of the body-protoplasm. Among such granules important distinctions are made out, especially by their behavior with staining- reagents ; these distinctions are especially serviceable in the study of leukocytes. Some gn mules will become stained by one kind of dye, others by another kind, these stain ing-peculiarities corresponding to differences in the chemical constitution of the granules.

Stains in which the coloring-agent is the acid part of the compound, as eosin, are called acid stains; those in which the basic portion of the dyestuff is the staining-principle, as methylene-blue, are called basic stains ; while stains composed of a mixture of acid and basic dyes are called neutral stains.

Granules which are colored by neutral stains are called “ neutrophile ” ; those that take basic stains are called “ basophile ” ; those that take acid stains are best called “oxvphile” Co~’k, acid, and < pdico , to love), though they are most commonly called “eosinophile ” (eosin being one of the most potent acid stains), also sometimes “ acidophile ” (a barbarous term).

Ehrlich’s much-quoted division of the granules of leukocytes and other cells into five classes is as follows: ^/-granules, coarse oxyphilic or eosinophilic granules, found in certain human leukocytes ; /9-granules, amphophilic granules (taking both acid and basic stains), occurring in the blood of some animals ; /-granules, coarse basophilic granules, found in mast-cells; ^-granules, fine basophilic granules, at times found in

CELLS AND EXTRACELLULAR ELEMENTS.

human leukocytes ; and e-granules, fine neutrophilic granules (by some considered oxyphilic), very common in human leukocytes.

The nucleus : Most cells contain in their interior a nucleus, a rounded structure distinctly marked oh* from the cell-body. It appears especially prominent when stained by nuclear and basic dyes, which impart to the nucleus a deep color, while the body of the cell is colored little or not at all. Nuclei are inclosed and separated from the rest of the cell by a membrane, the nuclear membrane . The nucleus consists of two portions: the nuclear fibrils , or reticulum, a network of fibers; and the nuclear matrix, a semifluid substance in the meshes of the reticulum.

The fibrillar substance, again, is composed of two parts, a homogeneous ground-substance called linin , supported in which are granules, fibres, and filaments of a substance called chromatin. In stained specimens the deep color shown by the nucleus is taken by the chromatin (whence the name), while the ground-substance, or linin, and the nuclear matrix are less colored.

From the phenomena of karyokinesis, the chromatin is supposed to be of the highest significance and importance in vital phenomena, especially in connection with reproduction and heredity. Chromatin has been conjectured to be identical with nuclein, a chemical constituent of cells which is regarded from physiological and chemical considerations as playing a highly important part in the economy of cell-activity.

In many cases, as in ova and nerve-cells, the nucleus contains a little nucleus of its own, or more than one, called the nucleolus. Most cells are uninucleated, or contain but a single nucleus each ; certain classes of cells, however, are multinucleated, containing several or numerous nuclei each, as the voluntary muscle-cells, osteoclasts, and the giant cells present in certain pathological processes.

In shape , the nuclei are usually spheroidal, oval, or discoid; but in different cases the shape varies greatly, and may be exceedingly irregular.

The location of the nuclei in the cells varies, being sometimes in the centre, sometimesexcentric, sometimes at the very periphery of the cell.

CILIA AND FLAGELLA.

Their size , in proportion to that of the entire cell, also varies; usually the nucleus comprises but a small part of the corpuscle ; but in some cases, as in the mononuclear leukocyte, the nucleus occupies the largest part of the cell.

Most animal and vegetable cells are nucleated. Nuclei have not been demonstrated in some of the unicellular organisms, however, though they are probably present. Among mammalian cells one important class, the red blood- corpuscles, is not nucleated. The nucleus seems such an essential feature in the life and reproduction of cells that cells, like the red blood-corpuscles, that are not nucleated are probably lacking in the full attributes of vitality.

The precise function of the nucleus is not clear; but it is evidently of high importance, especially in connection with reproduction and heredity. It is probably the most vital part of the cell, the body largely serving nutritive and mechanical purposes.

The centrosome, or polar corpuscle , is a minute round refractive body or point, situated in the interior of tin; cell. The protoplasmic granules around it are arranged in delicate radiating lines, forming the attraction-sphere. In resting or non-dividing cells it may be within the nucleus, or just outside ; but in this stage it is not conspicuous and is usually invisible. During the process of karyokinetic cell-division it appears prominently in the protoplasm of the cell-body, and it plays an important part in this process, apparently exercising some sort of polar, or directive, or attractive influence in the division.

The cell-wall, or cytolemma : Many cells are surrounded with a covering or wall, which gives support and protection to the soft protoplasm. This may be a distinct membrane, or a condensation and hardening of the outermost layer of protoplasm. Some of the lower unicellular organisms secrete around themselves a silicious or calcareous covering. The cell-walls of plants consist of cellulose, a firm substance belonging to the starch group, to which the hardness of wood is due. Some cells, as the leukocytes, appear to be devoid of a distinct cell-wall.

Cilia and flagella: Certain kinds of cells have fine, hair-like processes or filaments projecting from their surface, capable

CELLS AND EXTRACELLULAR ELEMENTS.

of active vibratory or undulatory movements. They are composed of protoplasm like that of the cell-body, and their motility is of the same nature as that of protoplasm generally. When they are comparatively short and thickly crowded on the surface, or a part of the surface, of the cell, they are called cilia; when they are long and occur singly or only in small numbers on the cell, they are called flagella. They occur not only on low organisms, like bacteria and infusoria, but are of wide distribution and great importance in the human body; e- g., where cilia occur extensively on ciliated epithelium, and flagella on the spermatozoa.

The motion of cilia is vibratory, and, as they act in unison, a wave-like motion results, which, acting from a fixed surface' as in mammalia, carries particles along the surface or creates currents in the fluids adjacent.

e n of flagtll a is undulatory, and when attached to free cells this movement rapidly propels the cells through the fluid in which they occur, acting in the same manner as the tail of a tadpole or fish. Flagella therefore are a means for rapid locomotion of spermatozoa, monads, and other freeswimming cells provided with them.

Other cell-processes: Besides motile processes like those just described, some cells possess permanent and non-motile projections, which may be very various in form and size, coarse or fine, long or short, branching or very irregular. Good examples are furnished by nerve-cells, bone-cells, connective-tissue cells.

Forms of cells : Cells vary widely in shape, according to the situation in which they occur and the purposes they serve. The typical shape is perhaps spheroidal or oval. The leukocytes, which are typical active cells, are spherical when at rest. Many cells which when mature are of diverse shapes are spheroidal when young. In a differentiated multicellular organism there is a great diversity of form in different localities. On exposed surfaces they become flattened or diskshaped ; in other situations they are spheroidal, or columnar, or elongated, or branching, sheath-like, or tubular, or altogether irregular. But however diverse their form, their fundamental type is identical throughout ; they are all definite protoplasmic bodies, usually nucleated.

VITAL PROPERTIES AND FUNCTIONS OF CELLS. 29

Size of cells: The size of cells varies much. Some of the bacteria are only about 1 micromillimetre1 in diameter; these are very small cells. The diameter of ordinary vegetable cells ranges from 20 to 100 fi ; while some plant-cells are fairly visible to the naked eye, nearly 1 mm. in diameter. The mammalian ovum is a very large cell, about 0.2 mm. (200 ft) in diameter. Human red blood-corpuscles are about 7 or 8 [i in diameter, and leukocytes 7 to 15 / 1 . Human voluntary muscle-cells range from 10 to 40 //. in diameter, and 2 to 4 cm. in length. The ordinary cells of human tissues range from about 5 to 40 p in diameter.

Vital properties and functions of cells : The study of function pertains especially to the science of physiology ; in histology it is, however, necessary to pay some regard to functions, since function and structure are intimately related, and a consideration of the former throws light on the latter, as a full understanding of the latter is essential to an adequate understanding of the former. The function expresses the meaning of the structure.

The properties and manifestations of life and organisms in general reside in the individual cells. The functions and activities of cells are the same as those of life itself. These activities are usually divided into three classes, nutrition , sensibility, and motion.

Nutrition broadly comprehends the ingestion of food-material; its elaboration and assimilation into the organic structure; the rejection of waste; the formation of the structural organization ; the preserving of it intact ; development to maturity; reproduction; decline; the passage through a

definite life-cvcle.

Independent free-living cells, as the unicellular organisms, leukocytes, etc., carry on all these vital operations alone— nourish themselves through their life-cycle, manifest irritability, and possess the power of quasi-spontaneous movement. The specialized cells of differentiated organisms each devote their respective energies to some particular part of the work of life, instead of each performing all the vital functions.

The linear unit employed in microscopic measurements is the micromillimetre, or micron, briefly designated by the Greek letter//: it is rAn th of a millimetre, or about 25iT<5^ th of an inch.

CELLS AND EXTRACELLULAR ELEMENTS.

Thus the functions of such cells become distributed and differentiated: one set of cells, in the muscular system, exercises the power of contractility; others, in the nervous system, are specially arranged as seats of sensibility and consciousness; other cells have chemical functions, in the secretory apparatus ; some build up the framework of the body, some serve as a covering to the surface, others provide for reproduction.

Movements of cells : The chief visible vital movements, of automatic or quasi-spontaneous character, of which cells are capable are: 1, amoeboid movement; 2, contraction; 3, ciliary movement; 4, cyclosis, or internal circulation. These are all probably varying manifestations of one fundamental mode of motion. Besides these, a purely physical, not vital, microscopic motion is sometimes observed in cells, namely, 5, Brown ian movement.

Amoeboid movement : Many free cells, as the leukocytes in the blood and some of the protozoa, possess the power of spontaneously protruding and withdrawing processes of the body-protoplasm. These processes are called pseudopodia ; and this kind of movement is called amoeboid , from the fact that it is characteristic of the protozoon known as the amoeba. At rest, the cells capable of amoeboid movement are usually spheroidal ; but when in motion their shape may become very irregular.

The pseudopodia have no definite forms or size, but are very variable and irregular. They may be broad, or they may be slender and filamentary ; they are always temporary and capable of retraction, unlike permanent cell-processes. By means of them the cells are enabled to seize food-particles, or to move themselves about, extending a pseudopodium in one direction, and then by enlarging it the body gradually follows.

The hyaloplasm , or clear outer part of the protoplasm, is

the more actively concerned in the amoeboid movements ; it is the first to be protruded in the pseudopodia, while the granular portion of the protoplasm more slowly follows. The throwing out of the pseudopodia is said to be due to currents of the fluid protoplasm, which, impinging on the periphery of the cell, unbounded by a stiff wall, cause it to bulge and protrude at that point.

Contraction is a mode of movement, closely allied to amoe-

INTIMATE STRUCTURE OF CELLS.

boid movement, which is manifested by many cells. The protoplasm surrounding contractile vacuoles exhibits it. It is especially t lie function of muscle-cells, which decrease in length and at the same time increase in thickness. This movement is also said to be accomplished by the flowing of the fluid protoplasm.

Ciliary movement : 1 he vibratory movement of cilia and the u adulatory movements of flagella have been already described. It is a vital protoplasmic movement.

Cyclosis : In certain vegetable cells currents of liquid and minute particles are observable coursing about in definite channels entirely within the cell. This movement is called cyclosis, or internal cell-circulation, and is perhaps due to spaces and channels in the cell-substance, along which the contained fluid is forced by contractions of the protoplasm.

Brownian movement: Fine microscopic particles of solid matter, if mixed with water or certain slightly viscid fluids, exhibit under the microscope a characteristic constant dancing or oscillating movement. This was first described in 1826, by Robert Brown, from whom it has been called the Brownian movement , it is also called pedesis. Its cause is not understood. It is a purely physical phenomenon, not vital ; but granules within cells sometimes exhibit this movement.

Intimate structure of cells : The description of cells above given covers the features observable by means of the microscope. When we contemplate how from a single microscopic cell, the ovum, a large organism can develop, composed of millions of cells of a highly differentiated and vastly complicated structure; and how ova indistinguishable from one another, though belonging to different species, produce their own kind with unerring fidelity : we are forced to conclude that the germ-cells must contain elements or mechanisms corresponding to and capable of developing all the various parts of the full grown organism— that is, that they have a vastly comp ex structure that is hidden from us beyond the limits of microscopic vision, and that what we see are but the coarsest featuresof their construction. Structural elements not ordinarily visible become manifest during karyokinesis. Between the atomic and molecular structure of which we gain some idea through chemical science, and the elements visible to us,

CELLS AND EXTRACELLULAR ELEMENTS.

there is in cells a large field of structural factors that is beyond our powers of observation. If we could penetrate within this invisible field, we might find much of histologic and structural organization that would be of the greatest interest and importance in explaining the mysteries of vital phenomena. But we cannot as yet penetrate it, and the various vital structures and units which eminent biologists have assumed as entering into the structure of cells, such as the hypothetical pangenes, plasomes, plastidules, biophors, determinants, and the like, have at present little more than a speculative value.

Extracellular elements: The non-cell ular, intercellular, or extracellular constituents of tissues serve to connect, support, and provide a mechanical framework for the cells, which of themselves do not possess the firmness requisite for a large organism. These elements are not the seat of any real vitality, which pertains exclusively to the cells; they are produced by the vital activities of the latter.

The intercellular substances exhibit considerable variety, and in different tissues occur in varying proportions to the total amount of the cells.

The simplest form is the intercellular cement , a scanty substance which cements cells together. I he plasma of the blood and the serum of lymph may be regarded as a fluid intercellular substance in which the cells are suspended.

The greatest variety and quantity of extracellular elements occur in the connective tissues, where the fibres, the hyaline matrix of cartilage, and the mineral matter deposited in bones are of this character.