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COMMON SENSE MEDICAL ADVISER IN PLAIN ENGLISH: OR, MEDICINE SIMPLIFIED.
BY R.V. PIERCE, M.D.
ONE OF THE STAFF OF CONSULTING PHYSICIANS AND SURGEONS AT THE INVALIDS' HOTEL AND SURGICAL INSTITUTE, AND PRESIDENT OF THE WORLD'S DISPENSARY MEDICAL ASSOCIATION.
ONE MILLION, SIX HUNDRED AND FIFTY THOUSAND.
Carefully Revised by the Author, assisted by his full Staff of Associate Specialists in Medicine and Surgery, the Faculty of the Invalids' Hotel and Surgical Institute.
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Entered according to Act of Congress, in the year 1895, by the WORLD'S DISPENSARY MEDICAL ASSOCIATION, In the office of the Librarian of Congress, at Washington, D.C.
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TO MY PATIENTS, WHO HAVE SOLICITED MY PROFESSIONAL SERVICES, FROM THEIR HOMES IN EVERY STATE, CITY, TOWN, AND ALMOST EVERY HAMLET, WITHIN THE AMERICAN UNION; ALSO TO THOSE DWELLING IN EUROPE, MEXICO, SOUTH AMERICA, THE EAST AND WEST INDIES, AND OTHER FOREIGN LANDS, I RESPECTFULLY DEDICATE THIS WORK.
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TABLE OF CONTENTS
PREFACE TO THE PRESENT EDITION PREFACETOTHEFIRSTEDITION INTRODUCTORY WORDS
CHAPTER I. BIOLOGY CHAPTER II. PHYSIOLOGICAL ANATOMY. THE BONES. CHAPTER III. PHYSIOLOGICAL ANATOMY. THE MUSCLES. CHAPTER IV. PHYSIOLOGICAL ANATOMY. THE DIGESTIVE ORGANS. CHAPTER V. PHYSIOLOGICAL ANATOMY. ABSORPTION. CHAPTER VI. PHYSICAL AND VITAL PROPERTIES OF THE BLOOD. CHAPTER VII. PHYSIOLOGICAL ANATOMY. CIRCULATORY ORGANS. CHAPTER VIII. PHYSIOLOGICAL ANATOMY. THE ORGANS OF RESPIRATION. CHAPTER IX. PHYSIOLOGICAL ANATOMY. THE SKIN. CHAPTER X. PHYSIOLOGICAL ANATOMY. SECRETION. CHAPTER XI. PHYSIOLOGICAL ANATOMY. EXCRETION. CHAPTER XII. PHYSIOLOGICAL ANATOMY. THE NERVOUS SYSTEM. CHAPTER XIII. THE SPECIAL SENSES. SIGHT. CHAPTER XIV. CEREBRAL PHYSIOLOGY. CHAPTER XV. THE HUMAN TEMPERAMENTS. CHAPTER XVI. MARRIAGE. LOVE. CHAPTER XVII. REPRODUCTION.
PART II. HYGIENE.
CHAPTER I. HYGIENE DEFINED.—PURE AIR. CHAPTER II. FOOD. BEVERAGES. ALCOHOLIC LIQUORS. CLOTHING. CHAPTER III. PHYSICAL EXERCISE. MENTAL CULTURE. SLEEP. CLEANLINESS. CHAPTER IV. HYGIENE OF THE REPRODUCTIVE ORGANS. CHAPTER V. PRACTICAL SUMMARY OF HYGIENE.
PART III. RATIONAL MEDICINE.
CHAPTER I. THE PROGRESS OF MEDICINE. CHAPTER II. REMEDIES FOR DISEASE. CHAPTER III. BATHS AND MOTION AS REMEDIAL AGENTS. CHAPTER IV. HYGIENIC TREATMENT OF THE SICK.
PART IV. DISEASES AND THEIR REMEDIAL TREATMENT.
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PREFACE TO THE PRESENT EDITION
The popular favor with which former editions of this work have been received has required the production of such a vast number of copies, that the original electrotype plates from which it has heretofore been printed, have been completely worn out.
The book has been re-produced in London, England, where six editions have already been necessary to supply the demand for it.
In order to continue its publication to meet the demand which is still active in this country, it has been necessary, inasmuch as the original electrotype plates have become worn and useless, to re-set the work throughout. This has afforded the Author an opportunity to carefully revise the book and re-write many portions, that it may embody the latest discoveries and improvements in medicine and surgery. In performing this labor he has been greatly assisted by contributions and valuable aid kindly supplied by his staff of associate specialists in medicine and surgery who constitute the Faculty of the Invalids' Hotel and Surgical Institute.
That part of the book treating of Diseases and Their Remedies will be found to be thoroughly reliable; the prescriptions recommended therein having all received the sanction and endorsement of medical gentlemen of rare professional attainments and mature experience.
BUFFALO, N.Y., January, 1895.
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PREFACE TO THE FIRST EDITION.
Every family needs a COMMON SENSE MEDICAL ADVISER. The frequent inquiries from his numerous patients throughout the land, suggested to the Author the importance and popular demand for a reliable work of this kind. Consequently, he has been induced to prepare and publish an extensive dissertation on Physiology, Hygiene, Temperaments, Diseases and Domestic Remedies. It is for the interest and welfare of every person, not only to understand the means for the preservation of health, but also to know what remedies should be employed for the alleviation of the common ailments of life.
The frequency of accidents of all kinds, injuries sustained by machinery, contusions, drowning, poisoning, fainting, etc., and also of sudden attacks of painful diseases, such as headache, affections of the heart and nerves, inflammation of the eye, ear and other organs, renders it necessary that non-professionals should possess sufficient knowledge to enable them to employ the proper means for speedy relief. To impart this important information is the aim of the author.
Moreover, this volume treats of Human Temperaments, not only of their influence upon mental characteristics and bodily susceptibilities, but also of their vital and non-vital combinations, which transmit to the offspring either health, hardihood, and longevity, or feebleness, disease, and death. It clearly points out those temperaments which are compatible with each other and harmoniously blend, and also those which, when united in marriage, result in barrenness, or produce in the offspring imbecility, deformity, and idiocy. These matters are freely discussed from original investigations and clinical observations, thus rendering the work a true and scientific guide to marriage.
While instruction is imparted for the care of the body, those diseases (alas how prevalent!) are investigated which are sure to follow as a consequence of certain abuses, usually committed through ignorance. That these ills do exist is evident from the fact that the Author is consulted by multitudes of unfortunate young men and women, who are desirous of procuring relief from the weaknesses and derangements incurred by having unwittingly violated physiological laws.
Although some of these subjects may seem out of place in a work designed for every member of the family, yet they are presented in a style which cannot offend the most fastidious, and with a studied avoidance of all language that can possibly displease the chaste, or disturb the delicate susceptibilities of persons of either sex.
This book should not be excluded from the young, for it is eminently adapted to their wants, and imparts information without which millions will suffer untold misery. It is a false modesty which debars the youth of our land from obtaining such information.
As its title indicates, the Author aims to make this book a useful and practical Medical Adviser. He proposes to express himself in plain and simple language, and, so far as possible, to avoid the employment of technical words, so that all his readers may readily comprehend the work, and profit by its perusal. Written as it is amid the many cares attendant upon a practice embracing the treatment of thousands of cases annually, and therefore containing the fruits of a rich and varied experience, some excuse exists for any literary imperfections which the critical reader may observe.
BUFFALO, N.Y., July, 1875.
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Health and disease are physical conditions upon which pleasure and pain, success and failure, depend. Every individual gain increases public gain. Upon the health of its people is based the prosperity of a nation; by it every value is increased, every joy enhanced. Life is incomplete without the enjoyment of healthy organs and faculties, for these give rise to the delightful sensations of existence. Health is essential to the accomplishment of every purpose; while sickness thwarts the best intentions and loftiest aims. We are continually deciding upon those conditions which are either the source of joy and happiness or which occasion pain and disease. Prudence requires that we should meet the foes and obviate the dangers which threaten us, by turning all our philosophy, science, and art, into practical common sense.
The profession of medicine is no sinecure; its labors are constant, its toils unremitting, its cares unceasing. The physician is expected to meet the grim monster, "break the jaws of death, and pluck the spoil out of his teeth." His ear is ever attentive to entreaty, and within his faithful breast are concealed the disclosures of the suffering. Success may elate him, as conquest flushes the victor. Honors are lavished upon the brave soldiers who, in the struggle with the foe, have covered themselves with glory, and returned victorious from the field of battle; but how much more brilliant is the achievement of those who overwhelm disease, that common enemy of mankind, whose victims are numbered by millions! Is it meritorious in the physician to modestly veil his discoveries, regardless of their importance? If he have light, why hide it from the world? Truth should be made as universal and health-giving as sunlight. We say, give light to all who are in darkness, and a remedy to the afflicted everywhere.
We, as a people, are becoming idle, living in luxury and ease, and in the gratification of artificial wants. Some indulge in the use of food rendered unwholesome by bad cookery, and think more of gratifying a morbid appetite than of supplying the body with proper nourishment. Others devote unnecessary attention to the display of dress and a genteel figure, yielding themselves completely to the sway of fashion. Such intemperance in diet and dress manifests itself in the general appearance of the unfortunate transgressor, and exposes his folly to the world, with little less precision than certain vices signify their presence by a tobacco-tainted breath, beer-bloated body, rum-emblazoned nose, and kindred manifestations. They coddle themselves instead of practicing self-denial, and appear to think that the chief end of life is gratification, rather than useful endeavor.
I purpose to express myself candidly and earnestly on all topics relating to health, and appeal to the common sense of the reader for justification. Although it is my aim to simplify the work, and render it a practical common-sense guide to the farmer, mechanic, mariner, and day-laborer, yet I trust that it may not prove less acceptable to the scholar, in its discussion of the problems of Life. Not only does the method adopted in this volume of treating of the Functions of the Brain and Nervous System present many new suggestions, in its application to hygiene, the management of disease, generation and the development and improvement of man, but the conclusions correspond with the results of the latest investigations of the world's most distinguished savants. My object is to inculcate the facts of science rather than the theories of philosophy.
Unto us are committed important health trusts, which we hold, not merely in our own behalf, but for the benefit of others. If we discharge the obligations of our trusteeship, we shall enjoy present strength, usefulness, and length of days; but if we fail in their performance, then inefficiency, incapacity, and sickness, will follow, the sequel of which is pain and death. Let us, then, prove worthy of this generous commission, that we may enjoy the sweetest of all pleasures, the delicious fruitage of honest toil and faithful obedience.
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In this chapter we propose to consider Life in its primitive manifestations. Biology is the science of living bodies, or the science of life. Every organ of a living body has a function to perform, and Physiology treats of these functions.
Function means the peculiar action of some particular organ or part. There can be no vital action without change, and no change without organs. Every living thing has a structure, and Anatomy treats of the structures of organized bodies. Several chapters of this work are devoted to Physiological Anatomy, which treats of the human organism and its functions.
The beginning of life is called generation; its perpetuation, reproduction. By the former function, individual life is insured; by the latter, it is maintained. Since nutrition sustains life, it has been pertinently termed perpetual reproduction.
LATENT LIFE is contained in a small globule, a mere atom of matter, in the sperm-cell. This element is something which, under certain conditions, develops into a living organism. The entire realm of nature teems with these interesting phenomena, thus manifesting that admirable adjustment of internal to external relations, which claims our profound attention. We are simply humble scholars, waiting on the threshold of nature's glorious sanctuary, to receive the interpretation of her divine mysteries.
Some have conjectured that chemical and physical forces account for all the phenomena of life, and that organization is not the result of vital forces. Physical science cannot inform us what the beginning was, or how vitality is the result of chemical forces; nor can it tell us what transmutations will occur at the end of organized existence. This mysterious life-principle eludes the grasp of the profoundest scientists, and its presence in the world will ever continue to be an astonishing and indubitable testimony of Divine Power.
The physical act of generation is accomplished by the union of two cells; and as this conjugation is known to be so generally indispensable to the organization of life, we may fairly infer that it is a universal necessity. Investigations with the microscope have destroyed the hypothesis of "spontaneous generation." These show us that even the minutest living forms are derived from a parent organization.
GENERATION. So long as the vital principle remains in the sperm-cell, it lies dormant. That part of the cell which contains this principle is called the spermatozooen, which consists of a flattened body, having a long appendage tapering to the finest point. If it be remembered that a line is the one-twelfth part of an inch in length, some idea may be formed of the extreme minuteness of the body of a human spermatozooen, when we state that it is from 1/800 to 1/600 part of a line, and the filiform tail 1/50 of a line, in length. This life-atom, which can be discerned only with a powerful magnifying glass, is perfectly transparent, and moves about by executing a vibratile motion with its long appendage. Within this speck of matter are hidden the multifarious forces which, under certain favorable conditions, result in organization. Magnify this infinitesimal atom a thousand times, and no congeries of formative powers is perceived wherewith to work out the wonders of its existence. Yet it contains the principle, which is the contribution on the part of the male toward the generation of a new being.
The ovum or germ-cell, is the special contribution on the part of the female for the production of another being. The human ovum, though larger than the spermatozooen, is also extremely small, measuring not more than from 1/20 to 1/10 of a line, or from 1/240 to 1/120 of an inch, in diameter.
The sperm and the germ-cells contain the primary elements of all organic structures, and both possess the special qualities and conditions by which they may evolve organic beings. Every cell is composed of minute grains, within which vital action takes place. The interior of a cell consists of growing matter; the exterior, of matter which has assumed its form and is less active.
When the vital principle is communicated to it, the cell undergoes a rapid transformation. While this alteration takes place within the cell, deteriorating changes occur in the cell-wall. Although vital operations build up these structures, yet the animal and nervous functions are continually disintegrating, or wasting, them.
Throughout the animal kingdom, germ-cells present the same external aspect when carefully examined with the microscope. No difference can be observed between the cells of the flowers of the oak and those of the apple, but the cells of the one always produce oak trees, while those of the other always produce apple trees. The same is true of the germs of animals, there being not the slightest apparent difference. We are unable to perceive how one cell should give origin to a dog, while another exactly like it becomes a man. For aught we know, the ultimate atoms of these cells are identical in physical character; at least we have no means of detecting any difference.
SPECIES. The term species is generally used merely as a convenient name to designate certain assemblages of individuals having various striking points of resemblance. Scientific writers, as a rule, no longer hold that what are usually called species are constantly unvarying and unchangeable quantities. Recent researches point to the conclusion that all species vary more or less, and, in some instances, that the variation is so great that the limits of general specific distinctness are sometimes exceeded.
Our space will not permit us to do more than merely indicate the two great fundamental ideas upon which the leading theories of the time respecting the origin of species are based. These are usually termed the doctrine of Special Creation and the doctrine of Evolution. According to the doctrine of Special Creation, it is thought that species are practically immutable productions, each species having a specific centre where it was originally created, and from which it spread over a certain area until its further progress was obstructed by unfavorable conditions. The advocates of the doctrine of Evolution hold, on the contrary, that species are not permanent and immutable, but that they are subject to modification, and that "the existing forms of life are descendants by true generation of pre-existing forms." Most naturalists are now inclined to admit the general truth of the theory of evolution, but they differ widely respecting the mode in which it occurred.
THE PROCESS OF GENERATION.
The vital principle, represented in the sperm-cell by a spermatozooen, must be imparted to a germ-cell in order to effect impregnation. After touching each other, separate them immediately, and observe the result. If, with the aid of a powerful lens, we directly examine the spermatozooen, it will be perceived that, for a short time, it preserves its dimensions and retains all its material aspects. But it does not long withstand the siege of decay, and, having fulfilled its destiny, loses its organic characteristics, and begins to shrink.
If we examine the fertilized germ, we discover unusual activity, the result of impregnation. Organic processes succeed one another with wonderful regularity, as if wrought out by inexplicable intelligence. Here begin the functions which constitute human physiology.
Generation requires that a spermatozooen be brought into actual contact with a germ that fecundation may follow. If a spermatic cell, or spermatozooen, together with several unimpregnated ova, no matter how near to one another, if not actually touching, be placed on the concave surface of a watch-crystal, and covered with another crystal, keeping them warm, and even though the vapor of the ova envelops it, no impregnation will occur. Place the spermatozooen in contact with an ovum, and impregnation is instantly and perfectly accomplished. Should this vitalizing power be termed nerve-force, electricity, heat, or motion? It is known that these forces may be metamorphosed; for instance, nervous force may be converted into electricity, electricity into heat, and heat into motion, thus illustrating their affiliation and capability of transformation. But nothing is explained respecting the real nature of the vital principle, if we assert its identity with any of these forces; for who can reveal the true nature of any of these, or even of matter?
In several insect families, the species is not wholly represented in the adult individuals of both sexes, or in their development, but, to complete this series, supplementary individuals, as it were, of one or of several preceding generations, are required. The son may not resemble the father, but the grandfather, and in some instances, the likeness re-appears only in latter generations. Agassiz states: "Alternate generation was first observed among the Salpae. These are marine mollusks, without shells, belonging to the family Tunicata. They are distinguished by the curious peculiarity of being united together in considerable numbers so as to form long chains, which float in the sea, the mouth(m) however being free in each.
"Fig. 2. The individuals thus joined in floating colonies produce eggs; but in each animal there is generally but one egg formed, which is developed in the body of the parent, and from which is hatched a little mollusk.
"Fig. 3, which remains solitary, and differs in many respects from the parent. This little animal, on the other hand, does not produce eggs, but propagates, by a kind of budding, which gives rise to chains already seen in the body of their parent(a), and these again bring forth solitary individuals, etc."
It therefore follows that generation in some animals require? two different bodies with intermediate ones, by means of which and their different modes of reproduction, a return to the original stock is effected.
UNIVERSALITY OF ANIMALCULAR LIFE.—Living organisms are universally diffused over every part of the globe. The gentle zephyr wafts from flower to flower invisible, fructifying atoms, which quicken beauty and fragrance, giving the promise of a golden fruitage, to gladden and nourish a dependent world. Nature's own sweet cunning invests all living things constraining into her service chemical affinities, arranging the elements and disposing them for her own benefit, in such numberless ways that we involuntarily exclaim,
"The course of Nature is the art of God."
The microscope reveals the fact that matter measuring only 1/120000 of an inch diameter may be endowed with vitality, and that countless numbers of animalcules often inhabit a single drop of stagnant water. These monads do not vary in form, whether in motion or at rest. The life of one, even, is an inexplicable mystery to the philosopher. Ehrenberg writes: "Not only in the polar regions is there an uninterrupted development of active microscopic life, where larger animals cannot exist, but we find that those minute beings collected in the Antarctic expedition of Captain James Ross exhibit a remarkable abundance of unknown, and often most beautiful forms."
Even the interior of animal bodies is inhabited by animalcules. They have been found in the blood of the frog and the salmon, and in the optic fluid of fishes. Organic beings are found in the interior of the earth, into which the industry of the miner has made extensive excavations, sunk deep shafts, and thus revealed their forms; likewise, the smallest fossil organisms form subterranean strata many fathoms deep. Not only do lakes and inland seas abound with life, but also, from unknown depths, in volcanic districts, arise thermal springs which contain living insects. Were we endowed with a microscopic eye, we might see myriads of ethereal voyagers wafted by on every breeze, as we now behold drifting clouds of aqueous vapor. While the continents of earth furnishes evidences of the universality of organic beings, recent observations prove that "animal life predominates amid the eternal night of the depths of the liquid ocean."
THE ORIGIN OF LIFE.
The ancients, rude in many of their ideas, referred the origin of life to divine determination. The thought was crudely expressed, but well represented, in the following verse:
"Then God smites his hands together, And strikes out a soul as a spark, Into the organized glory of things. From the deeps of the dark."
According to a Greek myth, Prometheus formed a human image from the dust of the ground, and then, by fire stolen from heaven, animated it with a living soul. Spontaneous generation once held its sway, and now the idea of natural evolution is popular. Some believe that the inpenetrable mystery of life is evolved from the endowments of nature, and build their imperfect theory on observations of her concrete forms and their manifestations, to which all our investigations are restricted. But every function indicates purpose, every organism evinces intelligent design, and all proclaim a Divine Power. Something cannot come out of nothing. With reason and philosophy, chance is an impossibility. We, therefore, accept the display of wisdom in nature as indicative of the designs of God. Thus "has He written His claims for our profoundest admiration and homage all over every object that He has made." If you ask: Is there any advantage in considering the phenomena of nature as the result of DIVINE VOLITION? we answer, that this belief corresponds with the universally acknowledged ideas of accountability; for, with a wise, and efficient Cause, we infer there is an intelligent creation, and the desire to communicate, guide and bless, is responded to by man, who loves, obeys, and enjoys. Nothing is gained by attributing to nature vicegerent forces. Is it not preferable to say that she responds to intelligent, loving Omnipotence? Our finiteness is illustrated by our initiation into organized being. Emerging from a rayless atom, too diminutive for the sight, we gradually develop and advance to the maturity of those conscious powers, the exercise of which furnishes indubitable evidence of our immortality. We are pervaded with invisible influences, which, like the needle of the compass trembling on its pivot, point us to immortality as our ultimate goal, where in the sunny clime of Love, even in a spiritual realm of joy and happiness, we may eternally reign with Him who is all in all.
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All living bodies are made up of tissues. There is no part, no organ, however soft and yielding, or hard and resisting, which has not this peculiarity of structure. The bones of animals, as well as their flesh and fat, are composed of tissues, and all alike made up of cells. When viewed under a microscope, each cell is seen to consist of three distinct parts, a nucleolus, or dark spot, in the center of the cell, around which lies a mass of granules, called the nucleus; and this, in turn, is surrounded with a delicate, transparent membrane, termed the envelope. Each of the granules composing the nucleus assimilates nourishment, thereby growing into an independent cell, which possesses a triple organization similar to that of its parent, and in like manner reproduces other cells.
A variety of tissues enters into the composition of an animal structure, yet their differences are not always distinctly marked, since the characteristics of some are not unlike those of others. We shall notice, however, only the more important of the tissues.
The Areolar, or Connective Tissue, is a complete network of delicate fibers, spread over the body, and serves to bind the various organs and parts together. The fibrous and serous tissues are modifications of the areolar.
The Nervous Tissue is of two kinds: The gray, which is pulpy and granulated, and the white fibrous tissue. The Adipose Tissue is an extremely thin membrane, composed of closed cells which contain fat. It is found principally just beneath the skin, giving it a smooth, plump appearance.
The Cartilaginous Tissue consists of nucleated cells, and, with the exception of bone, is the hardest part of the animal frame. The Osseous Tissue, or bone, is more compact and solid than the cartilaginous, for it contains a greater quantity of lime. The Muscular Tissue is composed of bundles of fibers, which are enclosed in a cellular membrane.
Various opinions have been entertained in regard to the formation, or growth, of bone. Some anatomists have supposed that all bone is formed in cartilage. But this is not true, for there is an intra-membranous, as well as an intra-cartilaginous, formation of bone, as may be seen in the development of the cranial bones, where the gradual calcification takes place upon the inner layers of the fibrous coverings. Intra-cartilaginous deposit is found in the vicinity of the blood-vessels, within the cartilaginous canals; also, there are certain points first observed in the shafts of long bones, called centers of ossification. These points are no sooner formed than the cartilage corpuscles arrange themselves in concentric zones, and, lying in contact with one another, become very compact. As ossification proceeds, the cup-shaped cavities are converted into closed interstices of bone, with extremely thin lamellae, or layers. These, however, soon increase in density, and no blood-vessels can be observed within them.
The bony plates form the boundaries of the Haversian, or nutritive canals of the bones. In the second stage of ossification, the cartilage corpuscles are converted into bone. Becoming flattened against the osseous lamellae already formed, they crowd upon one another so as to entirely obliterate the lines that distinguish them; and, simultaneously with these changes, a calcareous deposit takes place upon their interior. Bones grow by additions to their ends and surfaces. In the child, their extremities are separated from the body of the bone by layer of cartilage, and the cancellated, or cellular structure, which remains for a time in the interior, represents the early condition of the ossifying substances.
The bones contain more earthy matter in their composition than any other part of the human body, being firm, hard, and of a lime color. They compose the skeleton or frame work, and, when united by natural ligaments, form what is known as the natural skeleton; when they are wired together, they are called an artificial skeleton. The number of bones in the human body is variously estimated; for those regarded as single by some anatomists are considered by others to consist of several distinct pieces. There are two hundred distinct bones in the human skeleton besides the teeth. These may be divided into those of the Head, Trunk, Upper Extremities, and Lower Extremities.
THE BONES OF THE HEAD are classed as follows: eight belonging to the Cranium, and fourteen to the Face. The bones of the Cranium are the occipital, two parietal, two temporal, frontal, sphenoid, and ethmoid. Those composing the face are, the two nasal, two superior maxillary, two lachrymal, two malar two palate, two inferior turbinated, vomer, and inferior maxillary. The cranial bones are composed of two dense plates, between which there is, in most places a cancellated or cellular tissue. The external plate is fibrous, the internal, compact and vitreous. The skull is nearly oval in form, convex externally, the bone being much thicker at the base than elsewhere, and it is, in every respect admirably adapted to resist any injury to which it may be exposed, thus affording ample protection to the brain substance which it envelops. The internal surface of the cranium presents eminences and depressions for lodging the convolutions of the brain, and numerous furrows for the ramifications of the blood-vessels. The bones of the cranium are united to one another by ragged edges called sutures, which are quite distinct in the child but which in old age are nearly effaced. Some authorities suppose that by this arrangement the cranium is less liable to be fractured by blows; others think that the sutures allow the growth of these bones, which takes place by a gradual osseous enlargement at the margins. The bones of the Face are joined at the lower part and in front of the cranium, and serve for the attachment of powerful muscles which assist in the process of mastication. Although the soft parts of the face cover the bony structure, yet they do not conceal its principal features, or materially change its proportions. The form of the head and face presents some remarkable dissimilarities in different races.
THE TRUNK has fifty-four bones, which are as follows: The Os Hyoides, the Sternum, twenty-four Ribs, twenty-four vertebrae or bones of the Spinal Column, the Sacrum, the Coccyx, and two Ossa Innominata. The Os Hyoides, situated at the base of the tongue, is the most isolated bone of the skeleton, and serves for the attachment of muscles. The Sternum, or breast-bone, in a child is composed of six pieces, in the adult of three, which in old age are consolidated into one bone. The Ribs are thin, curved bones, being convex externally. There are twelve on each side, and all are attached to the spinal column. The seven upper ribs, which are united in front of the sternum, are termed true ribs; the next three, which are not attached to the sternum, but to one another are called false ribs; and the last two, which are joined only to the vertebrae, are designated as floating ribs. The first rib is the shortest, and they increase in length as far as the eighth, after which this order is reversed.
The Spinal Column or backbone, when viewed from the front presents a perpendicular appearance, but a side view shows four distinct curves. The bones composing it are called vertebrae. The body part of a vertebra is light and spongy in texture, having seven projections called processes, four of which are the articular processes, which furnish surfaces to join the different vertebrae of the spinal column. Two are called transverse, and the remaining one is termed the spinous. The transverse and spinous processes serve for the attachment of the muscles belonging to the back. All these processes are more compact than the body of the vertebra, and, when naturally connected, are so arranged as to form a tube which contains the medulla spinalis, or spinal cord. Between the vertebrae is a highly-elastic, cartilaginous and cushion-like substance, which freely admits of motion, and allows the spine to bend as occasion requires. The natural curvatures of the spinal column diminish the shock produced by falling, running or leaping, which would otherwise be more directly transmitted to the brain. The ribs at the sides, the sternum in front, and the twelve dorsal bones of the spinal column behind, bound the thoracic cavity, which contains the lungs, heart, and large blood-vessels.
The Pelvis is an open bony structure, consisting of the Os Innominata, one on either side, and the Sacrum and Coccyx behind. The Sacrum, during childhood, consists of five bones, which in later years unite to form one bone. It is light and spongy in texture, and the upper surface articulates with the lowest vertebra, while it is united at its inferior margin to the coccyx. The Coccyx is the terminal bone of the spinal column. In infancy it is cartilaginous and composed of several pieces, but in the adult these unite and form one bone. The Innominata, or nameless bones, during youth, consist of three separate pieces on each side; but as age advances they coalesce and form one bone. A deep socket, called the acetabulum, is found near their junction, which serves for the reception of the head of the thigh-bone.
THE BONES OF THE UPPER EXTREMITIES are sixty-four in number, and are classified as follows: The Scapula, Clavicle, Humerus, Ulna, Radius, Carpus, Metacarpus, and Phalanges. The Scapula, or shoulder-blade, is an irregular, thin, triangular bone, situated at the posterior part of the shoulder, and attached to the upper and back part of the chest. The Clavicle, or collar-bone, is located at the upper part of the chest, between the sternum and scapula, and connects with both. Its form resembles that of the italic letter f, and it prevents the arms from sliding forward. The Humerus, the first bone of the arm, is long, cylindrical, and situated between the scapula and fore-arm. The Ulna is nearly parallel with the radius, and situated on the inner side of the fore-arm. It is the longer and larger of the two bones, and in its articulation with the humerus, forms a perfect hinge-joint. The Radius, so called from its resemblance to a spoke, is on the outer side of the fore-arm, and articulates with the bones of the wrist, forming a joint. The ulna and radius also articulate with each other at their extremities. The Carpus, or wrist, consists of eight bones, arranged in two rows. The Metacarpus, or palm of the hand, is composed of five bones situated between the carpus and fingers. The Phalanges, fourteen in number, are the bones of the fingers and thumb, the fingers each having three and the thumb two.
THE BONES OF THE LOWER EXTREMITIES, sixty in number, are classed as follows: The Femur, Patella, Tibia, Fibula, Tarsus, Metatarsus, and Phalanges. The Femur, or thigh-bone, is the longest bone in the body. It has a large round head, which is received into the acetabulum, thus affording a good illustration of a ball and socket joint. The Patella, or knee-pan, is the most complicated articulation of the body. It is of a round form, connects with the tibia by means of a strong ligament, and serves to protect the front of the joint, and to increase the leverage of the muscles attached to it, by causing them to act at a greater angle. The Tibia, or shin bone, is enlarged at each extremity and articulates with the femur above and the astragalus, the upper bone of the tarsus, below. The Fibula, the small bone of the leg, is situated on the outer side of the tibia, and is firmly bound to it at each extremity. The Tarsus, or instep, is composed of seven bones, and corresponds to the carpus of the upper extremities. The Metatarsus, the middle of the foot, bears a dose resemblance to the metacarpus, and consists of five bones situated between the tarsus and the phalanges. The tarsal and the metatarsal bones are so united as to give an arched appearance to the foot, thus imparting elasticity. The Phalanges, the toes, consist of fourteen bones, arranged in a manner similar to that of the fingers.
We are not less interested in tracing the formation of bone through its several stages, than in considering other parts of the human system. The formation of the Haversian canals for the passage of blood-vessels to nourish the bones, the earlier construction of bony tissue by a metamorphosis of cartilaginous substance, and also the commencement of ossification at distinct points, called centers of ossification, are all important subjects, requiring the student's careful attention. The bones are protected by an external membranous envelope, which, from its situation is called the periosteum. The bones are divided into four classes, long, short, flat and irregular, being thus adapted to subserve a variety of purposes.
The Long Bones are found in the limbs, where they act as levers to sustain the body and aid in locomotion. Eachlong bone is composed of a cylinder, known as the shaft, and two extremities. The shaft is hollow, its wails being thickest in THE middle and growing thinner toward the extremities. The extremities are usually considerably enlarged, for convenience of connection with other bones, and to afford a broad surface for the attachment of muscles. The clavical, humerus, radius, ulna, femur, tibia, fibula, the bones of the metacarpus, metatarsus and the phalanges, are classed as long bones.
Where the principal object to be attained is strength, and the motion of the skeleton is limited, the individual bones are short and compressed, as the bones of the carpus and tarsus. The structure of these bones is spongy, except at the surface, where there is a thin crust of compact matter.
When protection is required for the organs of the body, or a broad flat surface for the attachment of the muscles, the bones are expanded into plates, as in the cranium and shoulder-blades.
The irregular or mixed bones are those which, from their peculiar shape, cannot be classed among any of the foregoing divisions. Their structure is similar to the others, consisting of cancellar tissue, surrounded by a crust of compact matter.
The vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, malar, two maxillary, palate, inferior turbinated, and hyoid are known as irregular bones.
The formation of the joints requires not only bones, but also cartilages, ligaments, and the synovial membrane, to complete the articulation. Cartilage is a smooth, elastic substance, softer than bone, and invested with a thin membrane, called perichondrium. When cartilage is placed upon convex surfaces, the reverse is true. The Ligaments are white, inelastic, tendinous substances, softer than cartilage, but harder than membrane. Their function is to bind together the bones. The Synovial Membrane covers the cartilages, and is then reflected upon the ligaments, thus forming a thin, closed sac, called the synovial capsule.
All the synovial membranes secrete a lubricating fluid, termed synovia, which enables the surfaces of the bones and ligaments to move freely upon one another. When this fluid is secreted in excessive quantities, it produces a disease known as "dropsy of the joints." There are numerous smaller sacs besides the synovial, called bursae mucosae, which in structure are analogous to them, and secrete a similar fluid. Some joints permit motion in every direction, as the shoulders, some in two directions only, as the elbows, while others do not admit of any movement. The bones, ligaments, cartilages, and synovial membrane, are supplied with nerves, arteries, and veins.
When an animal is provided with an internal bony structure, it indicates a high rank in the scale of organization. An elaborate texture of bone is found in no class below the vertebrates. Even in the lower order of this sub-kingdom, which is the highest of animals, bone does not exist, as is the case in some tribes of fishes, such as sharks, etc., and in all classes below that of the cartilaginous fishes, the inflexible substance which sustains the soft parts is either shell or some modification of bone, and is usually found on the outside of the body. True bone, on the contrary, is found in the interior, and, therefore, in higher animals, the skeleton is always internal, while the soft parts are placed external to the bony frame. While many animals of the lowest species, being composed of soft gelatinous matter, are buoyant in water, the highest type of animals requires not only a bony skeleton, but also a flexible, muscular system, for locomotion in the water or upon the land. Each species of the animal kingdom is thus organically adapted to its condition and sphere of life.
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The Muscles are those organs of the body by which motion is produced, and are commonly known as flesh. A muscle is composed of fascieuli, or bundles of fibers, parallel to one another. They are soft, varying in size, of a reddish color, and inclosed in a cellular, membranous sheath. Each fasciculus contains a number of small fibers, which, when subjected to a microscopic examination, are found to consist of fibrillae, or little fibers; each of these fibrillae in turn being invested with a delicate sheath. The fibers terminate in a glistening, white tendon, or hard cord, which is attached to the bone. So firmly are they united, that the bone will break before the tendon can be released. When the tendon is spread out, so as to resemble a membrane, it is called fascia. Being of various extent and thickness, it is distributed over the body, as a covering and protection for the more delicate parts, and aids also in motion, by firmly uniting the muscular fibers. The spaces between the muscles are frequently filled with fat, which gives roundness and beauty to the limbs. The muscles are of various forms; some are longitudinal, each extremity terminating in a tendon, which gives them a fusiform or spindle-shaped appearance; others are either fan-shaped, flat, or cylindrical.
Every muscle has an origin and an insertion. The term origin is applied to the more fixed or central attachment of a muscle, and the term insertion to the movable point to which the force of the muscle is directed; but the origin is not absolutely fixed, except in a small number of muscles, as those of the face, which are attached at one extremity to the bone, and at the other to the movable integument, or skin. In most instances, the muscles may act from either extremity. The muscles are divided into the Voluntary, or muscles of animal life, and the Involuntary, or muscles of organic life. There are, however, some muscles which cannot properly be classified with either, termed Intermediate. The Voluntary Muscles are chiefly controlled by the will, relaxing and contracting at its pleasure, as in the motion of the eyes, mouth, and limbs. The fibers are of a dark red color, and possess great strength. These fibers are parallel, seldom interlacing, but presenting a striped or striated appearance; and a microscopic examination of them shows that even the most minute consist of parallel filaments marked by longitudinal and transverse striae, or minute channels. The fibers are nearly the same length as the muscles to which they belong. Each muscular fiber is capable of contraction; it may act singly, though usually it acts in unison with others. By a close inspection, it has been found that fibers may be drawn apart longitudinally, in which case they are termed fibrillae, or they may be separated transversely, forming a series of discs. The Sarcolemma, or investing sheath of the muscles, appears to be formed even before there are any visible traces of the muscle itself. It is a transparent and delicate membrane, but very elastic. The Involuntary Muscles are influenced by the sympathetic nervous system, and their action pertains to the nutritive functions of the body. They differ from the voluntary muscles in not being striated, having no tendons, and in the net-work arrangements of their fibers. The Intermediate Muscles are composed of striated and unstriated fibers; they are, therefore, both voluntary and involuntary in their functions. The muscles employed in respiration are of this class, for we can breathe rapidly or slowly, and, for a short time, even suspend their action; but soon, however, the organic muscles assert their instinctive control, and respiration is resumed.
THE DIAPHRAGM, or midriff, is the muscular division between the thorax and the abdomen. It has been compared to an inverted basin, the concavity of which is directed toward the abdomen. The muscles receive their nourishment from the numerous blood-vessels which penetrate their tissues. The voluntary muscles are abundantly supplied with nerves, while the involuntary are not so numerously furnished. The color of the muscles is chiefly due to the blood which they contain. They vary in size according to their respective functions. For example, the functions of the heart require large and powerful muscles, and those of the eye, small and delicate ones. There are between four hundred and sixty and five hundred muscles in the human body.
Very rarely is motion produced by the action of a single muscle, but by the harmonious action of several. There is infinite variety in the arrangement of the muscles, each being adapted to its purpose, in strength, tenacity, or elasticity. While some involuntarily respond to the wants of organic life, others obey, with mechanical precision, the edicts of the will. The peculiar characteristic of the muscles is their contractility; for example, when the tip of the finger is placed in the ear, an incessant vibration, due to the contraction of the muscles of the ear, can be heard. When the muscles contract, they become shorter; but what is lost in length is gained in breadth and thickness, so that their actual volume remains the same. Muscles alternately contract and relax, and thus act upon the bones. The economy of muscular power thus displayed is truly remarkable. In easy and graceful walking, the forward motion of the limbs is not altogether due to the exercise of muscular power, but partly to the force of gravity, and only a slight assistance of the muscles is required to elevate the leg sufficiently to allow it to oscillate.
Motion is a characteristic of living bodies. This is true, not only in animals, but also in plants. The oyster, although not possessing the power of locomotion, opens and closes its shell at pleasure. The coral insect appears at the door of its cell, and retreats at will. All the varied motions of animals are due to a peculiar property of the muscles, termed contractility. Although plants are influenced by external agents, as light, heat, electricity, etc., yet it is supposed that they may move in response to inward impulses. The sensitive stamens of the barberry, when touched at their base on the inner side, resent the intrusion, by making a sudden jerk forward. Venus's fly-trap, a plant found in North Carolina, is remarkable for the sensitiveness of its leaves; which close suddenly and capture insects which chance to alight upon them. The muscles of the articulates are situated within the solid framework, unlike the vertebrates, whose muscles are external to the bony skeleton. All animals have the power of motion, from the lowest radiate to the highest vertebrate, from the most repulsive polyp to that type of organized life made in the very image of God.
The muscles, then, subserve an endless variety of purposes. By their aid the farmer employs his implements of husbandry, the mechanic deftly wields his tools, the artist plies his brush, while the fervid orator gives utterance to thoughts glowing with heavenly emotions. It is by their agency that the sublimest spiritual conceptions can be brought to the sphere of the senses, and the noblest, loftiest aims of to-day can be made glorious realizations of the future.
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THE DIGESTIVE ORGANS.
Digestion signifies the act of separating or distributing, hence its application to the process by which food is made available for nutritive purposes. The organs of digestion are the Mouth, Teeth, Tongue, Salivary Glands, Pharynx, Esophagus, the Stomach and the Intestines, with their glands, the Liver, Pancreas, Lacteals, and the Thoracic Duct.
The Mouth is an irregular cavity, situated between the upper and the lower jaw, and contains the organs of mastication. It is bounded by the lips in front, by the cheeks at the sides, by the roof of the mouth and teeth of the upper jaw above, and behind and beneath by the teeth of the lower jaw, soft parts, and palate. The soft palate is a sort of pendulum attached only at one of its extremities, while the other involuntarily opens and closes the passage from the mouth to the pharynx. The interior of the mouth, as well as other portions of the alimentary canal, is lined with a delicate tissue, called mucous membrane.
The Teeth are firmly inserted in the alveoli or sockets, of the upper and the lower jaw. The first set, twenty in number, are temporary, and appear during infancy. They are replaced by permanent teeth, of which there are sixteen in each jaw; four incisors, or front teeth, four cuspids, or eye teeth, four bicuspids, or grinders, and four molars, or large grinders. Each tooth is divided into the crown, body, and root. The crown is the grinding surface; the body, the part projecting from the jaw, is the seat of sensation and nutrition; the root is that portion of the tooth which is inserted in the alveolus. The teeth are composed of dentine, or ivory, and enamel. The ivory forms the greater portion of the body and root, while the enamel covers the exposed surface. The small white cords communicating with the teeth are the nerves.
The Tongue is a flat oval organ, the base of which is attached to the os hyoides, while the apex, the most sensitive part of the body, is free. Its surface is covered with a membrane, which, at the sides and lower part, is continuous with the lining of the mouth. On the lower surface of the tongue, this membrane is thin and smooth, but on the upper side it is covered with numerous papillae, which, in structure, are similar to the sensitive papillae of the skin.
The Salivary Glands are six in number, three on each side of the mouth. Their function is to secrete a fluid called saliva, which aids in mastication. The largest of these glands, the Parotid, is situated in front and below the ear; its structure, like that of all the salivary glands, is cellular. The Submaxillary gland is circular in form, and situated midway between the angle of the lower jaw and the middle of the chin. The Sublingual is a long flattened gland, and, as its name indicates, is located below the tongue, which when elevated, discloses the saliva issuing from its porous openings.
The Pharynx is nearly four inches in length, formed of muscular and membranous cells, and situated between the base of the cranium and the esophagus, in front of the spinal column. It is narrow at the upper part, distended in the middle, contracting again at its junction with the esophagus. The pharynx communicates with the nose, mouth, larynx, and esophagus.
The Esophagus, a cylindrical organ, is a continuation of the pharynx, and extends through the diaphragm to the stomach. It has three coats: first, the muscular, consisting of an exterior layer of fibers running longitudinally, and an interior layer of transverse fibers; second, the cellular, which is interposed between the muscular and the mucous coat; third, the mucous membrane, or internal coat, which is continuous with the mucous lining of the pharynx.
The Stomach is a musculo-membranous, conoidal sac, communicating with the esophagus by means of the cardiac orifice (see Fig. 28). It is situated obliquely with reference to the body, its base lying at the left side, while the apex is directed toward the right side. The stomach is between the liver and spleen, subjacent to the diaphragm, and communicates with the intestinal canal by the pyloric orifice. It has three coats. The peritoneal, or external coat is composed of compact, cellular tissue, woven into a thin, serous membrane, and assists in keeping the stomach in place. The middle coat is formed of three layers of muscular fibers: in the first, the fibres run longitudinally; in the second, in a circular direction; and in the third, they are placed obliquely to the others. The interior, or mucous coat, lines this organ. The stomach has a soft, spongy appearance, and, when not distended, lies in folds. During life, it is ordinarily of a pinkish color. It is provided with numerous small glands, which secrete the gastric fluid necessary for the digestion of food. The lining membrane, when divested of mucus, has a wrinkled appearance. The arteries, veins, and lymphatics, of the stomach are numerous.
The Intestines are those convoluted portions of the alimentary canal into which the food is received after being partially digested, and in which the separation and absorption of the nutritive materials and the removal of the residue take place. The coats of the intestines are analogous to those of the stomach, and are, in fact, only extensions of them. For convenience of description, the intestines may be divided into the small and the large. The small intestine is from twenty to twenty-five feet in length, and consists of the Duodenum, Jejunum, and Ileum. The Duodenum, so called because its length is equal to the breadth of twelve fingers, is the first division of the small intestine. If the mucous membrane of the duodenum be examined, it will be found thrown into numerous folds, which are called valvulae conniventes, the chief function of which appears to be to retard the course of the alimentary matter, and afford a larger surface for the accommodation of the absorbent vessels. Numerous villi, minute thread-like projections, will be found scattered over the surface of these folds, set side by side, like the pile of velvet. Each villus contains a net-work of blood-vessels, and a lacteal tube, into which the ducts from the liver and pancreas open, and pour their secretions to assist in the conversion of the chyme into chyle. The Jejunum, so named because it is usually found empty after death, is a continuation of the duodenum, and is that portion of the alimentary canal in which the absorption of nutritive matter is chiefly effected. The Ileum, which signifies something rolled up, is the longest division of the small intestine. Although somewhat thinner in texture than the jejunum, yet the difference is scarcely perceptible. The large intestine is about five feet in length, and is divided into the Caecum, Colon, and Rectum. The Caecum is about three inches in length. Between the large and the small intestine is a valve, which prevents the return of excrementitious matter that has passed into the large intestine. There is attached to the caecum an appendage about the size of a goose-quill, and three inches in length, termed the appendix vermiformis. The Colon is that part of the large intestine which extends from the caecum to the rectum, and which is divided into three parts, distinguished as the ascending, the transverse, and the descending.
The Rectum is the terminus of the large intestine. The intestines are abundantly supplied with blood-vessels. The arteries of the small intestine are from fifteen to twenty in number. The large intestine is furnished with three arteries, called the colic arteries. The ileo-colic artery sends branches to the lower part of the ileum, the head of the colon, and the appendix vermiformis. The right colic artery forms arches, from which branches are distributed to the ascending colon. The colica media separates into two branches, one of which is sent to the right portion of the transverse colon, the other to the left. In its course, the superior hemorrhoidal artery divides into two branches, which enter the intestine from behind, and embrace it on all sides, almost to the anus.
The Thoracic Duct is the principal trunk of the absorbent system, and the canal through which much of the chyle and lymph is conveyed to the blood. It begins by a convergence and union of the lymphatics on the lumbar vertebrae, in front of the spinal column, then passes upward through the diaphragm to the lower part of the neck, thence curves forward and downward, opening into the subclavian vein near its junction with the left jugular vein, which leads to the heart.
The Liver, which is the largest gland in the body, weighs about four pounds in the adult, and is located chiefly on the right side, immediately below the diaphragm. It is a single organ, of a dark red color, its upper surface being convex, while the lower is concave. It has two large lobes, the right being nearly four times as large as the left. The liver has two coats, the serous, which is a complete investment, with the exception of the diaphragmatic border, and the depression for the gall-bladder, and which helps to suspend and retain the organ in position; and the fibrous, which is the inner coat of the liver, and forms sheaths for the blood-vessels and excretory ducts. The liver is abundantly supplied with arteries, veins, nerves, and lymphatics. Unlike the other glands of the human body, it receives two kinds of blood; the arterial for its nourishment, and the venous, from which it secretes the bile. In the lower surface of the liver is lodged the gall-bladder, a membranous sac, or reservoir, for the bile. This fluid is not absolutely necessary to the digestion of food, since this process is effected by other secretions, nor does bile exert any special action upon, starchy or oleaginous substances, when mixed with them at a temperature of 100 deg. F. Experiments also show that in some animals there is a constant flow of bile, even when no food has been taken, and there is consequently no digestion to be performed. Since the bile is formed from the venous blood, and taken from the waste and disintegration of animal tissue, it would appear that it is chiefly an excrementitious fluid. It does not seem to have accomplished its function when discharged from the liver and poured into the intestine, for there it undergoes various alterations previous to re-absorption, produced by its contact with the intestinal juices. Thus the bile, after being transformed in the intestines, re-enters the blood under a new form, and is carried to some other part of the system to perform its mission.
The Spleen is oval, smooth, convex on its external, and irregularly concave on its internal, surface. It is situated on the left side, in contact with the diaphragm and stomach. It is of a dark red color, slightly tinged with blue at its edges. Some physiologists affirm that no organ receives a greater quantity of blood, according to its size, than the spleen. The structure of the spleen and that of the mesenteric glands are similar, although the former is provided with a scanty supply of lymphatic vessels, and the chyle does not pass through it, as through the mesenteric glands. The Pancreas lies behind the stomach, and extends transversely across the spinal column to the right of the spleen. It is of a pale, pinkish color, and its secretion is analogous to that of the salivary glands; hence it has been called the Abdominal Salivary Gland.
Digestion is effected in those cavities which we have described as parts of the alimentary canal. The food is first received into the mouth, where it is masticated by the teeth, and, after being mixed with mucus and saliva, is reduced to a mere pulp; it is then collected by the tongue, which, aided by the voluntary muscles of the throat, carries the food backward into the pharynx, and, by the action of the involuntary muscles of the pharynx and esophagus, is conveyed to the stomach. Here the food is subjected to a peculiar, churning movement, by the alternate relaxation and contraction of the fibers which compose the muscular wall of the stomach. As soon as the food comes in contact with the stomach, its pinkish color changes to a bright red; and from the numerous tubes upon its inner surface is discharged a colorless fluid, called the gastric juice, which mingles with the food and dissolves it. When the food is reduced to a liquid condition, it accumulates in the pyloric portion of the stomach. Some distinguished physiologists believe that the food is kept in a gentle, unceasing, but peculiar motion, called peristaltic, since the stomach contracts in successive circles. In the stomach the food is arranged in a methodical manner. The undigested portion is detained in the upper, or cardiac extremity, near the entrance of the esophagus, by contraction of the circular fibers of the muscular coat. Here it is gradually dissolved, and then carried into the pyloric portion of the stomach. From this, then, it appears, that the dissolved and undissolved portions of food occupy different parts of the stomach. After the food has been dissolved by the gastric fluid, it is converted into a homogeneous, semi-fluid mass, called chyme. This substance passes from the stomach through the pyloric orifice into the duodenum, in which, by mixing with the bile and pancreatic fluid, its chemical properties are again modified, and it is then termed chyle, which has been found to be composed of three distinct parts, a reddish-brown sediment at the bottom, a whey-colored fluid in the middle, and a creamy film at the top. Chyle is different from chyme in two respects: First, the alkali of the digestive fluids, poured into the duodenum, or upper part of the small intestine, neutralizes the acid of the chyme; secondly, both the bile and the pancreatic fluid seem to exert an influence over the fatty substances contained in the chyme, which assists the subdivision of these fats into minute particles. While the chyle is propelled along the small intestine by the peristaltic action, the matter which it contains in solution is absorbed in the usual manner into the vessels of the villi by the process called osmosis. The fatty matters being subdivided into very minute particles, but not dissolved, and consequently incapable of being thus absorbed by osmosis, pass bodily through the epithelial lining of the intestine into the commencement of the lacteal tubes in the villi. The digested substances, as they are thrust along the small intestines, gradually lose their albuminoid, fatty, and soluble starchy and saccharine matters, and pass through the ileo-caecal valve into the caecum and large intestine. An acid reaction takes place here, and they acquire the usual faecal smell and color, which increases as they approach the rectum. Some physiologists have supposed that a second digestion takes place in the upper portion of the large intestine. The lacteals, filled with chyle, pass into the mesenteric glands with which they freely unite, and afterward enter the receptaculum chyli, which is the commencement of the thoracic duct, a tube of the size of a goose-quill, which lies in front of the backbone. The lymphatics, the function of which is to secrete and elaborate lymph, also terminate in the receptaculum chyli, or receptacle for the chyle. From this reservoir the chyle and lymph flow into the thoracic duct, through which they are conveyed to the left subclavian vein, there to be mingled with venous blood. The blood, chyle, and lymph, are then transmitted directly to the lungs.
The process of nutrition aids in the development and growth of the body; hence it has been aptly designated a "perpetual reproduction." It is the process by which every part of the body assimilates portions of the blood distributed to it. In return, the tissues yield a portion of the material which was once a component part of their organization. The body is constantly undergoing waste as well as repair. One of the most interesting facts in regard to the process of nutrition in animals and plants is, that all tissues originate in cells. In the higher types of animals, the blood is the source from which the cells derive their constituents. Although the alimentary canal is more or less complicated in different classes of animals, yet there is no species, however low in the scale of organization, which does not possess it in some form. The little polyp has only one digestive cavity, which is a pouch in the interior of the body. In some animals circulation is not distinct from digestion, in others respiration and digestion are performed by the same organs; but as we rise in the scale of animal life, digestion and circulation are accomplished in separate cavities, and the functions of nutrition become more complex and distinct.
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Absorption is the vital function by which nutritive materials are selected and imbibed for the sustenance of the body. Absorption, like all other functional processes, employs agents to effect its purposes, and the villi of the small intestine, with their numberless projecting organs, are specially employed to imbibe fluid substances; this they do with a celerity commensurate to the importance and extent of their duties. They are little vascular prominences of the mucous membrane, arising from the interior surface of the small intestine. Each villus has two sets of vessels. (1.) The blood-vessels, which, by their frequent blending, form a complete net-work beneath the external epithelium; they unite at the base of the villus, forming a minute vein, which is one of the sources of the portal vein. (2.) In the center of the villus is another vessel, with thinner and more transparent walls, which is the commencement of a lacteal.
The Lacteals originate in the walls of the alimentary canal, are very numerous in the small intestine, and, passing between the laminae of the mesentery, they terminate in the receptaculum chyli, or reservoir for the chyle. The mesentery consists of a double layer of cellular and adipose tissue. It incloses the blood-vessels, lacteals, and nerves of the small intestine, together with its accessory glands. It is joined to the posterior abdominal wall by a narrow root; anteriorly, it is attached to the whole length of the small intestine. The lacteals are known as the absorbents of the intestinal walls, and after digestion is accomplished, are found to contain a white, milky fluid, called chyle. The chyle does not represent the entire product of digestion, but only the fatty substances suspended in a serous fluid.
Formerly, it was supposed that the lacteals were the only agents employed in absorption, but more recent investigations have shown that the blood-vessels participate equally in the process, and are frequently the more active and important of the two. Experiments upon living animals have proved that absorption of poisonous substances occurs, even when all communication by way of the lacteals and lymphatics is obstructed, the passage by the blood-vessels alone remaining. The absorbent power which the blood-vessels of the alimentary canal possess, is not limited to alimentary substances, but through them, soluble matters of almost every description are received into the circulation.
The Lymphatics are not less important organs in the process of absorption. Nearly every part of the body is permeated by a second series of capillaries, closely interlaced with the blood-vessels, collectively termed the Lymphatic System. Their origin is not known, but they appear to form a plexus in the tissues, from which their converging trunks arise. They are composed of minute tubes of delicate membrane, and from their net-work arrangement they successively unite and finally terminate in two main trunks, called the great lymphatic veins. The lymphatics, instead of commencing on the intestinal walls, as do the lacteals, are distributed through most of the vascular tissues as well as the skin. The lymphatic circulation is not unlike that of the blood; its circulatory apparatus is, however, more delicate, and its functions are not so well understood.
The lymph which circulates through the lymphatic vessels is an alkaline fluid composed of a plasma and corpuscles. It may be considered as blood deprived of its red corpuscles and, diluted with water. Nothing very definite is known respecting the functions of this fluid. A large proportion of its constituents is derived from the blood, and the exact connection of these substances to nutrition is not properly understood. Some excrementitious matters are supposed to be taken from the tissues by the lymph and discharged into the blood, to be ultimately removed from the system. The lymph accordingly exerts an important function by removing a portion of the decayed tissues from the body.
In all animals which possess a lacteal system there is also a lymphatic system, the one being the complement of the other. The fact that lymph and chyle are both conveyed into the general current of circulation, leads to the inference that the lymph, as well as the chyle, aids in the process of nutrition. The body is continually undergoing change, and vital action implies waste of tissues, as well as their growth. Those organs which are the instruments of motion, as the muscles, cannot be employed without wear and waste of their component parts. Renovated tissues must replace those which are worn out, and it is a part of the function of the absorbents to convey nutritive material into the general circulation. Researches in microscopical anatomy have shown that the skin contains multitudes of lymphatic vessels and that it is a powerful absorbent.
Absorption is one of the earliest and most essential functions of animal and vegetables tissues. The simpler plants consist of only a few cells, all of which are employed in absorption; but in the flowering plants this function is performed by the roots. It is accomplished on the same general principles in animals, yet it presents more modifications and a greater number of organs than in vegetables. While animals receive their food into a sac, or bag called the stomach, and are provided with absorbent vessels such as nowhere exist in vegetables, plants plunge their absorbent organs into the earth, whence they derive nourishing substances. In the lower order of animals, as in sponges, this function is performed by contiguous cells, in a manner almost as elementary as in plants. In none of the invertebrate animals is there any special absorbent system. Internal absorption is classified by some authors as follows: interstitial, recrementitial, and excrementitial; by others as accidental, venous, and cutaneous. The general cutaneous and mucous surfaces exhale, as well as absorb; thus the skin, by means of its sudoriferous glands, exhales moisture, and is at the same time as before stated, a powerful absorbent. The mucous surface of the lungs is continually throwing off carbonic acid and absorbing oxygen; and through their surface poisons are sometimes taken into the blood. The continual wear and waste to which living tissues are subject, makes necessary the provision of such a system of vessels for conveying away the worn-out materials and supplying the body with new.
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PHYSICAL AND VITAL PROPERTIES OF THE BLOOD.
Blood is the animal fluid by which the tissues of the body are nourished. This pre-eminently vital fluid permeates every organ, distributes nutritive material to every texture, is essentially modified by respiration, and, finally, is the source of every secretion and excretion. Blood has four constituents: Fibrin, Albumen, Salts (which elements, in solution, form the liquor sanguinis), and the Corpuscles. Microscopical examination shows that the corpuscles are of two kinds, known as the red and the white, the former being by far the more abundant. They are circular in form and have a smooth exterior, and are on an average 1/3200 part of an inch in diameter, and are about one-fourth of that in thickness. Hence more than ten millions of them may lie on a space an inch square. If spread out in thin layers and subjected to transmitted light, they present a slightly yellowish color, but when crowded together and viewed by refracted light, exhibit a deep red color. These blood-corpuscles have been termed discs, and are not, as some have supposed, solid material, but are very nearly fluid. The red corpuscles although subjected to continual movement, have a tendency to approach one another, and when their flattened surfaces come in contact, so firmly do they adhere that they change their shape rather than submit to a separation. If separated, however, they return to their usual form. The colorless corpuscles are larger than the red and differ from them in being extremely irregular in their shape, and in their tendency to adhere to a smooth surface, while the red corpuscles float about and tumble over one another. They are chiefly remarkable for their continual variation in form. The shape of the red corpuscles is only altered by external influences, but the white are constantly undergoing alterations, the result of changes taking place within their own substance. When diluted with water and placed under the microscope they are found to consist of a spheroidal sac, containing a clear or granular fluid and a spheroidal vesicle, which is termed the nucleus. They have been regarded by some physiologists as identical with those of the lymph and chyle. Dr. Carpenter believes that the function of these cells is to convert albumen into fibrin, by the simple process of cell-growth. It is generally believed that the red corpuscles are derived in some way from the colorless. It is supposed that the red corpuscle is merely the nucleus of a colorless corpuscle enlarged, flattened, colored and liberated by the bursting of the wall of its cell. When blood is taken from an artery and allowed to remain at rest, it separates into two parts: a solid mass, called the clot, largely composed of fibrin; and a fluid known as the serum, in which the clot is suspended. This process is termed coagulation. The serum, mostly composed of albumen, is a transparent, straw-colored fluid, having the odor and taste of blood. The whole quantity of blood in the body is estimated on an average to be about one-ninth of its entire weight. The distinctions between the arterial and the venous blood are marked, since in the arterial system the blood is uniformly bright red, and in the venous of a very dark red color The blood-corpuscles contain both oxygen and carbonic acid in solution. When carbonic acid predominates, the blood is dark red; when oxygen, scarlet. In the lungs, the corpuscles give up carbonic acid, and absorb a fresh supply of oxygen, while in the general circulation the oxygen disappears in the process of tissue transformation, and is replaced, in the venous blood, by carbonic acid. The nutritive portions of food are converted into a homogeneous fluid, which pervades every part of the body, is the basis of every tissue, and which is termed the blood. This varies in color and composition in different animals. In the polyp the nutritive fluid is known as chyme, in many mollusks, as well as articulates, it is called chyle, but in vertebrates, it is more highly organized and is called blood. In all the higher animal types it is of a red color, although redness is not one of its essential qualities. Some tribes of animals possess true blood, which is not red; thus the blood of the insect is colorless and transparent; that of the reptile yellowish; in the fish the principle part is without color, but the blood of the bird is deep red. The blood of the mammalia is of a bright scarlet hue. The temperature of the blood varies in different species, as well as in animals of the same species under different physiological conditions; for this reason, some animals are called cold-blooded. Disease also modifies the temperature of the blood; thus in fevers it is generally increased, but in cholera greatly diminished. THE blood has been aptly termed the "vital fluid," since there is a constant flow from the heart to the tissues and organs of the body, and a continual return after it has circulated through these parts. Its presence in every part of the body is one of the essential conditions of animal life, and is effected by a special set of organs, called the circulatory organs.
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Having considered the formation of chyle, traced it through the digestive process, seen its transmission into the vena cava, and, finally, its conversion into blood, we shall now describe how it is distributed to every part of the system. This is accomplished through organs which, from the round of duties they perform, are called circulatory. These are the Heart, Arteries, Veins, and Capillaries, which constitute the vascular system.
Within the thorax or chest of the human body, and enclosed within a membranous sac, called the pericardium, is the great force-pump of the system, the heart. This organ, to which all the arteries and veins of the body may be either directly or indirectly traced, is roughly estimated to be equal in size to the closed fist of the individual to whom it belongs.
It has a broad end turned upwards, and a little to the right side, termed its base; and a pointed end called its apex, turned downwards, forwards, and to the left side, and lying beneath a point about an inch to the right of, and below, the left nipple, or just below the fifth rib. Attached to the rest of the body only by the great blood-vessels which issue from and enter it at its base, the heart is the most mobile organ in the economy, being free to move in different directions.
The heart is divided into two great cavities by a fixed partition, which extends from the base to the apex of the organ, and which prevents any direct communication between them. Each of these great cavities is further subdivided transversely by a movable partition, the cavity above each transverse partition being called the auricle, and the cavity below, the ventricle, right or left, as the case may be.
The walls of the auricles are much thinner than those of the ventricles, and the wall of the right ventricle is much thinner than that of the left, from the fact that the ventricles have more work to perform than the auricles, and the left ventricle more than the right.
In structure, the heart is composed almost entirely of muscular fibers, which are arranged in a very complex and wonderful manner. The outer surface of the heart is covered with the pericardium, which closely adheres to the muscular substance. Inside, the cavities are lined with a thin membrane, called the endocardium. At the junction between the auricles and ventricles, the apertures of communication between their cavities are strengthened by fibrous rings. Attached to these fibrous rings are the movable partitions or valves, between the auricles and the ventricles, the one on the right side of the heart being called the tricuspid valve, and the one on the left side the mitral valve. A number of fine, but strong, tendinous chords, called chordae tendineae, connect the edges and apices of these valves with column-like elevations of the fleshy substance of the walls of the ventricles, called columnae carneae.
The valves are so arranged that they present no obstacle to the free flow of blood from the auricles into the ventricles, but if any is forced the other way, it gets between the valve and the wall of the heart, and drives the valve backwards and upwards, thus forming a transverse partition between the auricle and ventricle, through which no fluid can pass.
At the base of the heart are given off two large arteries, one on the right side, which conveys the blood to the lungs, called the pulmonary artery, and one on the left side, which conveys the blood to the system in general, called the aorta. At the junction of each of these great vessels with its corresponding ventricle, is another valvular apparatus, consisting of three pouch-like valves, called the semilunar valves, from their resemblance, in shape, to a half-moon. Being placed on a level and meeting in the middle line, they entirely prevent the passage of any fluid which may be forced along the artery towards the heart, but, flapping back, they offer no obstruction to the free flow of blood from the ventricles into the arteries.
The Arteries, being always found empty after death, were supposed by the ancients, who were ignorant of the circulation of the blood, to be tubes containing air; hence their name, which is derived from a Greek word and signifies an air-tube. Arteries are the cylindrical tubes which carry blood to every part of the system. All the arteries, except the coronary which supply the substance of the heart, arise from the two main trunks, the pulmonary artery and the aorta. They are of a yellowish-white color, and their inner surface is smooth. The arteries have three coats. (1.) The external coat, which is destitute of fat, and composed chiefly of cellular tissue, is very firm and elastic, and can readily be dissected from the middle coat. (2.) The middle, or fibrous coat, is thicker than the external, and composed of yellowish fibers, its chief property is contractility. (3.) The internal coat consists of a colorless, thin, transparent membrane, yet so strong that it can, it is thought, better resist a powerful pressure than either of the others. Arteries are very elastic as well as extensible, and their chief extensibility is in length. If an artery of a dead body be divided, although empty, its cylindrical form will be preserved.
The Veins are the vessels through which the venous blood returns to the auricles of the heart. They are more numerous than the arteries, and originate from numerous capillary tubes, while the arteries are given off from main trunks. In some parts of the body, the veins correspond in number to the arteries; while in others, there are two veins to every artery. The veins commence by minute roots in the capillaries, which are everywhere distributed through the body, and gradually increase in size, until they unite and become large trunks, conveying the dark blood to the heart. The veins, like the arteries, have three coats. The external, or cellular coat, resembles that of the arteries; the middle is fibrous, but thinner than the corresponding one of the arteries; and the internal coat is serous, and analogous to that of those vessels. The veins belong to the three following classes: (1.) The systemic veins, which bring the blood from different parts of the body and discharge it into the vena cava, by means of which it is conveyed to the heart; (2), the pulmonary veins, which bring the arterial, or bright red blood from the lungs and carry it to the left auricle; (3), the veins of the portal system, which originate in the capillaries of the abdominal organs, then converge into trunks and enter the liver, to branch off again into divisions and subdivisions of the minutest character.
The Capillaries form an extremely fine net-work, and are distributed to every part of the body. They vary in diameter from 1/3500 to 1/2000 of an inch. They are so universally prevalent throughout the skin, that the puncture of a needle would wound a large number of them. These vessels receive the blood and bring it into intimate contact with the tissues, which take from it the principal part of its oxygen and other elements, and give up to it carbonic acid and the other waste products resulting from the transformation of the tissues, which are transmitted through the veins to the heart, and thence by the arteries to the lungs and various excretory organs.
The blood from the system in general, except the lungs, is poured into the right auricle by two large veins, called the superior and the inferior vena cava,' and that returning from the lungs is poured into the left auricle by the pulmonary veins.
During life the heart contracts rhythmically, the contractions commencing at the base, in each auricle, and extending towards the apex.
Now it follows, from the anatomical arrangement of this organ, that when the auricles contract, the blood contained in them is forced through the auriculo-ventricular openings into the ventricles; the contractions then extending to the ventricles, in a wave-like manner, the great proportion of the blood, being prevented from re-entering the auricles by the tricuspid and mitral valves, is forced onward into the pulmonary artery from the right ventricle, and into the aorta from the left ventricle.
When the contents of the ventricles are suddenly forced into these great blood-vessels, a shock is given to the entire mass of fluid which they contain, and this shock is speedily propagated along their branches, being known at the wrist as the pulse.
On inspection, between the fifth and sixth ribs on the left side of the chest, a movement is perceptible, and, if the hand be applied, the impulse may be felt. This is known as the throbbing, or beating of the heart.
If the ear is placed over the region of the heart, certain sounds are heard, which recur with great regularity. First is heard a comparatively long, dull sound, then a short, sharp sound, then a pause, and then the long, dull sound again. The first sound is caused mainly by the tricuspid and mitral valves, and the second is the result of sudden closure of the semilunar valves.
No language can adequately describe the beauty of the circulatory system. The constant vital flow through the larger vessels, and the incessant activity of those so minute that they are almost imperceptible, fully illustrate the perfectness of the mechanism of the human body, and the wisdom and goodness of Him who is its author.
Experiments have shown that the small arteries may be directly influenced through the nervous system, which regulates their caliber by controlling the state of contraction of their muscular walls. The effect of this influence of the nervous system enables it to control the circulation over certain areas; and, notwithstanding the force of the heart and the state of the blood-vessels in general, to materially modify the circulation in different spots. Blushing, which is simply a local modification of the circulation, is effected in this way. Some emotion takes possession of the mind, and the action of the nerves, which ordinarily keep up a moderate contraction of the muscular coats of the arteries, is lost, and the vessels relax and become distended with arterial blood, which is a warm and bright red fluid; thereupon a burning sensation is felt, and the skin grows red, the degree of the blush depending upon the intensity of the emotion.