!«lfjiijjjllfl 'mi III ill Mim^ ■ |l'-.;:;|lilllllllllilllBIIIIIII(illiiii 11, i: lii mMi 11 1 1 1 mm i I lii ^.^ illlpllllllf^^ I am fcarfuUj- and vronderfuKy mid( THE HOUSE I LIVE IN: OR, POPULAR ILLUSTRATIONS OF THE STRUCTURE AND EUNCTIONS OF THE HUMAN BODY. FOR THE USE OF FAMILIES AND SCHOOLS. EDITED BY THOMAS C. GIRTIN, Surgeon. THE SIXTH EDITION. LONDON: JOHN \V. PARKER, WEST STRAND. MDCCCXLIX. LONDON : SATiLL And bdwauds, printers, 4, CHANDOS-STREET. EDITOR'S PHEFACE. This little work is founded on one published under the same title by Dr. Alcott, a popular American writer. In presenting it to the English public, the Editor proposes to supply a deficiency which is acknowledged to have been long felt by teachers in schools, and by instructors of youth in general. His hope is, that, from the unpretending plainness of its style, the clearness of its descriptions, and the author's happy tact in illustration, the book will be found a valuable addition to the elementary works for the instruction of youth of both sexes. When well grounded in its contents, the young reader will be the better enabled to comprehend and to appreciate the reasoning of Paley, and other writers on Natural Theology, to whose works this will be found an appropriate introduction. In preparing the present edition for the English reader, much was necessary to be done. With a large proportion of what is highly valuable, there VI EDITOR S PEEFACE. were, in the original work, many passages altogether inadmissible, and others, that required considerable alteration. Idiomatic forms of expression, peculiar to our transatlantic brethren, a redundancy of words, and frequent inaccuracies in the subject- matter, probably arising from errors of the press, rendered not merely a careful revision, but, for the most part, an entire reconstruction, necessary. Besides this, some entirely new articles have been added, and a fuller exposition of many of those in the original given, in order to make the work more complete, and to enhance its general interest. It was deemed desirable to effect these changes, without abandoning, or too greatly altering the quaint and explanatory style of the author, from which the work derives much of its peculiar character ; and it is confidently hoped that this object has been accomplished. T. C. G. Islington, Oct. 1837. AUTHOR'S PREFACE. The study of the human frame has usually been confined to the members of the medical profession. But wherefore ? Why should not a subject which so nearly concerns us all, engage the attention of others as well as that of surgeons and physicians ? Do we not carry about with us, through life, a machine so ingeniously constructed that, upon a contemplation of its wonders, an inspired writer exclaimed, " I am fearfully and wonderfully made !" Our minds, moreover, are the tenants of bodies so constructed, as to be continually liable to waste, as well as to become disordered ; and yet people in general are neither taught the way to keep them in order or to prevent them from premature decay. The condition of the body ac^ also upon the mind in a wonderful manner ; for whenever anything in the body is wrong, either our thoughts or our feelings, or both, are, in some degree or other, affected. Vm AUTHOK S TEEFACE. To keep tlie mind and heart right, therefore, we should know how to keep the body right. But who understands how to do this ? What persons, except medical men, as I said before, ever study the structure and functions of their bodies ? Is it not strange that knowledge of such vast importance should have been so long overlooked, and practically disregarded ? There are, however, many reasons for this neglect. People naturally connect with the study of the human frame the idea of violent deaths, dead bodies, skeletons, disinterments, and dissections. No wonder the mind should revolt at so horrible a picture ! No wonder that Anatomy and Physiology — for these are the hard names given to the study of the body and the laws of the body — should be neglected and shunned, if these things are in- separable from it ! But they are not so ; both anatomy and phy- siology may be studied with advantage, so far as a general and popular knowledge of those subjects extends, without at all entering into the details of practical anatomy. Much may be learned merely with the aid of a book and a few engravings ; or, in AI'THOE S PREFACE. IX fact, without even these. The body itself may be studied, and that is always at hand ; and even if experimental dissections should be deemed neces- sary, portions of fowls, or of the quadrupeds killed for food may be obtained, and these would be quite sufficient for all the purposes of the non-professional inquirer. The heart, for example, of most of the common domestic animals, nearly resembles that of man, and would do equally well for any ordinary examination. Man, as has just been observed, has a body as Avell as a mind. A system of education which overlooks either, is essentially defective. It was in this view, that the author first com- menced a series of essays on anatomy and phy- siology. The favourable reception they met with, and the solicitations of parents and teachers, together with an increasing conviction that something of the kind was really wanted, have induced him to go further, and prepare a work for families and schools. He looks forward to the period as not very far distant, when a knowledge of the physical nature of man will be as generally taught as arithmetic and geography now ; and he cannot but hope that his X AUTHOK S PREFACE. labours may tend to remove a little of the repug- nance which many feel to this study, by the peculiar manner in which he has here presented it. The general plan of the work is something more than mere theory; it has been tested by experiment, in school and elsewhere, and with complete success. There is one more hope that the author indulges, namely, that the publication of this volume will have a good tendency on morals. Still more — besides the favourable tendency which a knowledge of Physiology must have on human happiness ge- nerally — the writer believes that no branch of natural science is more likely to induce us to look " through nature up to nature's God," and to admire His '■' wonderful works among the children of men!" CONTENTS. CHAPTER I. GexetvAL Remakks IV — 21 CHAPTER II. Fbamewobk of the House. The Pillars. The Tbigli Bone. The Leg. Tlie Knee- pan. The Foot. Arch of the Foot. The Ankle . . 2'S--2S CHAPTER III. Material of the Frame. Structure of Bone. Shape of Bones. Particular descrip- tion of the Bones. Growth of Bone. Vessels in Bones ^O— 33 CHAPTER IV. Sills of the House. Situation of the Hip Bones. Structure. Hip Joint. An Abuse 34—36 CHAPTER V. Body of the House. Height. The Spine. Each Vertebra. General Descrip- tion. The Ribs. Breast Bone. Braces. The CoUar- Bone. The Shoulder Blade 37 — i5 XU CONTENTS. CHAPTER VI. Body of the House — Continued. Arms. The Hand. Uses of the Hand 40—54 CHAPTER VII. The Cupola. The Cranium. The Teeth. Growth of the Teeth. Struc- ture of the Teeth. Uses of the Teeth. Bones of the Ear. Boue of tlie Throat Do — 07 CHAPTER VIII. The Hinges. Hip Joint. Ligaments. Capsules. Wear of the Joints. Synovia. Ahuses of the Joints OS — 70 CHAPTER IX. Review. Number of Bones. Skeletons. Anatomy. Physiology. Bones and Shells bO— 88 CHAPTER X. Coverixg ov the House. The Periosteum. The Muscles. The Tendons. Struc- ture of Muscles. Action of Muscles. Illustrations. Fat. Reflections 80— 102 CHAPTER XI. COVEBIXO OF THE HoUSE. The Skin. Colouring of the Skin. Change of Colour. The Cuticle. Hair and Nails. Oil Glands. Cleanliness, 103 — III CONTENTS. Xm CHAPTER XII. The Covehixg. — The Windows. Geueral Remarks. The Human Eye. Situation of the Eye. Coats of the Eye. Optic Nerve. The Tears. The Eyelids. The Eyebrows. Reflections . . . 113 — 129 CHAPTER XIII. Tke Covering. — The Doobs. The Ear. The Nose. The Moutli 130—142 CHAPTER XIV, Apartments and Furnitube. External Ear. Chambers of the Nose. The Mouth In- ternally. The Tongue. The Salivary Glands. Pas- sages to the Ear. The Chest. Cavity of the Lungs. The Food-pipe, or Esophagus. The Stomach. The Intestines. Large Intestines. Gall Bladder. Apart- ment of the Circulation. Chambers of the Brain. Nerves 143— ICO CHAPTER XV. Furniture of the House, and its Uses. The Blood. Preparing the Blood. Mastication, or Cliev.ing. Trap-door. Digestion. Formation of Cliyme. Lacteals. Absorbents. Materials for Blood. Nature of the Blood. Uses of the Blood. Nature of Secretion. Motion of the Heart. Pulsation. Force of the Heart. Capillaries. Popular Summary of the process of the Circulation of the Blood 170 — 201 xir CONTENTS. CHAPTER XVI. Furniture and its Uses — Continued. rurificatiou of the Blood. The Lungs. Capacity of the Luugs. Breathing. Uses of Breathing. Nature of the Air. Breathing Air Twice. Ventilation. Free Motion of the Lungs. Tight Lacing 202—21-1 CHAPTER XVII. Temperature of Apartments. Curious Question. Variations of Temperature . . . 215 — 221 ILLUSTRATIONS. PAGE Thb Human Skeleton. The Framework of the House I Uve in . 22 The Foot, Leg, and Thigh Bones. The Pillars of the House . . 24 Arch of the Foot. Mechanical powers of Standing and Walking . 27 The Hip Bones. Sills of the House 34 Vertebrae of the Spine. The Pillar of the House 3S, 39 The Ribs, Spine, Shoulders, and Arms. Framework of the Body of the House 43 The Shoulder-Blade 45 The Hand and the Foot; showing the beautiful mechanism of both 48 The Sk\ill. The Cupola of the House 55 The Cranium (the Brain Case) 56, l6l Formation and succession of the Teeth 60 Growth of the Teeth in Children 63 Bones of the Ear 66, 67 The Hip Joint. Hinges of the House 60 The Shoulder and Elbow. Illustrations of the Ball and Socket Joints 71 The Knee and Foot'. Action of the Ligaments 75 The Kneeling Skeleton. Illustration of Physiology 9i The Biceps Muscle. Illustrations of Tendons and Sinews . . 94 The Arm, Elbow, and Hand. Action of Muscles 93 The Eye, its Nerves and Muscles H5 Optic Nerve. Phenomenon of Sight 121 The Ear. External and internal View, illustrating the process of Hearing 127 The Stomach, its Situation and Functions 154 Vessels of the Kidney 183 The Heart, and the Vessels connected with its action . . . .188 THE HOUSE I LIVE IN. Chaptee I. GENERAL REMARKS. " The House I live in" is a curious buildiug, one of the most curious in the world. jS'ot that it is the largest, or the oldest, or the most beautiful, or the most costly; or that it has the greatest number of rooms, or that it is supi^lied with the most fashionable furniture. But it is nevertheless one of the most Tvonderful buildings in the world, on account of the skill and wisdom of the great Master Workman who planned it. You cannot view it closely in any part, without being struck with the wisdom which is there evinced; nor without feelmg the mind elevated and improved by the contemplation of that goodness, which has provided everything so admirably contrived for the purposes intended to be fulfilled. I have said that it is not the largest building in the world — very far, indeed, from that. There are very many buildings — castles and palaces — churches and cathedrals, mansions and factories — which are thou- sands, tens of thousands, nay, hundreds of thousands, times greater than the House I hve in ; indeed, it can B 18 THE HOUSE I LIVE IN. hardly be said, that iu any country, barbarous or civilized, there is any human dwelling-place, from the hut of the savage to the regal mansion of the king, but what occupies a far greater space than the House I am about to describe to you. In truth, the latter is of very limited extent in any direction ; for though it may be said to have two stories, with a cupola or dome added thereto, yet the whole seldom towers beyond the height of six feet. It is not the oldest building in the world. The Pyramids of Egypt, erected 30)0 years ago, are proud monuments of the architectural skill of the designers, and even yet seem to defy the hand of time. The sepulchral monuments lately discovered in Etruria ; the splendid temples and other sacred edifices at Athens ; the gigantic ruins of Palmyra, Luxor, and Carnac ; the unmense and elaborately-constructed caverns of Ele- phanta, can all boast of a very high antiquity. Many churches, castles, and palaces, though with far less pretensions to age than the gi-and structures I have named, may yet claim an existence of several hundred years. Many bridges, too, and other buildings, now in the course of erection, are calculated to remain for ages to come ; but the building about which I am going to tell you, is never of very long duration, as compared with others, and seldom remains longer than three- quarters of a century. The House I live in is not without beauty, but its beauty is not of that kind for which the Temple of Solomon, in the days of his glory, was celebrated. Some, indeed, are of opinion, that it is much more GENERAL EEMAEKS. 19 beautiful, but on this point I leave you to form your own opinion, when I Lave told you more about it. l^or is it the most costly. Many palaces, cathedrals, and other edifices, have required very large sums of money to erect and furnish them ; on the contrary, the House I live in may be said to have scarcely cost me anything, for it was found ready to my hand. The necessary expense of keeping it in repair is but small, when the simple dictates of nature alone are fulfilled. Kor does it contain the greatest number of rooms ever known in a building, though it may be said to contain a large number for so small a place. Perhaps it may be considered that there are fifteen or twenty. Many public buildings contain an infinitely greater number than this, and even houses of ordinary dimen- sions far exceed this amount. As to the number of its occupants, it will hardly bear a comparison with any building ; for, like the huts of some of the rude tribes of New Holland, it never accommodates more than one person — and that one is myself But even with the rude huts of the New Hollanders, the comparison will, as I have said, not hold good. They are made with the bark of a single tree, bent in the middle, and placed with its two ends on the ground. "VMien one of the natives has taken up his abode in a hut of this kind as long as he has seen fit, he leaves it. He journeys to another place, and builds a new one, the old hut being taken possession of by any one who chooses to do so. Whereas I always carry my House with me wherever I go ; in all countries, in all climates, b2 20 THE HOUSE I LIVE IN. in all seasons, my House is ready for my use. The House I live in is ^ood for nothing to any one but to myself; and when I leave it, it will immediately fall into decay. The furniture of the House I live in is not of the most fashionable appearance. Of this the reader can judge for himself, when he understands that it has been the same in kind, in figure, and in purpose, since my House was first designed. Fashion, you know, in general, is of a varying nature ; and that which in one year is held in high estimation, becomes in the next of inferior value. But the furniture of my House, being at first admirably adapted to its wants, cannot require the slightest alteration. In Siam, the houses are frequently built on posts or pillars. This is because the country is low, and apt to be overflowed every year by the inundation of the rivers, and to build on high posts is the only way to secure them against these floods. In Venice and Amsterdam, also, the buildings are erected upon piles, to elevate and protect them from the inroads of the sea. My House, as you will see hereafter, stands on pillars, but these piUars are made for motion, and to enable the building to be transported to any place that may be desired. AMiereas an Amsterdam or Venetian house cannot be removed at all, and a Siamese house not without considerable injury. The House I live in is, after aU, most remarkable for its convenience ; nothing could possibly so well answer my purpose. I have already told you, that it would be good for nothing to any other person. Yoiu' House, GENERAL EEMAEKS. 21 my young reader, may be as cimous, as large, and even as commodious for you as mine is for me ; but it would never answer my purpose at all, even if I had it in my power, to exchange with you. In the progress of the following chapters, I shall give you many more particulars. I shall describe to you, in the best way I can, the Feame, the Coveeing, the Apaetmexts, the Fuenituee, and the Employ- ments, of the House I live in ; and shall briefly give you an account of the structm-e, uses, and abuses of each. At first I intended to insert a little dictionary, or vocabulary of the hard words wliich occur, with their meanings ; but I believe it is unnecessary, for there are but few words, if any, whose meaning you will not know at once, either by their obvious sense, or by the situation in which they are placed. THE HOrSE 1 LITE IN. FEAME-WOEK OP THE HOUSE I LITE IN. 23 Chaptee II. FRAME-WORK OF THE HOUSE. A GLANCE at tlie picture wliicli yon see on tlie opposite page, will at once nnravel all tiie mysteries of the last chapter ; the House I lire in, is my bocly — the present habitation of my immortal spirit. I will first proceed to call your attention to the framework of my House, which consists of bones. THE PILLAES, The pillars are the bones of the lower extremity. Standing by themselves, as they do in the next engrav- ing, and detached from all their connexions, you may be apt to think that they are not well proportioned ; but, as yoii see them on the opposite page, conjoined with the rest of the building, they will appear very differently. I spoke of the lower extremities of the human frame. These are commonly reckoned in three divisions — the thigh, the leg, and the foot. Besides these, there is the knee-pan, or ^patella. Each thigh has one bone, each leg two, and each foot twenty-six. Besides these — fifty-eight in the whole in both legs ^and the two patellas, or patellce, there are in some people, at the largest joint of the great toe, one or two 24 THE HOUSE I LIVE IX. small bones, liaving a slifi^lit resemblance to the knee- pan, or patella. Tliey are callccl sesamoid bones, be- W^ cause they have been supposed to resemble the seeds of the sesamiim, a wild Eastern plant. TEAJIE-WOBK OF THE HOl'SE. 25" THE THIGH-BOXE. Tlie bone of tlie tliigli is called the femur. It is the longest bone in the Trliole liimian frame. At its upper end, wliere it is connected "with the hip-bone, is a round knob or head. This head fits into a corresponding liolloAT, or cavity, of that bone, and is fastened there in a way which will be described in another place. The cut just referred to represents this important part of the human frame very correctly. THE LEG. The lower end of the femur joins with, or rather rests upon, the large bone of the leg. The leg below the knee consists of two bones. The tibia (so called because it resembles a tube, or pipe, or, as some have imagined, a hautboy) is much the largest. The other is called ihejihula. They are so placed that the fibula is on the outside. Where the tibia and the femur meet, they form what is called a hinge-joint, which means a joint that will only allow of motion backwards and forwards in one direction, like a door on its- lunges. But more about this in another place. THE e:>"EE-pan. On the fore-part of this lower extremity, where the femur meets the tibia and fibula, to form the knee- joint, the patella or knee-pan is placed. This is a round flat bone, not joined to the other bones, but lying yery closely upon them, and kept in its place by what 26 THE HOUSE I LIVE IX. are called tendons. You may see a little liow this bone looks ill tlie last engraving ; bnt I here present you with a picture of it on a larger scale. Although this bone might seem at first jview almost useless, yet it serves many im- ' port ant purposes ; and there is scarcely a bone in the body but might be spared as well, if not better than this. THE FOOT. The bones of the foot have a general resemblance to the bones of the hand, which I shall describe fully in another place. But they differ from those of the hand in several important particulars. The foot is composed of twenty-six little bones, strongly fastened together by gristles and ligaments. These ligaments yield, when we bear upon the foot, just enough to enable it to conform to the surfaces on which we tread. If the foot consisted of one solid bone, it would not yield or spring at all ; and it would be liable to be broken when we jump or fall on our feet. Think how clumsy a wooden foot would be ; and one of solid bone would be nearly the same thing. ARCH OF THE FOOT. The arcliing of the foot is a singular contrivance. It is very much like the arch of a bridge, upon its two abutments. I will explain. In the following engraving, the foot is not placed flat down upon the ground, but in the position it takes when we walk, and are just setting it down. Then, as FEAME-WOEK OF THE HOUSE. 27 may be seen by tlie tTTO lines cbta-wn, it descends in a semicircle from the point of tlie heel. The lowest extremity of the heel, and the ball of the great toe, may be considered as the abutments of the arch, while the bones of the instep fonoi the arch itself. Yon may easily perceive, by lashing a strip of wood to the bottom of the foot, how awkwardly we should feel if we were obhged to walk with a fiat foot. It is quite evident there would be no spring when we tread on it ; we could hardly walk, run, leap, or swim at all. The heel is not exactly under the leg, but runs back something like a spui', and is fastened to the main body of the foot by a very firm but springy (elastic) joint. On this account, when we walk, (the heel being th\TS projecting, and having a great deal of elasticity,) we put it down first, and the whole weight of the body does not come down with a jolt, which it would other- wise do, but more gently. Taken altogether, the foot is a most admirable con- trivance. It is, indeed, arched hoth ways; from the toes to the heel, and from side to side. Little, if any, 28 THE HOrSE I LIVE IN. of the middle part of tke foot toiiclies tlie ground at all. There is, however, a trifling difference in the form of feet ; some persons hare them much flatter than others ; though all people hare the soles of their feet consider- ably less arched than is shown in the plate, on account of the muscles, tendons, blood-vessels, &c., which in a great degi'ee fill up the hollow. I have said that the human foot is a most admirable contrivance ; and it is so. There is nothing like it to be found among the other animals, though we find wonders there also. When we examine the foot of the camel, the elephant, the horse, the dog, the cat, or the bird, we are struck with the wisdom of the Creator, in adapting their feet in so remarkable a manner to the sort of life they are destined to lead. The foot of the camel is so formed, that it does not sink deeply into the sand on which it travels. The horse, indeed, could not travel much in the deep sands of Arabia, his foot being more elastic, and adapted for firmer ground ; it is, indeed, so very elastic, that those who slioe the horse find it necessary to make the shoe as narrow round the edge as possible, so that the iron may not press upon the softer and more elastic part of the foot inside the hoof. THE ANKLE. Between the lower ends of the tibia and fibula, and the bones of the foot, are seven short bones, not unlike those of the wrist in shape, but rather larger. Of these you will get a tolerable idea, when I come to describe the bones of the upper extremities. 29 Chapter III. MATERIAL OF THE FRAME. You liave already seen that tlie frame-work of the House I live in consists chiefly of bone. I think, there- fore, before we go any farther, I ought to tell you how bones are constructed, and of what substances they are formed. STErCTUEE OF B02v^E. Timber is evidently full of Uttle holes. If you take a piece of wood, of several sorts that might be men- tioned, and placing your mouth at one extremity, blow hard, you can force a portion of air thi'ough it from end to end. This shows that there are httle holes, or tubes, running through the entire piece. If you could blow hard enough, you might force air through any kind of wood. The experimental philosopher, by the assistance of adequate machinery, will force water and quicksilver thi'ough the pores of almost every sort of wood. But you cannot blow through any of the pieces form- ing the frame -work of the House I live in. This shows that the internal structure of bone, though in appear- ance similar, is yet very different from that of wood. I will endeavour to show you wherein it is diS'erent. 30 THE HOUSE I LITE IN. SHAPE OF BONES, Bones are of tliree kinds : long bones ; hroad or flat bones ; and round bones. The long bones have a cylindrical channel nearly tbroughout their entire length, which contains marrow, or pith ; but the other two sorts of bones have no such cavity within them. They have, however, a great many Httle holes or cells in the inside. Some of them look, upon being broken, almost like sponge or honeycomb. Some of the long bones, besides being hollow, are also spongy. They are generally much larger at each extremity, and the spongy, or cell-like appearance, is there much more apparent. Towards, and at, the middle part, they are smaller, firmer, and contain fewer of these little cells. All the bones in the body are very hard on the out- side. Perhaps the teeth are the most so. The inside of the teeth is not much harder than other bones ; but the outside is coated with a substance called enamel, which is very hard indeed. PAETICULAR DESCRIPTION OF THE BONES. You have already been told that the long, round bones, such as the humerus, or bone of the arm, and ihefernvr, or bone of the thigh, are hollow, and contain marrow in their cavities. This marrow nearly, or alto- gether, fills up the hollow spaces.* These hollow spaces are lined by an extremely thin and deUcate membrane, * This is true of the bones of most other animals besides man. Tlie bones of many birds, however, are entirely hollow, and contain air, to assist tbem in flight. MATEEIAL OF THE FEAME. 31 which also runs in among the marrow. The same sort of fine membrane also lines the cells contained in the spongy bones. These cells have a small quantity of liquid in them, and none of them appear to be entirely empty. Most of the bones are pierced through their out- sides, with one or more holes of considerable size, through each of which is carried an artery to conve}^ blood to nourish the bones, and a rein comes out by the same aperture to bring back the blood when it has fulfilled its ofiice. You may wonder that I should talk about blood in the bones. But there is blood in them, though not a great deal. This blood, with its vessels, the nerves, and the membraneous linings, together ^ith the marrow, and liquid matters, amount to many pounds in weight : for after the bones of any animal have been thoroughly dried, and all moisture extracted from them, they become diminished to almost half the weight they originally were. The entire bones of the human body, when perfectly dry, weigh from eight to twelve pounds. When they appear entirely dry, if you burn them in a hot fire for a long time, you will lessen their weight a great deal more : I believe about one-half. What is burnt out is the animal substance, principally composed of gelatine, or a material very similar to glue. The half which remains is principally lime, combined with an acid, forming phosphate of lime, with which some portion of carbonate of lime, or chalk, is mixed. The great piu'pose which the Creator doubtless had in view, in giving us such a frame-work of strong -32 THE HOUSE I LIVE IN. "bones, was, tliat it miglit support, and give solidity to, the soft and fleshy parts. Suppose, now, that there were no bones ; and that the whole body was a mass of flesh only. Would not the legs give way, and finally be crushed down under the great weight of the body ? would not the arms fail in the duties required of them ? Most certainly they would. But there are several other important uses for bones, which might be mentioned. Some of them, however, 3"0u would not very readily understand till you know a little about muscles and tendons, which are the moving powers. I will, therefore, for the present omit them; GEOWTH OF EOXE. We are not born with the bones as hard as they become after we begin to walk and to run about. At first many of them are very soft, and a large number of them are in several pieces, with cartilage, or gristle, between them. After a few years they grow fii-mly together. The bones of the head, in particular, are at first separate ; and, without doing any mjury to the soft and delicate structure of the brain, contained within them, admit of some little motion, overlapping each other, as it were. But, after we become older, and the whole skull has acquired firmness and solidity, it would require a very considerable force to remove them from each other, and the consequences of so doing, if we were enabled to effect it, would be highly dangerous. There is, undoubtedly, life, as it is often called. MATEEIAL OF THE FEAME. 33 (tliougli we liardly know wliat life is,) in bones. "Wliile we continue in good health, and the functions of the body are duly performed, there is not much feeling- in them ; though in some cases of disease they are endued with exquisite sensibihty. When the surgeon am- putates a limb, the proceedmg of sawing through tlie bone is the least painful part of the operation, though people in general are apt to imagine that it is highly so. VESSELS IX BOIsES. There are also many minute blood-vessels and nerves running about in every direction through very small channels in the interior of the bones. That blood is certainly conveyed through and into bones, can bo made very evident, by forcing, by means of a suitable apparatus, compositions made of liquid wax and other substances, and coloured, to represent blood. Another method is also used to show that blood circulates through bones. If a rabbit, or other small animal, be fed upon madder-root, in a short time the bones will be found to be tinged with the colouring principle of the madder. We are now, I think, prepared to go on with our studies on the frame-work of the House. 34 Chapter IV. SILLS OF THE HOUSE. My readers, I dare say, know, tliat, in building a liouse, strong pieces of timber are laid upon the walls,, wliere openings are to be made, for the purpose of supporting, or, as the builders call it, carrying, the weight of that which is to be above the opening. These pieces are called sills, and they not only form a base upon which the necessary uprights may be placed, but they answer the further pui'pose of holding toge- ther both the upper and lower parts of the building in their true positions. SITI-ATION OF THE HIP-BONES. The sills of the House I live in, are two large irre- gular bones, placed at the top of what I have called, for conyenience' sake, the pillars. These two large bones are rery firm and strong. You will find so much difficulty in understanding my explanations of their shape without it, that I will show you a picture of them. These bones are called in books the ossa innominaia. SILLS OF THE HOUSE. 35 Os is a Latin word for boue ; and ossa is its plural, meaniiio^ more bones than one. Innominatum, of wliicli innomiiiafa is plural, means tvithout a name, or name- less : and the word innominata makes a tolerable name, though rather long. So if a very young child, found in the streets, whom nobody knew, should be called Peter ]N"ameless, that word nameless would answer all purposes. STEUCTUEE. I have said that the ossa innominata were very firm and strong. They are so in grown persons — but in a T'liild they are less so, and are in three pieces, each of which has a different name. They are joined together in front by a firm gristle, or cartilage. Behind, how- ever, is a strong weclge-like bone j)laced between them. Between this last bone, called the sacrum, and each of the ossa innominata, there is also a very strong gristle ; but it is not so thick or strong as the one I have just mentioned as situated in the front. The ossa innomi- nata and sacrum together make a kind of cup, or dee]5 bowl — open at the bottom, it is true, but still bawl- like in its shape. This bowl is called the ^:>e?i'/6\ HIP-JOINT. The manner of fastening the tliigh-bone, or femur, to the hollow of the innominatum, is very remarkable- I shall give a particular account of it, with an engraving, farther along in the book ; so that a ie^x words must answer for the present. The hollow where the femur is fastened, is shaped like the inside of an egg-shell, Avith the small end c 2 36 THE HOUSE I LIVE IN. broken off, and has received tlie name oi acetabulum, from its supposed resemblance to the cup with which the ancients measured vinegar. The round end of the femur is fastened into this deep cavity, by a very large and strong cord. This shoulder is often dislocated, or detached from its situation ; but this hollow is so deep, and the cord so strong, that nothing but very great violence will break the cord or slip the femur out of its place. AN ABUSE. I have said that these two great bones are united by a very strong cartilage. This is true ; but it is also true that while we are young, and even after we are older, if we have lived temperately, this cartilage, which is very thick, wiU stretcli or yield much more than you would at first suppose possible. It is of very great importance to everybody — though much more so to some than to others, and under some peculiar circum- stances of disease most highly so — to preserve the soft and yielding nature of these cartilages as long as pos- sible. To preserve this advantage you must, while young, run about and play, though not with violence ; you mxust labour moderately every day as you grow older ; you must rise witli the lark, and go to bed almost as early as the fowls ; you must breathe pure air ; your drink must be water, and your food must be of the plainest and purest kinds, and not in excessive quantity — and must be well chewed. Then you may hope to preserve your bones and cartilages in a good and healthy state till old age. 37 Chapter V. BODY OF THE HOUSE. HEIGHT. Houses consist of one or more stories, according to tlie taste or design of the builder. Each story, as you know, forms a separate row or tier of rooms. Many houses hare only one story. But the greater number of houses have at least two stories — some three. In cities, where land is very valuable, they are some- times built five or more stories high. Four stories in many large towns are common. A house ten stories high, accommodating ten rows, or tiers, of people, one above another, is a curious sight. Houses of this description are to be met with in Edinburgh, and in Paris, and in some other continental cities. The House in which I live has only two stories, besides a cupola. THE SPINE. The principal post — the main pillar of the building— the spine, rims through both stories, and is of singular construction. We usually call it the hacJc hone. Here is a representation of it— 38 THE HOUSE I LIYE IN. Tlie spine is composed of no less tlian twenty-foiu* separate pieces, each of wliicli is called a vertebra. Tlie plural of vertebra is vertebrce. The seven lower vertebra} are very large and sti'ong. These parts of the frame are the principal supporters of the first or lower story. The twelve next above them, belonging to the second story, are somewhat smaller, and the seven which form the communication from the upper story to the cupola, or the bones of the neck, are 3'et smaller still. Their size in general decreases — not suddenly, but gradually — from the lowest to the highest. The spine, or back bone, is not only curious in its shape and structure, but is of the utmost importance in the human frame. If we had no spine, the limbs, beautifully adapted as they are for their intended purposes, could not act ; they would fall powerless at each attempt to move them. It has been said, that *'if one member," in any part of the body, "suffer, all the members suffer with it." This is especially true with regard to the spine. EACH VEKTEBRA. Each vertebra has a hole of considerable size through its middle (see h in the engraving). Wliat is there BODY OF THE HOUSE. sliown, is tlie upper surface of one of the vertebrae, de- tached from its neighbours, and standing, as it were, by itself, for greater facility of description. TMien the twenty-four vertebrae are placed, one above another, in the position which they occupy in the living body, they contain a hollow channel throughout their entire length. This hollow is filled with a soft substance, very much resembling the marrow of other bones, but much more important in its offices. It seems Hke an arm or branch of the brain; for there is an open passage from the bottom of the cranium, or skull, into the hollow of the spine. There is a very curious mechanical contrivance for admitting the head to turn from side to side, without pressing on the spinal marrow, and consequently injuring its fimctions. This is effected by the top vertebrae of all, and which is called the atlas, moving upon and aromid an upward projection of the second vertebra, somewhat hke a tooth in shape, though of a much larger size, and situated in the front aspect of the bone, and confined in its exact situation by a transverse 40 THE HOUSE I LIVE IN. lig-ameut. Bj tliis moans lateral motion is given to the lioacl ^;\ithont the necessity of moving the main trunk of the spine, but simply by the aid of the first joint formed by the first and second vertebra. GENEEAL DE3CEIPTI0K. When the vertebree are put together, in their proper position, there are large notches at the sides bct^-een each two bones, so exactly matched together as to form a hole. Thus there are as many holes in each side of the spine as there are vertebrse. Through these holes large branches of the marrow of the spine pass off, like the branches of a tree, to all parts of the body. These branches are called nerves. At first, they are pretty large ; but they divide and subdivide, as they proceed towards the extremities of the frame, till they become very small. Their number, in aU the soft parts of the body, particularly in the skin, is very great. Those two upward projections in the plate, A^hich look like arms, by strongly interlocking with the bones above and below them, serve as braces to the whole spine. At the sides are drawn part of the ribs {c e) in outline. These show where the spine and ribs come together. That projection which in the engraving extends perpendicularly upwards is called the sjainous process of the vertebrae ; this forms no part of the joint but serves for the attachment of the large muscles which move the back and head. Between these bones, where the body of each (a) BODY OF THE HOUSE. 41 rests iipou the other, is a tough substance or gristle, very yielding, or elastic, almost Hke India rubber. This keeps the bones from wearing out too fast when they move, and yet allows of their moving pretty freely. The spine is really one of the most curious things in nature. Eope-dancers and tumblers will bend theu' heads back till they almost touch their feet, and bring this straight pile of bones nearly into the shape of a bow. The gristle, or cartilage, between the vertebrae, is very thick and sti'ong, but at the same time very yielding ; and it is so constructed and placed, as will best allow the spine to bend about in all the various ways which even timiblers and rope-dancers could wish. It is so elastic or springy, and also so readily com- pressed, that people who stand or walk much, are really a little shorter at night than they are in the morning. Eest gives the elastic cartilages time and opportimity to spring back again into their places while we sleep, so that by the next morning we are as tall as ever. I ought, however, to say— for it is a fact — that old people settle down a little, and are not so tall as in middle age ; which is partly owing to these cartilages yielding and yielding till they become at length some- what thinner. If the soft marrow of the spine (which runs down from the brain) should happen to be bruised or injured, there would be an end of all motion, at least of the lower limbs. If the spine gets broken, it cannot be mended, and the sufferer will never entirely recover. How happy, then, that it is so admirably contrived, 42 THE HOUSE I LIVE IN. and so firmly put togetlier, as rarely to be broken or dislocated ! Tlie other and shorter posts of the House will be mentioned presently. We are ready now, to study the frame of the upper or second story of the building. It consists of a much greater number and variety of parts than the frame of the first story. THE KIBS. The ribs may be compared to the girders of a building ; though they look more like the hoops of a cask than hke gu'ders. There are twelve of them on each side. Each of them is connected, b}^ one of its ends, to the large post, or spine ; and by the other, to a short post — the breast bone. Only seven, however, are joined closely to the breast bone itself. This jimction is efiected by means of cartilages, to allow of greater freedom of motion in the chest, so essential to full respiration and vigorous circulation of the blood. These cartilages are shown in the plate by fainter lines than those which represent the bony portions of the ribs. The other five go only a part of the way across, and then unite with the cartilages of the upper seven. Those ribs which are continued round from the spme, .and yo/;^ with, the breast bone, are called true ribs ; the others, which do not form this attachment, are called false ribs. Here is a view of this part of the frame — BODY OF THE HOUSE. The length of the ribs increases from the first or upper one, till you come to the seventh, which is the longest. From the seventh to the twelfth they grow shorter again, and the cartilages, of course, become longer in the same proportion. The twelfth rib is very short. The number of ribs is almost always twelve ; but sometimes there are only eleven, and at others, thirteen. But instances of more or less than twelve hardly occur iu one person in a thousand. 4A- THE HOUSE I LIVE IN. lu tke old by-gone days of ignorauce and super- stition, a notion prevailed, wliieli is not yet wholly extinct, that the man has one rib less on one side than on the other. It was said that as Eve was formed of a rib taken from Adam's side, he and all his male posterity have one rib the less for it. I hardly need say that this notion is wholly unfounded. BEEAST BONE. I have just alluded to the breast bone. The name of this, in books, is the sternum. It is usually considered as only one bone ; but, like many others of the human frame, in infancy and in youth it consists of several pieces (three in nimiber), closely united by gristle, or cartilage, but in advanced life the whole usually becomes one solid bone. Long-continued boiling, however, will separate almost any of the bones which are formed in this manner. BEACES. There are a few other parts of the frame of the second story which remain to be noticed, and which I shall call the braces. They are four in number— two before, and two behind. They are— 1. THE COLLAE BONE. This forms a kind of brace between the shoulder and the breast bone, and so nearly resembles a rib, that a separate cut, to show its shape and position, seems imnecessary. You will see it in two or three of the BODY OF THE HOUSE. 45 engravings, running across from the slioiilder to the breast bone, or sternum. 2. THE SHOriDEE BLADE. This is a broad, fiat bone, with ridges on it for the attachment of muscles ; and, at the fore-part, is the hollow, or socket, in which the round head or ball of the humerus, or arm-bone, lies and moves. Here is a view of it behind. I may as well mention that this bone is called by anatomists the scapula. 46 Chapter YI. BODY OF THE HOUSE.— Contixued. ARMS. These are not posts, for, in tlieir natural position, tliey support nothing. They are not braces, for they strengthen no part of the frame. They are properly appendages, but they are very convenient ones ; and though they can be removed without spoiluig the building, their loss very much injures it. They seem to answer, in a great degree, the purposes of stall's, ladders, tackles, pulleys, and other machinery for raising things from the groimd, and conveying them to the upper part of the buildiiig. These appendages, — we may as well at once call them the arms and hands — however, answer a much better purpose than any of these. The arm and hand, taken together, constitute a most wonderful apparatus for motion. The particidar struc* turc of the joints, as well as the peculiarities of the hand, must be reserved for another place ; but it is necessary to say a little about the arm. The bones of the arm have a general resemblance to those of the leg. The upper part consists of only one bone. This is long and round, and is called the humerus. It is fastened above the scapula : below, at the elbow, it is connected to the two bones of the lower half of the arm, by a joint like a hinge, and by ligaments or straps, which extend from near the loAver end of the BODY OF THE HOUSE. 47 upper bone to the topmost end of tlie otliers. The largest of the two latter bones is called the ulnay which is a Latin word for cubit, because the arm, below the elbow, is usually considered about a cubit in length. The smaller one is called the radius, or spoke,, from its suj^posed resemblance to the spoke of a wheel. It is the bone from the elbow, on a line with the thumb. The connexion at the shoulder is such, that the arm can be moved in almost every conceivable direction^ The elbow joint only admits of one sort of motion,, namely, forward, and backward, like a door on its hinges. But the connexion of the radius, or smaller bone of the arm, with the ulna, or larger one, is such that it more than makes up this deficiency. The upper end of the radius having a rotatory motion in a depression of the ulna, allows the hand to be placed with each of its surfaces upwards with equal facihty. These motions are usually designated by the terms jjronation, when the palm of the hand is downwards,, and supination, when the palm of the hand is upwards. Then the wi'ist, consisting, as it does, of eight bones, all moveable, and being so connected with the lower bones of the arm as to admit of very free motion, renders the arm one of the most usefid contrivances in the world. It will perform movements as various and as rapid as the trunk of the elephant ; and would probably, if it were not so common, excite as much surprise. It was said that this whole member could be torn off without spoiling the building. Cheselden, an eminent anatomist, relates that a miller had the whole 48 THE HOrSE I LIVE IX, arm, slioulcler-blade and all, torn off, and yet liis life was not injured. The great danger, in sncli cases, is from bleeding ; but torn blood-vessels do not bleed so freely as those which are cut. THE HAND. I wish to give you a few particulars about the hand. This extremity of the arm is by far the most curious part of it. Indeed, I do not know that there is a reater curiosity in the whole world than this same human hand. Yet, who thinks much about it ? THE HAND. THE FOOT BODY OF THE HOUSE. 49 Tlie tnitli is, many of the best, as well as the most e-iirious objects in the world, are neglected in the same manner. Think of the thousand uses of water. AMiat living thing coidd exist without it ? Yet, do we think much of all this, or are we even thanlvful for so valuable a gift ? The bones represented in the engraving are those of the left hand ; and jou look upon the top, or upper side of it. The foot is also inserted here, in the same position, but has been described in another place. See Chap. II. The whole hand and wrist contain twenty-seven bones ; nineteen in the former, and eight in the latter. The bones in the hand have a general resemblance, though some are much longer than others. The four longest, opposite to figm^e 1, support the palm of the hand, and are joined at one end to the wrist bones, and at the other to the first joint of the fingers. The junction of these bones is effected, as are all tlie other joints of the body, by means of cartilaginous tips, which allow of free motion, and are strongly secured by ligaments. This series is called the meta- carpal bones. The bones of the wi*ist are called the carpal bones. The}' are situated between the ulna (5) and the radius (6) at the one end, and the metacarpal bones and the first bone of the thumb on the other. The^^ are wedged together, like the stones of a pavement, only not quite so firmly; each bone being tipped with cartilage, and sustained by strong ligaments, which unite it to its D 50 THE HOUSE I LIVE ly. felloe s. All tlie boues wliicli compose the wrist liave liad names given to them by anatomists, from their supposed resemblance to other objects ; but as the enumeration of these names is quite needless in a work of this nature, they are omitted. It is only necessary to mention, that the bony structure of the wrist is of an arch-like form, with the convexity corresponding to the upper part of the hand. This configuration creates both additional strength and flexibility. The first four bones of the fingers, opposite figure 2, are the longest. Those opposite 3 are shorter ; the last, or those marked 4, are shorter still. The thumb has one bone less than the fingers. All the joints of the hand — and there are foui'teen, besides the wrist — are hinge- joints, and the ends of tlie bones are made a little like some of our door-hmges, but they only bend in one direction. AVhere the fingers join to the meta- carpal bones, there is much more freedom of motion than at the hinge-like finger joints, but the joint at the wrist admits of motion, very freely in every direc- tion. When the bones of the hand are not quite so naked as they appear in the engraviiig, but are dressed up with muscles, tendons, membranes, nerves, arteries, and veins, and furnished with skin, and nails, in a manner which I cannot now fully describe, the whole presents a most beautiful appearance. Beautiful and iisefid as it is, however, and placed before our eyes from the time we see the light till we sleep in death, there are few things in the whole visible world, of BODY OF THE HOUSE. 51 \^'liicli not only young persons, but adults also, are so ignorant ! So important is the Luman hand, as a member of tlie system, that Sir Charles Bell's Bridgewater Treatise — a pretty large volume — is wholly devoted to a descrip- tion of it. I will make a short extract from that admirable work. " The difference in the length of the fingers serves a thousand purposes, adapting the hands and fingers, as in holding a rod, a switch, a sword, a hammer, a pen or pencil, engraving-tool, &c., in all which a secure hold and freedom of motion are admirably combined. Nothing is more remarkable than the manner in which the delicate and moving apparatus of the palm and fingers is guarded. The power with which the hand grasps, as when a sailor lays hold to raise his body to the rigging, would be too great for the texture of mere tendons, nerves, and vessels ; they would be crushed, were not every part that bears the pressure defended with a cushion of fat, as elastic as that in the foot of the horse and the camel. To add to this, there is a muscle which nms across the palm of the hand, and supports the cushion on the inner edge. It is this muscle which, raising the inner edge of the palm, forms the drinking cup of Diogenes." USES OF THE HAND. Small as this member of the frame is, it is a part of the utmost consequence. Without it, the farmer could D 2 52 THE HOUSE I LIVE IN. not SOW Lis grain, or plant liis corn, or weed it, or lioe it wliile growing, or collect it wlien ripe ; nor, if it were grown, could the miller grind it, nor the baker make it into bread. Neither conld we raise anything to eat in its stead. We might get on for a few years with what is already raised ; but what then ? The roots and fruits which grow without cultivation — I mean without our labour — would not last very long for ourselves, and the thousands of beasts and birds which feed upon them. Do you say that, if we could get nothing else to eat, Ave might then kill and eat animals ? But we could not catch them. How could Ave ? Besides all this, the tailor could not make us clothes, nor the hatter and milliner hats and bonnets, nor the shoemaker boots and shoes. We should be obliged to go naked, summer and winter, in all climates ; for we could not get even the skins of animals. Then, again, we could not write to others for help, even if there were anybody to help us. JN'either could the mariner seek a cargo of food in other countries ; for he could not spread his sails, or guide the helm of his vessel. In short, we could do nothing long to any purpose ; but after gazing awhile upon each other's starving and emaciated frames, we should all He together in one common tomb — and that tomb would be the surface of the earth, arched over with the blue canopy of the heavens ; for nobody coidd be buried. Some may think this representation of the sad case we shoxdd be in rather exaggerated. *' We should not BODY OF THE HOUSE. 53 be sucli lielpless croatures," you may perhaps say. " Wliy, tliere is a story I have seen, about a IVench- vvoman, who was without hands, and yet she could do a g-reat many sorts of work, and even write, draw, and seiL-y Yes, and the story was undoubtedly true. I hare heard stories like it before. I have heard of a man in the same condition, who could write ■vvith his breast. His pen was fastened to a girdle, and then he coidd dip it in the ink, and write very well with it. But these are extraordinary cases, in which Nature is permitted, for some reason wliieh we cannot divine, to depart from her established laws. Such occurrences, however, no more prove that people, constituted as we are, could live upon^this earth without the aid of their hands, than does the existence among his fellow-crea- tures of a person afflicted with blindness that all could flourish without the use of their eyesight. The individuals already mentioned could not have made for themselves the pens and pencils to write and draw with, or the needles to sew with, nor could the man have placed the pen in his girdle ; and there are a thousand other neces- sary things which they coidd not do. The human tongue is spoken of by an inspired writer as being a "little member," yet boasting great things. So this small member of the frame which we are talking of is a "little" affair, but great things depend upon it. It is a sort of connectmg link, that serves to bind the human soul to the habitation it occupies for a few years — rarely reaching to a hundred. 54 THE HOrSE I LIVE IN. Without it, or neglecting to use it, our lives must soon terminate. '* He tliat would not work, neitlier should lie eat," is a di\'ine law ; and we could not work much without the aid of tliis beautiful piece of mechanism, the HrMAN HAND. 55 Chapter YII. THE CUPOLA. We come noAv to tlic cupola ; by which term I mean the Skull, which is placed on the top of the great post before described. I have already told you that seven of the twenty-four pieces which form that post are situated above the second story of the building, and unite the skull to the trunk. You will observe the vaulted chamber at the upper part, and you may see, also, the places for doors and windows. I must stop here long enough to say that — unlike what is seen in ordinary d^vellings — the doors and windows of the House I live in are in the cupola: there is not one door in either the first or second story. The windows, and some of the doors, are placed in 56 THE HOUSE I LIVE IN. front — tlie rest of the doors arc at the sides. The doors and windows tkemselves, as you know, properly belong to the covering. They will therefore be described' imder that head. I have called the month, and ears, and nostrils, doors, in order to keep np the metaphor which pervades the Avork ; the ej/es may, with propriety, be regarded as Avindows. All sound, smell, and taste, pass through the passages before mentioned, and the machinery or organs near and within them. THE CEAXir^I. At the beginning of this chapter I showed you a picture of the whole skidl. T^ow if the bones of the face and neck were taken quite away, and nothing left but the hoUow braiurcase, {cranium,) the appearance would be very different. Here is a view of the frontal bone, from which all the other bones have been removed. THE CUPOLA. 67 Yoli see, in front, tlie top of the cavit j or socket for eacli of tlie two eyes ; and on one side, tlic place where the ear wonkl be in the livmg person. This brain-case is composed of eight bones, most of which are closely imited by a rough-edge, like that of a saw, the notches of which shnt into each other as the teeth of a saw would do, and form what may be called seams. These seams are by anatomists called sutures, and are nine or ten in number, of different lengths, according to the size of the bones which they separate. They are said to be of use in Hmiting the extent of fractures of the skiLQ, and in some diseases of the brain ; and doubtless, like everything else which has been formed by the beneficent hand of the Creator, they perform some important part in the great economy of nature. One of the most important bones of the skull, or brain-pan, is that which stretches across the whole forehead, and is called the osfrontis, or frontal bone. Another across the back of the skull, and of a somewhat triangular shape, is the os occipitis, the pointed extremity of which reaches to the crown of the head. Another piece, shaped a little hke a clam-shell, lies aroimd each ear ; this is the os temj^oris, and there arc of coiu'se two of them, one on each side. On the upper sides of the head, surrounded by those already described, are the two parietal bones. At the bottom of the skull, and wedging m and locking together nearly all the bones of the head and face, hes the OS sphenoides. This is in shape something like a bat with extended wings, and has attachment to fourteen distinct bones. The os oetkmoides, so called 58 THE HOUSE I LIVE IN. from its resemblance to a sieve, being perforated witli a great number of holes, for the transmission of tbe power of smell, lies at the root of the nose, joining the bones of the face to those of the head properly so called. Now, as I shall hereafter show more fully, this whole space is filled up with brain. In an adult, the brain weighs from two and a half to three pounds and a quarter. In a few instances it has been found some- what larger. It would be impossible to convey a very definite and correct idea of the bony structure of the head without a plate of each distinct bone, and its several attacliments ; and even vrith this assistance, it could hardly be effected. The bones of the skuU— more especially of the lower part — are so irregular in shape, and so grotesque, it may be said, in their arrangements, as to defy description. Perhaps enough has been mentioned in this place, to give a general description of what is meant to be explained. In truth, throughout the whole body, there is not so complicated and difficult a study as the anatomy of the head ; and of its great importance you will be aware, when I remind you that all the senses are more or less con- nected with the healthy performance of its functions. Concerning the bones which compose the face and jaws, much need not be said. There are six bones on each side, which form the face, and are grouped together under the common name of the iipper jaw. All of these l3ones, like those of the skull, have fanciful names assigned to them, and, like them also, they have sutures at their uniting parts. THE CUPOLA. 59 Tlie lower jaw is one strong bone, wliicli has been compared to a liorse-shoe, or a crescent ; but a reference to the plate will give yon a very good idea of it. Both the upper and lower jaws serve for the attach- ment of very powerful muscles, which are concerned in the business of mastication, as will be explained more fiilly hereafter, THE TEETH. Aroimd one of the doors of the cupola, and by far the largest of the whole, is a most remarkable arrange- ment, which requires a particular description. There is here a sHght resemblance to a wheel, with its compo- nent parts, or cogs. There are, however, no wheels, but there is something like a mill, and an operation similar to grinding is performed; the motion by which this gi-inding is effected, is very much like that of a pestle and mortar. One of the segments of a wheel, with its cogs, remains still during the operation, while the other moves up and down upon it, and breaks in pieces the substances which are interposed. In addition to this motion, there is a sliding from side to side which takes place, and thus the process of grinding is complete. Look now at the engraving. This view represents the left side of part of the bones of the human face, as it woidd appear, if the outside of both the upper and lower jaw were taken away. 60 THE HOUSE I LIVE IN. By tliis vio-w, you ^yill pcrcciyc tliat tlic upper row of tectli, and tlie corresponding jaw, form the wheel and its cogs wliicli remain still ; while the moA^ing wheel, which biniises the food submitted to its operation, is the lower jaw, and the teeth contained in it, the arti- cidar surface of which mores very freely in a depres- sion at the base of the skull, beneath the ear. When the number of teeth is complete in an adult/ and none have been lost, or drawn out, each jaw contains sixtecxi ; and both together, of com'se, hold thirty-two. In the engraving, you see there are eight teeth above and eight below ; that is, just half of the whole. Children have but twenty teeth at first, or ten in each jaw. These twenty are sometimes called the milk teeth, because they appear while the child's principal food is milk. These are gradually shed, between the ages of seven and fourteen years ; and thirty-two new ones grow in their places. There is a period in every child's life — say at about THE CrPOLA. 61 the age of six years — wlieu, if it liave not yet begun to sliecl its first set of teetli, tliere are forty-eigJd in botli jaws ; twenty in sight, and twenty-eight beneath them, lying deep m the jaws, at the roots of the former. When you look at the jaw-bone of a man, or any other animal, however, you do not see the roots or fangs of the teeth. They are encased or biu'ied deep in the jaw. Those in front have only one root each ; the grinders, or double teeth, have two, and sometimes more. There are four kinds of teeth in each jaw, namely, four front teeth, two canine teeth, called also eye-teeth, four small grinders, and six large grinders. Of these, half are of course on each side. The fore-teeth and eye-teeth have but one root each. The small gi-inders do not often have more than one, but they are usually indented lengthwise, so as to give the appearance of two. The large grinders of the lower jaw have two roots, and those of the upper have three — two before and one behind, or on the inside. Who does not admh-e a good set of teeth? With many people they are one of the principal marks of beauty. But they are also useful as Mell as handsome, so long as they remain sound. The teeth of some persons remain sound and beautifid all their days. Woidd you like to have yours the same ? Let us then attend to the following particular account of them ; and perhaps, when we know their nature and structure more fully, we may better know how to take care of them. The teeth are not set into the jaw-bone itself. 62 THE HOUSE I LIVE IN. although they appear to be so, but into a bony appen- dage, which is called the alveolar jprocess, which forma the true sockets of the teeth. These sockets, in old age, and when the teeth arc no longer contained within them, become absorbed, and are carried away into the mass of circidating fluids by a process yet to be mentioned; hence arises that flatness of the lower jaw, and apparent shrinking of the face, which we obserA'c in elderly persons. Like the rest of the bones, the teeth consist princi- pally of earthy substance — I mean lime. But at first, children can hardly be said to have bones of any kind. Some have become to be a little solid, others have not. TMiere the bones afterwards are, there is at first a piece, or lump, of something which is nearly trans- parent, and more like jelly than bone. This in time ossifies, that is, becomes solid ; and thus forms bone. GROWTH OF THE TEETH. The teeth, as well as the other bones, are at the first mere pieces of jelly. They do not appear at birth, for they are within the jaw-bone. And what may seem strange, the lumps of jelly-like substance which make hoth sets of teeth, (those wliich are shed early and also those which come afterwards in their place,) are there at tlie same time ; one set near the edge of the jaw-bone, for early use, and the other a little deeper within it. It will greatly assist you in understanding me, if you examine the following engraving. It shows the teeth THE CUPOLA. 6^ as tlier appear in a cliild, before it has shed many ot the first set. When the soft pieces of jelly which form the teeth become hone, the process is as follows : — First, a hard speck commences in the centre of a tooth, which is deposited by the blood-vessels which nourish it, and this gradually growing larger, all the jelly becomes absorbed, and its place occupied by bone. The teeth, howeyer, consist of something else besides solid bone. If they did not, they would yery soon wear out. Do you think a piece of common bone put in the place of a tooth, would last us to chew with for half a century or more ? By no means. I will therefore tell you of the STEUCTURE OF THE TEETH. Each tooth consists of three parts — the crown, the necl', and thefaug. The fang or root is the part which is set firmly in a socket in the jaw-bone, as if it were driven in like a nail. The neck is close to the edge of , when driven into planks or timbers. The bones THE HINGES. 69 of the head, too, are joined firmly together in adults, as you have already been told. Some of the joints of the human frame are real hinges. To this class belong the knee-joints, the joints of the toes and fingers, and those of the elbow. The lower jaw may also be called a hinge-joint. The ankle- joints, the joints of the wrist, and indeed many others, sometimes move like hinges, but they perform other and very different motions besides. HIP JOINT. But the most curious joints in the human frame are what are called the ball and socket joints. The more important of these are the shoulder and the hip. I will show you a plate of the one at the hip. 70 THE HOUSE I LIVE IX. At a you see the deep hollow or socket in the bone, where the round head of the femur, or thigh- bone, moves. This round liead is drawn back from the bottom of the socket a httle way, in order to show the round hgament near a. The latter is a very tough, strong cord, fixed by one end at the bottom of the socket very firmly, and by the other fastened as strongly to the round head of the femur. If it were not for this ligament, the joint woidd be dislocated, or shppcd out of its place a thousand times more fre- quently than at present, for indeed it now but seldom happens. I ought also to say that there is a tough, gristly rim around the socket at the hip, which greatly increases its depth. This socket is called the acetahu- luni; meaning vinegar-cup. It was supposed, as I observed before, to resemble one kind of ancient vinegar-cup in use among the Romans. I will show you a figure of another ball and socket joint, and also of a hinge joint — the shoidder being an illustration of the ball working in a socket, and the elbow acting upon the principle of a hinge. Every one understands the nature of a hinge, which is in such constant use, and therefore the motion of the elbow-joint will be very readily understood. It has been asserted by some authors, that the first mechanic who ever formed a door-hinge, took the idea of it from the hinge-joint of some dead animal. But of this, of course, we know nothing. Now for the engraving. THE HING-ES, 71 I will first describe tke joint of the elbow. The lower portion of the arm is formed of tAVO bones, one large, called the ulna, and the other smaller, called. the radius. The upper end of the small bone d, is a little rounded, and it lies against a small holloAA", or depression in the other bone, the uhia, at ^, to which it is tied by cords, called ligaments, particularly by one which goes round it like a band. The ends of these two bones, thus imited, turn on the end of the upper one, which is rounded and tipped with cartilage, and thus fitted for the purpose, as you may see at f. They are kept together in a living person (as indeed all tZ THE HOUSE I LIVE IN. boues arc) by broad and sliort straps or cords, called lig-amcuts, which adhere to each end of the bone a little "vvay from the joint, and are very tic^ht and stronof, and yet not so tif^ht as to hinder the proper degree of motion. Let lis here stop to reflect upon the great proof of intelligence and design -which i& here so admirably displayed. To enjoy the entire use of the arm, two distinct motions are reqmsite, which may be employed sepa- rately or together, at will. For this piu'pose, while one of the bones of the fore-arm only, the ulna, is attached to the humerus, or bone of the upper-arm, the smaller bone of the fore-arm^ or radius, is enabled to move in a hollow, or depression of the ulna, by means of its rounded upper end. A glance at the plate will readily explain this. At the lower end of the arm, this arrangement is reversed: the radius, instead of furnishing the head or rotating tubercle, becomes in turn the recipient, and the prominence of the ulna plays T^-ithin a depression on its surface. By means of tliis reversed arrangement, the greatest freedom of motion is admitted, and, by the greater pliability which is gained, fractures and dislocations rendered less likely to occur. But a ball and socket joint is more curious still. The bone which is represented at h, is the scapula, or shoulder-blade. The hollow place at e, is the socket in which the round heacj or ball, a, of the upper bone of the arm, (the humerus) plays freely when the arm is moved. The socket is so shallow, and the ligaments THE HINGES. 73" SO long, in order to enable us to make almost every kind of motion with our arms, that it is much more easily slipped out of joint or dislocated than are the hinge-joints. Even the hip, which is also a ball and socket joint, has a much deeper socket; and it is partly on this accoimt, and by a different arrangement of muscles, that we can s\ving our legs round with as much freedom as we can our arms. But though the shoulder-joint is rather easily dis- located, it is not so readily put into its place again, when it once gets out, as you may imagine. It some- times requires all the skill of a surgeon, and the strength of one or two strong men. The number of hinge and other joints in the frame of the House I live in is very great. It must be nearly, if not quite, a hundred and fifty. You see the wisdom of the great Creator fully dis- played in this structure and connexion of the bones. A^liat if the joint of the knee could move in every du-ection like that of the shoulder ? Do you not see that, when we walked, the legs would have dangled about strangely, instead of moving backwards and forwards in one direction only ? And is it not plain that we never could have stood firmly on the groimd? In like manner, how very inconvenient it would have been, to have our finger-joints move one way as well as another! On the contrary, how confined and cramped would have been the motion of the arm, if the shoulder had been like the knee, and had only per- mitted the arm to swing backwards and forwards, without our being able to carry it outward from the body. 74 THE HOUSE I LIVE IX. The builders of machines have sometimes made joints in their machinery very much like the shoulder- joint; but it is doubtful whether they ever could have contrived such, if they had not first looked at the bones of man, or some other animal; for other animals have these various sorts of joints adapted to their peculiar wants, as well as man. LIGAMENTS. But how are the joints held in their places? ^Tien we take up a bone which has lain, perhaps for years, bleaching in the sun and rain, we see that the ends are smooth, and some of them liinge-like; but if we take up two such bones, and put them together, they will not stay in that condition a moment, ujiless they are fastened by strings or wires, or something of the kmd. How, then, are they kept together in the living person? This is what I am now about to tell you. They are held together by short and strong straps, called ligaments. Some of them, however, are longer, and begin at a considerable distance, say an inch or two, from the very end of one bone, and then, after passing over the joint, are fastened into the next. This strap, or ligament, does not adhere or stick to the joint, as it passes loosely over it, but is only fastened strongly, where it rises, and where it is inserted, as if it were there glued to the bone. The inside, where, in crossing, it lies against or rests gently on the joint, is very smooth; so that the joint, in moving, may not THE HINGES. 75 These ligaments are wliite and sliining, but not always very thick. They are usually very strong. Some of them are as narrow as a piece of tape. Others, as at the side of the knee, or at the shoulder, are very wide. Some cross each other, as in the knee-joint. The latter are shown in the engraving a. There are others that go all roimd the joint, and com- pletely shut it up: as if the ends of the two bones were put into the two open ends of a short cylinder, or rather of a short bag or purse, and the open ends were then gathered round, and fastened tightly to the two bones ; in this AA'ay, the joint would be completely shut up, as in a sack. This sort of ligament is called a capsular ligament. It would be difficult, nay, even impossible, to enmnerate aU the ligaments in the body ; they are in many instances so interwoven with each other, and frequently inseparably united. It will be sufficient here to mention that the junction of the head with the spine, the whole length of the spine itself, the hand and the foot, are literally crowded with ligaments of different shapes and attachments, as may be best adapted for imparting strength and flexibility; and that each of the larger joints has several ligaments in connexion with it, the knee-joint alone being considered by some anatomists as having fourteen distinct ligaments to its own use. THE HOUSE I LIVE IX CAPSULES. Tlic bags, or sacks, called ccqjsular ligaments, are principally intended to prevent the joint from being easily slipped out, or dislocated. They also serve for another purpose, scarcely less important — a purpose which shows the wisdom of the great Creator in the contrivance of the human frame, more than almost any other; if, indeed, any comparison can be made where all is excellent. WEAK OF THE J0I>-TS. Ts^ow, what prevents the joints of the human body from rapidly wearing out, when we walk much or run swiftly ? The Father of the universe is the preserver as well as the creator of this " wondrous frame." "VVas there not something done to keep these joints oiled, if I may so call it, they would not last long. Take the knee, for example, and think what a vast deal of friction or rubbing together of the end of the thigh bone and of the two leg bones there must be. A traveller probably swings each leg, in walking, about 1200 times in a mile. If he should walk thirty miles a-day all the year, excepting Sundays, he woidd swing each knee 15,024,000 times. "Were he to do this every year, from tlie time he was twenty years old till he was seventy, or for a period of half a century, the number of movements would be 7-5 l,2r>0,000 times! THE HINGES. 77 " A continual di'opping:," it is said, and it means tbopping of water, " will wear away a rock." And tlie saTing, tlioiigli old, is true. This continued rub- bing of the bones of the knee together, if they were allowed to get diy, would wear them so much in a single day, that we should hear a gi'ating noise at every step long before night, and in a very few days, the bones would be completely worn out, and unfit for use. I question if they would last even a whole day. Iron or steel, or even the hardest material you can think of, would wear out in a very short time. Y\'hat, then, can be the reason why the knees and all the other joints do not wear out? There is no place to put in tar or oil to prevent it, as is done in various mechanical contrivances which are of human construction, and without which their due operation could not be sus- tained. SYNOVIA. I have said that many of the joints are completely shut up, as if they were in a sack. Xow the Author of the frame has so contiived it, that a substance, called synovia, which answers all the piu'poses of oil of tar, continually oozes out on the inside of the ligaments, at the joints, and keeps the ligaments themselves and the joints soft and moist. Can anything be more curious? Can anything prove more clearly a great Designer, or, as I might say, a great blaster Builder? One thing may be advantageously remembered: — The synovia, or liquor which thus oozes out to lubrirate the joints, will be of just the right quality and quantity 7y THE HOUSE I LIVE IN. i^lien we are in perfect liealtli. If we are unwell, there may be too little or too much, or it may be too tliicli: or too tliin. When we use food or drink that is too heating or irritating, after awhile the synovia will become less in quantity, or of poorer quality. It is said that persons who use much spu'its or opium, or continually eat improper or heating food, are very apt, in the end, to have a grating in their knees and other joints. In all such cases, and in other evils, prevention — where we can prevent them — is better than cure. Those who live on a moderate quantity of plain food, and avoid strong drinks, and work steadily but mo- derately, rarely have any trouble of this sort. It has been said that the ligaments hold the joints together. They do so; but the tendons or straps which go off from the ends of the muscles, and are fastened into the several bones aroimd their joints, materially help to hold them together. There are other wondcrfvd contrivances to keep the joints firm and yet moveable, but it woidd take too long to go fully into the subject now. ABUSES or THE JOINTS. That the great Creator made the joints to be used, is proved from their curious structure, and from the substance prepared to moisten them; but that they were not made to be used too violently, is also proved by the fact, that if thus used they become diseased. ►Sometimes the liquor called the sijnovio. dries away: in THE HINGES. 79" these cases, -^e hear tlie grating sound already men- tioned, and tlie limb becomes stiff and incapable of motion; at others, the joints become painfid and often enlarged. It is but seldom, however, that they become diseased from mere walking, if we walk ever so much, pro^dded our habits are temperate and regular; though occasionally rheumatic, and other painful affections, will encroach upon the ease of our sensations, and the symmetry of our forms. 80 Chapter IX. EEVIEW. Let us liere sum up, or review wliat we liave read; it will be very useful in fixing more strongly in tlie mind that knowledge which we have already gained; and enable us to start with greater confidence and advantage upon the topics which will next demand our attention. NUMBER OF BONES. The cranium, or that part of the head which contains the brain, consists of eight different bones. There are fourteen bones of the face, besides thirty -two teeth. Then there are four very small bones in each car, and one at the root of the tongue. Thus the whole head about the neck contains sixty-three. The neck has seven, but as these form the upper part of the spine, they are usually reckoned with those of the body. Here let us stop to comment on the simple, yet effectual, contrivance for increasing the security of the brain. Had the cranium, or brain-case, been com- posed of one entire bone, instead of several, fractures would have followed almost every injur}- on its sm-face, and such fractm*es as do occasionally take place, would probably be of greater extent, and of corresponding danger. The spine, or back-bone, contains twenty-four pieces, called vertebra? ; and betvN een these and the lower extremities are four bones more. There are twenty- EEVIEW. 81 four ribs; tliat is, twelve on each side, aud a breast- bone, or sternum, down the middle of the front. Thus, that which is commonly called the body, contains fifty- three bones. The upper extremity, including the hand, arm, clavicle, or collar-bone and scapula, or shoulder-blade, consists of thirty-t"^\o pieces, or sixty-four on both sides. Each lower extremity includes thirty bones; and thus both together make sixty, besides the small sesamoid bones. jN'ow, if we add together these several numbers, we shall find that a complete himian skeleton contains no less than two himdred and foi-ty bones! Who would suppose this, from a mere view of the human figure, either while standing, or with the limbs in motion? "We now see that it has a great many joints within it, and of course a great many bones. At every part bf the body where the bones meet, there is more or less of motion, (excepting at the junction of the several portions forming the head, face, teeth, and hips,) and these may all be moved, nearly at the same instants Thus there are in the human frame about a hundred and eighty joints. "S^^e may, indeed, add to this number the small sesamoid bones, which are found in the thumbs and great toes of older persons, and somewhat resembhng' the knee-pan in shape, though very diminutive in size. Of these there are often two in each large joint of the great toe, and as many in the large joint of each thumb. Adding these, then, to the two hun- - dred and forty, we shall have, for the whole number F 82 THE HOUSE I LIVE IN. of bones in the liiiman frame, two liimdi'ecl and forty- eight. Some make the number about two hmidred and sixty; but in this, fourteen sesamoid bones are inckided. It should be remembered that the number of sesamoid bones greatly varies in different individuals, though nearly all adult persons have some of them, and some individuals have them in other parts of the body besides those already mentioned. They are hardly ever larger than half a pea. In addition, it may be mentioned, that some individuals have two or more supplementary bones in the skull, called ossa wonniana; these, when they occur, arc of an irregular shape, and seldom larger than a small Windsor bean. Besides all these, the breast bone, the ossa inno- ininata, and many other bones of the body, are in young persons composed of several pieces, and some of them are often not very strongly united even when they become older. Some few individuals are occasionally met with, who have a still greater nmiiber of bones ; but these may generally be considered as diseased persons. A bony or chalky substance is often formed in the flesh of those who have the gout; and some of the gristly parts of the body — I mean the cartilages and ligaments —occasionally become ossified, that is, converted into a substance resembhng bone, as do also small portions of the great arteries, or tubes which convey the blood. In some diseases, also, the bones become soft and readily bend, owing to a deficiency of the earthy matter of which they are composed. EEVIEW. 8^ Occasionally persons are met witli who liave six fingers on each hand, or six toes on each foot, and sometimes both; but these supernimierary fingers and toes do not always have bones in them. SKELETONS. 'S'Slien all the bones of a human being, or of any other animal, are put together, and fastened to eac-h other by pieces of wire, the whole is called a skeleton. There is, too, another kind of skeleton, but it is not so commonl}^ met with; nor is it so convenient for use. It is made by stripping off all the soft parts of the body, excepting the ligaments; these are suffered to remain, and the whole is thoroughly dried. This is called a natural skeleton, in cojitradistinction to the former, which is called an artificial sTceleton. The engraAdug on the next page represents the human skeleton, fastened together by wires, in the manner in which it is usually prepared. It is repre- sented in this posture, in order to give a different view from that focing page 22. ANATOMY. The study of the nature and structure of the bones, and nothing but the bones, is called osteology, that of the muscles, and nothing else, mijology, &c. But as most people who study these, go further, and learn also the shape and structure of the heart, the lungs, the brain, the blood-vessels, and, in fact, all parts of the body, some more general name seems necessary f2 8i THE HOUSE 1 LIVE IN, EETIEW. 85 for what they do. Therefore we say of those who study all parts of the human body, just as it appears the moment the soid leaves it, the bones, muscles, ten- dons, brain, nerves, heart, blood-vessels, lungs, skin,&c. that they are studying Anatomy. FHYSIOLOGY. Physiology is something more than all this. It is the study of the liWng animal; how the heart, the brain, the eye, the ear, the muscles, the bones, and every other part, act. David, the inspired psalmist, felt this, when, meditating on the curious structure of his own body, he exclaimed, " I am fearfidly and wonderfully made." King David, however, had pro- bably never seen a complete himian skeleton, or even had much insight into the interior of the human frame; for in those days it was generally thought improper to employ the bodies of men for the pui-- poses of anatomical research, instead of which, the remains of the brute creation, particularly dogs and other domesticated animals, were used. Hence many of the technical terms by which the various parts of our complicated structure are designated, though now appearmg fanciful and erroneous, were at the time of their invention more correct, and the analogy much more obvious. For many years past, we have been accustomed to consider it not only as allowable, but highly proper, and even necessary, to examine and dissect the human body after death, as it is by such means alone that the 86 THE HOUSE I LIVE IN. true structiu'C of tlic limiiau macliiiie can be under- stood and explained, and the knowledge of its various derangements acquired. That the most intimate ac- quaintance Trith the different branches of Anatomy^ Fliysiology, and PaiJioJogy, is highly requisite for those to possess who undertake to cure or to relieve- the various " ills which flesh is heir to," is admitted by all who are competent to form an opinion on the subject. I will here take the opportunity of defining the tliree words above mentioned. By the word Anatomy^ is meant a knowledge of the structure and propor- tions of the human, or of any other animal body; by 'Physiology, is meant a knowledge of the functions which the various parts of the body perform during health; and by Pathology, is understood an acquaint- ance with all those changes and alterations in tJie structure or functions which are efi'ected by disease. In Avriting this book, it is my intention to describe a little both of anatomy and physiology, but into patliology I shall not enter, as that will be unnecessary for the general reader. Heretofore I have treated principally of anatomy; the remaining chapters will embrace a large proportion of physiology, combining, as we proceed, the two subjects together, showing the structure of a part, and at the same time pointing out its uses, by which method, after what has bcfcn-e been explained, a tolerably correct idea of the subject will be acquired. 87 BONES AND SHELLS. Before closing this chapter, I would obserye that, although, except in very extraordinary cases indeed, the bones of deceased human beings are left to decay in the grave, the bony parts of the inferior animals are turned to great account in the domestic and useful arts. The handles of common kuiyes, and innumerable little articles in every-day use, are made of bone; from which, also, some valuable products are obtained by the aid of chemistry. Ground bones make excellent manure for certain descriptions of land, and thus not only become valuable to the farmer, but fiu'nish a beautiful illustration of the laws of nature, by wliich the constituent elements of the animal frame are made to contribute to the growth of vegetables, upon which human existence so greatly depends. Ivory is another kind of bone, for it is the tooth of the elephant; as is also that useful substance, whale- bone, which is part of the structure of the enormous javrs of the whale. From-the Jiorns of animals, combs, lanterns, whip-handles, and many other articles, are made, while the covering of the tortoise, and the shell of a certain species of oyster, furnish us with those beautiful substances, tortoise-shell and mother- of-pearl. The shells and bones of animals not only serve as a support to the softer parts, but also as a firm defence. What woidd become of the tender frame of the poor tortoise, the lobster, the crab, the oyster, and many other living things, if they were not covered over, and 88 THE HOUSE I LIVE IN. protected, as witli a sliield, by a liard buelder of slicll? The soft parts of the human body, which are most essential to hfe, are in many instances well defended in the same manner by the solid, unyielding materials Trhich envelop them. As, for instance, the brain, the spinal marrow, the lungs, the heart, and the liver. JSTow a portion of the shell of every animal is formed of lime. There is not so much difference between the bones of man and the shell of the tortoise or the lobster, as may be supposed, though the colour is very different. A very large proportion of the lobster-shell is lime; in the tortoise-shell the quantity is much less; and horn contains but very little. Bones, as I have before observed, contain a large proportion of this earth. 89 Chapter X. COVERING OF THE HOUSE. The covering of tlie House I live in differs more from other buildings — that is, possesses more peculiarities — than almost any other part of it, though every part is peculiar, admirable, and demands the highest praise. It differs from ordinary buildings, in containing no sharp corners, or square edges, for everything, even the smallest part, is more or less rounded. It seems as if the great Architect of nature had regarded round- ness as a beauty, and squareness as a deformity, while, on the contrary, square sides, square edges, and angles of various degrees, appear to be regarded by the human architect as points of beauty; for not only are single buildings erected with regard to squareness of form, but whole towns and cities, where practicable, are often constructed on the same principle. THE PERIOSTEUM. How different the structure of the House I live in! Every bone in the frame, as if to prevent the possibility of having any rough sides or corners, is neatly covered with a very thin membranous substance ; this is called the periosteum. Perl means around, and OS means the bone or bones. There is a plain reason for tliis periosteimi being used; our buildings, the work of men's hands, are fixed and stationary; they are not intended for motion: while the frame, and almost 90 THE HOUSE I LIVE IN. every part of tlic liiimau body, is made to mo^'C; and \\'liero there is motion, it is desirable tliat the parts should be rounded, and every possible means used to prevent friction or wearing. Besides this, the peri- osteum has another and very important office — that of conveying nourishment and vitality into the very interior of the bone which it surroimds, by means of innumerable little blood-vessels which ramify upon its surface. After every bone* is covered over with this thm sul)stance, we have the muscles with their tendons, and it is the muscles, generally, which give round- ness and beauty to the human body and limbs. A large number of them are situated on the bones, especially the long bones, but a few are extended between them. The bones are generally smallest in the middle, and increase in size towards the extremities, at the joints; but the muscles are usually the reverse of this. They are largest towards the middle of the bones, and grow smaller towards their extremities. TN^^ have a striking example of what I ha^e just stated, in the case of the arms. The bones of the arm, as seen in the skeleton, arc so large at the joints, and so small in the middle, as to make the limb appear * Or ratlier every bone except the teelli, ■svliicli, wlicre tlicy stand out of the gums, are covered with enamel. A thin membrane, like the periosteum, would do no good, as it would boon wear out in eating. The ends of the bones, also, where they rub against each other — 1 mean at the joints — are covered with a white and somewhat elastic substance, iu wliich the cartilage and the periosteum disappear. COVEKING OF THE HOUSE. 91 almost iigij. But wken we see it dressed up witli muscles and covered witli the skin, it is very well pro- portioned. The elbow in most persons is scarcely larger tlian tlie arm is, botli above and below it, and tliis is caused, as I liave said before, by the muscles. Tliey are larger wliere tlie bones are smaller, and gi'ow smaller till tliey arrive at tlie joints, where they run into tendons. But before I go further, I must tell you what Muscles and Tendons are. THE MUSCLES. The muscles are the flesh, — that is, the lean part of it, and are of a reddish colour, as jou have probably observed. The red colour is caused by the blood; for it is not only true that blood, in small veins and arteries, runs through them in every direction, but it also tinges their whole substance. We know this is so, because, in the case of animal flesh used for food, when the muscles have been soaked and boiled long enough, the redness disappears. Even when boiled for the table, the muscular parts of animals are of a paler red than they were when they were first sepa- rated from the mass of flesh to which they belonged. THE TENDONS. Some of the muscles are fastened immediately to the bones, and grow, as it were, into them; and m this case, the covering of the bones, or periosteum, seems like a sort of glue, intended to cement the 92 THE HOUSE I LITE IX. muscle and bone togetlier. In general, liOAvever, the muscles are not themselves fastened to tlie bone, but terminate towards each end by one or more tendons. These tendons are white, flattened substances, like belts or straps, and are very tough and unyielding. "Wiien properly prepared, they are sometimes called whit-leather; and it is almost as difficult to break this as it would be to break real leather. The muscles, then, usually terminate in tendons, and it is the latter which grow to the bone; though the muscles some- times adhere to the bones directly at one of their ends, without the intervention of tendons. STEUCTUKE OF MUSCLES. The substance of muscles is thready or fibrous. You have probably observed that a piece of lean meat, when boiled, has a thready, fibrous appear- ance, but there is one thing about muscles which does not so readily appear after boiling as it does before. A piece of meat, to be boiled, is cut oft" in such a manner, that it usually includes parts of several difie- rent muscles; and the v.hole, in this way, seems like a solid, or nearly solid mass; whereas, with a very little care, it could be parted out, each muscle by itself, though not so easily after cooking. Such is the case with a piece of beef taken from the leg of the OX; and such would be the case with a piece of iiesh taken from the human leg or arm. These separate muscles are connected to each other by means of what is called cellular suhstancc — a fine COVEEING OF THE HOUSE. 93 sort of membrane which I shall have occasion to describe hereafter. Each tlu'ead or fibre of every muscle is also connected to each other fibre which lies next to it by the same sort of cellular or yroolly membrane. Thus, as you see, a mass of lean flesh, similar to that which we obtain from the limbs or other parts of animals, consists of smaller bundles of flesh, con- nected together by the cellidar membrane, but not so tightly as to hinder each bundle from moving or sliding about a little among the rest. Now each muscle, in like manner, consists of a great multitude of fibres, also connected together by cellular membrane. It is also thought by many anatomists, that each fibre is made up of a great many smaller fibres, so small as not to be visible to the naked eye. The number of muscles in the human body is very great. Anatomists do not agree about the number, because there are many which some reckon as only one muscle, while others call them two, (for they have really a double appearance) ; and because a fcvr are so small that some do not count them at all. They are usually, though not always, arranged in pairs; that is, there is one on the right side of the body exactly like one on the left side opposite to it; and so on. We camiot reckon the whole number at less than four hundred and fifty, and some make it five hundred and twenty, or even more. I have said that many of these muscles end in tendons, or thin, wliitish straps. Sometimes they terminate in two tendons. The hicej^s muscle (so D4 THE HOUSE I LIVE IN. called from hi, two, and cajput, a head) lies on tke front part of the arm, havmg its upper extremity fastened to the top of the scapula, or shoulder-blade, by two separate tendons, or sinews, while the lower end is attached to the upper part of that bone of the fore- arm called the radius in the usual manner, by one tendon only. COVERING OF THE HOUSE. 95 The annexed engraving will convey a tolerably coiTeet idea of the shape of the muscles I have just been speaking of, as Avell as of muscles and tendons in general. You will perceive in the figm*e, at a short distance from the bottom, a sort of square projection, by which the artist means to represent a small portion of a tendinous expansion, which goes off at this part of the muscle, and, dipping do^^Ti amongst, and uniting with, the muscles of the forearm, assists in binding the whole together, and preserving a unity of action. Few muscles only have double tendons, and of those which have this peculiarity, few present so perfect and so beautiful an appearance as the biceps. ACTION OF MUSCLES. In front of St. Peter's church, at Eome, stands an obehsk of red Egyptian granite, upwards of one hundred and twenty feet in height. It was conveyed from Egypt to Rome by order of the Eoman Emperor Caligula, where it remained partly buried in the earth on the spot where it had been deposited, until about two hundred and fifty years ago, when Pope Sixtus the Fifth, with the assistance of forty-one strong and elaborate pieces of machinery, and the further aid of eight lumdi-ed men, and one hundred and sixt}' horses, succeeded in getting it out of the ground. Four months more were required to remove it to a fiu-ther distance of fifty or sixty rods, and in that situation it at present stands. "VMien they had at length conveyed it to the spot, the great difficidty was, how to raise it. A pedestal 9G THE HOUSE I LITE IN. Avas erected for it to stand upon, designed in the form of four lions; and by means of powerful mackines, and many strong ropes and tackles, its lower end was at length placed upon the pedestal. They then commenced, by the aid of machinery, to raise up the column, but when it was so far elevated as to be almost ready to stand, the ropes, it is said, had stretched so much by the enormous weight of the huge mass of granite, — so much more than had been expected and provided against, — that the cohmm could be moved no further. What was to be done? Fontana, the master workman, had strictly forbidden aU talking ; and the men stood stiU, holding iipon the tackles so silently, that a whisper might have been audible. Suddenly an English sailor, who happened to be present, cried out, " Wet the ropes." This was no sooner said than done; when, to the surprise and satisfaction of everybody, the ropes contracted sufficiently to raise the obelisk to its place upon the pedestal, and there it has now remained for nearly two hundred and fifty years. You probably begin to wonder what connexion this story has with anatomy and physiolog}'. I will tell you. The muscles are those parts by means of "v^hich the head and limbs are moved, and by which locomotion is effected. In short, from the most rapid and energetic movements which we are capable of performmg, to the slightest motion of the little finger, or the eyelid, all is i)ei formed by the aid of the muscles. COVERING OF THE HOUSE. 97 This motion, or, as it is usually termed, muscular motion, is effected by an alternate contraction and relaxation of one or more of tlie muscles, either singly or in combination. Being fastened to the bones at each end — and in the case of those muscles which move the Hmbs, each extremity is generally attached to a dif- ferent bone — whenever they shrink, or contract, by an effort of volition, they dra-w- one of the bones to which they are fastened towards the other. If the muscles which lie between tlie shoulder and the elbow shorten, or contract, either the shoulder must be pidled down- wards towards the elbow, or the arm below the elbow must be drawn upwards towards the shoulder ; and the same thing happens in other situations. The muscles are not capable of shrinking or contracting a great deal, it is true, but they will do so to a much greater extent in proportion to their length, than wetted ropes can. ILLUSTRATIONS. I must explain this matter by another engraving. Here is a picture of the right arm. It is represented as if everything had been cut away from the bone, except the single muscle of which I was just speaking (the biceps), and a portion of the skm. It is repre- sented, too, as already contracted, and the arm drawn up as far as possible towards the shoulder ; and you see how large this muscle is in the middle, when thus shortened. 98 THE HOUSE I LIVE IN. In one respect, a muscle does not slirink UJce a rope ; for tlie latter, when it shortens, or grows larger, swells all the way alike ; but when a muscle contracts to draw up a Hmb, it swells principally in the middle. Some muscles do not swell so much as this one does when they sliorten, but they are all enlarged more or less when any part of the body is moved by them. Perhaps you do not understand how a muscle, by contracting, or shortcnmg, pulls up the arm. I will endeavour to make it more plain. I now sit at my table — my right arm lying upon it, which, for the sake of explanation, I will consider to be as helpless as a stick. Now, if I wish to get my hand to my head, how is it to be done ? If a piece of dry rope, fastened by one end at the shoulder, and by tlie other to my hand, were moistened, it woidd shrink a little, and raise my hand from the table, but not very far. COTEEIXG OF THE HOUSE. 99 JBiit suppose tlie lower end of the rope were fastened round the middle of my arm, and then caused to shrink ; would it not raise the hand higher than before — the elbow remaining where it was? It certainly would, but still it would not brmg the hand up to the head, nor even half way towards it. But suppose, once more, that the lower end of the rope were fastened still nearer to the elbow ; it would of coui^se draw up the hand still more than the last. jS"ow the end, or tendon, of the principal muscle which shrinks to draw the hand up towards the head, is fastened to the aim below the elbow, and close to it, so that, in shrinking only an inch or so, it draws the Jiand up to the head. If you lay your other hand on the arm, between the shoulder and the ^Ibow, you can feel the contraction, and at the same time see the muscles swell out. If the lower end of the tendon of this muscle were fastened lower down, that is, farther from the elbow, it would start out so far, when the arm was raised, as to cause a very singular and awkward appearance, unless a band were put around it at the clljow, to keep it down, which would have been very inconvenient. As it now is, the tendon starts out a little way, as you may know by placing your hand upon it, or under the knee, while you are bending the limb. But the matter IS so admirably contrived by the great Architect, that it renders the arm usefid, gives it a good shape, and ought to raise our thoughts in gi-atitude to Infinite Wisdom. But it must not be thought that there is onlv one G 2 100 THE HOUSE I LIVE IX. muscle concerned in bending the arm. Tlie truth is, that in performing almost any motion of the body, a great number of muscles are employed. In moving the hand alone, we use nearly forty ; and in using the whole arm, not much less, I presume, than a hundred. I have mentioned that a muscle acts only by con- traction ; after a short time, this energetic state which it has acquired ceases, and the limb or joint which it has moved falls passively back into its origina! quiescent condition. But for many purposes of hfe, a rapid alternate contraction and relaxation of parti- cular sets of muscles is required ; for this pm'pose^ most muscles are provided with antagonists, that is, every muscle which performs a contractile motion, has, generally, on the opposite side of the limb, an opposing muscle, which acts not only in restoring the equihbriimi which had been disturbed, but, with a corresponding degree of power and energy, causes an extendinr/ motion. These two sets of muscles are called j^e.ror* and ejcte7isor». To illustrate this more clearly, let us revert to the Inceps. This powerful muscle, in conjunction with another, called the hracJiiaVts internus, and which lies- dose upon the fore part of the upper arm, by their united contraction bend the elbow. Wlien they liad spent all their force, tlie arm would slowly fall straiglit again ; but to effect this straightening with vigour and swiftness, a set of muscles are provided, whicii lie upon tlie back part of the humerus, or bone of the upper arm, wliich, by their sudden contraction, extend the arm with as much force as the JjIccj^s and its coadjutor had bent it. COVERING OF THE HOUSE. 101 If you look upon a skeleton, yon see Iioav the bones at the joints project, and also how ragged the spme and many of the flat bones appear. JS^ow the several hundred muscles of our frame fill up all these spaces, cover the ragged bones, and produce that round, plump, and smooth surface which a healthy human body displays. FAT. But I must not leave an impression that the muscles and tendons perform all " the filling up" of the human frame, for this is not the case. They are covered by the Skin, which is to be described in the next chapter. jSTor, indeed, is this quite all, for there is in most persons a small quantity of fat intermixed with the muscles ; and m some persons a great deal of it. The fat is found in the soft, white, cellular substance which is placed everywhere between the muscles separately, and the little bundles of which each are made up. You will now be able to understand and remember the meaning of the word cellular, for it means made up of cells, something hke honej^comb, and the fat is depo- sited in those cells. A small portion only of fat is necessary to health, and when found, as is frequently the case, in imusually large quantities, in man, or in other animals, it rather indicates disease. EEFLECTIONS. Thus we sec that the great purposes which the muscles and tendons subserve are, the filling up and beautifying of the frame, and furthering the due 102 THE norsE i live ix, motion of its several parts, separately and in combina- tion. Without the muscles and tendons so wisely blended in the construction of the human frame, we shoidd be much more helpless than the brutes, and be the most miserable of all animals. But with the large uumber of muscles which we happily possess, how midtiplied are our motions. For it must be recollected, that not only the movements of the head, arms, hands, fingers, back, legs, &c., are performed by these means, but also the movements of the chest in breathing, and of the heart in the perform- ance of its important functions. These two last vital phenomena are too often imnaturally checked by those unwise or ignorant persons who indulge in clothmg too closely and tightly fitted to the form. Besides these uses, the curious processes of mastication and swal- lowing, of speaking, singing, crying, and laughing, are chiefly effected by the assistance of the muscles. The muscles have other uses, besides those of aiding beauty and creating motion ; but the reader will not be prepared to understand them, till he knows more about the Blood and the Circulation. 103 Chaptes XI. COVEEING OF THE HOUSE. THE SKIN. I HAVE ali'eady told you what cellular membrane is. Now the first layer of the covering of the house I live in, that layer placed almost internally, for there are three of them, consists of this membrane, in large quantity, and, as it were, firmly pressed together. It has a closely interwoven fibrous appearance, all the fibres crossing each other in every direction, like the felt of a hat; is strong and elastic, and capable of great distention and contraction. This material forms the principal part of the skin, or, more properly, of the common integuments, for it has received the name of true skin in contradistinction to the other two layers, which complete the formation of the covering. This true skin — cutis vera of anatomists — is so abun- dantly supplied with blood-vessels, that it seems to be composed of them in endless numbers, running along and crossing each other in almost every direction, together with nerves quite as numerous intermingled with them. Upon the surface of the cutis, the nerves become somewhat enlarged, forming Httle rows of eminences or pimples. These are most plainly visible on the tongue, at the edges of the lips, on the palms of the hands, and the tips of the fingers, at the extre- mities of the toes, and soles of the feet. Though most plentifully distributed in those situations, yet they lOi THE HOrSE I LIVE IN. exist more or less over all parts of tlie skin, and, from their great number and extreme sensibility, are consi- dered as forming more particularly the organs of touch. The blood-vessels and nerves are so extremely numerous in this portion of our frame, that a needle's point cannot be inserted without drawing blood, and producing pain, both which circumstances show that a wound has been given to a blood-vessel, and that a nerve has been irritated. It is this true skin of oxen, deer, sheep, and other animals, which is employed m the arts for the pro- duction of leather. In tanning, currying, and dressing leather, the outer layers of integument are scraped oft', and nothing remains but the true skin, which is then submitted to various processes to complete the prepa- ration. Bu.t leather does not solely consist of this skin; for tannin, the active principle contained in the oak bark, which is employed in its preparation, combines with the raw hide, condenses it, and gives it a preser- vative property. coloukixct or the skin. We have now arrived at the consideration of the colour of the human body. As far as I have already described the skin, the colour is exactly ahke in all people, whether black, red or white. Here, spread over the true skin — the part which forms the leather —on a thin, gauze-like membrane, technically termed 7'cte mucosum, and underneath the outer covermg of all, (yet to be described,) is a soft, pulpy, or jelly- like substance, which contains the colour. In the COVEEING OF THE HOUSE. 105 African, this pulpy substance is black ; in the native American, it is red or copper-coloured ; in the Asiatic, it is yellow ; and in tlie European, wliite : in M u- lattoes, of course, it is of various shades. Here, then, you see the cause of that variety of colour which exists among the different families of the human race. It is surprising to find how ignorant most persons are on the subject of coloui*. Some have never thought of it at all ; others suppose that the whole mass of our bodies is darker or lighter thi'oughout, accord- ing to the indication of our faces ; others suppose that the colour is in the blood ; and some, again, that it is in the true skin, or that part which can be formed into leather. But we see that none of these are right — that the skin itself — the true skin, properly so called — is ahke, both in textiu-e and hue, thi'oughout the whole himian race. That this colouring matter effects some important purpose connected with our well-being we may be thoroughly assured, although philosophers have hitherto failed in discovering it. In the JN^egro, it is not only darker, but of a more dense substance, than in fairer races ; and even among Europeans, it varies in thickness in different parts of the body — hence the different shades of coloiu* in various parts of the body of the same individual. There have been a great many conjectures about the uses of this colouring matter j but there is very little true knowledge concerning it. We know, indeed, that a dark skin, as it allows the heat of the body 106 THE HOrSE I LIVE IN. to escape more rapidly tlian a light one, renders a person cooler, in hot weather, in sultiy climates ; but it is difficult to believe that this is the principal reason for its existence, as we know that natives of different countries under the same latitude, have a range of colour, from perfect black to a complexion almost as fair as Europeans. CHANGE OF COLOUR. There is a curious fact which deserves to be men- tioned in this place. The colouring matter of some persons has been known to change. There have been several Negroes, and a few Eed Indians, observed, upon whose limbs spots of a chalky white have appeared, which enlarged and spread until the whole body be- came white. These changes, however, are ascribed to a disease, partaking, in some degree, of the nature of leprosy. THE CUTICLE. I observed that the integuments of the body con- sisted of three distinct layers, separable by the art of the dissector. I have already described the two which lie most internally, and it remains now to describe the outer superficial coating. This is generally known by the name of cuticle; sometimes it is called e_pidermis, or scarf sMn, but cuticle may perhaps be considered as the best name. It is an extremely thin, semi-transparent membrane, which covers over, in every part, the other layer* I have described; yet, though so closely adherent COVERING OF THE HOUSE. 107 in a state of liealtli, by the application of boiling water, or bKstering substances, it is readily sepa- rated from its connexions. This must be familiar to everybody, as scalds, burns, and tbe production of blisters, are of too common occurrence. Many diseases also cause the cuticle to be cast off, wben its place is readily supplied by a new deposition of the same material. Here we may stop to admire another great proof of the beneficence which the all -wise Creator has displayed in his nimierous works. The facility with which the cuticle is renewed after accidents, or dis- ease, is wonderful. The new production appears with so much rapidity, that it might be thought that it was already formed under the old one, as are the second, or permanent teeth, under the primary set, which they push out. But it is not so. The new cuticle never grows till the old one is either dead or separated from its attachments. Were this not the case, to what pain and inconve- nience should we be subjected, after even trivial injuries, and the sHghtest accident would prevent us from fol- lowing our accustomed pursuits. Here, again, temperance helps us much. These little injuries to the skin, though readily healed in such individuals as are correct in their habits, and simple in their diet, yet often become foul and exten- sive sores, lasting for years, and even idtimately pro- ducing death, in those imfortunate beings who addict themselves to gluttony and intemperance. The colouring matter, if destroyed, is renewed, or 108 THE HOUSE I LIVE IN. appears again almost as readily as tlie cuticle ; but the real skiii, if once destroyed, never grows again. This is the reason why scars are the consequence of a deep injm*y to the skin. The loss of the cuticle, or the rete mucosum, never causes a scar ; they are reproduced exactly as they were before : but the true skin, being a much more highly organized sub- stance, never recovers the accident. The destroyed portion is supphed by a toughish material, somewhat resembling the original structure in appearance, and which in a degree answers the purpose ; but it is not real skin, nor are the proper functions performed by it. The cuticle is not equally thick throughout its whole extent, for even in young children and infants, the palms of the hands and soles of the feet are of much greater density of structure than elsewhere, and the pressm*e to which those parts afterwards become sub- ject, still further increases their substance. You will perhaps form the best idea of what the cuticle is, as far as the naked eye can give it you, b}^ examining a portion aa liich has by accident be- come separated or grazed off from the body. You will then perceive how extremely fine and delicate it is — much more so than it appears to be when sepa- rated by an artificial blister, because by the latter ap- plication, it is so much soaked with the sermn^ or watery part of the blood, which has been dischar ged that it has become thickened, and does not present its natural aspect. In its healthy condition, this scarf skin is scarcely COTEEING OF THE HOUSE. 109 a iiftietli i)art as thick as the covering of a blister; besides which its transparency is so much greater, enabling the coloiu'ing matter which lies under it to be plainly visible. Although by inspection with the naked eye, a tole- rably correct idea of this membrane may be formed, and sufficient for all practical purposes, yet, when viewed luider powerfid lenses, its structure is found to partake very much of the nature of fish-scales. HAIB AND ^^iILS. As appendages to the skin may here be mentioned the Nails. These are too well known to require minute description in this place. They are supposed to be prolongations of the cuticle, or outer skin, as boiling water, or long maceration, will remove them together. They are of a closely-packed, laminated structure, and of a horny appearance, serving as protectors to the ends of the toes and fingers, and assisting in the appre- hension and retention of small objects. It will not here be out of pla<^e to speak a word upon the Hair. Hair, in greater or less quantity, is found on all parts of the body, excepting the palms of the hands and the soles of the feet, but more parti- cularly it abounds upon the head. Hairs have their origin in little roots or bulbs, which are situated in the true skin, and are supplied with blood-vessels ta aflford them nourishment. There is an evident rela- tion between the colour of the hair and the shade of the skin ; dark-skinned individuals have generally dark 110 THE HOUSE I LIVE IN. hair, while the hair of fair persons is usually of a cor- responding colour. The hair, like other parts of the body, is liable to diseases. In this country, we are not much in the habit of observing it, but in some parts of Poland and Hungary, the peasants, who greatly neglect the necessary virtue of cleanliness, and are addicted to many bad and filthy habits, are afflicted with a grievous disorder of the roots of the hair, by which the whole becomes matted and tangled together in a most disgusting manner. This disease is called the jjlica 2Dolonica. OIL GLANDS. All animal frames seem to require frequent lubri- cating, or oiling. In some of the feathered tribes this is effected by means of the beak. They have a little gland, as it is called, which furnishes them with oil, which they press out with the bill, and apply it to the feathers, which overlap each other, that the rain and other moisture may be the more effectually warded off. But most other animals, histead of the oil being con- tained in a single bag or gland, have it in numerous little receptacles, almost too small for the naked eye to detect, and deeply imbedded in the skin. In the skin of the sheep they are very thickly scattered indeed, and hence the wool of a healthy animal of this class has always an unctuous feel. They are very numerous, too, about the roots of the hair of most animals ; and hence it is that the hair — even the human hair — in a state of health, appears more or less oily. COVERING OF THE HOUSE. Ill Besides these glands, which secrete the oily fluid at the roots of the hair, there are many others, situ- ated in large numbers on various parts of the human body. They are called sebaceous glands, or follicles, and are foimd imder the cutis, in great abundance, wherever there is considerable exposure to the air, or much friction, as in the nose, ears, groins, arm-pits, &c. There are also other glands, situated imder the skin, over the entire surface of the body, which are supposed to be connected with the function of per- spiration. All these glands or foUicles secrete more or less an unctuous fluid, which lubricates the skin, affords it suppleness, and assists in protecting it from the weather and from the effects of friction. This lubricating fluid, healthy and necessary as it is, yet, without due regard to cleanliness of person, is apt occasionally to become a source of disease. CLEANLINESS. Besides these glands, which I have described, there are numerous exhalent vessels which pervade the surface of the whole body, giving exit to a con- stant vapoury fluid, which is known by the term insensible persjyiration, to distinguish it from a more oily secretion from glands appropriated to the pur- pose, which is more properly termed siceat. This insensible perspiration is continually escaping from living bodies in a state of health, while the other secretion is formed only diu'ing violent exercise, or from a high state of temperature. 112 THE HOUSE I LIVE IN. That the perspiration is constantly escaping through the skin, though insensible to the eye, may be seen by holding a bright miiTor, or plate of polished metal, over any part of the surface of the body. If, unfortunately, this insensible perspiration is checked by the application of cold, damp, or other causes, for any length of time, danger, in the form of inflammation, fever, rheumatism, or consumption, may ensue. If the perspii'ation is also checked by neglect of cleanliness, in keeping the pores of the skin free and unclogged, much mischief may arise. "^ There are also other offices performed by the skm, which are very curious, but I need not mention more of them here. The more you become acquainted with the structure of the human body, and particularly of this part of it, the more you will perceive how important it is that it should be kept thoroughly clean by frequent washing, according to the heat of the climate, and other circimistances. And yet how many persons there are who pay no attention to this important duty, who seldom or never wash at all, excepting perhaps their hands and faces ! Such persons are hardly fit to be trusted with a habitation so fearfully and so wonderfidly wrought. In truth, by their own want of precaution, and utter neglect of so obvious a means of preservation, they are seldom as long entrusted with it as are others, who are more impressed with the importance of the charge committed to them. How true arc the oft-quoted words, that *' Cleanliness is a virtue !" 113 Chaptee XII. THE COYEEING.— THE WINDOWS. GENEEAL EEMAEKS. Befoee glass was inyented, the windows of dwelling- lioiises were small, and made in different ways. In summer, tliey often consisted of a mere hole in the side of the building. In the houses of some eastern nations mere were no windows of any kind in front, or towards their neighbours ; and in China, and some other oriental countries, this is the custom to the present day. In winter, these holes or windows were closed up with something which would partially exclude the cold, the rain, and the snow. In some countries of Asia, and in ancient Britain, oiled paper was used for this purpose. In France, besides oiled paper, they used talc, isinglass, white horn, or thinly-shaved leather. In ancient Eome, the rich sometimes used very precious stones, frequently employing agate for the windows of their baths. They had also the art of working out the horns of animals into large and thin plates, which they used in the place of glass for their windows. The Chinese used a very fine cloth, covered with a shining varnish; and, sometimes, split oyster-shells. The first windows of common glass, which is made of sand, potash, &c., melted together and formed into plates, are said to have been made in the time of H 114 THE HOUSE I LIVE IN. CoDstantine the Great, in tlie foiirtli century after Christ; though it appears from later inquiries, that glass windows were known in Rome long before that period. But it was not till the fifteenth or sixteenth century that glass was brought into common and general use. THE HUMAN EYE. The windows of the human frame are unlike those of paper, isinglass, agate, horn, leather, cloth, oyster- shells, or common glass ; nor are they situated in the back part of the house, like those of some eastern nations ; nor are they very large or numerous. There are but two of them, and those of inconsiderable size, and they are set in the front of the house, in the cupola. Both of them open and shut, rise and fall, have the curtains drawn or removed, and the blinds opened or closed, at the same time, or separately, as required. Most windows are only made to be raised, or moved, in one direction; but these move every way, and with the greatest ease and rapidity, by means of the pulleys with which they are supplied. The curtains may be drawn or removed almost with the swiftness of lightning, and hundreds of times in a minute. SITIUTION OF THE EYE. The human eye is of a spherical form, the better to collect and concentrate the rays of light ; in an adult person it is not more than an inch in diameter, and is THE WINDOWS. 115 situated in tlie cavity of tlie orbit. It is not fixed, like tlie eyes of some animals ; but can be made to roll about, upward, downward, and sideways. For tliis purpose, it does not adhere closely to the bone, but lies on a soft bed of fatty substance, and bas many muscles or cords fastened to the sides and back part of it, as you see in the engraving. If the eye of a dead person were cut in half down the middle, from the top to the bottom, with the handle of the knife held forward, and the point towards the back of the head, a side view of one of these halves might be supposed to look hke the engraving. This view of anything is called a section, and this plate consequently represents a sectional view of the eye. A large whitish cord, which you see running from h to the back side of the eye, comes from the brain, and is called the o^tic nerve. The rest of the cords between d and e are muscles, or little bimdles of flesh ; and they become tendons, or hard h2 116 THE HOrSE I LITE IN. wliitisli cords, of extreme delicacy, at the smaller part, where they are fastened to the eye. The tendon of the upx3er muscle goes round a little piece of bone in the orbit, like a hook, as you find at e. The lower one, f, is also fastened in a very ingenious manner. The tendon that passes roimd the smaU projection of bone is fastened to the eye-ball nearly at the top. Now it is easy to see that, if the upper muscle at d should contract or shrink, it would separate just as if it were a rope, and somebody puUed it ; — that is to say, it would pull the top of the eye-baU forward, and cause the fore-part, at a, to turn downward, so that the person would look towards his feet. The eye-ball is moved by sLx muscles, which are divided into four straigJit and tivo oblique muscles, and the names "« liicli they bear are given from their several uses and situations. The straight muscles are placed one on each side of the ball, one at top, and one at bottom ; they have their origin from a small hole in the skull, through which the optic nerve passes from the brain, and which they envelop, and their insertions insensibly blend with the common covering of the eye. One of the oblique muscles arises with one of the straight ones, and the other comes from the fore part of the orbits ; they both unite imperceptibly with the tunics of the eye. The four straight muscles, and which can bo seen in the plate, move the ball to either side, ungj^ds or downwards, as may be wished, accordiiSgto which of them is employed. THE WINDOWS. 117 If all of tliem are put in motion at tlie same time, their imited action draws the eye-ball further \A4thin the socket. The oblique muscles, acting separately^ roll the eye to either side ; when they act in con- junction, they draw the eye-ball forwards, thus having the direct contrary action of the straight muscles. In the real eye, the tendinous expansion of the muscles is not so distinctly divided as it appears in the engraving, the fat and cellular membrane, which is very abundant, being there all removed, that the pecidiar structure may be more easily perceived. COATS OF THE EYE. The eye is a round hollow sac, containing fluid, which is of two quahties, and is covered by several layers or coats. The outside, or sclerotic coat, as it is called, can be seen in the engraving. It is very thick, and a small portion of it at the fore-part is wanting. In this vacancy or openmg is set the cornea, a piece of membrane which is transparent, that is, can be seen through Uke glass. This transparent part you AviU find near a. It is placed in the sclerotica, as a crys- tal is set in a watch ; or, if we compare the eye to a window, just as a pane of glass is set in the frame ; with this difference, however, that a pane of glass is seldom round, but the cornea is as round as a six- pence. It also projects like^Ulj^ crystals of most watches, and through it the rays of light enter 118 THE HOUSE I LITE IN. tlic eye and pass to its back part. What we caU tlie white of the eye is the sclerotica, or window- frame, as far as we can see it, siUTOimdinir the cornea. The tunica sclerotica, or sclerotic coat of the eye, is lined by another and thinner coat called the chovoides. The internal surface of the choroides is covered aU over, excepting at the back part, where the optic nerve enters, with a thin sooty kind of black paste, called by anatomists i]io i^ig^nentum nigrum, which means black pigment. The use of this black pigment, as I shall explain more fidly hereafter, is for the purpose of suffocating or absorbing the rays of light after they have performed the duties required of them. "Where the sclerotica and cornea join, a kind of circular membrane or curtain runs inwards, and is represented in the cut by two white lines approaching each other, but not quite coming together. "When we look at the eye of a livmg person, this curtain is sometimes light blue ; in other persons it is grey, hazel, or black, '\^^[len this curtain — called the ivis — is blue, the person is said to have blue eyes ; when black, he is said to have black eyes, &c. The circular hole in the middle of the iris is called the pu2:>il of the eye. It is larger or smaller in pro- portion as the iris is more or less diminished ; for the iris will shrink or contract a Httle, like the muscles : and indeed it is endowed with minute muscular fibres. The stronger the light is before the eye, the smaller is the pupil. "VMien we are in the dark, it becomes very THE WINDOW^S. 119 l-di'^o, ill order to admit as mauy rays of light as possible to pass tliroiif^li to tlie optic nerve, at the back part. The greater portion of the remainder of the eye-ball consists of a substance which I told you had some resemblance to the white of an egg, or that ropy but clear fluid in which the yolk swims. Anatomists, however, say that the greater part of it resembles melted glass, which I suppose few of you have seen : but as we have called the eye a window, the comparison is a very happy one. This fluid substance is termed \he vitreous Jaimour : it fills up the whole back of the eye, and preserves its globidar figure. There is still another liquid contained in the eye, though in much smaller proportion than the last, and is of a more watery consistence. This, as its name implies, is the aqueous humour. The edges of the iris, or curtain, like a partition, divide this fluid into two portions ; that \^ hich lies in front of the curtain is called the anterior chamber, and the portion which lies behind the iris, and which is much the smallest, is known as the posterior chamber. Just at the back of the iris, exactly behind the pupil, is a small body, clear, and in a degree trans- parent, like the vitreous humour, but much harder, and imbedded in the midst of it; without ever removing from its place. This body has a close investment, of an extremely fine nature, which binds it more closely to the contiguous parts, and is called in anatomical language its capsule. This body, with 120 THE HOUSE I LIVE IN. its enclosing capsule, is about as lar^je as a midtUing- sizcd hazel-nut when divested of its sluU, and in consistence is somewhat like a piece of lialf-iiu'lted^iini. It is called the cn/stalline Icux. It is rounded, or convex on both sides, and resembles two watch-glasgee, ^^ith their hollow or concave sides placed together. This is represented in the engraving. There is a disease of the eye, called cataract, in which the lens becomes opaque ; and as the rays of light can no longer ]>ass through it, the individual so affected becomes blind. The most effectual remedy for this complaint is by the removal of the lens from its situation, either by taking it away altogether from the eye, or else by pushing it downwards out of the sphere of vision. These methods, of course, can only be accomplished by the aid of the surgeon. OPTIC >"EEVE. Tlie optic nerve, which I mentioned as entering at the back part of the eye, expands or spreads itself as it enters, over the whole choroidcs ; and this expansion is called the retina. The retina, though a prolongation of the optic nerve, yet materially differs from it in appearance, the trunk of the nerve being of a cordy and toughish texture, while the retina is composed of a tender and pulpy-hke substance, and is of a light grey colour. The rays of light, entering from all directions, in passing through the eye, strike first upon the cornea, then pass through the aqueous humour, and enter the crystalline lens ; having arrived there. THE \yiNDOWS. 121 the rays diverge, as from a centre, towards tlie circumference, and, traversing the vitreous humour, impinge upon all parts of the retina ; and it is here — upon tlie retina — that the phenomenon understood by the word sight is e fleeted. A. — Rays of light from all parts. B. — Cornea, through wliich they pass. C. — Crystalline Itus, where they sutler refraction. D. — Divergent rays. I2K. — lictinn, upon which the picture is formed. Y. — Optic nerve. There is a curious circumstance connected with this operation of vision, which is, that the image or picture, in front of the eye, is formed on the retina, in an inverted position, or as we should say, upside down. Thus, if I am looking at a horse or a tree, there is a kind of image, or shadow, of that horse, or tree, on the retina of my eye, with its lowest part upwards. Why everything seen by the eye does not appear inverted, rather than in its true position, is not known, though many very ingenious theories have been invented to accoimt for it. 122 THE HOUSE I LIVE IN. Tliere are mauj- individuals who have a peculiarity of vision, so that they are unable to perceive objects distinctly, without holding the thing to be viewed close to the eye. These persons are said to be short- sighted, and it is commonly observed in them, that they possess an eye somewhat more prominent than the generality of people. A principal cause of this defect arises from that very circumstance ; the cornea, or that portion of the front of the eye which em- braces the outer circle (the pupil, or aperture in the iris, being the inner and smaller one,) being too convex in its shape, permits the rays of light which fall through it, in every direction, to form a point, or focus, before they arrive at the crystalline lens to undergo that divergence which it is the object of the lens to effect. Thus, instead of aU the energy of the rays which have been admitted through the pupil being concentrated upon the lens, they reach it feebly, and, as it were, dissevered from each other, and, consequently, the proper degree of divergence is interfered with. The same defect is also supposed to be attributable to the crystalline lens itself being too convex at its anterior surface. I told you before, that this lens was composed of two portions ; in fact, it is formed of two segments of spheres, of different sizes, united at theu' flat surfaces, and with such relation to each other as best suits the object to be attained. !N'ow, if that segment which lies towards the front of the eye be the least out of proportion — be ever so little more convex than the laws which regulate vision THE WINDOWS. 123 permit — the same eril may exist, as in tlie case of a too prominent cornea. It is not possible to ascertain tliis for certainty during life, though, according to the known laws of optics, it is highly probable j but when the shortness of sight depends upon a too great convexity of the cornea, it is readily detected upon inspection. In order to remedy this great defect as much as possible, short-sighted persons are in the habit of holding all objects which they wish to see distinctly within a few inches of the eye ; by this means, the rays of light emanating from the object to be riewed, fall upon the cornea, in a shorter line, and the focus is thereby formed in its proper situation at the crystalline lens. There is also a pecuUar action of the oblique muscles of the eye-ball, which forces the inner and backward parts of the eye more forward, thus enabling them still further to shorten the axis of vision, and which may be perceived by the contrac- tions of the muscles of the forehead, and the x^nrsing up of the integuments under the lower lip ; by which means, also, the quantity of light admitted into the eye is regulated. Now that we have spoken of short-sighted persons, a good opportunity is afforded us of inquiring into the cause of long sight, which is the very opposite of the former, and is more commonly met with in individuals in the decline of life. Here is the reverse of the case we have just had under consideration ; the cornea has become too flat, partly from a diminution of the aqueous humour, by which its proper distention 124 THE HOUSE I LIVE IN. is not maintamed, and partly from tlie natural shrink- ing of parts to which age is subject. In like manner, as the focus of the rays of light admitted into the pupil was formed too sooyi in those individuals affected with short sight — in the case we are now inquiring into, the focus is formed too late. The rays of light, striking through the cornea and aqueous humour, fall upon the lens, from whence to diverge towards the retina, before the focus can be formed ; hence arise indistinctness and confusion of sight, unless the object to be viewed is held at sufficient distance from the eye to lengthen the axis of vision, and throw the focus to the proper situation. The skill of the optician greatly enables persons afflicted with either of these defects in their sight to alleviate their wants. By means of convex glasses, to aid the vision of those who are near-sighted, and by concave glasses, to assist those who have long sight, regulating according to circumstances the admission of the rays of hght, and forming the focus at the points best adapted to the purposes for which the eye was constructed, he can form very efficient substitutes for the original structm'cs. Truly it is said, that he who invented spectacles was one of the great bene- factors of mankind. There are many curious phenomena connected with the subject of vision, which would be highly interesting for you to know, but it would not be easy to explain the peculiarities so as to convey a correct notion of them, without the aid of diagrams. It may be sufficient here to observe, that the eye. THE WINDOWS. 125 perhaps, of all parts of tlie liimian frame, is the most wonderful. When we consider that a few pieces of membranous material, with the assistance of a gummy substance, and a little water, form an organ which effects that astonishing phenomenon called sight, we may well elevate our thoughts to the contemplation of that great Being, to whose ever-provident care we are indebted for so great a blessing. THE TEAES. From a small gland, over the outer top corner of each eye, and contained just within the orbit, flows iu small quantity a clear liquid, and, by means of the eye-lids, operates as a moist cloth would do over the windows of an ordinary house. This liquid is carried over the whole surface of the eye, and keeps it con- stantly moist and clear, the superfluous fluid being carried ofl" through a very narrow passage, which de- scends from the inner corner, and is conveyed jjy a pipe or duct into the nose. The little gland over the eye is called the lachrymal gland; the liquor which it furnishes to wash the eye is well knoTSTi as the tears, and the tube through Trthich the tears escape into the nose is called the lachrymal duct. If this duct becomes permanently obstructed, which occasionally happens, the tears overflow the eye, and rim down on the outside of the cheek, causing much inconvenience. . To remedy this evD, the surgeon is often obliged to adjust an artificial tube, to convey the fluid to its proper outlet. 126 THE HOrSE I LITE IN. THE EYELIDS. Tlie -^elids are appointed to guard tlie tender organ beneatli tliem from injury in various ways. One of tlieir Uses is to regulate the strong light of the sun when too powerful. If the eyelids were cut off, we should most probably soon become blind. Those people who are in the habit of allowing the full blaze of a lamp, or a bright fire, to shine for a long time in their eyes, run a great risk of doing injury to their sight; though sometimes many years elapse before much mischief ensues, yet ultimately disease, or defective vision, is almost sui'e to be the eon- sequence. Besides veiling the eyes during sleep, another use of the eyehds is to ward off small bodies, such as dust, chips, or stones. The power of the eye itself in this respect is extraordinary. It will sometimes close with such swiftness as to exclude an object, which it is barely possible could have been seen, almost as if it felt the approach before it arrived. It does not, however, always close quickly enough ; for blacksmiths, stone-cutters, cutlers, and many other artificers, have then' eyes more or less injured, from the continual ingress of small particles of stone or iron, which irritate their tender coverings. THE EYEBEOWS. The eyebrows serve as a sort of defence to the eyes, by attracting part of the dust which would otherwise fall into them. They are supposed to THE WINDOWS. 127 assist in sliielding the eyes from receiving too strong a glare of liglit ; tliey are also ornamental, and assist in giving expression to tlie emotions of tlie mind. The eyelashes co-operate with the brows and lids to prevent the intrusion of extraneous substances, and also materially contribute to the beauty of the coun- tenance. Something might be said concerning some other parts connected with this wonderful organ, but the limits of a work like this forbid. REFLECTIONS. I cannot close this chapter without drawing your attention to the extreme care which has been taken to guard this dehcate and valuable structure from injury. Observe its situation — placed in a deep bony socket, and immediately reposing on a thick cushion of fat, thus uniting strength with softness. How ad- mii'ably adapted, too, in a situation for the purposes it is intended to fulfil ; placed in front of the head, it commands an extensive range over the whole face of created things ; it equally surveys the boundless pro- fusion of the earth, and the spacious magnificence of the heavens ; and, comprehending all things, it, as has been elegantly expressed, " Looks up through nature imto nature's God." The eyes of animals, also, bear the same marks of adaptation to the mode of life to which each is ap- pointed as do those of man himself. The organs of vision in carnivorous animals are placed almost in the front of the head, the better to enable them to pour the 128 THE HOUSE I LIVE IN. fiill powers of sight upon the object of which they are in pursuit ; while the peaceful animals of the herhworous class, as the sheep, the hare, &c., have their eyes suited laterally, for the pm-pose of guarding against the danger of surprise, and of more readily avoiding their ruthless enemies. The eyes of serpents, and most reptiles, are placed upon the upper surface of the head ; any other situa- tion would have been inconvenient : everything they require to see is above them, and to look downwards would be an unnecessary privilege, not in accordance with the accustomed operations of nature, which does nothing in vain. The internal arrangements, too, of the eye of various animated beings, is well worthy of investi- gation. Observe the facility with which the iris of the cat tribe nicely adjusts itself to the greater or less quantity of light which is before it. The badger, the fox, and most night-watching animals, have the paint at the back of the eye, which is usually black, of a blue, or other bright colour, the better to reflect all the light which it receives upon the retina. In the eyes of those birds which inhabit groves and woody locaUties, a great flatness of the anterior part is dis- cernible, to prevent any injury to these organs whilst flying through the thick and tangled bushes. The crystalline lens of fishes is found to be of a more globular shape, and of a more dense structure, than it is in land animals ; this peculiarity enabling all the rays of light which come from the water to be more completely refracted. THE WINDOWS. 129 Many other points of difference in tlie organs of vision, in tlie various kinds of animals, adapted to tlieir several uses, might be described, by which a highly valuable lesson would be conveyed; but enough has been mentioned to show the fostering care which a kind Deity has taken of the wants of even the meanest of His creatures. 130 Chapter XIII. TTIE COVERING.— THE DOOES. The doors of the House I live in are the mouth, cars, nose, &c. These I call doors, for reasons which have already been given, and for others which will presently he seen. THE EAK. Some account of this has been given in treating of the bones. The reader has already been told that it is constructed for the admission of sound; that if there were no ear, we could hear no sounds; and that a part of this curious organ lies deep in the bones of the head. There are, in fact, two great divisions of the human ear — the external and the internal. The external ear is that part which we see in the living indi- vidual; consisting of a somewhat semicircular portion, spreading outwardly, the shape of which everybody knows ; and a passage in the middle leading into the head. The external ear — that part which is visible — is made of gristle or cartilage, covered with skin, and is concave, for the better collection of sounds. Such is the curious structure of the eye, that the rays of light from all directions are collected to the seat of vision at its posterior part ; and, in n similar manner, the THE DOOES. 131 stnactmre of the external ear is so arranged, that sound is collected by it towards the passage in the centre. This passage is lined by a membrane of the same texture as the skin, excepting that it is a little thinner; the minute oil glands are more numerous, and the secretion which they furnish is very bitter, ^^'^lat is called ear-wax, is the fluid m an inspissated state, and which sometimes accumidates in so large a quantity as to cause deafness, by mechanically ob- structing the admission of the sound into the internal chamber of the ear. Tliis wax, by its bitter quaHty, is supposed to be useful in preventing the intrusion of insects, they having a great disHke to all bitter substances. There is, however, less danger from insects getting into the ear than is commonly supposed, as they are unable to penetrate far into the head, being intercepted hj the drum of the ear, which extends completely across the passage; yet, by the irritation which they woiild produce, considerable inconvenience might be occasioned. The external ear, as I mentioned, is formed of car- tilage, and is moved by several muscles. You may perhaps wonder what I mean by speaking of the motions of the ear, when we so generally see this organ in a quiescent state. But in truth, in the uncivilized state of man, the ears possess consider- able powers of motion, and the individuals of most savage nations are enabled visibly to elevate and alter the situation of their ears, when rendered necessary by the approach of an enemy, or by other circmn- i2 132 THE HOUSE I LIVE IK. stances. The loss of this power, in addition to the deprivation of some other faculties, is amongst the penalties which we pay for our social condition. The passage from the onter part of the ear is of a somewhat oval form, with a slight curve, and at about the distance of an inch, or an inch and a half, the memhraaa tympam, or drum of the ear, is situated. This is of a texture partly muscular and partly mem- branous — is firm, though very thin, and nearly trans- parent; its shape partakes of the nature of the passage, across which it completely extends. Eeyond the membrana tympani, or cbum, is a chamber, called by anatomists the cavity of the tym- panum; it is about half an inch in width, and has several protuberances on its bony floor, which are more or less concerned in the functions of the part. From it, several passages extend, which communi- cate with the adjacent parts, one of the most im- portant of which is known by the name of the Eustachian tuhe, so called in compliment to its first discoverer, Eustachius; and many other parts of the hmnan frame have taken their names from those of the investigators who first described them in their works. This pipe or tube is about an inch and a half in length, and runs from the upper part of the cavity of the tympanum obliquely forwards to the posterior opening of the nose, which is just above the arch of the palate. It is partly bom^, partly carti- lagmous, and partly membranous, in its structure, narrow towards the ear, and of considerable width towards the nose, even so much as to admit the inser- THE DOORS. 133' tiou of a quill.* Among the little projections wliich. rise from the bony floor of the tympanum, there is one rather more elevated than the rest, dignified by the title of the promontory, and just above which is an orifice of an oval shape, called the fenestra ovalis, or oval window, which is closed by a membrane similar to, but smaller than, the membrana tympani. If you place your finger behind the outer loose cartilage of the ear, you will feel a large protuberance in the bone. TJiis is full of cells of a honeycomb appear- ance, which communicate with each other, and with the cavity of the tympanum ; they are called the mastoid cells, and they assist the sense of hearing by their vibrations. In addition to these, there are other little apertures ; but those which I have mentioned are the most im- portant. Besides the air which is always contained in this chamber, there are four small bones, which I men- tioned in a former part of the work — the malleus, or hammer; the incus, or anvil; the stapes, or stirrup; and the OS orhiculare, which is of a very minute and globular shape. It would be out of place here to * This tube seeins for the purpose of admitting air iuto the tyinparaim, to equalize fUe pressure of the drum, and to allow of fi'ee vibration. Were there no passage of this kiud, and conse- quently no air within the ear, the drum would inevitably be raptured, from the great pressure of the atmosphere on its outer side; even when the quantity is merely diminished, or not properly renewed, in consequence of an enlargement and obstruc- tion of its capacity, arising from quinsy and other disorders, a degree of deafness is frequently the result. 134 THE norsE i lite ik. describe tlic peculiarities of tliese little bones minuteljy a general and correct idea is all tliat can be expected r indeed, were the subject too fully entertained, it would tend to confuse, rather than enlighten, the intricacy of the parts is so great, and the structure sa deHcate. The malleus, then, has a round head, a long handle^ and two projecting spikes branching out from near the neck; the handle lies lengthways across the membrana tympani, and closely adherent to it, haying its head receiyed into a depression of the incus. The incus, being in shape somewhat Uke a molar tooth, with diyerging fangs, has one of them fixed to the edge of the opening into the mastoid cells, while the other, remaining free, receiyes the attachment of the os orhi- culare, which, again imiting with the head of the stcfpes, forms the chain of bones contained in the cayity of the internal ear. All these bones, small as they are — and the smallest of them is much less than a grain of mustard seed — liaye a separate coyering of periosteum, and are united to each other, like the rest of the joints, by capsular ligaments. These bones, also, haye extremely small and delicate muscles connected with them, which, pulling in yarious directions, as may be required, relax or tighten the drum. If the sound to be heard is faint, then muscles for that purpose, pulling the chain of bones in one direction, stretch the membrane ; and if the noise be too powerful, another muscle is read}^ to relax it. The next part of the internal ear for description THE DOOES. 135 is tke lahyrinth, aucl truly so it is named, for liere the intricacies multiply almost to confusion. It is situated still more inwardly tliau tlie structure T^e have been trying to understand, and is formed of several parts, eacli of wliicli, as usual, liave separate names peculiar to tliem. Tliere is tlie vestihule, or j)orcli; tlie cochlea, or sliell; and tlie semicircular canaU. Tlie vestihule is a small cavity, about tbe size of a grain of pearl barley, liaving several openings, one of wliicli receives tlie base of tlie stapes; thus form- ing a communication outwardly with the cavity of the tympanum, while others, opening into the coclilea and semicircular canals, continue the connexion to the most internal parts. The coclilea bears a resem- blance to the spiral turns in some species of shells, or like a cork-screw staircase; it performing two turns and a half around a central pillar, and, though chiselled out of the soHd bono, is yet so delicate, that the paper on which this book is printed is much firmer. The various portions of the cochlea receive many different names, to enumerate wliich would be un- necessary; suffice it to mention, that the whole of the dissection is so difficult, owing to the extraordinary delicacy of this part of the apparatus of hearing, and the intense hardness of the bone which surrounds and closely invests the whole, that many preparations are spoiled before a perfect specimen can be displayed. jSText in order come the semicircular canals. These are three in number, and are named according to their situation. They form three-fourths of a circle in extent, and are of size sufficient to achnit the head of a small 13G THE HOUSE I LIVE IN. pin, all of wliicli open into the vestibule. The difi'erent intricacies of the cochlea, as well as the semicircular canals, are all lined with periosteum, the same as the largest bones in the body, upon which is carefully distributed a soft, pulpy substance, upon which bed lies, guarded by the tenderest care, the auditorij nerve. This nerve is received into the internal ear by a small aperture, and is divided into several portions, which disperse themselves over the canals, the cochlea, and the vestibide. The auditory nerve bears the same relation to the organ of hearing that the optic nerve does to the eye. Both may be considered as the principal part of the apparatus, to which all the others are subservient. Besides these contents of the labyrinth, a small qua. Hy of fluid is foimd, sufficient to keep all the parts of this involved structure constantly filled, and which fluid is of the same nature as the aqueous humour of the eye. If you read this description over very carefully, you wiQ, I thiak, be prepared to understand the mechanism of hearing, for which purpose observe the engraving. First, then, the sound is collected and concentrated by the concha, or outer ear, and is transmitted by the meatus aiiditorius externus, a, to the drum, which is marked b; striking upon the dnmi, it is conveyed along the chain of bones, d e f g, to \h.Q fenestra ovalis, upon the membrane closing which, h, the stapes is adherent. In accordance with the degree of impulse conveyed by the bones, is this little membrane shook, which, by its motion, agitates the liquid contamed THE DOOES. 137 within the labyrinth, and thus acts upon the auditory nerve, which is distributed throughout the whole extent of the semicircular canals, i, the vestibule, j, and the cochlea, k. This agitation of the fluid, greater or less, according to the degree of sound admitted, which is partly regulated by the muscles within the tym- panum, excites the peculiar action of the nerve, and the sense of hearing is the result, c indicates the Eustachian tube, wliich, admitting air to the internal ear, counterbalances the pressure from without. 138 THE HOUSE T LIVE IN. How mucli do we perceive, in all tliis wonderful contrivance, to evince tlie consmnniiite wisdom, as well as the beneficent intentions of the Almighty! How complicated a structure, and yet how admirably adapted to its end! How carefully guarded, too, is this tender organ — deeply imbedded in the substance of the hardest bone, yet penetrable to the shghtest whisper — adapting itself with admirable facility to the loudest thunder, or the roaring of artillery — to the softest breathings of music, or the tender utterance of afiection ! The same adaptation which is observed in the eyes of dilFerent animals to fit them for their several wants, is also apparent in the organ of hearing. Those animals which pursue their prey by night, and are consequently much guided by the sense of hearing, have many more, and much larger, muscles to move their ears than man has. Animals, also, which fly from pursuit, such as the sheep, deer, &c., are possessed of the same advantages. In animals of the whale kind, and most others which dive in the water, a valve is placed within the aperture of the external ear, to moderate the pressure of water iipon the drum; and the aperture itself is of a tortuous shape. Birds and fishes also have pecuHarities, constructed according to the wants of their possessors. THE NOSE. TJiis is a more important door of the human habita* tion than may be at first supposed. All, or nearly all, animal and vegetable bodies are constantly emitting- THE DOOES. 13^ small particles, the quantity of wLicli, when they are received into the nose in its healthy state, can be readily detected. This is undoubtedly one great purpose of this organ, and especially of its curious internal structm*e; and in order that the nature of bodies, of whose particles the air is constantly fidl, may be readily detected, the interior of the nose is of very ample dimensions . The form and appearance of the outer portion are well known. Its upper half is composed of bone covered with integuments, and the lower half of car- tilage, with the same addition, divided into two por- tions by a bony and cartilaginous partition down its middle, the whole of which is moved by various muscles. The nosti'ils run backwards in nearly a hori- zontal position, to terminate in the throat, and their whole surface is lined with a thick spongy substance, closely adherent to the periosteum, and plentifully imbued with a mucous secretion, in the soft bed of which is distributed the innumerable ramifications of the olfactory nerve. Still further to increase the capacity of smelling, and to admit of an enlarged surface upon which the nervous filaments may spread, the bones within the nose contain many irregular shelf-like pro- jections; in addition to which, in each cheek-bone there is a hollow cavity, of size sufficient to hold a table-spoonful of fluid, which communicates with its interior. There are also cavities in the forehead, just over the inner angles of the eyes, wliich in like manner open into the same receptacle. Over the whole of this extensive internal surface is 140 THE HOUSE 1 LIVE IN. Spread the olfactory ncrye, though not to so great an extent in the remoter parts as it is in that which may more properly be called the nose. It is extremely probable that, in a more natural state of life, the organ of smell would be enabled to detect all substances of an injurious natui'e. Most animals are endowed with this property, rejecting whatever is noxious to the species, and, doubtless, savage nations partake more or less of this qualifica- tion: how else would their lives be preserved, sur- rounded as they frequently are with poisonous leaves and roots, and often urged by excessive hunger? Those who do not accustom their nostrils to strange mixtures of scents, to the narcotic properties of snufF, tobacco, and things of that kind, and to spirituous potations, the whole of which immediately injure the organs to wliich they are applied, and indirectly affect the functions of the whole body, may hope to enjoy the sense of smell, in common with other faculties, which naturally dimmish by age, to a much greater extent tjian those who abuse them by indulgence. There is yet another x^nrpose which the nose fuliilg, connected vriih. the voice, and with respiration. If we hold the nose tightly, so as to xn'event the trans- mission of air, and then speak, or sing, we find that the sound is materially altered — in fact, becomes quite dis- agreeable, and of a nasal character. These chambers, then, or hoUow spaces, serve as vaulted arches, through which to reverberate the sound, and modif}^ the tone; of a somewhat analogous nature to the sounding boxes, or boards, placed over the pulpits in churches. THE DOORS. 141 THE MOUTH. Tliis is, in many respects, tlie most important door of the liiiman frame. For,if the nose should cease to per- form its office, we could supply its place, in some measure, by the eye, the ears, and the touch. The same is true of the ear, and even of the eye. But if the mouth were to fail — if this door were closed for ever — there is no substitute. We may, indeed, receive a part of the suppHes necessary to our existence (I mean air) through the nose; but a far greater part could not be received even in this way; and the frame would soon decay, and mingle with its kindi'ed dust. There has, I believe, been but one complete instance recorded, in which an effectual substitute for the mouth was provided. Several years ago, a young Canadian, by the name of Alexis St. Martin, was wounded by a musket-ball, which shot away part of the flesh of the side, and wounded the stomach. When he recovered, an opening was left, somewhat like the mouth of a purse, directly from his left side into the stomach. So complete was this artificial mouth, that notwith- standmg the natural delicacy of the part, food and drink could be introduced into it through a pipe ; and, if care were used, it could be done without pain. The contents of the stomach — the fluid contents at least — which had been swallowed by the mouth, could also be let out at any time; and, indeed, a piece of solid food, if a string was attached to it, could be withdrawn, and re-introduced at will. Some curious experiments on digestion were performed in this way. 142 THE HOUSE I LIVE IN. I liave seen Alexis once myself; and liave witnessed wliat I state. But this is perhaps a solitar}^ case ; I do not know tliat any other case of the kind ever existed, and most probably never will again. The particular structure of the mouth — cmious as it is — is so weU known, that it does not seem to require a particular description under this head. "VATien I come to speak of the apartments, and especially of the furniture and employments of the House I live in, I shaU have occasion to say more about it. It was only necessary to mention it here as a part of the covering, and for the sake of method. 143 Chapter XIY. APARTMENTS AND FURNITURE. Haying mentioned and described some of the doors and windows of tlie House I live in, and spoken of tlie rooms contained in it, it is necessary to call your attention to one essential and important difference between it and buildings erected by liuman means. Tlio rooms in many dwellings are often partially or entirely empty; or at least there is nothing in them excepting a small quantity of furniture, and the air. But excepting a few very small and not very important apartments, all the rooms of my House are completely filled. Such a thing as empty space is hardly known in them. The furniture, or whatever else they contain, at all times completely fills them; for when anything is removed, theu* walls are accustomed to shrink accordingly; and when anything is introduced into them, these walls have the power of gradually 3-ielding, so as greatly to increase the capacity of the apart- ments. It is true that the fiu*niture, &c., in each room, does not so entirely fill it as not to leave place for air, for, as I have already said, all the various rooms of which I am now treating, have communication with the open air, in such a manner that, in a small c(uantity, it can reach them. But it is time for me to speak of these apartments i^ith more particularity. I have already shown you 144 THE HOUSE I LIVE IX. tliat all tlie carities, or passages in the liiimau body wMck open to the air, such as the ears, nose, and mouth, are lined with a membrane of the same quality as the skin, only much thinner. It has its thickish layer, or real skin, on a dehcate cellular cushion; then its soft thin layer of pigment or paint, if this has any existence beyond the commencement of the openings, as at the edge of the lips;* and, lastly, its cuticle. This membrane is not usually called skin, however^ till it arrives at the surface. Its usual name is mucous membrane, because it everywhere secretes on its sur- face more or less of a fluid substance, which is called mucus. EXTERNAL EAE. The passage into the ear, as we have ah'eady seen, is lined with this membrane. But the passage or cavity is so small, that it can hardly be called an apartment. The cavities connected with the nose are of much more consequence. CHAMBERS OF THE NOSE. These, as we have seen, are the hollow, but very irregular passage of the nose itself; the cavity in each cheek bone ; and the cavity in the forehead, on each side of the root of the nose. AH these cavities are real cavities ; for they are situated in hollows in the * Anatomists are not agreed on tliis point. The general opinion is, that this membrane -o'liicli contains the colour, does not exist at all in the internal cavities of the bod v. APARTMENTS AND FURNITURE. 145 bones, and tlierefore the sides cannot fall together and close up the space. All these cavities, moreover, become in some cases the seat of painful diseases. The nose is subject to the polypus — a pear-shaped swelling, with usually a narrow neck. This sometimes renders breathing very difficult; and, if not extracted, has been known to extend further, and become the means of destroying life, and even if it be removed, it is very apt to grow again. Painful diseases also occasionally arise in the cavity of the cheek-bone, which are sometimes mistaken for tooth-ache : the extraction of the tooth which appears to cause the pain, unless its roots extend quite through into the cavity, thus giving exit to the ^jz?5 or matter which has formed, in general affords no permanent relief. Some kinds of headache have their seat in the hollows of the frontal, or forehead bone, near the root of the nose. A very common disease in sheep is known to be produced by worms being contained in these hoUows, which are produced by some of the species of flies depositing their eggs up the noses of the animals, where they are hatched by the heat. The dull lieavy pain so often felt over the eyes, especially when we have what is commonly called a cold in the head, is owing to a slight inflammation of the lining membrane of this cavity. We ought to be cautious in smeDmg substances which cause much pain; and, probably, the too fre- quent use of smelling bottles and pungent scents is, in the end, injurious to the extremely fine and deli- It 146 THE HOUSE I LITE IN. catc lining of all tKc "rooms" connected with tlie nose. Much snuff certainly is, and so is the smoking of tobacco and cigars, and the chewing of opium — practices so common in most Eastern lands, and which are too frequently indulged in, even in this country, by the thoughtless epicure and the fashion- able fop. THE MOUTH INTESNALLY. The mouth of itself is one of the apartments of the human body, and a very curious apartment too. When I spoke of it as being one of the doors, I refen-ed more particularly to the aperture formed by a cleft of the lips, or the external mouth, and not to the infernal or more important part. In this chamber, the entrance chamber of the front door, we find the teeth, the tongue, the palate, and several small glands. This entrance chamber is larger than the hall or space beyond it, from which doors also open into several other apartments. I described the nature and uses of the teeth in a former chapter ; the tongue, therefore, next demands our attention. THE TONGUE. This muscular organ is sup]3orted by a bone of a horse-shoe form, situated in the throat, by means of ■v\ hich it is connected to the various muscles which put it in motion, and which form part of its substance, and hy which also it is attached to the adjacent parts. It APAETMENTS AND FUENITURE. 147 is covered with a continuation of tlie outward skin, tlie upper surface of wkich is thickly covered Ts-ith little eminences called papillce, which, when any sapid body is applied to them, seem to erect themselves, as it were, to meet it, and are a very principal feature in the formation of the taste, — in this it is assisted by the palate, and some other parts of the great cavity of the mouth. THE SALIVARY GLANDS. The bodies which perform the office of secreting the saliva are very numerous : there are three, however, on each side, which are larger, and more essentially concerned in the fimction than the others — namely, the parotid, the suhmaxillary, and the sublingual glands. The principal of these is the parotid, which lies beneath the ear, close to the angle of the lower jaw, a large duct from which, penetrating the muscles of the face, enters into the mouth between the second and third molar teeth of the upper jaw. The sub- maxillary gland is smaller than the last, and, as its name implies, is situated on the inside of the angle of the lower jaw, the passage from which, running through the muscles of the face and tongue, perforates tlie membrane of the mouth, just on the side of the little bridle which is visible under the tip. The sub- lingual gland is yet of less dimensions than the sub- maxillary, is found imder the front sides of the tongue, and has various minute openings at the inner side of the lower gums. All these glands secrete a fluid, called saliva, which k2 148 THE HOUSE I LIVE IN. is of great service in digestion ; tliis, mingling witli tlie morsel imder mastication, facilitates the process, aids deglutition, and prepares tke food for tlie grand opera- tions of the stomacli. PASSAGES TO THE EAR. Further on, in the upper and l3ack part of the mouth, are two doors of considerable size, connecting with the chambers of the nose ; and in the same region the passages begin which lead to the middle cavity of the ear, which has been already mentioned, called the tympanum; but enough has been said about these various apartments in another place. A little behind the root of the tongue is an opening, whose structure has a strong resemblance to what is usually called a trap-doo)\ It leads to the limgs or breathing apparatus, occupying a very large upper apartment of the body, and is one of the most curious parts of the human system. No real gate, or door, set on hinges, and guarded by an active and intelligent porter, could better answer its intended purpose. I have said that there is a strong resemblance here to a trap-door. The passage to the lungs, where it commences, is a mere slit ; though, it is true, it very soon becomes larger. Over this slit is placed a lid or flap, called the epiglottis, not imlike the tongue in shape, but of course much smaller, which fits to the opening as exactly as a trap-door was ever fitted to its frame. It is not usually shut, however, except when we APAETMENTS AND FUENITrKE. 149 attempt to swallow. Then the substance, and the motion caused by this ojDeration, press it down, and close it perfectly tight ; and it is well that it is so ; for if it were not, the food would often drop into the passage to which this trap-door opens, and create great inconvenience, and probably disease, and even death, might ensue. How painful this is, may be remembered from the irritation which is felt when a crumb of bread, or other small body, may, as is commonly said, " go the wrong way !" THE CHEST. Beyond the door the passage greatly enlarges, and proceeds downwards into the chest — that large apart- ment in which the lungs and heart are contained. This apartment is one of the most capacious in the House I live in, and nearly fills the upper story, and is one of those which has no outer doors, neither is it connected with any other cavity or room. It is sup- ported on all sides by strong bony walls, having the breast-bone in front, the back-bone behind, and the ribs at the sides. Above, at the fore-part of the neck, it is of course less guarded with bone, and at the bottom there are no bones at all. It is separated from the second, or lower story, by a strong membranous muscle, called the diaphragm, or midriff, a large muscle, which completely divides the cavity of the chest from that of the abdomen, and is greatly con- cerned in the function of respiration. 150 *HE HOUSE I LIVE IN. CATITT OF THE LUNGS. Tlie trap-door of wliich I hare spoken does not lead directly into this large apartment, but into a bag or sack, called the lungs, which Hes within, and nearly fills the entii'e space. It is divided into two portions, one on the right side, and the other on the left. The passage from the doorway at the top of the throat into the lungs is at first tolerably large, and its projection may be both felt and seen externally. It appears, at first view, to be a long bony tube ; but it is not so, being composed of firm cartilage, almost as hard as bone. Soon after it gets fairly within the chest, it ceases to be cartilage, and becomes degenerated into nothing more than common membrane. This passage or pipe is composed of about sixteen or eighteen cartilaginous rings, varying a little in number according to the length of the neck. Each of these rings forms a large segment, or nearly two- thirds of a circle, which are united to each other and to the channel for the food, which lies behind it, by an elastic ligamentary substance, and the tube remains constantly open for the transmission of au'. At the top of this tube, or, as it is called by ana- tomists, the trachea, is a firm cartilaginous box — the visible projection of which I just mentioned, — con- taining the apparatus for producing the voice ; but of this I will treat more fully in a short time. The trachea having arrived in the chest, divides APAETMENTS AND FUKNITUKE. 151 into two cliannels, like tlie trunk of a tree when it divides into two main branches, and are named the hronchi, one of these passing to the right side of the hmgs, the other to the left. Soon each of these parts divides again, and thus continue to divide and subdivide, until, after a short space, the branches become as nmnerous as the boughs of the thickest tree, and becoming gradually smaller, they at length form a countless nmnber of capillary tubes, which terminate in the cells of the lungs — extremely small in extent, but having free communication with each other. The limgs are two bodies of a soft and spongy texture, which fill nearly the entire cavity of the thorax, or chest, and are each separately contained in two bags, made of the lining membrane of the ribs, and called the pleura. Thus situated, they are de- scribed as the right and left lungs ; they act inde- pendently of each other, and have no communication, excepting by the common passage through the wind- pipe. Each of these divisions is formed into large portions, or lohes, three belonging to the right lung, and two only to the left, the heart in the latter occupy- ing the place of the corresponding lobe on the opposite side. Each of these masses becomes subdivided into lobules, which, gradually duninishing, terminate in the membranous air-cells, which make up the chief substance of the organ ; the whole of which is somewhat conical in shape, and in colour approaches to a blueish-grey. I will now proceed to speak a little concerning the production of the voice. 152 THE HOUSE I LITE IN. That part of the throat-pipe which is principally concerned in the formation of the voice, is called the Jarynx, and is situated towards the upper part of the tube, and becomes veiy visible when the head is thrown backwards, forming an obvious projection — more particularly in males. This larynx may be compared to a box, and is formed of several pieces, which are made of cartilage, and are five in number. That which composes the upper and fore-part, being by far the largest, is called the thyroid cartilage, or sometimes the shield-like cartilage, from its supx^osed resemblance to that piece of armom\ From its upper and posterior corners, a hgament extends, which imites it with the bone of the throat, [os hyoides,) before mentioned. At the bottom of this portion of the larynx another cartilage is placed, the cricoid ^ and there are two others at the sides. In this box are contained four Hgamentous cords, which are called the vocal ligamenis, and the opening which is left between them is th'e glottis, an opening appearing hke a triangular sHt, widest at the back part ; upon the due expansion or contraction of which, aided by the operation of muscles, the tone of the voice depends. When the chink of the glottis is narrowed, the voice is acute or shrill; and when the chink is wider, it becomes grave or low in equality. I have yet mentioned only four of these cartilages, the description of the fifth is still due. This, knowu by the name of epiglottis, is situated at the top part of the box, is of a very elastic nature, and of a somewhat APAETMENT8 AND TUENITUEE. 15B oral form ; being attacliecl to the root of the tongue, it is pressed do^^m. by the action of that body during the efibrt of swallo-^dng, shutting up the glottis, and com- pletely defending it from intrusion of the food. It also serres to regulate the current of air into the box. This is the very same frajj-dooi' of which mention was made a few pages back. THE FOOD-PIPE, OE ESOPHAGUS. The back part of the mouth, where the food-pipe, or passage to the stomach, commences is funnel-shaped, but the passage or food-pipe itself is tolerably regular in its form. This muscular canal proceeds down- wards, close upon the spine, behind the wind-pipe, and at the back of the heart, till it has fairly passed the apartment of the chest, and then it enters the borders of the great apartment below, which occupies the lower story of the building. Wlien it has reached the confines of this apartment, the passage enlarges into what, keeping up the same analogy, may be called a spacious saloon. THE STOMACH. The human stomach, resembling in shape the Scotch musical instrument called the bag-pipes, lies with its greatest length directly across the body, immediately imder the diaphragm, just within the edge of the ribs, and is composed of muscular and membranous coats. The place where the gullet enters is called the cardiac orifice, and the termination or outlet of this 154 THE HOrSE I LIVE IN. spacious saloon is named the p_yloms, or pyloric orifice, a most important situation, tlie meaning of wliich TTord will be explained hereafter. This viscus is abundantly supplied with blood-vessels to fit it for the grand offices of life which it is destined to perform, and its capacity, when moderately distended, is about two or thi'ee pints. '^^M^^M In this representation of the human stomach, the letter a represents the lower part of the gullet or food- pipe ; h, the upper or concave surface of the viscus ; c, the left, or large extremity ; d, the end, or small ex- tremity ; and e, the pylorus. APAETMENTS AND FUENITUEE. 155 THE INTESTINES. From tlie pyloric extremity of tlie stomacli, tlie intestines commence. These consist of a long cylin- drical canal, which, winding about in different direc- tions to the extent of about six times the length of the whole individual, at last terminates in the inferior outlet of the body. The largest proportion of the entire abdomen, or great internal cavity of the hu- man frame, is filled up by the intestines, which are divided into large and small, according to their size. The small intestines form the commencement of the passage, the upper portion of which is named duodenum; tliis, first making a short turn upwards, and a Httle backwards, turns upon itself in a down- ward direction, and towards the right side. When it gets so low as to be opposite the lower side of the right kidney, it turns to the left, and crossing the spine, receives the name of jejunum, so called from being generally found in an empty state ; thence, forming numerous convolutions or folds, it at length acquires the appellation of lUum, which name it retains for about three-fifths of the length of the whole small intestines. When the ilium has performed a certain number of convolutions, and has arrived at the top of the right haunch-bone, or os ilium, it enters into the first of ihQ^ 156 THE HOUSE I LIVE IN, LAEGE INTESTINES. Tlie colon is the first portion of tlie lower or large bowels which unites with the upper, and this junction is effected m a verj'^ curious manner — a moveable valve or flap being placed across the opening. Just under the part where the union takes place, the gut dilates, forming a bag, or pouch, with its concavity downwards, three or four inches in length, and about the same in width, which lodges in the cavity of the haimch-bone on the right side. This pouch has received the name of ccBcum, and from it projects a portion of bowel, about three or four inches in length, sometliing like the finger of a glove in shape, though much smaller in diameter, called appendix vermiformis ccaci, and which, being impervious at its lower end, nothing can pass through it. The colon, continuing its course, in dia- meter much larger than the small intestines, ascends upwards on the right side, as high as the top of the kidney, and crosses the abdomen just under the stomach, and over the duodenum, imder the name of the transverse arch of the colon ; from thence, turning a little backwards, it descends down the left side, and forms two convolutions, in shape like the letter S, being the sigmoid Jlexiire, and then, assuming the name of rectiun, continues in a straight direction to its outlet. Lying in front of, and spread out over the intes- tines, and continuing from the stomach, as seen in the plate at g, is a fatty membrane ; this is called the APAETMENTS AND FUENITUBE. 157 omentum, or caul. This membrane also dips between all parts of the bowels, enveloping them as in a bag, under the general name of peritoneum, and serves as a medium of communication from the blood-vessels of one portion of the intestines to other parts of the same canal. It also contains glands which are sub- servient to the nutritive processes going on : and it is also supposed, by its thickness, to assist in pre- serving the proper temperatm*e which is necessary to be maintained for the performance of the highly im- portant functions which are here almost constantly in operation. GALL-BLADDER. Under the large lobe of the Hver is situated the gall- bladder, which, as its name impHes, contains the gall or bile. JSTot far from the stomach, there enters from it into the intestines a duct, or pipe, which conveys the bile to the chyme, or food which has undergone the action of the stomach, and materially assists in the nutritive process. The gall-bladder is about as large as a man's thmnb, or sometimes larger. In the same neighbourhood is the pancreas or sweet-bread, between wliich and the main passage through the body there is also a communication, though its use is not precisely ascer- tained. In this lower story of the House I live in — the abdomen — there are several other apartments besides those I have already described, some of which open externally, and others do not, but which need not 158 THE HOUSE I LITE IN. be Tciy particularly specified. I must now describe another class of apartments — those which do not have communication with the air. One of these has already been mentioned — it is the cavity of the chest. Another is the cavity of the cranium, or bones of the head. Others still are in the central parts of the brain, or contents of the cranium. The last, but most curious and most important, which I shall describe, is the great cavity of the circulation; I mean the circulation of the blood. APARTMENT OF THE CIRCULATION. This is a larger apartment than many would first suppose. It must of course be large to contain, as it does, twelve or fifteen quarts of blood. It may be compared to two gi*cat underground reservou's, formed by the imion of thousands of large or smaller (but most of them very small) streams, running side by side with each other, and in an opposite direction ; and which, having no communication with each other in their course, so they have no outlet — at least none of any considerable size. To talk here about the circidation of blood, when my professed object is to describe a chamber, may perhaps seem out of place ; but to me it appears indispensable. For such is the irregularity of this circulatory apartment, that it is next to impossible to describe it in any other way than by telling you some- thing of its course and its contents. But I wiU be very short. APARTMENTS AND FrEXITUSE. 159 Yon may first think of all these streams as if they were filled with blood ; and afterwards, imagine them as if emptied of their blood, and hollow. In the latter case, if a quantity of Hquid, such as water, or melted wax, or even blood, were thrown into the cavities of the heart by means of a syringe, and if considerable effort were made, the liquid thrown in would soon run into all the large, and even the small, branches of this multiplied channel, or apartment, and fill it entirely ; and the amount it would contain, as I have before intimated, would be in an adidt about three or four gallons, or equal in quantity to a common-sized pail- fidl. Thus you see that, though the apartment of the circulation is strangely irregular, it is nevertheless a very spacious apartment ; and has been considered as almost, if not quite, equal to the whole cavity of the chest, in which the lungs and heart are placed ; and not much inferior, in point of size, to the cavity below it, that of the abdomen. But I must tell you here something more of that part of the circulatory department which lies in the heart itself, or in what may be called the little sea or lake, into wliich all these imseen rivers constantly poiu" their various crhnson floods. The heart has really four cavities within it, two on the right side and two on the left. The blood which has been sent into all parts of the body tlu*ough the arteries, returns to the first or upper part of the right side, the auricle, and then passes through into the right ventricle. As soon as this ventricle is full, it 160 THE HOUSE I LIVE IN. contracts, and presses its contents, tke blood, into a great artery, called the pulmonary artery, wliich carries it to all parts of the lungs, whence it comes back into the left side of the heart ; first into the left aui'icle, and next into the left ventricle. From the latter it is discharged, when the heart contracts, into the great artery, or aorta, and distributed all over the body. These four small cavities in the heart together hold, in an adult, about three or four ounces of blood. The length of an adult heart, measured on the outside, is about five inches, or we may say, in general terms, that it is about the size of a man's fist. A great deal more is to be said about the heart — its cavities, structure, motion, situation, &c., but I have mentioned all that is necessary, in this pai't of the work, to give a general idea of the circulatory apart- ment. CHAMBERS OP THE BEAIN. Before I describe these, I must say something more of the brain itself, though I have partly described it in a former page. Here is a picture of some of the bones of the craniimi — those M'hich contain the brain. It is the same plate which you saw at page 56, but, for the sake of convenience, I have introduced it again in this place. APARTMENTS AND FUENITUEE. 161 \ The brain, tlieii, is a somowliat soft, pulpy mass, which, \Yith its envelopes, fills up the entire cavity of the skull, and in colour and general appearraico is not unlike those of domestic animals, but considerably larger in proportion to the size of the body. To possess a more accurate idea of its exact size, however, take a piece of twine and tie it round your head, from the bottom of the eye-brows or edge of the forehead to the nape of the neck, letting it come down close behind the root of the ear. JSTow all above this string, except the skull itself, and the skin, flesh, hair, &c., is brain ; and the whole covering, bone, fiesli, skin, &e., can hardly be more than half an inch thick iu the thickest part, and in some places scarcely a quarter of an inch ; so that there is a very considerable Cjuantity of brain, as you perceive. There is even a liitle brain below the Hue of the string, but not much, unless that may be called brain which runs dov.n into the hollow cavity of the spine, like a large whitish cord, and which I have ah'cady told you is the spinal marrow. L 162 THE HOUSE I LIVE IN. The substance of the brain is nsually described by- two names ; tlie upper and front part, wbich is by far tlie largest, is termed the cerehrum, and tlie posterior and lowest portion is named cerebellum, botb of wLicli, being united togetlior, are closely and firmly enveloped in three distinct membranes or coats ; and tlie whole weight of which, m an ordinarj^-sized man, is about three pounds. The cerebrum is divided by a prolongation of the outer and strongest covering of the brain, for a short distance down its perpendicular extent, mto two por- tions, or hemispheres, which are of a somewhat oval shape, and convex on their upper surfaces ; at its lower part it separates into six lobes, two in the front, two at the sides, and two at the back part. The whole surface of the brain is divided into several fissures, which are made up of a multiplicity of convolutions or windings, into which the thiimest of its coverings everywhere dips, and, from its protecting nature, continued presence, and delicate texture, is named the ^9/« mater, or tender mother, in contradis- tinction to which the outward, tough membrane last spoken of, is called the dura mater, or firm mother. Of all the intricate parts of our wonderful frame, none is more apparently complicated, and the functions of no part so little understood, as the structure now under consideration. Anatomists have at all times- made it a peculiar object of study, and although the- greatest research, the most extensive experiments, and the most imtiring industry have been displayed by its cultivators, yet victory has hitherto eluded their grasp. APARTMENTS AND FURNITURE. 163 From the boundless labour wbich bas been bestowed upon this part of the internal economy, great accuracy of anatomical detail has been acquired, and a profusion of names given to its various differences, real and imaginary, but from a sound physiological view of its operation we seem as far remote as ever. That it is intimately connected with sensation, motion, digestion, in short with every function in the body, by means of its nervous communications, we are sure of; but how these results are effected, and from what special part of the cerebral mass each derives its influence, we must remain content at present to be unable to explain. In an organ intricate and so delicate as this is, it would be absolutely impossible, without the aid of many plates, to convey any idea of its separate parts, and even with their help, the general reader woidd glean but little information. It will be suiEcient here, in addition to what has been described, to mention that the brain is divided throughout its extent into two substances, of a somewhat different appearance, termed the cortical and the medullary portions, of which the former is situated the most outwardly, and is of a greyish colour, and the latter approaches more to white. It is from this last — the meduUary portions^ that the different nerves take their origin. Besides the larger portion of the brain, tlie cerebrum, above described, there is the cerebellum, or, as it is sometimes called, " the little brain." This is situated in two cavities in the base of the occipital bone, or that bone of the skull which lies at the back and lower part, and is in size about one-sixth part of the brain, l2 164 THE HOUSE I LIVE IN. properly so called. It partakes of tlie same general appearance as the rest of the structure, but is appa- rently less complicated. As we haA^e been pursuing an analogy to the chambers in a dwelling, the parallel may also here be carried out, for the brain contains several cavities, or, as they are called, ventricles, of which there are four, though some anatomists also add a fifth. These, in the natural size, are exceedingly small, yet when, by the operations of disease, they become distended, they enlarge to an enormous size, and being filled with an aqueous fluid, they exliibit that formidable malady commonly known as "water in the head," or liydrocephalus. To what particular purposes these ventricles are subservient, we cannot say ; but without doubt they have specific duties allotted to them. One of the cliambers in the interior of the brain was supposed, by the philosopher Descartes, to be the particular residence of the spiritual inhabitant ; and many other parts, by fanciful speculators, have been assigned as the seat of the soul. These theories have long since been abandoned as untenable ; and I can assure the reader with certainty, that my immortal spirit does not reside exclusively in any one part. It lives in all parts of the brain, spinal marrow, and nervous system in general, and they may all be considered as simply an extension of one great and important central communication, which forms the connexion between the material organization and the mental phenomena. APAETilENTS AND FUB]^ITITSE. 165 NEEYES. From tlie base of tlie brain, niuo, or, as some say, ten, pairs of nerves take tlieir origin ; of wliicL. that pair lying towards tlie front of the head is named the olfactory nerves : these, piercing the skull through a number of small apertures, di\'ide and subdivide into innimierable minute filaments, which distribute them- selves over the whole interior of the nose, and form the organ of smell. The second jyair, which he behmd the last, are thicker and rounder in sulistance, and proceed towards the eyes, mider the name of optic nerves, to form the peculiar seat of vision, the retina. The third pair, smaller than the last, are distributed to the muscles of the eye-balls. The fourth pair come next in order; these are the smallest trunks of nerves in the whole body, and are chiefly dispersed over the superior oblique muscle of the eye. Proceedmg still backwards, we find the largest nerves in the brain, the ffth pair, or trigeriiini, each having three separate branches on each side. The first of these branches ramifies over the forehead, upper eyelid, and nostril of the same side, and, pene- trating the eyeball, forms the minute ciliary nerves ; the second branch supplies the upper jaw, the palate, and the contiguous parts, while the third branch is found meandering among the muscles and glands of the lower jaw. The sixth pair chiefly suppHes one of the muscles of 166 THE HOUSE I LIVE IN. tlie eyeball. Next in the backward order is a very important nerve — the seventh pair — which is composed of two portions, called the portio mollis, and the portio dura. The portio moUis, entering into the internal part of the ear, splits into several divisions which form that soft and pulpy nervous texture which I have before explained as lining the several parts of the labyrinth, and is the medium by which sounds are received. The portio dura sends its branches to the muscles of the internal ear, the parotid gland, the muscles of the face, and the adjacent neighbourhood. The eighth pair is another nerve of great import- ance in the human economy. After sending twigs to the back part of the throat, root of the tongue, &c., it descends down the neck in common with the main artery, (the carotid,) and, joining the great sympathetic nerve, is distributed to the substance of the heart. The ninth pair are the furthest back of any which have been mentioned, and principally supply the tongue, and the muscles connected with it. There is yet another influential nerve, which, though not, strictly speaking, ha\'ing its origin directly from the cerebral mass, is yet so nearly connected with it, that its consideration ought to come in this place. I mean that nerve which, from its commimication with almost aU the rest of the nervous system, and from the magnitude of the office which it fulfils, is truly described as the great sympathetic. This nerve, being formed by filaments from the fifth and sixth cerebral nerves, and uniting ^ith a branch from the eighth, and also with several of the nerves of the neck, extends APARTMENTS AND FURNITURE. 167 downwards by the spine, enters the cavity of the chest, and afterwards of the abdomen, where, distributing itself to all the viscera contained therein, it associates all the several functions, and conveys their united sensibilities to the brain. It is by the special operation of this nerve that disturbances in the function of one particular organ are often painfully felt in remote parts, they, as it were, sympathizing with the afflicted spot ; hence the name great sympathetic. Next in order come the spinal nerves. In the sides of the pile of bones called the spine, ai'e apertures all along from the top to the bottom, which are formed by notches in each vertebra. There are also six or seven pairs of holes, similar to these, through the sides of the strong bone below, on which the spine stands, and through each of the whole of these run large branches of the spinal marrow. These branches or cords are whitish, like the marrow itself, and like the brain, and their number is about thirty on each side, parting into branches almost innumerable, and distributing themselves to nearly all parts of the body. The nerves divide as minutely as do the arteries and veins, which is proved by the fact, that we have feeling almost everywhere within us. A puncture with the point of the smallest needle gives us pain, but this could not be unless there were nerves in the part which is woimded. They are so numerous, that if there were any way of destroying all parts of the human body, excepting the nerves, without in the slightest degree injuring or displacing the 163 THE IIOrSE I LIVE IN- latter, tliey would present a large mass, generally resembling in shape the complete and perfect living body. The arteries — the vessels which carry blood from the heart to all parts of the body — if all else vrere destroyed, would present the same appearance ; and so also of the veins. There is, however, one important difference between the nerves and the blood-vessels. The latter are all hollow tubes, but the nerves are not known to be so. Some have supposed that the little white pulpy threads or fibres of which they are aU made up are hollow ; but this is not generally admitted. Now the uses of these nerves are to convey sensation from the various parts of the body to the brain, which may be considered as their common centre. I have just told you that nine pairs of nerves emerge from the base of the brain. jN"ow the uses of these are to convey the various impressions of sight, hearing, smelhng,. and some other functions connected with the eayression of the countenance. If by any accident, disease, or surgical operation, the communication between the extremities of any one of these nerves and its connexion with the brain were destroyed, the function which that nerve performs, whether of seeing, hearing, &c., would be almost entu'ely suspended. In like manner, the thirty pairs which are connected with the spinal marrow, from its junction with the head to its termination at the pelvis, carry sensations of pleasure or of pain ; and also give the power of motion to the muscular parts of the body. To effect these purposes, each of the larger nerves. APABTMENTS AND FUENITUEE. 169 tliough apparently single, are dmded at their roots into two portions ; one of tliem is the medium by which the impressions of feeling &e. are communicated, and the other serves the purpose of giving motion to the muscles it supplies ; and these two portions of the nerve are hound up, as it were, so intimately together, during the whole of their course, that no difference can be perceived in them. Here, then, we see the reason why, in some diseases of the human frame, the power of motion is destroyed in a part, while feeling and sensation remain entire; and why the voluntary movements are not at all affected in others, when the capability of receiving pain, or the impression of touch, are annihilated. 170 Chapter XIV. FURNITURE OF THE HOUSE, AND ITS USES. We now come to tlie furniture of the House I live in, and its various uses. This will make a long, but, I trust, an interesting cliapter. Here, however, our similitude begins to fail ; for wliile the House I occupy, like all other houses, is liable to waste and decay, there are in the human habitation certain pieces of furniture — machinery, perhaps I should say — by means of which, under ordinary circumstances, repairs are constantly going on, equal, at least, to the waste. But in no ordinary dwelling can any such process be found. All dwell- ings can indeed be repaired, but usually by external aid, and not by any operation of their own from within. The habitation of the human soul is kept in repair principally, by means of the rivers which run through tlie circulatory chamber, and it was this fact that made it necessary for me to dwell so long upon this apart- ment m the previous chapter. THE BLOOD. There is nothing in the whole imi verse which so much resembles the economy of the human body, showing the means by which its constant waste is sup- plied, and the whole kept in repair, as the manner in which water is conveyed to the surface of the earth. FURNITrEE, AND ITS USES. 171 Evaporation and tlie growth of plants, with the de- mands of the animal creation, are constantly wasting and drying up the soil : but there are numerous hidden streams, some of them very small, that wind their way in almost every direction, and continually furnish new moisture. It is true, there are also large streams which appear on the surface, very different to what takes place on the outside of the human body ; neither is it to be forgotten, that the earth is watered in part directly from the atmosphere. Yet, with these deductions, there is still a general resemblance between the two great processes. The one constantly recruiting the wants of a world: the other supplying the demands, and repairing the waste, &c., of what, for the sake of its near relation to the immortal inhabitant, is worth far more than any known globe. PREPiLEINa THE BLOOD. But how is this blood, flowing through its tens of thousands of crimson streams, prepared and supplied to the human body ? for it must be first made before it can be supplied. Indeed, a most curious and really wonderful process is this, and one which demands a particular description. MASTICATION, OE CHEWING. I have aheady told you about the teeth, their number, their uses, &c. They are principally de- signed for breaking down and grinding the food. 172 THE HOUSE I LITE IN. tliG material from wliicli the blood is to be made ; for the great Author of our frames has so ordered, that after a certain degree of waste has taken place in the system, a feeling of necessity for its reparation arises within us, which we call hunger ; and in the gratifica- tion of which much pleasure is experienced. And in order to gratify that hunger properly, and accordingly to recruit the waste of the body, which is continually proceeding, there is that duty for the teeth to perform, of which I have just spoken. But while the teeth are breaking down the food into smaller pieces, the salivary glands, described in another place, are continually secreting, and pouring through small tubes into the mouth, a quantity of saliva, just sufficient to moisten, and render the mass somewhat of a pulpy consistence : the other little glands also, lying imder the tongue, assist in this work. When the food is beaten fine, and sufficiently moistened, it is gathered together upon the tongue, and by a series of curious movements, which I have not room in a work like this to explain, it is pushed along beyond the root of the tongue to the top of the gullet, or food-pipe, whence, by muscular action, it is conveyed downwards into the stomach. In its passage towards this receptacle, it passes directly over the trap-door of which I have ah*eady spoken ; and were not this little flap most accurately fitted, and most ingeniously contrived to effect its pui-pose, we should often be in the greatest danger of suf- focation ; for in speaking, coughing, or laughing. FUENITUEE, AKD ITS USES. 173 •while tlie food was in tlie act of being conveyed into the stomach, it might perchance descend into the air-passage, or trachea. TEAP-DOOE. It is true that this door usually closes, when any substance approaches, almost as quickly as I for- merly told you does the eye, when anytliing comes too near to that organ ; but it is also true that, as in \h.e case of the eye, it does not always close quite soon enough, and substances actually do fall into the trachea. When this accident happens, great irritation and coughing is produced, by which, at length, the offendmg body is frequently expelled. When this speedy dislodgement does not take place, the coughing generally subsides, and if the substance is a morsel of bread, or other food, it shortly dis- solves ; but if it be of a hard or tough nature, as a piece of bone or wood, it usually creates great pain and inconvenience, and, unless it can be removed by mechanical aid, or by a surgical operation, often ends in death. TMiile wilting this cliapter, I have read, in one of the medical journals, of a little girl, five years of age, who, in playing wdth a brass nail, was so unfor- timate as to liave it fall into her windpipe. It pro- duced a little coughing, and then all was quiet, and the parents and friends thought all danger was over. More than a year afterwards, on taking cold, there came on a severe cough, with hectic fever, night per- spirations, and bleeding from the mouth : she died 174 THE HOUSE I LIVE IK. of a rapid consumption ; and, on opening lier body, the brass nail was found imbedded in lier lungs. I hope that every young person who reads this account, will avoid holding nails, pins, buttons, and other such things, in the mouth, as well as all laughing and talking while eating ; for it is at the least always dangerous, and may probably prove fatal. When the food is faii4y beyond the tongue, and has passed the little trap-door, it goes into the top of the food-pipe, as into a sort of a funnel-top. Eelow this, the pipe becomes smaller ; but if we eat and swallow slowly, not so small but that the food will pass readily ; but if we do not properly masti- cate our food, or if we swallow it too rapidly, it is sometimes retained in the passage, causing great inconvenience, and even recjuiring an operation to dislodge it. Many individuals have very nearly lost their lives by a large piece of meat, or other unchewed substance, remaining in the gullet, and only by sur- gical aid was the danger averted. DIGESTION. The food, however, arriving in the stomach, remains a short time, gradually softens, and becomes con- verted into a greyish or whitish pulp, called chyme; the formation of which is materially promoted by a fluid called the gastric juice. This fluid does not travel a long way through pipes, like the saliva, but seems to ooze, as it were, from the inside of the stomach in large drops, as you have seen the drops FUBNITUEE, AND ITS USES. 175 of water or sweat from tlie forehead of a laboiiriiig^ man in a liot day: and tliis process is called sect^e- iion. Wlien the outside of the mass which is in the stomach — that part in contact with its sides — Le- comes softer, it is slowly conveyed, hy a curious motion of this receptacle, to its right and lower extremity, which I have already told you is called the 2>ylori>s, by which term is meant the door, or outer gate of the stomach, or, as some call it, the door-keeper. It may well be called a door-keeper, for it really does seem to exercise a sort of choice ; for, if any- thing presents itself there which is not proper to be conveyed into the system, or not well adapted for making blood, it does not, for some time, suffer it to pass ; though, after the substance has repeated its efforts a great many times, it appears to yield, as if to importunity. True chyme, made of good and proper materials, it never refuses, but suffers it to go at once into that portion of the intestines which joins to the stomach, called the duodenum. The oiitside of the mass of food in the stomach having been subjected to the process just named, that portion immediately under it is submitted to the same treatment, and so on, till the centre portion is brought into contact with the gastric juice, and the whole converted into grey, pulpy fluid. FOEMATION OF CHYME. AiTived in the duodenum, it becomes a still more perfect chyme, and is gradually mixed with a bitter fluid, the hile, which comes through a small pipe^froiu 176 THE HOUSE I LIVE IN. the liver, and also witli a liquor resembling saliva, pro- ceeding from the _pancrcas, or, as it is popularly termed, stceet-hread. The liver, as I before described, is a very large viscus which fills up a considerable portion of the abdomen, principally on its npper and right side — and the pancreas is a gland lying in its neighbourhood, close upon the spme. The chyme being mixed with the secretions from these glands, passes slowly along, spreading itself over nearly the whole of the internal surface of the intestines ; always, however, in the greatest abim- dance in the duodenum, and a few feet of the intes- tines beyond it. LACTEALS. !Xow there is in the himiau body a set of minute vessels called lacteals, which begin in great numbers, as if by roots, from the inner sides of the intestines, and gradually uniting as they proceed, at last all unite together mto one principal trunk, or main pipe, which might be compared to the stem of a tree, with its branches. These vessels seem to begin on the inside of the duodenum, and the other intestines, with open or funnel-shaped mouths, with which they suck iip the finer or better parts of the ch3mie Avithin them, and which, during the operation of being removed, is changed into a pearly-coloured or milky fluid, called cliyle ; and this process is called ahsorption. The chyle, after being absorbed, is conveyed along FURNITURE, AND ITS USES. 177 in the minute vessels it begins with. : they, uniting with others, like small streams with larger ones, continually add to each other's size, until they all at length meet in a common trunk or receptacle, upon the first or upper rertebra of the loins. From this receptacle, one or more pipes, or ducts, cany the chyle which is con- tained in it upwards, on the right side of the spine, towards the top of the left shoulder, where, meeting the great vein which brings back the blood from the left arm, it empties its contents. The cliyle thus mixes with the blood, which, immediately descending into the heart, passes through the lungs, to undergo a pecu- liar and important process, which will be afterwards explained. Although performing so principal a part in the animal economy, yet the main duct, (and there is frequently but one,) called the thoracic duct, is in size extremely small ; although loaded with all the nutritious materials for repairing and re-invigorat- ing the entire body, yet it is only equal to the dimen- sions of a very small quill. ABSORBENTS. There is yet another series of vessels which are found in almost all parts of the human frame, both internal, among the viscera — and external, among the muscles and skin. These are very extensive, of minute size, and are situated in great numbers at the inner parts of the thighs and arms, at the neck, and in the groins. They are much the same, in arborescent M 178 THE HOUSE I LIVE IN. appearance like tlie blood-vessels, only very mucli smaller, indeed seldom visible to the naked eye, ex- cepting when made promment by disease. These vessels are called Absoebents, the office of which is to absorb or suck up any particles not wanted in one place, and carry them back into the blood, to be sent round again by the circidation, to be used where they are really wanted; or else to be expelled from the body. The liquid which is thus found in these vessels is called lympli; it is of a pale red colour, but entirely different from blood. Besides having the general name of absorbents, these vessels are sometimes called lymphatics. The chyle, in its pure state, is similar to the blood, excepting in colour. The little globules, which swim in the blood, and are the cause of its colour, are numerous in the chyle; but instead of being red, as in the blood, they are white. I have said that the c-hyle, in its nature, is like the blood ; and concerning the nature of the latter, I shall have occasion to say more presently. "^^Tiether the chyle is changed to a red colour as soon as it is mixed with the blood, or whether the change docs not take place till it has passed with it through the lungs, we can better judge, perhaps, when we come to speak of the blood, and the changes it un- dergoes in those organs. Having thus traced the food, or raw material, through the whole of a most wonderful manufacturing process, till chyle, and perhaps blood, is formed from it, it may be well to pause, and consider, for a few moments, the FUBNITUKE, AND ITS USES. 179 different materials from which this most important fluid is prepared. MATERIALS FOR BLOOD. The great Creator has so formed this wonderful apparatus, that it has the power of forming chyle from almost every substance, either m the animal or vege- table kingdom. Some create more, others less : some make it of excellent qnahty ; others of a very inferior nature ; from some, it is formed very rapidly ; from others, very slowly: some things, in the process of digestion, give out a great deal of heat ; others, very little : lastly, some produce great excitement and dis- turbance of the stomach and other organs, while others produce hardly any disturbance at all. As a general rule, those thmgs which produce the least derangement of the digestive and the other organs of the body, as well as give out the least heat, make the best chyle and the best blood, and are, of course, most adapted to our use. It must be observed, however, that much depends upon habit ; and that a substance which is naturally rather inferior to another may, by habit, be rendered for a time even more useful. Among the best materials for subjecting to the process of digestion are, bread made of wheaten flour, from one to two days old ; puddings made of rice, sago, tapioca, or flour ; potatoes, and other garden vegetables, with the addition of plain meats, fish, eggs, butter, &e., and fruit. For inf\mts, who have no teeth, milk, as is well known, forms the best 180 THE HOUSE I LITE IN. chyle, and creates the best blood. All thes^e sub- stances may be better or worse, according as they are well broken down and masticated with the teeth, and didy mixed Avith the saliva ; and also according to their quantity. The best of them, if not well masticated, makes but an inferior sort of blood ; and those AA-hich are the least nutritious, if duly sub- jected to the action of the teeth, make chyle, and blood which answers, in a great degree, the purposes of health. So of quantity : those which are even excellent in their nature, are not so advantageous if taken in too great abundance. Spirits make no chyle or blood at all ; wine, cider, ale, beer, coffee, and tea, very little. Besides this, they contain, more or less, qualities which not only do no good, but are positively hurtful. Even water can hardly be said to make either chyle or blood ; but then it quenches thirst, supplies the waste caused by evaporation, and answers many important and even indispensable pur- poses. I am now to tell you about the blood ; — first, what it is ; secondly, its uses ; thirdly, how it is kept in a good and healthy condition. NATURE OF THE BLOOD. If we open a vein with a lancet — as you know sur- geons often do — and draw out a quantity of blood into a bowl, or any other vessel, and let it stand in the open air, it soon begins to clot, or thicken, or, as it is usually called, to coagulate. FrENITUKE, AST) ITS t^SES. 181 From tlie surface of this coagulated part, a yellowish watery fluid oozes out, in numerous small drops, which gradually increase and imite, till, in a short time, there is more of this thin liquid than there is of the thicker coagulated part. This M-atery part is called the scrum. If we take the coagulated part of the blood, and wash it thoroughly, though carefully, we may divest it of nearly all its colouring matter, and leave it white. This white substance is called Jihrine, and strongly resembles the fibrous or thread-like substance, of which I have already told you the muscles are formed. The colouring matter, which is washed out, consists of small roimd or cjlohular particles, Avhich, before the blood coagulates, float in it ; but in the act of coagu- lation become entangled in the fibrine. You have also been informed, in another place, that these globules exist and float in the same way in the chyle, before it mixes with the blood. In the chyle, however, they are colourless. What gives the colour to these globules in the blood we arc ignorant of: some suppose it is the iron, or rather phosphate of iron, which, as is well known, exists in the blood in a small quantity ; of which Dr. Good thinks that there are about three ounces con- tained in an adult. Sulphur also is foimd in the blood ; but its exact proportion is not known. Thus we see that the three principal ingredients of the blood are the colouring matter, the fibrine, and the serum. The serum is principally albumen 182 THE HOUSE I LITE I^^ and water ; tliougli it also contaius, in small propor- tion, besides sulpkiir and iron, a great variety of sub- stances, especially tlie alkaline salts. Albumen is a substance "wliich may be considered as resembling the white of an egg : for the latter is almost entirely com^- posed of it. USES OF THE BLOOD. All parts of the himian body, whether solid or fluid, and whatever may be their appearance or structure, are formed from the blood. I have told you how this fluid is sent out by the heart to all parts of the system, even to the bones ; and I have also said a few words about the saliva, and the gastric juice, and the bile, and have called them secretions. It may be necessary to observe, in this place, that by the word secretion, as used in this sense, is meant something formed from the blood. Kot only the saliva, the tears, the gastric juice, the pancreatic fluid, and the bile, are secretions, but the mucus which is everywhere found in the mucous membranes of the body, the water which is in the brain, the lungs, &c., in short, whatever fluid is met with in the bodj^ — in all parts of it, excepting the ahmentary passages — is formed from that common reservoir, the blood ; and all these fluids are called secretions. You will perhaps ask how secretion is efiected : sometimes it is by the intervention of glands, and sometimes without their aid. A gland is a soft body, full of vessels, arteries, veins, nerves and absorbents^ and which are so numerous that the organ seems to rUENITUEE, AND ITS USES. 183 be entirely composed of them. . Here is a representa- tion of the vessels of the kidneys, as they would appear after the intermediate parts had been corroded away, which can be effected by means of an acid preparation. The kidney, however, is not so good a specimen of the nature of a gland, as is the liver. The larger glands of the human body are, the liver, the spleen, the pancreas, the parotid, with the other sahvary glands, &c. Besides these, there are small glands almost in- numerable. The cerumen of the ear, and the oil of the skin, of which I have already spoken, are secreted by Httle glands. The lymphatic or absorbent vessels are everywhere connected, in their passage through the body, with glands. Some of these are comparatively large, some 184 THE HOUSE I LIVE IN. smaller, and most of them are very small indeed. Those little swellings called Jcernels, whick sometimes appear in the sides of the neck, or in the armpit, are nothing but inflamed lymphatic glands. AU these glands (except the lymphatic glands, whose use is unknown,) secrete something ; and the material from which all secretion takes place being the blood, it is sent to them from the heart, and distributed to their innumerable little vessels. NATUEE OF SECRETION. I have ali"eady observed that some of the liquids, &c., of the human body seem to be secreted without the help of glands. They appear to be formed directly from the blood-vessels : how, we do not know. It has been conjectured that they ooze through the sides of the vessels, and some late ex- periments seem to corroborate this opinion. Here, perhaps, in one vessel, is blood; there, on the out- side, and hardly a haii"'s breadth from it, is gastric juice, or some other entirely new substance. In one place is simple chyme or chyle, and closely conti- guous to it is blood, arterial and venous. Here is chyme or chyle, made of ordinary alimentary sub- stances, with neither sulphur, nor iron, nor nitrogen in its composition; there, perhaps, not the twelfth part of an inch distant from it, is a fluid made from the very same liquid — the blood — containing all these materials. By what secret and incomprehensible laws of the FTJRNITUBE, AND ITS USES. 185 Creator have these little vessels this wonderful power ? By what mysterious process can they change, in an infinitely short space of time, a bland, milky substance, made from simple bread, or milk, or vegetables, into iron, or sulphur? Of all this we know nothing, but so it is. Well, indeed, might David the Psalmist express wonder. ^STot only the liquid, but the solid parts also, are made from the blood. The very bones themselves, at first gelatine, are gradually converted into bone, by a deposition from the blood contained in its little vessels. First a particle of gelatine is taken away by the absorbents ; then comes along a particle of blood, or something that the blood contains, and remains in its place, and so on. These particles, which are thus conveyed to form bone in the place of gelatine, are most of them lime, or phosphate of lime, or at least something which makes lime, before it can become bone. Wlio directs the Httle particles of lime to the places where they are wanted ? "Who tells them to stop at the bones, and not before? The same beneficent Creator who arranges all the other wonderful things contained in our bodies. The power of the system to take out from the blood what is wanted for its growth and support, is aptly, though quaintly, shown by Dr. Edwards. Speaking of the wonderfid distribution of the blood, in the little arteries, to every part of the body, he thus adds : "Along, on the lines of these tubes or canals, 186 THE HOUSE I LIVE IN. (the arteries,) tliroiigli wliicli the blood, with all its treasures, flows, God has provided a vast multitude bf little organs or waiters, whose office is, each one, to take out of the blood, as it comes along, that kind and quantity of nourishment which it needs for its own support, and also for the support of that part of the body which is committed to its care. And, although exceedingly minute and delicate, they are endowed by their Creator vrith. the wonderful power of doing this, and also of abstaining from, or of expelling and throwing back into the common mass, what is imsuitable, or what they do not want, to be carried to some other place, where it may be needed ; or, if it is not needed anywhere, and is good for nothing, to be thrown out of the body as a nuisance. "For instance, the organs placed at the ends of the fingers, when the blood comes there, take out of it what they need for their support, and also what is needed to make finger-nails ; while they will cau- tiously abstain from, and repel, that which will only make hair, and let it go on to the head. And the organs on the head carefully take out that which they need for their support, and also that which will make hair, or, in common language, cause it to grow ; while they will cautiously abstain from taking that which is good for nothing except to make eye- balls, and let it go to the eyes, and will even help it on. And the organs about the eyes will take that, and work it up into eyes, or cause them to grow. And so throughout the whole." FUEIflTrEE, AND ITS USES. 187 By tliis it is plainly seen that there must be a constant waste in every part of the system. It is impossible but that the friction — the "wear and tear" of himclreds of muscles and tendons, and thousands of rapid streams — should gradually produce decay, let the parts be ever so hard : a continual di'opping will wear away a rock. Now the blood not only carries out httle atoms or j)articles to cause all parts of the body to grow, and to replace the atoms that were worn off by friction, but it also takes away the worn-out and good-for-nothing particles, and carries them clean out of the body. It is true that they are taken up by the absorbents in the first place ; but then the absorbents carry them to the blood, and empty them into it, which amounts to the same thing. In this way, as you may easily see, the blood is Kable to lose [its purity and excellence, since it is constantly giving out good particles, and receiving bad ones.* MOTION or THE HEAET. The heart is kept in motion, we know not how ; nor can the wisest anatomist or physiologist in the world tell us. We know that the lungs have something to * The manner iu which the bad or waste particles are removed from the system is very curious. Take the kidneys, for instance, which seem to be a sort of sieve or filter; witli this difference, however, tliat while a sieve only permits the finest and best parts to pass through it, the kidneys filter out the worse or coarser parts. These are carried in two pipes, called xireters, to the bladder, whence they are conveyed immediately out of the system. 188 THE HOUSE I LIVE IN. do in the case ; and when once set a-going, we can form some idea of what keeps it in action ; but, after all, the real cause of the continual motion of either the heart or the limgs is a great mystery, and ■v\all probably remain so for ever. You are aware that the motion of the heart can be felt when a hand is placed on the left side, near the middle of the ribs. This important organ — not much larger than a man's fist, and strong and muscular — is situated slanting, or obhquely, as you see in the above FUKNITVEE, AND ITS USES. 189 engraving. It is represented nearly in the position in wliicli my lieart would appear, if you could stand before me tliis moment, and see it just as it no\Y is, in full motion. I mean, its position is just wliat it would then be. In other respects, it would appear dijBferently, especially in its connexions ; for the vessels which go to it and come from it are here represented as partially removed. This engraving represents the heart with its prin- cipal vessels divested of their covering, called in technical language the ^pericardium, or, familiarly, the heart-piu'se, which closely envelops the entire heart, and the 'commencement of the great vessels connected with it. This is one of the strongest membranes of the body, and, hke all other parts, is supplied with arteries, veins, and neiwes. In the view now represented, this heart-purse is cut away, and the heart itself exposed to view. I mentioned a little about the heart in a former chapter, but, as I am now about to explain its functions, it will be necessary, for the elucidation of the subject, to go a little more into detail. The heart, then, is a hollow muscle, and, in per- sons of the ordinary standard, is about a pound in weight, varying, however, in this respect ; its shape is conical, and it is placed in the chest, under the cartilages of the ribs and the breast-bone. The base, wliich is much the broadest part, and whence the great apertures are placed, is turned obhquely upwards and backwards, almost facing the spine, while the point or narrow end projects forwards 190 THE HOUSE I LIVE IN. and towards the left side. The heart contains within it four distmct chambers or cavities, two on the right side and two on the left ; an auricle and a ventricle on each side, one of which, on the upper and right side of this discus, is called, for the sake of distinction, the right auricle, and which receives the terminations of the two great veins of the body, the vence cavce. The next chamber js the right ventricle, a cavity much larger and thicker than the last, and lined with strong muscular pro- jections. The orifice between these cavities is en- circled by a tendinous ring, which gives attachment to a valve, and from the circimistance of its havmg three divisions in its substance, is called the tricus- 2nd valve,' 'SiW^ which is fixed to the strong muscular columns just mentioned by several thm tendinous cords. From the upper and left side of the right ventricle emerges the ^j?(7;/2o;mr^ artery, which has also valves at its entrance, called semilunar valves. This artery is of considerable size, and passes behind the breast- bone, dividmg into two branches, corresponding to the right and left lobes of the lungs, and these again, ramifying in still smaller divisions, gradually become more minute throughout the enth-e substance of the lungs. At the extreme ends of the- smallest branches of the pulmonary artery commence, iii a series of cor- responding minuteness, the 2n<'lmonary veins; these, gradually uniting, form fom* great trunks, which find then? termination in the left auricle of the heart. FUENITUEE, AND ITS USES. 191 TLe left auricle is in appearance and size very simi- lar to its companion on tlie other side, excepting that it is much stronger in its texture. Adjoining to it, and towards the front of the body, is situated the left ventricle, separated from the last chamber by a valre, which, from its supposed resemblance to a bishop's mitre, is named the mitral valve. This ventricle is considerably thicker and stronger than its fellow on the right, though much the same in pomt of si^e : it is separated from the right ventricle by a very strong fleshy partition, which completely sepa- rates the two cavities, and allows of no communication between them. The same division also exists between the auricles, and, in like maimer, they are totally distinct from each other. From the upper part of the left ventricle is sent off the aorta. This great blood-vessel, where it begins, is in size about the same as the pulmonary artery, and has, hke it, at its commencement, three semilvmar valves ; it passes upwards, making an arch of great capacity, and, travelling between the pulmonary artery and the great vein, the vena cava, before mentioned, turns downwards, piu'suing its course along the spine, distributing large branches to various parts as it proceeds. It is now time to call your attention to the plate, and to refer you to the figures which illustrate the different parts. The divided extremities of the two vence cavce, or veins which bring the blood to the heart from all parts, are shown ; the upper and lower are marked o and q, with some other veins contiguous 192 THE HOUSE I LIVE IN. to tliem at ^j>. The right auricle is shown at n, and the left ventricle at b; k represents the pulmonary artery, of which I I are the right and left branches ; m m exhibit the pulmonary veins, emptying into the left auricle ; and a shows the left ventricle. The great arch of the aorta is shown by c, e, f; and the branches of this artery, which are distributed to the heart and upper extremities, are marked g, h, i. The direction in which the circulation proceeds is shown by the little arrows, following the course that an arrow woidd fly if shot from a bow ; and the letter s describes the coronary arteries, or the vessels which feed and nourish the heart itself. Now, the circulation of the blood proceeds in the following manner. The veins from all parts of the body unite to form the two vems cavce, which, en- tering iuto the right auricle of the heart, discharge their contents, contaminated by its traversing through the body, into that receptacle. By a muscular con- traction of the part, the blood is pushed into the right ventricle, or second chamber, and is prevented from returning, partly by the tricuspid valves, and partly by the pressure of blood from behind. The right ventricle, being filled, contracts with great force, striking against the ribs, and producing the stroke of the heart, and discharges its contents into the pulmonary artery, which is again prevented from going back by the semilunar valves ; by means of this vessel it is dispersed throughout the lungs. Here it meets the atmospheric air, which is continu- ally being received into the lungs, and imbibing a FUENITUEE, AND ITS USES. 193 portion of the oxygen, or rital principle of tlie air, wliicK is contained witliin it, becomes altered in colour and quality, losing tlie dark, venous hue which it had acquired while in circulation, and assiunes a scarlet tinge, thus becoming true arterial blood, fit for the purposes of nutrition and secretion. Having thus received its vivifying principle from the atmosphere, it is conveyed by innumerable chamiels — the pulmonary veins — into the left auricle, by the sudden contraction of which it is propelled into the left ventricle, the mitral valve, aided by the continual pressure from behind, prohibiting a retrograde movement. From the ventricle — the fourth cavity of the heart — it rushes through the great arch of the aorta, from whence, by means of the arteries, it is distributed to every part of the body in a pure state ; when, after performing all the duties demanded of it, in the various secretory processes to which it is subjected, it is returned by the veins in a contaminated condition, again to undergo the same passage through the heart, and to receive a similar revivification in the lungs. There is one thing more which demands notice among the phenomena of the circulatory apparatus, which is, that both sides of the heart fill at the same instant, the two auricles contracting at the same moment, and the two ventricles obeying the same law — thus, at the identical time that the right ventricle is pushing its blood into the pulmonary artery, the left ventricle is propelling its contents into the aorta, by which it will be seen that the auricles and ventricles contract and dilate alternatelvj the auricles and the arteries acting 194 THE HOUSE I LIVE IN. together, and the same with the ventricles and the veins. Yalves, somewhat similar to those in the heart, are found in the larger veins all over the body; and now comes the reason why the blood can run up- hill. The pressure in the veins is all the while dijninishing, as you may easily see, on the side towards the heart, even though it is the up-hill-side; and as the arteries, at their extremities, are all the while pouring their blood into them, the pressure must be as constantly and certainly increasing on the other side. Besides this general pressure, there is also local pressure. Veins lie, most of them, in the skin, or among the muscles, or among parts that are per- forming some sort of motion, and this motion must push the blood in one dii-ection or another. But as the valves prevent its going back, the pressure is firm enough to make it go slowly up-hill; and thus it moves onwards and onwards, till it finds its way to the heart. It is the contraction of the ventricles, wliich I have described, that causes the beat of the heart, and which is felt so plainly on the outside of our bodies. It takes place in an adult male, in good health, about once in a second; in females it is rather more frequent. It is greatest, both in males and females, at birth; and diminishes in frequency till we arrive at middle age. FUENITrKE, AND ITS USES. 195 PULSATION. This beating of tlie licart, as tlie blood is puslied from it into tlie arteries, seems to be felt in the large arteries all over the body. I say seems to be ; but the subject is not vi^oW understood. We only know that, if we lay oiu' finger on an artery at the wrist, or in, the ancle, or any other part of the body, where the vessels lie near the surface, we feel the pulse, as it is called ; this beating in the extremities corresponding exactly with the beating of the heart. It is from the frequency, force, tension, and other quahties of the pulse, that the medical practitioner is enabled to judge of the condition of the circulatory system, and for which purpose the beat at the \\Tist is generally preferred, and considered to be the same as all other parts of the body. In China, however, they think differently — there the physician is in the habit of feeling the pulse in various parts, being firmly impressed with the belief that it really varies in different places. FOECE or THE HEART. The force with which the ventricles press the blood to push it out of the heart has been variously estimated. Some reckon it at only a few ounces; others at much more, and some even at 180,000 pounds. The truth is, it presses very hard, with a force apparently equal, if not superior, to that of the gripe of a very strong man with his fist. But it is more than doubtful if it exerts N 2 196 THE HOUSE I LIVE IN. a force equal to thousands of pounds, or even of limi-' dreds. Perhaps it may arerage, in an adult, from twenty to thirty poimds. One reason why anatomists have made such strange calculations is, that they could not conceive how the blood could otherwise be carried so swiftly through the system— and the distance it has to travel, in some instances, is very great, for the arteries are often extremely tortuous. But it seems to have been for- gotten that, by the curious structure just mentioned, the veins are all the while getting empty, and a sort of vacuum* forms in the cavities, into which the blood naturally rushes from the arteries, so that the pressure, or rather the resistance of the latter, to the contents of the heart, is constantly diminishing, and thus there is. a tendency to a regular current of the blood. CAPILLAEIES. They appear to forget also the structure and fimc- tions of the little arteries — sometimes called capillaries — found in such great numbers in the skin, in the muscles, and, indeed, everywhere throughout the body. The truth is, that the coats of these Httle vessels, hke other arteries, are muscular, and it is a pretty well established fact, that they have the power of drawing the blood from the heart. Some eminent professors of surgery have thought that these capillary vessels did almost all the work, the heart itself doing very little. * It is said, and with some truth, that nature abhors ft vacuum. FUENITUEE, AND ITS USES. 197 Tlicy have considered tliem sometliing in tlie light of little pnmps, in every part of the body, that were continually pumping np the blood from the deep well of the heart, to the exti-emities of the remotest chambers of the frame. You may form some idea of their meaning, by recaUing to your recollection houses, in which water is carried up, by means of X^imips and other machinery, to every room in the house, even to the highest story, and to the remotest chambers. The truth here, as almost always happens, falls between the extremes. The heart reaUy pushes the blood with considerable force; and the muscular capillaries, at the same time, act in some slight degree like little pmnps. Then the vacuum I have spoken of has some mfluence; and there may be other causes in operation which I have not mentioned. The whole process of circulation is wonderful, and it requires a volume to illustrate and explain it fidly. POPULAR SUMMARY OF THE PROCESS OF THE CIRCULATION OF THE BLOOD. I will here insert an eloquent description of the circulation of the blood, extracted from that useful and popular periodical the Saturday JIagazine, a work which blends somid instruction with forcible lessons of piety. Though this wiU involve a repetition of some parts of the same subject, yet its importance is so great, that the time bestowed on the perusal will be amply repaid. 19S THE IIOI'SE I LIVE IN. " The lieart, uliicli is the principal organ of circula- tion, is placed within the breast, between the two lobes of the lungs. It is a fleshy substance, and has two cavities, which are separated from each other by a valve. From the left ventricle, a large blood-vessel, called the aorta, proceeds, and soon divides into several branches, which ascend and descend by innmiierable ramifications, become smaller as they proceed, and penetrate every part of the body. "VMien the right ventricle contracts, the blood is propelled into the arteries with so much force, that it reaches the minutest extremities of their most remote ramifica- tions. This motion is called the pulse, which is merely the effect of the pulsation of the heart, and is. quicker or slower according to the frequency of its contractions. " ^ATieu the blood arrives at the extremities of the arteries distributed through the body, Nature employs it in the wisest manner. Certain vessels absorb the watery, oily, and salme parts. In some parts of the body, where the arteries are distributed, the secretion of milk, fat, and various fluids is perfomied : the re- maining portion of blood flows into the extremities of the veins. These vessels gradually enlarge in size, till they form very large tubes, which return the blood back to the right ventricle of the heart. The blood is then propelled into the x>uhnonary artery, which disperses it through the limgs by innumerable small branches. It is there exposed to the action of the air, is afterwards received by the pulmonary veins, and by them is conveyed to the left auricle of the FURNITUKE, AND ITS USES. 199 heart. Tliis contracts, and sends it into the left ventricle, which, also contracting, pushes it into the aoi'ta, whence it circulates through every part of the body. " For this compHcated function, four cavities, as we have seen, become necessary, and four are accordingly provided : two called ventricles, which send out the blood (one into the lungs in the first instance, the other into the mass after it has returned from the lungs): two others, called auricles, which receive the blood from the veins (one as it comes immediately from the body, the other as the same blood comes a second time, after its circulation through the lungs, for without the lungs one of each would have been sufficient.) " Such is the admirable circulation of the blood in man and most animals. But there is still much ob- scurity in this interesting subject. We meet with wonders here, that prove how incapable the human mind is of explaining this work of Divine wisdom. 'The wisdom of the Creator,' saith Hamburgher, 'is in nothing seen more gloriously than the heart ;' and how well doth it execute its office! An anatomist, who understood the structure of the heart, might say beforehand, that it would play; but he would expect, I thmk, from the complexity of its mechanism, and the delicacy of many of its parts, that it would always be liable to derangement, or that it would soon work itself out. Yet shall this wonderful machine go night and day for eighty years together, at the rate of one hundred thousand strokes every twenty-four hours, 200 THE HOUSE I LIVE IN. having at eacli stroke a great resistance to overcome; and shall continue this action for this length of time without disorder and without weariness ! *' From Keill's Anatomy, we learn that each ven- tricle will contain at least one ounce of blood. The heart contracts four thousand times in one hour, from which it follows that there pass through the heart every hour four thousand ounces, or three hundred and fifty pounds of blood. The whole mass of blood is said to be about twenty-five pounds, so that a quantity equal to the whole mass of blood passes through the heart fourteen times in one hour, which is about once in every four minutes. "'Consider,' says Paley, 'what an affair this is, when we come to very large animals. The aorta of a whale is larger in the bore than the main pipe of some waterworks, and the water roaring in its passage through a pipe of that description is inferior, in impetus and velocity, to the blood gushing from the whale's heart.' Dr. Huntee, in his account of the dissection of a whale, says, ' The aorta measured a foot diameter. Ten or fifteen gallons of blood are thrown out of the heart at a stroke, with an immense velocity, through a tube of a foot diameter. The whole idea fills the mind with wonder.' " The account here given wUl not convey to a reader ignorant of anatomy anything like an accurate notion of the form, action, or the use of the parts, or of the circulation of the blood (nor can any short and popular account do this) : but it is abundantly sufficient to give him some idea of the wonderful mechanism bestowed FUENITUEE, AXD ITS USES. 201 on liis frame, for tlie continuance of life, by tlie hand of a Being who is all- wise, all-powerful, and all-good, and whose bountiful care is ecjually extended to the preservation and happiness of the humblest creature in existence, which has been, equally with ourselves, called into life at his Divine behest, and for a wise and good purpose." 202 Chaptee XYI. FURNITURE AND ITS USES— Coxtixued. We are now prepared to enter npon another subject — the study of the process by which the purity of the blood is promoted, notwithstaudino; the many causes which are continually in operation to render it unfitted for its pur]30se. PURIFICATION OF THE BLOOD. This is effected by the aid of atmospheric air. But how is air to be introduced into the human body? Can we eat it? Can we drink it? Can it enter by means of the eyes, or the ears, or the nose? Not exactly in either of these ways. It can, indeed, enter through the nose, but, without some other machinery, it would go no further than the throat before it would return, or pass out at the mouth: a Httle, it is true, is swallowed, both in our food and in our drink; but the quantity in this way is very inconsiderable. There is air, moreover, in almost every part of the body; all the great cavities — the chest, the abdomen, &c. — contain air; were it not thus, we should soon be crushed. The atmosphere in which we Hve presses upon the whole frame with a tremendous force, com- puted at about fifteen pounds' weight upon each square inch of the body ; and its entire pressure on a middling- sized man is estimated at about thirty-two thousand THE HOrSE I LIVE IN. 203 pounds. But as tliere is air Tritliin us, in almost every part, both solids and fluids, wkich forces outwardly, while the atmosphere keeps up a pressure in the opposite direction, we are not sensible of its weight. But when I said that the blood must be purified through the agency of the air, I meant in a manner much more rapid and effectual than could be done by its gradual introduction and circulation through the vessels. The manner in which this great change is effected I will now explain. THE LUNGS. The House I live in contains a curious apparatus, which may be compared to a great bellows, by whose wonderful operation the blood is cleansed and puri- fied. This is contained in the upper story, and fills nearly the whole of it, leavmg but a small chamber on one side for the heart. It blows its blasts at the rate of twenty or twenty-five in a minute in an adult person, and at a still greater rate in children ; and it continues these blasts, whether standing or sitting, sleepmg or waking, as long as we live. I refer, as you will readily perceive, to the lungs. I have already spoken briefly concerning these organs. I have told you about the windpipe, which leads by its various branches to the myriads of little cells witliin them; and I have told you that all those cells were lined throughout by mucous membrane, a membrane con- structed in all its essential properties like the skin, but much thinner. But I believe I have not yet told you 204 THE HOUSE I LIVE IN. liow mucli air these miiiute cells, wMeh fill up tlie whole substance of the limgs, will contain, nor how great is the superficial extent of the membrane over which the air is spread for the purpose of purification. So numerous are the pipes and cells in the lungs, that it is commonly considered that the extent of the mucous membrane which lines them must be equal, at least, to the extent of the skin, which is, in a middling-sized adult, about fifteen square feet. Over all this surface, the fresh air which we breathe^ while we are in health, circulates, fulfilling its office in efiecting that change in the blood of which I am presently to speak. CAPACITY OF THE LUXGS. As to the quantity of air which the lungs will contain, it is very differently estimated. Many phy- siologists think it to be about two hundred cubic inches, or three quarts, in the adult male ; but more recent experiments have led to the beHef that two quarts is nearer the average quantity. AVhen we breathe out, or expire, as it is called, all the air which is actually in the lungs is not expelled, but only a small part of it. Of course, when we draw in, or inspire, we merely introduce air in quantity sufficient to supply the place of that which is discharged. The process of inhaling the air is called insjjiration — that of expelling it, expiration, and the whole process of breathing is called respiration. The amount which we di'aw in or inspire at each FrEXITUEE, AND ITS USES. 205 breath (still speaking of an adult) is tkouglit to be about forty cubic inches, or sometlmig more than a pintj but this estimate has also been considered as too high. Females, Avhose lungs are generally somewhat smaller than those of males, inspire a quantity still less, and children consimie a much smaller portion of ah' than either. BKEATHINa. But how is the process of breathing performed ? To understand this, it is necessary to revert once more to the structure of the frame-work of the human system. The ribs, though fastened to the spine, or back- bone, are not so firmly fixed but that they admit of considerable motion, and this motion is very curious, though somewhat difficult to describe in a work of this kind. I can only say that it is of such a nature, if un- confined by external pressui'e, or unrestrained by disease, as materially enlarges the cavity of the chest when inspiration is performed, and in expiration diminishes it to a corresponding extent. This motion of the ribs is partly caused by the shortening or contraction of the muscles about the chest ; of these, there are two between every two ribs ; and as there are on each side twelve ribs, making twenty-four in the whole, there are forty-eight of these muscles concerned in moving the " bellows" every time I breathe. In addition to these, there are nearly one hundred other muscles that are more or less con- cerned in this operation. 206 THE HOrSE I LIVE IN. In a Lealtliy adult, from twenty to twenty-five of these inspirations are usually performed in a minute, as I have before observed. "WTien violent exercise is taken, as in running, leaping, or swimming, the motion is more rapid. So, also, in childhood, and frequently iji fevers and other ailments. TNTien the lungs are put into unusual operation, by great exertion of the body, the motion of the heart is accelerated in the same degree ; the breathing and the contractions of the heart bearing an exact proportion to each other. IN'ow what is the object of all this motion? For what purpose is a pint of air drawn into the lungs, and spread over fifteen square feet of internal surface, every three seconds, and another pint exhaled from them as often? To wliat advantage is all this un- ceasing machinery directed ? This I can in part ex- plain to you. rSES OF BEEATHING. In its healthy and natural condition, before it is distributed throughout the body, the blood is com- posed of four materials, called by chemists simjple elementary substances. They are called elementary substances because they do not suffer decomposi- tion, or, in other words, are not capable of being divided into several parts or proportions. Formerly, there were more substances comprehended imder this title than are now considered as such. By the power- ful aid of galvanism, many bodies are decomposed which were once thought to be simple or elementary. FUENITURE, AND ITS USES. 207 and the number is being still further reduced. We need here only mention four of them — viz., oxygen, nitrogen, hydrogen, and carbon. The blood, then, is composed of the four materials just mentioned, in these proportions — in a hundred parts of blood, there are fifty-three parts of carbon, twenty-four of oxygen, sixteen of nitrogen, and seven of hydrogen. But when it has been circulated throughout the body, and has been returned through the veins to the right auricle and ventricle of the heart, its pro- perties become greatly changed. It is now of a deep purple hue, and has hence often been called black blood. In this state, it is found to be loaded with too great a proportion of carbon ; and this, too, not- withstandriig what has been done in the way of clearance by the skin ; for it is a most striking fact that this very work of purifying the blood, of which I am about to speak as taking place in the lungs, takes place in a smaU degree aU over the whole surface of the body. Still, it does not complete the work, and the blood yet comes from the heart, through the pulmonary artery, to the lungs, in its impure black or purple state, not only overloaded with carbon, but mixed with other noxious ingredients, which it has acquired in its passage through the body, and which additions render it unfit for the use of the organs to which it is again destined, in forming their various tissues, secretions, &c., until it has received purifica- tion. It also brings back with it, at least a few hours after every meal, a mass of chyle, with which it has been lately mixed, and which probably needs a change 208 THE HOUSE I LIVE IN. to be eff'ected in the lungs before it is enabled to become blood, and to afford proper noiu-islunent to the system. Arrived in the lungs, it is spread almost immediately- over the vast space which is afforded by their numerous cells, and is thus exposed to the influence of the atmo- si^heric aii*. A most surprising change is thus pro- duced ; the blood is now sent back into the left auricle and left ventricle of the heart in a purified and reno- vated state. Its colour is changed to a bright scarlet ; it has lost its superabimdance of carbon, and other deleterious quahties, and has acquired new life and renewed vigour. Concernmg the precise natui*e of this change — whether the blood takes in something from the air, or whether the air takes something from the blood, — there has hitherto been a great difference of opinion, and even now the point is not completely decided. It is sufficient for us, in a book like this, to know that a change does take place, and what the results of that change are in regard to health. NATUEE OF THE AIE. But I must not pass over this part of my subject without mentioning the changes which take place in the air during its detention in the lungs, coming, as it does, in such close contact with the blood. This air, in its natural state, and when in a proper con- dition for respiration, consists of about eighty parts of nitrogen gas, and about twenty parts of oxygen FUENITI^EE, AND ITS USES. 209 gas. Oxygen gas is frequently called vital air, on account of its property of supporting life ; and, indeed, without a due admLxture of this gas, neither the animal nor the vegetable kingdom could continue its existence. On the other hand, piu'e oxygen, or even if mixed in too large a proportion with the other compounds, would be quickly destructive of life, by causing a rapid consumption of the energy of the body. In addition to the oxygen and nitrogen gases, the air is generally considered to have a proportion of carbonic acid gas mixed with it, even in its purest and healthiest state. But no sooner has it passed through the lungs — even once — than the oxygen is greatly diminished in quantity, apparently being ab- sorbed by the blood, while the carbonic acid has much increased in abundance by what it has acquired from the same source. If we continue to breathe the same air twice, thrice, or more, the carbonic acid becomes still more abimdant, while the oxygen as rapidly de- creases, till it is at last perfectly irrespu-able. BEEATHING AIR TWICE. ^" ^ ^- !Xow if we breathe air twice over, or if we %f athe that which has a superabundance of carbonic acid, in it, derived from any other source, it does not sufficieiStly change the blood from its black to its scarlet colour. It is consequently sent back to the heart, and distri- buted all over the body in a state totally imfit for the purposes for which the great Creator designed and. gave it ; and if this abuse is long permitted, the health O 210 THE HOrSE I LIVE IK. materially suffers. Instances have been too frequently before us, in tlie crowded state of prisons, infirmaries, wortbouses, &c., and one j)articularly in tbe too cele- brated Black Hole at Calcutta, to need our saying- mucli more in tliis place. Tlie air is cbanged by inspiration at a most astonish- ing rate. We inhale, probably — speaking now of adults, for children inhale proportionably less — more than a gallon in a minute, or about forty hogsheads full in twenty-four hours. Air which has been once breathed may be consi- dered as imfit for further respiration, and as totally spoiled for the purposes of animal life. Admitting tliis to be the case, we spoil the air for the purposes of breathing at the rate of more than a gallon a minute. Dr. Franklin, half a century ago, advanced this opinion, which has been since- amply verified by succeeding^ philosophers. VENTILATION. Now, if these statements are correct, and that they are so admits of no doubt, how careful ought we to be that the rooms in which we sit, and particularly those in which we sleep, are not too tightly closed, or too long shut in ! What pains ought to be taken to promote ventilation, by frequently opening the doors or the windows ; and this is the more necessary where there are no fires, for a fire assists in ventilating a room, by causing a draught of air from all directions towards the chimney. In rooms where there is no chmmey, a fii-e is very prejudicial, since it deprives the FUENITUEE, AND ITS USES. 211 atmosphere of its oxygen, and rapidly increases the carbonic and other poisonous gases which are given out during the process of combustion. The news- papers have at various times teemed with accounts of persons having been found dead in rooms where char- coal had been burning, and from which fresh air was excluded. School-rooms, concert-rooms, theatres, churches, how dangerous must it be to crowd and continue in them for so long a time as we sometimes do, without ventilation ! How easy is it to raise a window, or to open a door ! And though we might thus expose an individual here and there to cold, yet how much more injurious on the whole, must it be to sit in close apartments, and continually to breathe a contaminated atmosphere ! FEEE MOTION OF THE LUNGS. Not only should the air be good in quaHty, but the limgs should have free play in inhaling it. From youth to maturity, no employment should be followed which for any considerable time will cramp or confine their operation. iN'either should we sit or stand for a great length of time in a bad position, as young people in schools or factories are too apt to do. JSTor should our dress be so tight as to press closely against any part of the chest. How much is it to be regretted that there are parents and instructors, and even teachers in military schools, who think it necessary to injure the functions of the lungs, and thus induce disease, and excite a ten- o2 212 THE HOUSE I LIVE IN. dency to sliorten life, in order to teacli tlieir claildren, pupils, or cadets, the art of putting back tlieir slioulders and walking erect ! TIGHT LACING. Health is always injured hy every kind of lacing, as well as by stays, braces, corsets, tight vests, &c. Not only is the body the more exposed to colds, pleurisies, fevers, and consumptions, but also to dis- eases and malformations of the very bones them- selves — the breast-bone, the ribs, and the spine. I say again, therefore, beware of anything tight about the chest. The Prussian physicians recommend people to wear no cravat or stock, and to leave their bosoms unbuttoned and bare; and no people in the same climate, and under the same circumstances in other respects, are more free from consumptions and all sorts of diseases of the lungs, than are those who observe this rule, though it may be doubted if in so humid a climate as Great Britain, the practice of exposing the chest could be long adopted with impunity. It is very strange that so many people — and some, too, who consider themselves very wise — should still entertain the idea that lacing the chest in a moderate degree improves the action of the lungs, and gives strength to the muscles of the part. A popular writer of Lectures to Young Ladies, inculcates this erroneous idea ; and too many others who have been hold up as monitors of youth, have been under the influence of the same delusion. rUKNITUKE, AND ITS USES. 213 The fair sex, in most European countries, have been siuo^ularly in error in this respect ; under the false impression of improving the figure, they have taken pains to distort it. Few of our fashionable belles, with all their intended aids and appliances, can rival in the beauties of form, and the harmonies of symmetrical proportion, the females of Turkey, of Georgia, of Otaheite, and other coimtries where nature is left to her own unrestrained luxuriance. We generally succeed far better in our attempts to mend or alter the works of human ingenuity, than in those of the great Creator. He appears to have made the himian frame so perfect, with such complete unity of design, and such adaptation of means to an end, that it is wonderful that in our ignorance we should continue such vain attempts to improve it. Were we not con- tinually endeavouring, by various mistaken means, to interfere with the due and just performances of the animal machine, it might continue in healthy operation for a much longer period than it now does. * In closing this chapter, I will show you a picture of the bones of two himian chests, which have been accurately copied from nature ; one is in a perfect state of health and elegance of shape, the other has been injured in form by tight lacing. You will observe that the one which has been distorted by the pressure of stays, has much less capacity for the free ex- pansion of the lungs, and with consequently diminished means for the due oxidation of the blood. I may also remark that this pictiu'e by no means exaggerates the evil effects of tight lacing. "This 21'1 THE HOUSE I LIVE IN. (Icformity," saya a loarmnl pliysician, upon whoso authority the engravings are given, " is not nearly 80 great as what we behove often talies phice in many instances of tight lacing." If wliat I liave said on tlie nature and structure of the cliest should lead any person to study tlio functions performed by its contained important organs, the lungs — if he shoidd be induced by nunnis of this little work to apply his r(>;isouiiig iaculties to the elucidation of the laws by wliich the vital processes of nature are carried into efl'ect — I sliall have reason to rejoice that my labour has not been misdirected, and I am sure that he will look back with satisfaction to that day on which his attention was first arrested, and tlie powers of his mind directed to the subject. 215 Chapter XVII. TEMPERATURE OF APARTMENTS. Few, if any, ordiuary biiilclings, whetlier cliiirclies, houses, shops, or factories, are so constructed as to preserve exactly the same temperature in every apartment at all seasons of the year. As for heat- ing themselves, and preserving one uniform tem- perature by means of the very employments or manu- factures which are being carried on within them, probably no one ever heard or thought of such a thing. A self-heating house ! 'WTiy, it would excite as much astonishment, as would a machine that was really endowed with the power of perpetual motion. And yet the House I Hve in has this power, wonderful as it is, not only of heating itself, by the process of generating and purifying the blood, con- cerning which I have before treated, and by other very curious processes, but also of regulating that heat, and keeping it at the same point, with scarcely any per- ceptible variation. The heat of the human body is never far from ninety-eight degrees of Fahrenheit's thermometer. By this is meant, that if the bidb of the thermometer, which contains the quicksilver or mercury, could be plunged into the flesh of the body, or even if it were to be held in the mouth, the mercury would rise in the tube till it arrived at the mark which indicates 98° or thereabouts, and there would remain. 216 THE HOUSE I LIVE IN. Now wiiy does this heat eontmue nearly the same at all times and in all places P If you were to take a piece of wood, or iron, about the size and shape of a man, and heat it to 98"^, and set it np in Greenland or Lapland, where it is so cold that the mercury would sink to 20° in the open air, do you think this iron would remain heated to 98° P Would not the air cool it do\^Ti to about 20° ? How would it be with a man of wood or straw? How would it be even with the body of a dead man ? Does any one suppose that the body of a dead man, heated to the same temperature as that of a living being, would remain warm very long? Then why should the limng body of a man ? Why does not the cold air rob it of its spare heat, just as it would a mass of straw or iron? Yet the daily experience of our lives proves that it does not. The skin and the outside of the hands, the face, and other parts of the body, may be very cold, and sometimes even actually frozen, but the blood and the flesh will generally remain at about the same temperature, unless the individual be absolutely /)^c^e;? to death. In that case, the heat very rapidly escapes; the dead, as you know, very quickly be- coming cold. CURIOUS QUESTION. But why the heat does not escape from everybody under ordinary circumstances, so that they become frozen to death, is the point in question. You will hardly suppose that there is a fire in the inside of TE3IPEEATURE OF APARTMENTS. 217 lis wliich keeps up the heat: for, if so, what sup- plies the fuel?. Spirits will burn, it is true, and when applied to many chemical and other purposes, afford the means of giving heat. Yet in the hiunan body this is not the case, except perhaps for a very limited ^ period. Although many persons adopt the pernicious habit of frequently drinking intoxicating liquors, yet their blood is in reahty no warmer than is the blood of those who refrain from this practice ; nay, it is even asserted by some experimenters, that the blood of the dram-driiiker is actually a little colder than the blood of him who drinks little else but pure water. When we think of all this, and remember that individuals can live very comfortably in climates like Labrador, and G-reenland, Norway, Lapland, and Siberia, where everything around them — air, water, earth, trees — is cooled down to less than half the heat of the himian body, for the greater part of the year, and as low as the freezing-point (32° of the thermometer) a considerable portion of the time, is it not a wonder that all our bones and flesh and blood can retain a temperature of 98°, not only through an hour, a day, or a year, but throughout the whole of perhaps a very long life ? It is indeed almost a miracle, or would be thought so if we concerned ourselves at aU about it. It shows, at least, how wonderful life is. For not only man, but aU livinc/ animals have this same power. Birds have even a higher degree of heat than man. The blood of some birds reaches a temperature of about 218 THE HOUSE I LIVE IN. 108°. If it were not so, tliey would soon become frozen to death in tke cold season, and their bodies would probably become separated and fall to pieces, in like manner as the frost in swelling sometimes cracks the frozen ground, or as trees are sometimes split into fragments in very severe winters. You should be told, also, that living trees and shrubs, and plants, and seeds, have this same power of resisting cold, though in a less degree than is possessed by animals. Trees do not often freeze very hard; and were it not for this contrivance of the great Creator, everything would perish in the winter, and we should have no beautiful foliage and verdant meadows in the spring. Seeds and roots would perish in the ground, and the regular return of the seasons woidd not produce those beneficent results which gladden our hearts and supply our wants. But we not only have this wonderful power of resisting cold ; we are also equally able to resist ex- treme heat. By long practice, men have been enabled to remain in ovens, and other j^laces, heated to 220°, and even to 260° of Fahrenheit, for ten or twelve minutes at a time. The only serious incon- venience which arises in such cases is an extremely profuse perspiration.* But a piece of flesh without * Perspiration always modifies the heat of the human body. more or less, and is one means of keeping us cool. The reason is, that the moisture on the surface of our bodies evaporates ; and this produces cold. It is said that you may almost freeze a man in midsummer, by keeping him wet with ether ; so rapidly does the ether evaporate. TEMPEEATTJEE OF APAETMENTS. 219 life, if subject to so great a heat for only a few minutes, would be thoroughly baked, and the organiza- tion of the part irreparably destroyed. This heat is much greater than that of boiling water, which, as you know, is 212°, measiu^ed by the same thermo- meter. Having laid down and illustrated the general rule, that the temperature of our bodies does not admit of much variation, it may be as well to mention some of those shght varieties which under different cu'cum- stances are found to exist. VAEIATIOXS OF TEMPEEATUEE. Infants, excepting when newly born, have a tem- perature only of about 94°. The heat increases as the body advances towards maturity, after which it remains nearly stationary at about 98°, imtil it begins to dechne, when a shght diminution takes place. In the spring, and in the beginning of summer, it increases a little in people of every age ; but it again declines towards winter ; and when a person is greatly enfeebled by sickness, or otherwise, the temperature is slightly diminished. In fevers and in inflammatory diseases, it sometimes increases to 104° and even to 107°. But I have not yet told you hoio this steady tem- perature of 98° is kept up in the human system, notwithstanding the extremes of heat and cold to which it is exposed. Indeed I cannot do it j for I do not know the cause. It is in some way connected with 220 THE HOUSE I LITE IN. the principle wliicli we call life, but about the nature of which we are at present entirely ignorant. I have already told you that the evaporation of the matter of perspu'ation from the skin has some effect in keeping the body cool; but this cannot be the sole cause why men can remain with impunity in places heated to a greater temperature than boiling heat. There are doubtless other and more important causes, but the limited sphere of human understanding has not at present enabled us to discover them. As to the reason why we retain so high a temperatui'e as 98°, when the atmosphere is at a considerably less degree of heat, we know nothing. There have been a great many speculations started by ingenious philosophers in various ages and countries, but they have been in general mere guesses; in many instances hardly amounting to plausibility. The process of digestion, the formation of chyle, the change of chyle into blood, and the alteration made in the blood during its passage through the lungs — but more particularly the latter — are all beheved to have a part in the work. Yet it is considered that by all their united efforts they do not accomphsh one-half of it ; and it remains for future anatomists and physiologists to investigate the subject more deeply, and to endeavour to throw additional light upon the obscurity in which it is at present involved. Of late it is considered that electrical agency has much to do in the matter. How far the laws by which the gi'eat Creator governs this imiverse, and keeps all its parts in har- monious action with each other, may ultimately be TEMPEEATUEE OF APAETMENTS. 221 discovered, we cannot say. In this, as well as in a thousand other things which are in daily operation, and on every side surround us, our ignorance is made manifest. "WTiether the extent of human knowledge will ever enable us to penetrate fully into these mys- teries of creative wisdom is a problem yet to be solved. At present we can add but little to the exclamation of the Psalmist, — We are fearfully and wonderfully made I INDEX. PAGE Abdomen, or great internal cavity of the human frame 153 Absorbents, or Lj/mphutics, their situation and offices 178 Absorption, the process and ef- fects of 176 Air, proper condition of for breathing 208 Anatomy, or the knowledge of the structure of the body ... gQ Ankle, structure of 28 Aorta, situation and size of this great blood-vessel 191 Apartments of the House Hive in 21 Arms, their structure, func- tions, and peculiarities ... 46 ^4m)7W^s of the heart 190 Bile, use of 175 Blood, great cavity of the cir- culation of 158 its importance in the ani- mal economy 171 materials and nature of... 1/9 secretion, nature of ... 184 circulation of 192 popular summary of the whole process of cii-culation 197 purification of 202 vessels in bone 33 Bone, nature, structure, and growth of 29 and shells 87 of the thigh 23 of the leg 25 of the foot 26,48 of the ankle 28 in the throat 67 Bones of the hip 34 of the spine 37 of the trunk 46 of the shoulder-blade ... 45 of tlie arm 46 of the hand 48 of the wrist 49 of the skull 56 162 PACE Bones of the face 5S of the teeth 59 of the jaw 60 of the ear 65 Brain, chambers of the 16O its nature, weight, size, and uses 161 Breathing, process of 205 Bronchi, or channels from the /;-ac/iea to the lungs 151 Capillaries, where found, and their office in the circulation of the blood 196 Capsules, or capsular ligaments 7^ Cataract, a disease mthe eye... 120 Cerebrum, the upper and front part, and the largest portion of the brain Cerebellum, the back and lowest portion of the brain 162 Chest, its situation and contents 149 Chewing, or mastication of food 171 Chyle, the formation and dis- position of 176 its connexion with the blood V... 17s Chyme, a pulp into which food is converted in the process of digestion 175 Circulation of the blood; popular summary of the whole theory 197 Cleanliness, importance and comfort of Ill Colour, change of 106 Cranium, or brain-case 56 Cuticle, epidermis, or scarf-skin 106 Diaphragm, or midriff 149 Digestion, nature and process of 174 Dura Mater, or firm covering of the brain Ear, bones of .. situation, functions of drum of 162 65 structure, and 130 132 Epidermis, cuticle, ox scarf-skin 106 PAGE Epiglottis, its functions in swal- lowing, and in the admission ofair 153 compared to a trap- door 152, 1/3 Esopfiag7is, its structure and functions l63 Etruria, sepulchral monuments of IS E.rhalant vessels Ill Eye, compared to windows ... 113 situation, structure, and functions of. J 14 passages to 148 Eyes, peculiarities of in animals 127 Eyelids, use of 125 Eyebrows, use of 126 Fat, its situation, nature, and tendency 101 Follicles, sebaceous glands, or oil glands ill Foot, general description of ... 26 Gall-bladder 157 Gastric juice, its nature and uses in digestion 174 Glottis, its functions in the pro- duction of voice 152 Hair, nature, growth, and use of 109 disease of, in Hungary and Poland 110 Hand, beautiful mechanism of 51 Heart, its situation and form... 189 auricles of ventricles of valves of mystery of its motion ... pulsation and force Hifdrocephalus, or water on the brain Intestines, then- names, descrip- tion, and functions Joints, compared to hinges ... wear of abuses of Kidney, representation of, show- ing the blood-vessels in con- nexion with it Knee-pan, or patella, described INDEX. 22a PAGE Lachrymal gland, the source of the tears 12S duct, the passage of the tears 125 Lacing, tight, evil consequences of 212 Lacteals, their situation and functions 1/6 Larynx, or part of the throat- , pipe concerned in the produc- tion of voice 152 Leg, bones of, namely the tibia, and the >"5M/a 25 Ligaments, their nature and uses 74 Liver, situation of 1/6 LoZies of the lungs 151 Long- sight, cause of 123 Lungs, their situation and struc- ture 150 their situation, structure, and capacity 201 evils of obstructing their free motion by dress, or otherwise 211 Lymph, a fluid differing from the blood 178 Lymphatics, or absorbents, their situation and functions ... 178 Midriff, or diaphragm 149 Mouth, peculiar importance of to the animal frame 141 curious instance of an artificial one 141 Muscles, nature, structure, and action of illustrationsof their uses 91 97 and action Myology, or the study of the muscles 83 Nails, nature, growth, and use of 109 Nerves, the situation and func- tions of the ceri^ira/, described l65 \hQ optic 120 the auditory 136 i\\e olfactory 130 the great sympathetic 167 New Hollanders, their huts ... 19 224 INDEX. PAGE Nose, situation, structure, and functions of 139 chambers of 144 Oil glands, sebaceous glands, or follicles 110 Olfactory nerves, their origin and functions l65 Optic nerve tXescrihed 120 Osteology, or the study of the na- ture and structure of the bones 83 Pa^fi;/«, or knee-pan 23 Pathology, or aknowledgeof the changes produced by disease on the structure and func- tions of the animal body ... 86 Periosteum, or membraneous covering of the bones 89 Perspiration, insensible Ill Physiology, or the study of the functions of the living animal 85 Pia Mater, or delicate covering of the brain l62 Pillars of the House I live in 23, 24 Pleura, or lining membranes of the ribs 151 Plica Polonica, a disease of the hair, in Poland and Hungary 110 P^/o;-«s, outlet from thestomach 154 Pyramids of Egypt, their great age and magnitude 18 Respiration, theory of 208 condition of air pro- per for 208 Ribs, general description of . . . 42 lining membranes of, or pleura 151 Salivary gla^idSy their names and offices 14" Sebaceous glands, follicles, or oil-glands Hi Secretion, nature of 184 Shells and bones, their nature and uses 87 Short-sight, cause of 122 JAGB Skeletons, preparation of ... 83 Skin, nature and varieties of... 103 colour of Spinal nerves marrow Spine, or back-bone, its struc- ture vertebra of general description . . . 104 167 169 37 38 40 Stomach, its situation and shape 154 Sweat, nature and effects of ... 112 Sympathetic nerves 187 Synovia compared to oil for the joints 77 Tears, nature and uses of ... 125 Teeth, their action compared to that of a wheel 59 their formation and decay 6i necessitj- of cleanliness ... 65 their uses in chewing, or the mastication of food ... 171 Temperature, importance of at- tending to 215 variations of 219 Temple of Solomon, its beauty 18 Te?i£fo/is, description of 91 Thigh-bone, or femur, described 25 Thoracic duct, its situation and functions 177 Thorax, or chest 151 Tibia, a bone of the leg 25 Tongue, situation, form, and uses of 146 bone of 67 Trachea, a cartilaginous appa- ratus concerned in the pro- duction of voice Ventilation, importance of ... Ventricles of the brain of the heart Vision, how effected Vocal ligaments Voice, apparatus for the pro- duction of 150 210 164 189 121 152 Savill & Ed-wards, Printers, 4, Chandos- street. University of California SOUTHERN REGIONAL LIBRARY FACILITY 405 Hilgard Avenue, Los Angeles, CA 90024-1388 Return this material to the library from which it was borrowed. DCf 6 zuud lilllllllilillllllllllllllllllllllllllll B 000 003 035 3 I So i L lliilii 1; •::': , lir- ■ ■! ■ .' . ' " ill Hi - ■■■ i ' ' ^k :::':( ^ 1 !'!''.' i)!'.-',- i'' liliiii^;!!!!^ i it h': ! 'I