it LIBRARY OF THE UNIVERSITY OF CALIFORNIA. OIF S T OF" Mrs. SARAH P. WALS WORTH. Received October, 1894. ^Accessions No . $% \ / ^ . Class No , NEW AND IMPORTANT WORKS. 7 From Prof. Burnham, a Teacher of experience, Principal of the English Depart- ment in the well-known Burr Seminary , and also Superintendent of Public Schools. "MANCHESTER, BURR SEMINARY, October 30, 1850. "DR. LAMBERT: " DEAR SIR, I have attentively and for practical purposes examined your books on Physiology, more particularly the Second Book, which I consider better than any with which I am acquainted, to be used as a school book, on the subjects of which it treats. The intelligent and faithful teacher cannot fail to make it an interesting and valuable branch of study. Many excellences might be named ; I will specify but one, as rare : the discriminating language in which the questions are put to the pupil. I should be pleased to have this book introduced into the schools of this town, and to hear that its use was general. I think, also, that your book will be found exceedingly interesting to the general reader, and be used with great advantage as a reference book. " Yours truly, W. A. BURNHAM." PI.1 Fig, 4. Zig.l Fig. fig. /. Fig. J. II. PI. 5. POPULAR ANATOMY AND PHYSIOLOGY, ADAPTED TO THE USE OF STUDENTS AND GENERAL READERS. BY frof. T. S. LAMBERT, M. D., . of Anatomy and Physiology in Pittsfield (Young Ladies') Institute, Brooklyn (Qreenleaf 's Young Ladies') Institute ; Author of Notes to Erasmus Wilson on the Skin, Popular Treatise on Bathing, etc. WITH ONE HUNDRED AND FIFFY WOOD-CUT AND BEAUTIFUL LITHOGRAPHIC DESCRIPTIVE ILLUSTRATIONS. PORTLAND: SANBORN & CARTER. NEW YORK: LEAVITT & CO. 1851. V BIOLOGY LIBRARY G Entered, according to act of Congress, in the year 1849, by T. S. LAMBERT, In the Clerk's Office of the District Court of the United States for the Southern District of New- York. MULLER AND LIEBIG, AUZOUX, MAGENDIE, FLOURENS, ORFILA, AND CRUVELHIER, PEREIRA, WATSON, WILSON, CARPENTER, LISTON, AND MARSHALL HALL, As most distinguished ornaments of their profession and humanity; JOHN AND SIR CHARLES BELL, COOPER, LAWRENCE, GOOD, HOME, RICHERAND, AND LAENNSO, (Who though dead yet live,) As those whose writings have given me the greatest pleasure and much instruction ; AND TO THE MEDICAL PROFESSION OF THIS COUNTRY, Whose members as a body I love and respect, from too many of whom to particu- larize I have been the recipient of courtesy, and from whose works and conversation a rich store of knowledge has been gathered, and used with profit in the following pages; THIS BOOK S tespectfultB trcDfcatett, With the intention of rendering honor where it is so richly due, and as the only token of his admiration and indebtedness which can yet be presented by THE AUTHOR CONTENTS. tip ADDRESS TO THE READER, . > . .9 INTRODUCTION, . . y ", . S r '-3 BOOK I. THE FIRST CLASS OF ORGANS. CHAPTER I. THE ORGANS OF VOLUNTARY MOTION- SEC. 1. The Bones, Cartilages, and Ligaments, . . 17 2. Muscles, Tendons, &c., . . . .50 3. The Brain and Nerves, . ? ..." . CHAPTER H. THE ORGANS OF SENSATION OR FEELING. SEC. 1. Sensations, . . .. ... . ; ' . 112 2. Objects producing Sensations, . . V 119 3. The Organs of Sense, '.' V* . . 122 4. The Nerves of Sensation, . V- * . 195 5. The Brain as an organ of Sensation, . . ' . 205 6. The Mind in respect to Sensation, . v. : . 211 7. Concluding Remarks on the Organs of Sensation, . 218 CHAPTER HI. FHE MIND AND ORGANS WITH WHICH TO THINK. SEC . 1. The Brain, Y V ' v" ; V * , -224 2. The Mind, . 240 CONTENTS. BOOK II. SECOND CLASS OF ORGANS. FAOB GEKERAL OBSERVATIONS, . . 243 CHAPTER 1. THE DIGESTIVE ORGANS. Ssc. 1. The Mouth, \* *V "V ^ ' '. < - 254 2 The Stomach, . . 273 3 The Second Stomach, Liver, Pancreas, Spleen, Colon, &c., 317^ CHAPTER H. THE CIRCULATORY ORGANS. SEC, 1. The Heart, . , - . 335_~ 2. The Bloodvessels and Lymphatics, . . . 340- 3. Causes of the Circulation, i'i> . . . 353-- CHAPTER in. THE RESPIRATORY ORGANS. SEC. 1. The Air Passages, *:'*" . .363 2. Circulation of the Blood about the Air Passages, . 365 3. Inhalation and Exhalation of Air, .-..^ . . \\ ', *: 366 4. Action of the Blood and Air upon each other, .. .,.;. 370 CHAPTER IV. ** 5 THE VOICE. SEC. 1. Expulsion of Vocal Air, . f A ^* . V 382 2._Modifiers of Sound, '. - ; - : ^ K ; "+ '' c . . 383 3. The Larynx, . / . . yi'fi *fct& 386 CHAPTER V. ORGANS OF EXCRETION. SEC. 1. The Second Stomach, Colon, &c., O^\ * 391 2. The Liver, . ^ h -- . . 4 ^ .. 393 3. The Lungs, .... . :-, . . i-" ; : . 395 4The Kidneys, . . . . : I : . 396 5. The Skin, ,j< :^ ; -Urj . . .397 CHAPTER VI. THE ORGANIC NERVOUS SYSTEM. General Observations, . . . . 406 DESCRIPTION OF LITHOGRAPHIC PLATES. PI. 1, Fig. 1. Represents the muscles and tendons a* they appear when the skin is removed, except that the external muscles are also rerao^ ed from the left side ; they are ehown upon the right side. The direction of the stripes shows the direction in which the muscles and parts of the muscles contract, and of course the direction in which they have a tendency to produce motion. Fig. 2. The bones of the ankle and the internal muscles of the lower part of the leg. The tendon of 84 is seen in the most beautiful manner, turning around the outer joint of the ankle and under the foot, beneath which it passes to be attached to the bone back of the great toe. Fig. 3. Back portion of the jaw, the ear ; and, 36, temporal muscle attached to a prominent point of the jaw, K. Fig. 4. Lower portion of the chest, with the front portion of the ribs removed to show ihe diaphragm 7, below which is seen a portion of the upper part of the abdomen, with its front wall and organs removed. 2, 3, The back lower edge of the diaphragm, the "pillars" of which are seen attached to the back-bone. The front lower edge of the diaphragm is lower than here represented, especially at the side. PI. 2, Fig. 1. View of the external muscles of the back, except upon the left side, where the " middle" layer of muscles is brought to view. Fig. 2. Internal muscles of the back. Fig. 3., 4. Muscles and tendons beneath the foot. PI. 3, Fig. 1. Front half of the chest and abdomen removed, presenting the organs of those parts as they would appear in front, during life. They would not appear thus how- ever, when the body is opened, as they would flatten and change their position, hence it must be kept in mind that the organs are not flat, but project toward the observer, in the centre, rounding back at the sides, as the body does when viewed in front. 1, Right lung. 2, Left lung. 3, Diaphragm which arches up under the lungs, its front and lower edge being attached to the front and lower edge of the ribs as seen. 4, The liver, which lies up under the diaphragm in such a manner that if a knife should be thrust through where the dotted line from 3 terminates, the liver would be wounded. 5, Stom- - up under the lower curvature of food. 6, Colon, where it passes the three longitudinal bands of muscles which contract the colon into pouches, as seen. 7, The second stomach, the commencement of which is seen in some of the woodcuts dispersed through the work. 8, Front surface of a small part of the spleen, the chief part of which, when the breath is thrown out, is above and back of the part seen. 9, The base of the gall bladder which lies forward 10 the edge of the liver, the upper part being found underneath the liver, between it and the colon and stomach. Fig. 2. Ideal view of the left lung 2, cut from side to side perpendicularly throueh the middle. The right lung is seen contracted, as when the chest is opened. The heart is between them. The object is to convey the idea that the air inhaled passes through the windpipe and its divisions 1, 1, into air-cells, and that the blood passes into the lungs through the artery 6. from the right heart 4, and after the blood has passed round the air-cells and been acted upon by the air, comes back to the left heart 5, through the vessels 7, of which there are two, leaving the lungs. Fig. 3. A greatly magnified view of the net- work of capillary bloodvessels upon the sides of the air-cells. It is not so extensive as would in fact cover the sides of a mus- tard seed. The blond passes in through one set of vessels and passes back through an- other, as the colors exhibit. DESCRIPTION OF LITHOGRAPHIC PLATES. PL 4, Fig. 1. The red vessels represent the arteries of the entire body branching to the various parts of the system, not precisely after the manner of the arteries of tho body, but sufficiently accurate to convey a general idea. The blue vessels represent the veins. Fig. 2. R, Right heart. L, Left heart, from which the red vessels lead the blood into the capillaries C, C, of the body, from which it comes back to the right heart, pass- ing thence into R, L ; L, L, the capillaries of the lungs, thence back to L, left heart. Fig. 3. Hearts and vessels separated from each other. Fig. 4. Portal system of vessels. 1, Spleen. 2, Pancreas. 3, Portion of duodenum. 4, Gall bladder turned up, as better seen in woodcut. 5, Tube or duct, from the gall bladder. 6, Duct from the liver. 7, 8, Veins from the second stomach ; 9, those from the stomach, which with those from the spleen and pancreas unite to form the portal vein 10, which divides and subdivides in the liver. PI. 5, Fig. l.-B, Candle giving off blue light. Y. Candle giving yellow light. R, Candle giving red light. In all cases the light passes from a candle in all directions, but only so many rays as would enter the opening a, are represented. Such rays passing through the opening a, fall upon the very much magnified commencing points of the nerve 1. The light from no two candles is seen to act on any of the same nerves. 2, Outer coats of the eye. 3, Pigmentum nigrum. Neither this nor any of the succeeding figures are intended to convey any correct idea of the eye, except as it respects the ac- tion of light thrown upon the nerves. Fig. 2. The light is seen passing through a lens, by the action of which, the entire yellow light passing through the pupil a, is made to act on one point ; the same is also true of the light from R and B. Fig. 3. R, Y, B, As heretofore. But in this case the lens has not acted upon tho light sufficiently to cause it to act on a single nerve, but the red light acts over the nerves between 4 and 6, the yellow light acts on the nerves between 5 and 7, and the blue .light on the nerves between 6 and 8. The nerves between 4 and 5, and between 7 and 8, are acted on by one kind of light only, the nerves between 5 and 6 by both red and yellow (orange), and the nerves between 6 and 7 by blue and yellow (green). This is the case with long-sighted people. Most old people have indistinct vision from this effect being produced by the insufficient action of the parts through which light passes to the nerve. Fig. 4. R, Y, B, As before. In this case the light is acted upon so powerfully that it is bent to points or foci before it reaches the nerve ; it passes the point or focus there- fore, and when it reaches the nerves, the red light acts over the space between 4 and 6, the yellow light upon the nerves between 5 and 7, the blue light on the nerves be- tween 6 and 8, and the same cause of confusion exists as in case of Fig. 3 ; that it is BO, is evident by bringing a thing so near to, and removing it so far from the eye, that it becomes indistinct ; the sensation is similar in each case. So also when the locus of a microscope or telescope is brought toward or removed from the eye. the effect is simi- larly indistinct. This is the near-sighted eye. Fig. 5. A, B, Are two rays of different colored light passing through the hole 2, in partition 1, 1, and acting on the end of one nerve D, producing the effect of compound light. Fig. 6. A, B, Two rays of different colored light acting on two nerves, a simple effect being produced on each nerve. Fig. 7. W, a ray of white light passing through the pin-hole a, and bent upward aa it is passing through the prism P. The blue light is bent the most, the yellow more than the red but not as much as the blue, while the red is bent, but less than the yellow and blue. Fig. 8. The three colors which compose white light upon a small card. If it be whirled rapidly on a pin thrust through the centre, the light from each part will act on the same nerves, and the card will appear white. Fig. 9. A mirror reflecting all kinds of light. Fig. 10. A black object not reflecting any light. Fig. 11, reflecting only red. Fig. 12, reflecting only yellow. Fig. 13, only blue. ADDRESS TO THE READER. EVERY one desires to be happy. It seems to me a high degree of happiness can be obtained by every person if he will constantly ask himself two questions : 1st. What can he do to make others happier. 2d. What is the cause of any effect he sees. The first will improve his disposition, the second will cultivate his intellect. That increased ami- ability and humanity will render a person happier, needs no argument to prove ; while the instant a person begins to seek the why and wherefore of things, he begins to acquire know- ledge, so satisfactory and delightful to the mind, that it is stimulated to farther investigations, and soon rewarded by the most profitable results, not the least of which will be an inquiring mind. It seemed to me, I could answer the first question in no way so well as by writing the present volume. In thus rendering others happier, my own happiness will be increased in three ways: by the pecuniary compensation received, by the esteem of community, and by the conscious- ness that the book is a public benefit. That the greatest effect may be produced in each of these ways, no pains have been spared to make the book valuable. That it has real 10 ADDRESS TO THE READER. faults, there is not the slightest doubt. Many things also which displease some, will please others. Some things appear as blemishes to me, which have been allowed to remain in ac- cordance with the opinion of some whose judgment was re- spected. It was intended to meet the general approbation of many, and cannot therefore, in every particular, satisfy each person, who will it is hoped consider, that our best friends have faults, on account of which many times we love them the better, as they do not seem to be more perfect than our- selves. That the treatise may render others happier, the object has been to communicate satisfactory knowledge upon the principle that, " To please, is the first step towards instructing j" and with the importance of the second question constantly in mind, to wit : It has been the constant endeavor to induce the reader or student to think, to inquire into causes, to lead him on step by step to the fruits of knowledge ; that he may be practically convinced, that it can be usefully applied to alle- viate the ills of life and increase its blessings. To know the success with which this has been accomplished, would deter mine in the author's mind the value of the book, to a great degree. It is therefore hoped that his opinion will never be considered decisive upon any point. The purported truths here set forth, are of the highest interest and value, if truths ; they are susceptible of illustration and support, or of refutation and condemnation, in the every-day oc- currences of every person's life, And so much confidence ADDKESS TO THE READER. 11 is placed in the correctness of the views brought forward, that it is believed when they are thoroughly tested, the causes of effects, and the reasons for the beautiful operations taking place in the system, will be so clearly seen, that natural curiosity will be ripened into enthusiastic inquiry, and a spirit of investigation produced which will spurn the dicta- tion of any writer, and acknowledge but one teacher, TRUTH. Questions have not, therefore, been connected with the present volume, but have been placed in a separate book, because, when questions are in the hands of the scholar, he too frequently merely commits a clause which answers the question ; and again, as will be seen by looking at the book of questions, many are of such a nature that the answer is not in the text, but is intended to cause the scholar to think ; while as sometimes teachers, and frequently parents who would wish to instruct, might not feel inclined to take the responsibility of deciding on an answer, a correct one is given with the question, and various illustrations of the text, which might not otherwise suggest themselves to teacher, parent or scholar ; many teachers also prefer to ask their own questions, suggested by the text. As the treatise is designed to be a book for general reading as well as a text- book for students, it was thought an advantage to have the questions optional ; though, being separate, many facts can be communicated and suggested by them which could not consistently be introduced in the text, and will render it a pleasure for the general reader to notice the questions. With them the parent can with perfect ease teach his child the important truths of this science, at an early age, there 12 ADDRESS TO THE READER. being but one suggestion to make ; that the child, older or younger, receive very short lessons. A lesson containing one practical truth will be sufficient ; this being so illustrated and applied, which the questions will do, that it will become part of the student's nature to be actuated by the grand prin- ciples which the Creator has appointed to govern the physi- cal welfare of man. These truths, these principles, he should learn so thoroughly, by having them frequently brought before the mind and fully illustrated, that he shall be actuated by them unthinkingly, and entirely forgetful of their source, consider them merely as indubitable, and teach them to others as truths, the observance of which bestows the greatest physical blessings. That thus the knowledge which it is believed this book can impart, may be the means of add- ing to the happiness of many who shall never hear of the, name or existence of the author, is my sincere wish. New-York, Nov. 1, 1849. THE ANATOMY AND PHYSIOLOGY OF THE HUMAN SYSTEM. M INTRODUCTION. 1. The object of the following pages is, to prove that Beauty, Health, Strength, and Length of Days, mental and physical, depend upon observing certain Laws to unfold and illustrate these Laws, and enforce the importance of obey- ing them. 2. This will be attained by imparting the knowledge establishing these laws, and by examining the four sources from which it is derived. 3. First. The structure of the Human System HUMAN ANATOMY. 4. Second. The uses of the Human Organs HUMAN PHYSIOLOGY. 5. Third. The concurring testimony of all men UNA- NIMOUS EXPERIENCE. 6. Fourth. The particular experience of each person PERSONAL EXPERIENCE. 7. Three difficulties attend an investigation of these sources of knowledge : 8. The first arises from want of proper means to see and 14 INTBODUCTION. dissect minute parts of the body, and examine the delicate operations that take place therein. 9. The second is owing to the infrequency of opportuni- ties for observing the interesting phenomena of internal life. 10. The third and greatest difficulty is found in recon- ciling conflicting testimony, and sifting from it all prejudice and bias. 11. However, a doubt will but rarely exist if the testi- mony from each source be obtained upon any point. For the testimony from three sources agreeing, it would correct the contradictory testimony from the other. 12. The knowledge from the fourth source being per- sonal, can only be obtained by learning the experience of each person, when the laws peculiar to him may be estab- lished. 13. The laws based upon the knowledge drawn from the first three sources are to be learned and observed by all, since they are universal and invariable. They may with propriety, therefore, be laid down in books, and profitably acquired therefrom. 14. To do this most successfully and concisely, man may, firstly, be considered under the heads of Mind and Body. 15. The Mind is that which thinks, feels, and causes voluntary action ; is properly the man. 16. The Body is a beautiful piece of mechanism, com- posed of many parts, adapted to the use of the mind, with which the mind thinks, feels, and acts. 17. Mind and body are so intimately connected with each other, and so powerfully influence each other, they cannot be considered distinctly. The state of one always affects that of the other. The tears flow profusely when the mind is over- come with grief. Anger reddens the cheek, which is paled by fear. While, vice versa, too much food unfits a person for study ; but wholesome food, and a healthy digestion of INTRODUCTION. 15 it, give vigor to the mind and life to the spirits. As Tupper so eloquently writes, " The best cosmetic is a holy conscience f or as Thomson, " E'en from the body's purity, the mind Receives a secret sympathetic aid." 18. Indeed, whatever elevates the intellect, regulates the passions, sweetens the disposition, or cultivates the affections, tends to develope beauty, preserve health, increase strength, and prolong life. 19. On the other hand, ignorance, ungoverned temper, moroseness, and sensuality, will despoil the fairest intentions of nature, develope disease, enervate the system, and produce untimely death. 20. This is not the place to treat on morals ; yet it may be observed, that our Quaker friends are not a little indebted for their celebrated complexions, good health, and long lives, to the healthful moral influences with which they surround themselves. 21. So much do the manifestations of the mind depend upon the state of the body, some have too hastily concluded, mind was only the necessary result of action of certain parts of the body. 22. An attempt will be made in various parts of this work, to show clearly, that the distinction between mind and body is correct. 23. As they depend so intimately upon each other, if one be considered, the other is necessarily involved ; and it is enough, therefore, that especial attention be given to one ; and in the present work, it is our duty to take the body for the particular topic of discourse. 16 INTRODUCTION. 24. Of the body, two classes of organs will be consider- ed. For though it is a whole, and each part affected by every other part, yet 25. One class of organs is used with which to think, feel, and act ; 26. Another, to keep the first class, and also itself, in good condition. 27. The first class may be subdivided into three classes of organs, which include 28. 1st. The brain, with which to think ; 29. 2d. The organs of sense, nerves, and brain, with which to feel ; 30. 3d. The bones, cartilages, ligaments, muscles, nerves, brain, and some minor organs, with which to act. 31. The utility of the second class of organs will be better 'perceived after the first class has been described. 32. The propriety of dividing my subject into two books will now be seen, and the subdivisions of the first book will be anticipated. BOOK I. THE FIRST CLASS OF ORGANS. CHAPTER I. THE ORGANS OF VOLUNTARY MOTION. SECTION 1. The Bones, Cartilages, and Ligaments. 33. These parts form the framework of the human system. 34. The use of this framework is to give form to the body,* to support the soft parts in their proper positions, to protect some of them, to allow motions of one part upon an- other, and of the whole, from one place to another. 35. To fulfil these requirements the frame must be very strong, of sufficient size to admit the attachment of the nu- merous soft parts, yet very light ; it must be composed of many pieces, very strongly united, yet in such a way as to allow the desirable motions, with the least friction. * Since the general form depends upon the skeleton, every lady de- siring to possess, or desiring her child to possess a fine form, will feel exceedingly interested to know all that can be learned in respect to the bones, and anxious to do every thing which will perfect them. 18 ORGANS OF VOLUNTARY MOTION. Fig. 1. Skeleton, Front View. [CHAP. I. 36. Composed of bone, cartilage, ligaments, with some minor adjuncts, the frame is perfect in all these respects ; I know not which to admire the most the perfection of the bones, the elasticity of the cartilage, or the strength and beau- tiful arrangement of the ligaments. Our hearts are moved with adoration when we read the handiwork of the Creator SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. Fig. 2.- Skeleton, Back View. 19 in the superlative form and texture of the skull ; but not less are they moved with gratitude as we view the cushion-like cartilages supplied to the back, or the powerful bands which unite all parts into one. ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 3. Skeleton, Side View. 37. The bones are adapted to their purpose by their com- position, form, and being hollow. 38. They are composed of two substances ; one soft, the other hard. The two and their nature can be easily per- ceived, if two similar bones be placed, one in fire, and the other in some diluted mineral acid. In a short time, if taken out, though both have the same form as before, one will bend, indeed may be tied in a knot (Fig. 4), the other will crumble like chalk, the acid having removed the hard or earthy por- tion, and the fire destroyed the softer or cartilaginous portion. The form of each being the same as before the experiment, it will be seen that the hard and soft parts are intimately blended throughout the bone.* * Sometimes, by disease or some cause, the hard part is removed from the bone during life, and the bone thus affected will bend in any direction, SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 21 Fig. 4. 39. The proportions of the two parts to each other vary much under different circumstances. 40. In earliest life the soft parts only would be found ; at a certain time a few particles of the hard part are deposited in one or several points of the soft part, called " points of os- sification ;" additions are then made, till throughout the soft part the hard part would be found, but in very small propor- tion ; this, however, is gradually increased by fresh additions throughout, till at last the bone has sufficient strength to bear the weight of the child. The hard or earthy part continues to increase till old age, in mature years giving the bones the greatest degree of strength, and in advanced life making them extremely brittle. 41. In some bones the deposit is made much earlier and more rapidly than in others of the same body. 42. In some children also than in others. 43. These statements will account for the bones of chil- dren bending easily and breaking with difficulty, while those of old people break easily and do not yield to pressure. The and people will say the bone is gone. I have seen one such case, the tipper arm bone of a young man, 18 years old : the cause I could not learn ; the ultimate effect I have not yet heard. In other respects he seemed to enjoy usual health . 22 ORGANS OF VOLUNTARY MOTION. [CHAP. I. predominance of the soft part is also one reason why, if the bones of children be broken, they unite readily, while in old people the predominance of the earthy part retards the pro- cess of restoration and sometimes prevents it. 44. It would be inferred, that a child does not walk ear- lier because it is not fitted to do so ; therefore no pains should be taken to teach a child to walk by using standing-stools or the like. Even leading a child, or standing a child upon its feet must be wrong ; placing a child in one position, long or often, should be avoided ; so also, placing or carrying a child in such a position, that much weight shall be borne upon one part of the body, cannot be right. 45. It must be evident that the heavier a child, the greater the effect and necessity for care. 46. Is it not probable, also, that if a child be backward it is for some good reason, and will it not prove injurious to attempt to teach the child to walk ?* 47. That this hard part may be deposited, it must be fur- nished to the child in its food. Now, it must be evident that milk contains this substance, as it has been designed by the Creator for the use of young animals, and because we see the bones of animals become strong and good, when nothing but milk is used as food. As the works of the Creator are so perfect, can it be best to go contrary to his evident in- tentions, and feed a child with any thing but milk ? In- deed it is not impossible that chicken-breasted and other defor- mities, the result of too soft bones, may be in part or wholly * I do not believe that a child can be advanced one day by attempts at teaching. It seems to me that a child walks as other animals, actu- ated by an instinct, and will of its own accord, and untaught, walk as soon as it should, as soon as it can. Some may say that exercising a child will give it strength earlier ; but, with the delicate muscles of the child, over- exercise, rather than want of it, is to be feared ; and the bow-legs, chick- en-breasts, and other deformities so common, show that the other animate are more favorably situated in this respect than the human species. SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 23 produced by feeding the child with arrow-root and the like, especially as it will be hereafter shown that such things tend to increase the weight of the child by fat, an end not desirable, and cannot strengthen the bones, which is of pri- mary importance. 48. The forms of the bones are so various, and the bones are so exceedingly irregular, it would at first seem there could be no general plan by which they were all made. Quite the reverse opinion will be formed on examination. 49. The numerous indentations upon the surface of the bones, are evidently for the purpose of obtaining a greater extent of surface for the attachment of soft parts ; the promi- nences serve the same purpose, and also act as levers (Fig. 5). Many times a ridge is seen upon a bone (Fig. 6), which adds greatly to its strength and scarcely any thing to its weight. Fig. 5. Fig. 6. Fig. 5. r, A resistance, p, A power acting on the lever (r p), of which the skul. is a part. From r to the skull, ana from p to the skull, represent prominences upon the bones ; the longer these are, the greater the effect of any force acting upon them. Fig. 6. Section of a bone, with a ridge (B) to strengthen it. A, The hollow of the bone. 50. If the bones be examined in almost every exposed position, the form will be that of the arch, the strength of which is seen in the stability of the bridge supported by arches. See the beautiful form of the Skull, which has been demonstrated to be the most perfect possible. 51. The bones being hollow (Fig. 7), is an exceedingly ingenious arrangement, as thereby they may be large and 24 ORGANS OF VOLUNTARY MOTION. [CHAP. I. strong, and yet light. At first it does not seem consistent that the bones are as strong, being hollow, as they would be if solid. But if a green twig be broken, the outer layers will be seen to give way first, when the inner layers immediately break. Notice also how heavy a head of grain a single straw will support, even when the wind is blowing furiously, and it will be evident the hollowness of the bone is as it should be. Fig. 7. 52. The outer surface of the bone is more solid or dense than the part within, which grows more and more spongy - like in appearance, though it is firm to the touch, till in the centre of the long bones a perfect hollow would be found. 53. The bones are also able to resist the effect of blows and weight, by the assistance of the soft parts, which being attached to the bones, act sometimes as stays, and being elastic, at first yield, but gradually resist, and at last very firmly. 54. All the bones are covered by a very thin but strong skin or membrane ; when dry and peeled from the bone, it appears like tissue parchment. It is called the Periosteum (about bone). Upon particular bones, however, it is called by specific names, as that upon the skull is called the Peri- cranium (about cranium). 55. Wherever the bones are hollow, a similar membrane exists lining the cavity. 56. Upon the healthy condition of these membranes de- pends the healthy state of the bony layers under their imme- SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 25 diate influence. Hence disease of this membrane speedily produces the most tedious diseases of the bone. 57. Two diseases, called in common language, " fever- sore, 7 '* and " felon," are similar affections; one, of the perioste- um of the long, bones ; the other, of that of the shorter bones. 58. " Felon " is usually soon detected, but " fever-sore," which is much more serious in its consequences and extent, is usually mistaken, till it is too late to call in the assistance of the skilful surgeon with the most effect. 59. There is, however, a striking difference between the pain produced by this complaint and rheumatism. It usually occurs in young persons who are not likely to be troubled with rheumatism, which is apt to manifest itself about the joints, and either affects several at once, or wanders from one to another. In fever-sore the pain is not felt at the joints, is local, continuous, and increasing. 60. The instant the existence of the disease is suspected, the advice of experience is required, as the disease can be readily conquered, only during a few days of its commence- ment. If it be decided that an operation is required, such as cutting down to the bone to cause bleeding from the inflamed bloodvessels of the diseased membrane, or perforating the bone, that the internal membrane may be reached, it will not answer to hesitate, for while indecision is waiting, the disease will gain a firm foothold ; or if it be determined that the con- tinuous application of cold will disperse the blood from the part and change its action, it is plain that directions must be very promptly and thoroughly followed, as the danger is im- mediate and imminent. 61. If the bones were brought directly in contact with each other, their composition is such, that the most unpleasant jars or concussions would be produced, even when walking in the gentlest manner, and every motion would produce harmful friction. 26 ORGANS OF VOLUNTARY MOTION. [CHAP. I. 62. To prevent such results, the bones at the points of contact are covered with cartilage, or what is commonly called gristle ; it also serves to lengthen out some of the bones (as the ribs, Figs. 1, 2, and 3) ; to increase the secu- rity of the joints (Fig. 8) ; and as cushions (Fig. 9), by the yielding of which as a whole, or upon one side or the other, the supported parts are carried with the greatest safety, or bent with the greatest ease. Fig. 8. Fig. 8. D, Body of a bone, at the end of which a socket is found. C, Cartilage, thick at the des, and thin in the centre. B. Body of a bone, at the end of which a round head is found. A, Cartilage, thin at the sides, and thick in the centre. 63. Cartilage is admirably adapted to its purpose, by its capability of receiving a smooth finish, of which any one may satisfy himself by examining almost any movable joint of an animal, but especially by its elasticity ; that is, when acted upon by force it yields, but returns to its former posi- tion and conditions when the force is removed. 64. Its elasticity depends upon its composition, which varies with its situation and use, the person examined, and the period of life when the examination is made. 65. The general rule is, that the cartilages grow thinner, firmer, and less elastic, with increasing age. This will ac- count for the shortened stature of old people, as well as the stooping form ;* for by Figs. 1, 2, and 3, it will be seen * Would it be a good thing for the old man to be straight, when the elastic springs, cushions, or cartilages of his back have become unfit for the fulfilment of their duty 1 Evidently not. Every jar received by the lower paits of the body would be transmitted in a direct line to the head and nervous system ; and such continually repeated concussions, though slight as possible, would shortly destroy life. 1.] BONES, CARTILAGES, AND LIGAMENTS. 27 Fig. 9. Fig. 9. Back bone, spinal column, vertebral column. 6, c, d, Bodies of verte- brae ; the projections on the opposite side are called spinous processes ; above b they incline down but little ; between b and c they incline very much ; between c and a, but little, if any. Spaces between vertebrae are filled, in life, with the cushion-like cartilages. Above 6, are the cervical (neck) vertebra ; 6 to c, dorsal (back) or cheat vertebrae ; c to d, lumbar (loins) vertebrae ; d, e, sacrum ; e,f, coxcyges. 28 ORGANS OF VOLUNTARY MOTION. [CHAP. I. that the cushions of the back, if diminished in thickness, will allow the head and entire trunk to fall forward. 66. But with the head leaning forward, works on Natural Philosophy (see "Composition of Forces") will show, and ex- perience proves, the danger is avoided. I would here observe how, upon examination, all things are found to be most ad- mirably adapted to our good, when at first glance there would seem to be something to correct. There is a rich treat and great practical source of knowledge to the man who will ask the why and wherefore of what he sees* 67. In some instances the cartilages become bony, or technically, " ossified," in advanced life. 68. To retain the bones and cartilages in their places at the movable joints, something of great strength, yet possessing a certain degree of flexibility, is required, to stretch across from one part to another and be firmly united to each. Such is the nature of the ligaments. 69. They are the pearl-colored, lustrous, strong parts, found about the joints of any animal. They are in the form of straps (Fig. 10); in the form of bands completely sur- rounding (Fig. 11); or in the form of cords. They are sometimes found within the joint, but usually without, stretch. ing between, growing to, and binding together the different parts, allowing motion in required directions and preventing it in others.* * It does not seem judicious to speak of any course which should be pursued, till its propriety has been proved. But sprains, strains, or wrenches of the ligamentous parts are so common, a word in respect to them will be expected here. They will be again spoken of in an ad- vanced part of the work, when the why and wherefore will be clearly given ; as it is easily shown, that lotions, plasters, and all this class of things so commonly used, are of little worth, and cause fruitless expen- ditures of trouble, time, and money ; while time, patience, the applica- tion of heat or cold, with rubbing, are chiefly to be depended upon. If there be heat or redness of a sprained part, and almost always if there be pain, the part must be kept perfectly quiet, rubbing avoided, and cold applied till relief is felt and the heat subsides. Sometimes persons have, SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 29 Fig. 10. Fig. 10. Represents the strip-like ligaments which pass across from one bone to another in the hand, and also the inter-osseoua (between-bone) ligament which connects the bones of the lower arm. 70. Atmospheric pressure is also thought to exert a pow- erful influence in retaining the bones. I have seen a state- ment that forty pounds weight was required to draw the thigh under such circumstances, pumped cold water upon a sprained ankle, and learned from experience the benefit. If the part be cold and inac- tive, brisk rubbing and the application of heat will be advisable ; and application of substances irritating to the skin may be made, if desirable. The part may be wrapped in flannel or a cloth dipped in warm water, and covered with oiled silk ; but the chief dependence must be placed, in all cases, on time, patience, and rest. If the part be used from time to time, it will be a long while, perhaps years, in recovering. By long disuse a part is apt to be stiff, when in fact it is well ; it should then be rubbed often and thoroughly, it being certain that no inflammation exists, which will be manifested by pain and soreness ; and forced motion be produced, slight at first, but increased from day to day till perfect action of the part is obtained. The restoration of sprained parts is so slow, there is great difficulty in persuading a person to wait and avoid exercise. ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 11. Pig. 11. The hip joint opened. C L, Capsular ligament, which, like a band, passes round the joint, attached on one side to the hip, and on the other to the thigh bone. R L, Round ligament passing from nearly the centre of the round head of the thigh cone to nearly the centre of the deep socket. bone from its socket, after all its connections had been sever- ed, indeed, after it had been entirely removed and was re- placed. We see this principle so simply and successfully used by the dentist and others, that there will be no objection to allowing its application in case of the joints. 71. The fleshy parts clothing the bones serve also to re- tain the bones when in place, but exert an equally powerful influence to prevent their return when dislocated. 72. Notwithstanding the admirable structure of the car- tilage, the almost constant, slight or extensive motion at the joints would produce serious friction. 73. To prevent this as far as possible, the movable joints are lined with a membrane or skin called " synovial mem- brane." It is attached by one side to the cartilage (Figs. 12 and 13), the other being " free," that is, not attached to any thing. 74. In this membrane an exceedingly glairy fluid, well adapted to its purposes, called " synovial fluid," is found. It SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 31 Fig. 12. Fig. 12. C L, Capsular ligament. R L, Round ligament. F, Thigh or femor bone. B H, The same sawn open, exhibiting the marrow-filled cells composing the internal parts of many bones, as at P P also. P P P, Hip bone. S S, Space rilled with svno- vial fluid, but here represented as much greater than in reality, the surfaces of the eynovial membrane in fact being closely in contact. exudes from the free surface as the minute drops of perspi- ration, when scarcely perceptible, on the face. 75. But the fluid would accumulate, or remaining, would be liable to the same fault as even the most delicate oils which human art has obtained : viz., would thicken, and render a " cleaning" of the joints necessary, were it not for another ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 13. Fig. 13. Knee joint. 1, Lower end of thigh bone. 5, Upper end of " shin " bone. 3, Knee-pan. 2, Tendon of muscles acting on knee-pan, or patella or rotulla. 4, Liga- rnent connecting patella to " shin-bone," or tibia. Stars show the synovial membrane. 6, A buraa, or pouch or purse. duty the synovial membrane performs. It continually takes up and removes the fluid which a short time before was de- posited.* 76. The bones of the skeleton are 240 in number, not counting several small bones, which are considered as acci- dental and not necessary to the framewcrk. 77. Most of these are united, so as to form movable joints, some so as to form immovable joints. 78. The eight bones of the skull (Fig. 14) are of this last * Though only a drop of fluid, perhaps not as much, would be found in a healthy joint at any one time, one author has computed that not less than five quarts of synovial fluid is required in 24 hours by. the joints of a laboring man. In this, as in many other cases, it is evident that one part performs more than one duty, though the contrary is frequently asserted ; it is also evident that the same symptoms may be exhibited by different causes ; for an accumulation of fluid in the joints may take place, either because it is formed too rapidly, or not removed as it should be. How absurd then the idea that one medicine shall cure all diseases having the same symptoms and how much more absurd that any medicine or course of treatment shall cure all diseases. It must be evident, if disease exist, the cause must be looked for ; if this be done in season, and the cause pre- vented from further action, rarely will any thing else be required. But it will be perfect nonsense to attempt to remove disease while its causes are still existing to reproduce it. SEC. l.j BONES, CARTILAGES, AND LIGAMENTS. 33 Fig. 14. Fig. 14. The bones of the skull separated. 1, Frontal, only half seen. 2, Parietal (wall). 3, Occipital (back), only half is seen. 4, Temporal. 5, Nasal (nose). 6, Ma- lar (cheek). 7, Superior (upper) maxillary (jaw). 8, Unguis (nail form, being about the size and thickness of tne fingernail). 9, Inferior (lower) maxillary (jaw). Be- tween 4 and 6, a part of the spenoid or wedge-shaped bone is seen. Another bone assisting to form the skull, but not here seen, is called the ethmoid (sieve-like, from being full o ' holes) and situated between the sockets of the eyes, and forms the roof of the nose 2, 4, 5, 6, 7, 8, are double. The small bone, and others like it, seen in a line between 3 and 1, are called ossa triquetra. 79. Each of the eight is composed of three layers differing from each other in their structure. 80. The outer layer is quite tough, and called the fibrous or external table of the skull ; its edges are notched very irregularly to appearance, but so that each bone of the skull perfectly corresponds with its neighbor, into which it is lock- ed, or dovetailed, as the expression is ; hence it must be formed upon some uniform and general principle. 2* 34 ORGANS OF VOLUNTARY MOTION. [CHAP. I. 81. The joints formed between the external tables are called sutures or seams ; these are also called by specific names, as the sagittal suture, coronal suture, squamous su- ture, &c. 82. Small bones, called ossa triquetra, are also seen in Fig. 14, which may or may not be present : their utility is not appreciated 83. The middle layer or table is cancellated or spongy, and lessens the jarring effect of blows upon the skull. 84. The internal table is called vitreous or glassy, as it is very brittle. If its edges were like those of the external table, a slight blow upon the head would break off the points ; hence its edges are square, and an even-looking joint is the result. 85. In advanced age the sutures are sometimes closed up by the bones uniting together firmly. In early life, on the other hand, the firm bone has not covered the whole brain, but " soft spots" exist : the one on the top of the head, called a fontanelle, being an example, where, by pressure, the head may be lessened in size, and other benefits obtained. 86. The bones of the face, fourteen in number, are im- movably united, except the lower jaw ; its joint allows of motion downward, upward, forward, backward, and from side to side. 87. The socket in which the lower jaw moves is so shal- low, that sometimes a person, by opening the mouth wide while gaping or the like, throws the jaw from its place, and cannot have his " gape out," till something be done. 88. To replace the jaw, let the thumbs of a person be placed against the~lower back teeth, and the fingers under the chin ; press downward and backward with the thumbs, and try at the same time to raise the jaw with the fingers. From the frequent and powerful motions of the jaw, its joint is sub- jected to unusual friction. To diminish this the joint is sup- SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 35 plied with an extra cartilage, and with two synovial mem- branes. By means of these the same end is obtained as the machinist gains by friction wheels (Fig. 15).* Fig. 15. Fig. 15. Section of the joint of the lower jaw. 3. Cartilage dividing the joint Into two parts. 4, The upper, 5, the lower cavity, both lined with synovial membrane. 1, The socket in the bone which receives the upper surface of the cartilage. 7, A por- tion of the lower jaw, which moves upon the under surface of the cartilage. 6, Th cartilage taken out of the joint 89. Composing the back-bone are found 24 vertebrae, placed one above the other, the lower one resting on the sa- crum, which is terminated by the coccyx (Fig. 9). 90. Between the upper or first bone and the head, what is called a hinge-joint is found, which allows the nodding mo- tion of the head, and with great rapidity, if desirable. 91. The first and second bones are united in a very cu- rious manner. From the second bone a prominence, called a tooth or pivot, rises up through the first, and is attached to the skull by a ligament passing between them. Another ligament passes from side to side of the first, behind the tooth, which has a kind of neck at the point, where this ligament acts against it. Thus every thing is held firmly in its place, and yet the most desirable rotary motion of the head with great quickness is allowed. * The bones of the ears, the teeth, and the TJ-like or hyoid bone wiH be described hereafter. 86 ORGANS OF VOLUNTARY MOTION. [CHAP. I. 92. Motion of the other bones of the back is obtained by cartilages situated between the " bodies" or front parts of the " vertebrae "(Fig. 9). These are much thicker between the lower than between the upper bones of the back ; they are also much more firm at the outer surface than within, where the substance more resembles jelly. In some animals, indeed, the centre is found occupied by a bag or bladder of quite fluid substance, by means of which still greater suppleness is obtained. 93. As the bones are drawn towards each other, this sub- stance pressed upon, yields, becoming thinner at that point and thicker at the opposite side. Thus, by acting upon the bones in the proper way, any desired motion is obtained. But joints of this kind do not allow of the greatest rapidity of motion, even to the frequently exercised back ; hence a different arrangement is found in case of the two upper bones, by means of which the desirable rapid motions of the head are gained to perfection. 94. To the " back-bone" the ribs are attached, forming hinge joints, by means of which they can be moved upward and downward. By their form and composition they are remarkably elastic for bone ; they pass around to form the sides of the chest, and are lengthened out by means of car- tilage, which is very elastic in early years, but firmer in advanced life, and sometimes, in old age, changed into per- fect bone. From the upper seven, which are called the true ribs, the cartilage becomes attached to the " breast bone. 1 ' From the three or four next, the cartilage passes up and be- comes part of that from the rib above ; while the lower one or two ribs are merely tipped with cartilage, and called floating ribs. 95. Such a framework as the chest was required to give support to the arms, and was also needed to protect the lungs and heart ; hence the ribs are used to fulfil both purposes ; at SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 37 the same time it was necessary also that the ribs should not be immovably attached to the back-bone, or how could a person bend the back 1 Motion of the ribs was also neces- sary in the process of breathing ; hence we see that not only one end, but several, are gained by the same beautiful and simple means. 96. The shoulder-blades are suspended, as it were, by the fleshy parts, to the ribs and back-bones, and they lie upon the ribs, though not directly, as the flesh beneath prevents them from coming in contact with the ribs. It is important that the arms of man hang by his side ; in the cow, or horse, or dog, &c., it is important that they be, as it were, in front. In man, therefore, the shoulder-blades are prevented from falling upon the chest at the sides, by the collar-bones, which are wanting (except mere rudiments) in the animals above- mentioned. 97. At one extremity the collar-bones are connected to the breast-bone ; at the other to the shoulder blades (y, Fig. 1), forming joints which allow of limited but sufficient motion. 98. Placed in this manner the shoulder-blades can move upward, downward, backward, forward, or in a rotary man- ner, with the greatest freedom, and without particularly af- fecting the ribs, while their position in relation to the ribs is such, that all deformities of the chest, at the back part, wheth. er of the back-bone or ribs, will be exhibited by the shoulder- blades. 99. At the shoulder, the upper arm bone (&, Fig. 1) is connected with the scapula or shoulder-blade in such a man- ner as to form what is called a ball and socket joint. 100. By this means and the mobility of the shoulder- blades, the greatest latitude of motion is allowed to the arm and hand. That this may be increased to the utmost possible degree, the socket has been made exceedingly shallow. Were it not for the cartilage that deepens it, it could hardly be 38 ORGANS OF VOLUNTARY MOTION. [CHAP. I. termed a socket. On this account the bones at. the shoulder are more easily dislocated than any others. 101. A hinge joint is found at the elbow, by which the hand can be raised up and thrown down ; but lateral motion is prevented both by the form of the bones and the arrange- ment of the ligaments. At the lower and back part of the upper arm bone or humerus, a cavity is found, into which the hook-like prominence felt at the elbow shuts, when the hand is thrown down. It is so arranged that the bones of the lower arm will never be in precisely the same plane with the upper bone. 102. Another but smaller cavity, opposite to the first mentioned, will be found at the front and lower part of the humerus. A correspondingly small point of one of the bones in the lower arm shuts into it, preventing the bones of the lower arm from being brought parallel with the humerus, whereby great safety of the joint is insured. 103. No arrangement in the body is more ingenious than the combination of the two bones in the lower arm, by means of which we turn a gimlet, a key, and perform all such use- ful motions. Here are two bones, the "ulna" (e, Fig. 1) and "radius" (d, Fig. 1). The upper end of one, with the hu- merus, forms the elbow joint ; the lower end of the other, with the wrist bones, forms the wrist joint, and vice versa the upper end of the radius forms no part of the elbow, neither does the lower part of the ulna assist in forming the wrist joint. 104. The rounded upper end of the radius, which is the bone back of the thumb, turns in a slight cavity in the upper part of the ulna, its fellow, and is fastened there in such a manner as to forbid release, but yet allow of a turning mo- tion. Between the bones (Fig. 10), for their entire length, a ligament is found, strong but very complying, and at the lower extremity of the radius, the hand is attached ; when, there- SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 39 fore, the radius is rolled over the ulna, which remains quiet, the hand is made prone or supine (palm downward or upward). 105. The wrist joint is a compound hinge joint, permitting motion of the hand up and down, as well as from side to side. 106. The wrist is composed of eight bones, small, but united in a manner so exceedingly strong, that the hand must be crushed before they can be displaced. 107. To the wrist are connected the several bones which form the frame of the hand ; to these again the bones of the fingers, the arrangement of which is so simple and evident, that a child may study them without a tutor. 108. To the lower part of the sacrum (Fig. 9) the coc- cyx is attached. This is composed of several bones, early in life ; at a later period they become consolidated with each other and, also with the sacrum. 109. To the sides of the sacrum (w, Fig. 1) are attached the hip bones (s s, Fig. 1), bound in their places very strong- ly by ligaments. They are very irregular in form, and unite with each other in the front central line of the body by a joint called " symphysis pubis." It is of the kind which does not allow of motion or separation of the bones, except with the severest effort. 110. In the outer sides of these bones, looking somewhat downward, deep sockets are excavated, in which are placed the heads of the thigh bones. These heads will be observed not on the end of the shaft, but connected with it (Fig. 16) by the neck. 111. "Hip disease" may profitably be noticed, as its worst results may often be attributed to ignorance of its early symptoms or injudicious neglect. One of its first symptoms is, pain at the knee, with no apparent cause. Secondly, the child will stand mostly on the sound leg. Thirdly, if pres- sure be made upon the hip joint and the leg rolled around, j>ain will be felt in the hip, if disease exist. The advice of a 40 ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 16. Fig. 16. H, Head, or ball. N, Neck. P, Prominence. T b, Body of thigh bone. S, Socket. H 6, Hip bone. skilful surgeon must then be very strictly followed, and it is advisable to read some good treatise (Liston or Cooper) on surgery, that speaks of the disease in particular, as almost every thing depends upon good nursing for a long time, of which the patient must be persuaded, or he will perhaps be seduced by the promises of unprincipled quacks, whose cha- racter he learns too late. 112. The twisted form of the thigh bone or "femur" (z, Fig. 1 ), is remarkable ; being uniformly so, it doubtless serves some important purpose. At its lower extremity (7, Fig. 1) it is much enlarged, and forms, with the enlarg- ed upper extremity of the "tibia" or shin bone (m, Fig. 1), the knee joint, by which the foot and lower leg is flexed SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 41 backward to the greatest degree, and brought again into a perpendicular below the femur, its further motion forward being prevented by ligaments. At first view this would seem to be one of the weakest joints, but the motions required of it are so simple that it can be, and is, made exceedingly strong by ligaments. Subject to great and almost constant pressure, it has been furnished with extra cartilages (Fig. 13), which placed between the bones and covered on both sides with synovial membrane, render it quite perfect. 113. In front of and sliding over this joint, is found the "knee-pan," to be hereafter spoken of. 114. In the lower part of the leg are two bones, stronger and presenting more surface than if but one, especially as there is a ligament stretching between them for their entire length. They also serve as supports to each, if either be broken. 115. At their lower extremities is found the ankle joint, a part exceedingly subject to be sprained, as it was necessary to produce by it a double motion, up and down, and from side to side. It could not, therefore, be endowed with the strength" of the knee. The force which is exerted when the weight and entire lever power of the body is brought to bear on the ankle, placed in an improper position, is but little appreciated. With a sprained ankle, therefore, the greatest care must be tak. en ; for a slight misstep will undo the curative process of weeks. 116. The ankle bones, seven in number, resemble the wrist bones in the strength of the bands which confine them together. With the bones stretching forward to the toes, they form an arch (Fig. 17), which should not be depressed by setting the child upon its feet prematurely ; nor should a de- formity of the feet be produced by shoes which cramp. How- ever genteel a slender foot may look, an attempt to produce it, by wearing tight shoes, will not only cause great dis- comfort, but also a very ungraceful, gait, and prove a great discount to personal appearance in several respects. 42 ORGANS OF VOLUNTARY MOTION. [CHAP. 1. Fig. 17 Fig. 17. Section of the bones and ligaments of the foot and ankle. The figures refer to the bones, and the letters to the ligaments, except 0, which is the "heel cord," a tendon of certain muscles. 117. The joints of the toes appear to be of very limited use ; but upon further observation, they will be found to es- sentially aid in walking with ease, and if used as in case of some born without hands, become almost as perfect as the finger joints. 118. Considered as a whole, nothing could be better adapted to its purposes than the foot, when perfect ; when imperfect, it is usually the fault of man. It was designed to be used with ease in walking, and to disperse the force which acts upon it when striking the ground. 119. Composed of twenty-six bones, more or less cellular internally, united by cartilaginous joints, so as to form an elastic arch, a step must be very unfortunate the force of which is allowed to act in a great degree even upon the knee. Yet by ligaments how strong the foot is made ! A loaded cart has passed over it and caused but a severe bruise. 120. The perfection of all the bones in preventing the transmission of concussion, or the effect of blows, will be seen by placing several solid ivory balls in contact with each other and striking one with force the last will fly off correspond- ingly ; but interplace a bone of the foot, and the movement of the last ball will be but slight, on account of the spongy nature of the inside of the bone. SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 43 121. When the foot strikes the ground, the joints of the body are more or less flexed, and the force which acts upon the lower parts of the body is more and more dispersed in the direc- tion of the dotted lines, Fig. 3. This, together with the nature of the cartilages furnished to the joints, especially the cushions of the spinal column, gives to the delicate and easily injured brain the most perfect security. Fig. 3, B. Fig. 3, B. Represents the outline oi Fig. 3. The dotted lines represent how the foot, when walking, is put upon the ground. The force acting on the heel, at a } ia scattered, viz : a part of the force acts through the ankle and is lost in the direction a 6, only a part of the force acting in the direction of the line a c ; of this, only a small part will act in the line cf- and of this, only a part will act in the direction e h ; of this, only a part in the direction g k ; and of this, only a part in the line t /. In fact, these lines represent but a email part of the directions in which the force is scattered ; for by the curve of the thigh bone, its neck and the connection of the hip bones with the back bone, as well as the continued curvature of this, the head is saved from the Budden jar produced when the body is as erect as it can be ; for instancy when a mis- Btep ia made, or a person falling strikes upon his feet. 44 ORGANS OF VOLUNTARY MOTION. [CHAP. I. 122. While the beautiful structure and admirable adjust- ment of the various parts of this framework excites in the mind the strongest feelings of pleasure, still greater satisfac- tion will be felt if we turn our attention to the wonderful ope- rations which from birth till death preserve the perfection of this piece of mechanism. 123. First, the attention is arrested by the increase of size which is constantly taking place till the period of matu- rity, with the most exact regard to just proportions and the uses to be fulfilled. 124. This enlargement is accomplished by the gradual removal of every part, and the deposition of new substance in place thereof. (The teeth of the human species are an exception ; they will be spoken of hereafter.) 125. The new deposition takes place within certain bounds, in accordance with the requirements of the parts ; hence, if a boy be put to work early in life, the bones will become consolidated earlier ; if worked too hard, deformities of the bones will be produced, that they may fulfil what is required of them, at an unnatural period of life. 126. Second; all through life even the hardest parts of the system are wearing out : in youth, in mature years, in old age even, it is so. The worn-out parts are continually re- moved and new parts laid down instead. In youth this pro- cess is most active, in middle age sufficiently so, in old age it takes place slowly. In early years, therefore, an injury is easily recovered from, in old age its cure is tedious. 127. The body, therefore, does not die, nor is it born once only ; but, with the exception of some of its parts, is con- tinually dying and being born, even in youth. 128. Of what consequence then, is this identical frame- work, which a few years ago we had not, and a few years hence we shall not have ? Like the garments that cover us, " thread after thread it is worn away," but not like those does SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 45 any part become threadbare, for its perfection is restored con- tinually by the deposit of renewing substance. The mind, then, is the man. 129. Third ; when the bones are broken, a remarkably active condition takes place as a usual thing. The limb be- comes exceedingly painful, so that a person may not move the broken part. Sometimes this does not occur, when the motions of the limb, which the patient will allow, prevent the parts from uniting, and cause them to be displaced. Under such cir- cumstances it is usual for the surgeon to adopt such a course as shall produce the desired action and excite pain. 130. As genuine bone forms very slowly, an amount of cartilage is first formed about and within the bone, which supports the broken bones in their places, and allows the pro- cess of " knitting" to go on between the bones. After this is accomplished, the cartilage will be gradually removed and the bone left as before. 131. As, when a limb is broken, a person's health is not affected in other respects, he does not always appreciate the importance of observing the surgeon's advice, which seems unnecessarily strict. The splints are to be thrown aside, he thinks, when he can raise the limb without bending it or feeling pain. 132. If a limb be broken, and no surgical assistance is at hand, the limb is to be placed as nearly in a natural position as it can be, and slips of thin wood or the like, applied as ingenuity shall suggest, bound on, not very tightly, but so as to give general support, and padded, to obtain the purpose better. Trust chiefly to the painfulness of the part to keep the limb quiet, for bandages which would do this, would be likely to stop the circulation of blood. It will be best to wear the splints longer than necessary, rather than go upon the other extreme, as people usually do. Remem- 46 ORGANS OF VOLUNTARY MOTION. [CHAP. i. ber, that a part is not cured because it is desirable, neither will opinion alter the state of the bone. 133. With this view of the framework, the reader will appreciate the effect upon it of female dress, .as usually worn, and of male attire, as sometimes worn. While yet an infant, the belt of the girl is pinned snugly, for the purpose of pro- ducing a " trim figure." Too often this is the case, even with the boy. 134. The ribs are not yet firmly fixed in their sockets, are easily bent, while the slightest pressure is sufficient to produce deformity of the pliable cartilages, which form the front part of the chest. There is no doubt, that the usual custom will lessen the size of the waist. But is this an improvement ? (Figs. 18, 19.) If the reader disagree with the writer on this point, he cannot think the ultimate results favorable. (Fig. 20.) Fig. 18. Fig. 19. Fig. 18. The form of the Venus de Medici ; beautiful to the eye, graceful in move- ment, healthful, and long-lived. Fig. 19. The compressed chest of mistaken taste ; pity-causing, ungraceful, dis- proportioned ; productive of ill health, deformity, a sallow complexion, premature wrinkles, and untimely death. SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 47 Fig. 20. Fig. 20. 1, 1 represents the spinal column or back-bone very much curved, causing the right shoulder to be very prominent. 135. Fig. 20 is of course an exaggerated view of the or- dinary effect of tight dress, but worse deformities frequently occur. Within the ribs are found organs, which are both compressed and displaced by lessening the waist. To dimin- ish the evil, and give these parts as much room as possible, nature causes the upper part of the chest to yield. 136. In the first place, this causes square shoulders, in- stead of the graceful " falling" shoulders so much admired ; or the shoulders will be prominent what is called " round,' 7 and much disliked. From the constant size and firmness of the liver, on the right side, while on the left the stomach is sometimes full, sometimes empty, the effect of pressure will be greater on the right side. 137. In the second place, there will be a greater "shrug" or projection of the right shoulder than of the left, also a dis- placement of the spinal column, towards the right shoulder. These deformities render others necessary, that the system may be balanced. The head is inclined to the left, while the back-bone, in the loins, is displaced in the same direction. The hips are distorted, and the heads of the thigh bones can- not be opposite each other. Can the form of such a person be beautiful, or the movements graceful ? 48 ORGANS OP VOLUNTARY MOTION. [CHAP. I. 138. During the day a person grows shorter, while the height is restored by repose during the night. A French physiologist says, a son of his, during a single night's dance, lost an inch of stature, which he regained in two days. This is owing to the elastic nature of the cartilages, especially those of the back, and the restoring processes which are con- tinually taking place in all parts of the body. 139. To sit or stand, most of the time, with the back in a curved position, will tend to produce permanent comparative thinness of one side of the cartilage, and consequent deformi- ty ; while on the other hand, a variety of exercise in a vari- ety of positions, will not only prevent deformity, but from use, give a suppleness, vigor, and health to the cartilages, which can be obtained in no other way. 140. To sit, stand, or lie, in almost any position which gives comfort, cannot be productive of harm, if other posi- tions be frequently taken. No class of people are straighter than the tailor, who sits much of the time in a curved posi- tion ; but knowing that the fit of his coat is an advertisement of his skill, as soon as he is off " the board " he straightens himself. 141. A continued crooked posture is not to be recom- mended, neither is a lounging attitude always to be chided. Deformity is frequently caused by nature, to prolong the life which tight clothing tends to shorten ; it cannot therefore be remedied by the oft-repeated advice to "sit straight;" na- ture will remove the deformity as soon as the cause for which it was produced is removed.* 142. The ligaments, cartilages, and other parts are of * Experience has testified, that the tight clothing, supports, and di- rections to " sit up," without exercise, heretofore used, with hard seats, straight-backed chairs, and no allowance of easy positions, have most signally failed to accomplish the desired object ; and as it seems reason- able to trace the general deformity to these very things, will it not be well to try something else ? A new course cannot be worse. SEC. 1.] BONES, CARTILAGES, AND LIGAMENTS. 49 such a nature, when the system is " growing fast," that easy seats, chairs, rocking-chairs, sofas, and a reclining and sup- ported position, will be often required, to give rest and strength. I never saw an Indian sit erect, and the cat and dog repose themselves much. It is neither the curved position which does harm, nor the erect position that gains benefit ; but any position too often indulged in, or too long continued, produces evil results, while a variety of positions, and all kinds of exercise, give beauty and health to the form, and vigor and gracefulness to the movements. 143. If deformity exist, can the exertion of force merely, effect a cure ? What will prevent the recurrence of -the de- formity, when the force is removed ? Nothing. Experience has proved, that the end is worse than the beginning. The reasonable use of any part improves it ; disease enfeebles it. Exercise, gentle but gradually increased, is the required means for curing deformities. Years of patient persever- ance will sometimes be necessary, to gain the rich reward. 144. When force, supports, and exercise have been com- bined, to effect cures of deformities, the cure, if effected, should have been attributed to the exercise, which not only cured the deformity, but also overcame the effect of the force and supports. 145. Horseback riding is one of the best kinds of exer- cise, or riding in an easy carriage, the use of dumb-bells, the elastic exerciser, and other specific exercises which in the judgment of a skilful physician are best adapted to correct the deformity. The ordinary deformity of round shoulders, caused by neglect, can be corrected in a few weeks, by exer- cise every morning for five, ten, or fifteen minutes, with the perfect exerciser, dumb-bells, or throwing a chair around the head, and the like. 50 ORGANS OF VOLUNTARY MOTION. [CHAP. I. SECTION 2. Muscles, Tendons, fyc. 146. The muscles are what is usually called the lean meat. The tendons are the pearly white, strong parts, ter- minating the muscles, and connecting them with the parts upon which they act. 147. The appearance of these will be well understood by examining the " drum-stick " of a fowl, and the cords which extend to the claws, so amusing to children. 148. If the cord upon one side be drawn, the claws will be shut ; if the cord upon the other side be drawn, and the first slackened, the claws will be opened. 149. If both cords be drawn to an equal degree, the claws will be firmly held in any position where they are placed. 150. In the living bird, it is the contraction and relaxa- tion of the muscles in the leg above, which draws the cords acting upon the claws, either causing them to move or re- taining them in any desirable attitude. 151. The first use of the tendon is evident; for if the muscles had continued down to the foot, it would have been so clumsy as to render it unfit for use ; and again, the fleshy muscle could not form so strong a unison with the bone, as to resist its own action. 152. The use of the muscles is also evident, viz. to pro- duce motion of the various parts of the frame, and retain them in desirable attitudes ; for though the ligaments are ar- ranged so as to prevent motion in certain directions, they have been designed to permit it in others, flexion in the per- mitted direction being caused or restrained by the muscles.* * The frame being perfect, in respect to its structure, a beautiful form and gracefulness of action depend entirely on the muscles. In this sec- tion, therefore, especial attention will be given to explain what is for the good or ill of the muscles ; for it is not only proper, but our duty, to do all in our power to improve personal beauty, both because in all that sur- SEC. 2.] MUSCLES, TENDONS, ETC. 51 153. To fulfil these duties, it is requisite that they be numerous, contract and relax with promptitude, and with a greater or less degree of power ; that they should combine their action or oppose each other, or act in harmonious suc- cession. 154. Their ability to answer these requirements de- pends upon their structure, number, size, their position and mode of attachment, the passage of blood through them, their exercise, and the action upon them of certain influences called nervous. 155. By nature, the muscles are perfect in all respects; but their condition depends so much upon their treatment, and this is so faulty, that they are usually very deficient in the fulfilment of their important duties. 156. Structure. This is seen by observing a piece of lean boiled salt pork, salt fish, or almost any cooked lean meat. It will be noticed as composed of fleshy strings, easily separated in one direction ; in doing which, a very delicate sheet-like substance will be seen clinging to and uniting the separating parts, somewhat loosely with each other. This is called cellular substance or membrane. 157. With proper instruments, the fleshy strings so easily perceived can be subdivided, till those will be found not as large as a spider's thread. These are covered with a sheath proportionably delicate, which extends beyond the fleshy fibre, and with the cellular substance connecting the fibres, is con- densed into tendon. 158. Hundreds or thousands of these sheathed fibres are gathered into a bundle, and covered with a sheath somewhat thicker than the first, forming what is called a fasciculus. rounds us, and in the functions of the human system, we have evidence that the Creator intended every thing should be beautiful and attractive, and because what really improves or obtains beauty is equally influential in gaining and preserving health.- 52 ORGANS OF VOLUNTARY MOTION. [CHAP. I. Few or many of these covered with a sheath, called a fascia, form a muscle. Several muscles covered with a sheath, called also a fascia, form the arm. Place the hand upon the lower arm, then open and shut the fingers, and various mus- cles will be perceived. The fascia is for the purpose of binding the fibres, fasciculi, and muscles together, when they contract; the advantage of which will be seen, when a per- son grasps his arm with the hand and thereby raises a greater weight. 159. The fibres in any fasciculus are parallel and act together ; but the fasciculi of a muscle may be parallel or otherwise, and may or may not act together, or may act in succession. Thus some of the muscles are fusiform (Fig. 21).* By this arrangement, the attachments of the muscle occupy but small space, and the neat and commodious hand is moved with great power. Fig. 21. Fig. 21. f, t. Tendons of a fusiform (spindle-shaped) muscle. 160. Some are radiate, as the sticks of a fan (Fig. 22). This is the case with the temporal muscle, the thin edge of which is attached to the side of the head, without deforming it, while as the fibres converge toward the lower jaw, they are received in a hollow of the skull. The trapezius is an- other example (Lith. plate 2). This was evidently thus form- ed with a view to convenience of action, as well as personal appearance. By its action the shoulder is drawn upward, back- ward, or downward, while by a successive contraction of its parts, a graceful rotary motion is given, which could not so well have been obtained in any other way. f The stripes on the figures explain the direction of the fasciculi. SEC. 2.] MUSCLES, TENDONS, ETC. Fig. 22. Fig. 22. Fan-shaped, or radiated muscle. 161. In some instances the fasciculi are arranged upon one or both sides of a tendon, as the barbs of a pen (Fig. 23). By this arrangement a great number can act upon tho same point. This arrangement is particularly seen in the leg, where a great amount of muscular substance must act upon small points. Fig. 23. Fif. S3. Penniform (pen-form) muscl. 162. In some instances the fasciculi form circular mus- cles, orbiculares, or sphincters (Fig. 24). These may par- tially or wholly close any opening which they encircle ; the mouth, eyelids, &c. Fig. 24. 163. In some portions of the body circular fasciculi are placed by the side of each other, forming a muscular tube (Fig. 25). By the successive contraction of these rings, any thing can be moved through the tube, as is exhibited in the neck of a horse swallowing water. 64 ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 25. Fig. 25. Section of oesophagus, or meat-pipe, a, 6, Circular fibres, c Shows longi- tudinal fibres in another layer of the same tube. 164. Sometimes the fasciculi curve around, either in dis- tinct layers or interlacing each other, so as to form a muscu- lar pouch, bag, or bladder (Figs. 26 and 27). By the con- traction of the muscular substance of a pouch, its contents will be expelled, as when the heart throws out its blood, or by the alternate contraction and relaxation of its various parts, its contents can be moved about in it, as when the food is digesting in the stomach. Fig. 26. Fig. 26. Stomach muscles. L M, One layer of fibres running in one direction. C M, A layer running in another direction. E, Lower part of meat-pipe. P, Pylorua D, Commencement of second stomach. 165. The number of the muscles is about four hundred and eighty. The number will vary in different persons, and according to the plan adopted in counting them. Some per- sons divide a muscle into two, of which others make but one. Their number is such, that by the action of some one or its parts, or by the action of several or their parts, I know not a SEC. 2.] MUSCLES, TENDONS, ETC. Fig. 27. Represents the heart cut open, or rather, with a piece removed, the thick sides (o n) being composed of muscular fibres interwoven in every possible directiou desirable motion that cannot be performed, muscles only being considered. The lithographic plates represent most of them. 166. Size. In size, the muscles are extremely various. The six which produce the lively motions of the eye, are very delicate and beautiful (Fig.67) while the glutei are very large. Where much power is required, the muscle will be large if there be no objection, but if a large muscle would produce deformity or render the part awkward in the fulfilment of du- ties, a small muscle will be found, and its power increased by the action of nervous influence upon it. In some con- stitutions, the muscles are naturally much larger than in others. 167. In every person the muscles will increase or dimi- nish, within certain limits, by use or disuse ; and as, in any given person, the larger the muscles the stronger, so ought every person who wishes strong muscles, to exercise the back and give vigor to the movements, to avoid the use of all sup- ports which throw the muscles into disuse, enfeeble them, and produce deformity. 168. To gradually require more and more of any part is, therefore, a sure way to increase the power of perform- ance, if in other respects proper attention be given. 66 ORGANS OF VOLUNTARY MOTION. [CHAP. I. 169. The positions of the muscles can only be appreci- ated after a consideration of three kinds of ^evers, represent- ed by Figs. 28, 29, and 30. An example of the first is seen in the common steelyard, and in the board used by children in playing seesaw. It requires a very heavy boy on the short end of the rail to balance a light boy on the long end, and the small boy moves through a long distance in the same time the heavy boy moves through a short space. Fig. 28. Fig. 28. P,W, Lever. P, Power. W, Weight F, Fulcrum. Fig. 29. Pig. 29. F,W, Lever. P, Power. W, Weight. F, Fulcrum. Fig. 30. Fig. 30. F,W, Lever. F, Fulcrum. W, Weight. P, Power. 170. The muscle on the back part of the arm (Fig. 31) corresponds to the heavy boy, and the hand to the small one. By a slight contraction of the muscle, the hand is quickly SEC. 2.] MUSCLES, TENDONS, ETC. 57 moved through a long distance. Extent and celerity of mo- tion is what the muscles are usually called to produce. But the muscle must be much more powerful than if the arm had extended in the dotted line (A E), and the muscle had been situated in the dotted lines (A S). But as a muscle can only shorten to a given degree, viz. about one-third its length, the motion of the hand would have been very limit- ed. What an awkward thing the arm would have been ! Fig. 31. Fig. 31. Represents, at S, the ball of the upper-arm bone, which extends to the el- bow at E, from which the two bones (radius and ulna) extend to the wrist, to which the hand is attached, supporting the weight (W) T, T, represent the tendons, and B, the belly of the muscle upon the front part of the arm, attached at L to the lower-arm, and at O to the shoulder. On the back of the upper-arm is seen the muscle attached to the shoulder above, and to the projecting point of the elbow below This point, it will be remembered, is a part of the lower-arm bone the ulna. When, therefore, the muscle on the front of the arm contracts, the muscle upon the back must lengthen. When the muscle upon the front part of the arm contracts, the third kind of lever is represented ; for the fulcrum is at the elbow, and the power, viz. the muscle, acta be- tween the fulcrum and weisht, and the nearer the weight the power acts, the easier is the weight raised. If, therefore, the power or muscle should act in the dotted line above the arm, a very small muscle would be sufficient to accomplish what is now done by O, I. But it would require as long to shorten the muscle an inch in one po- sition as in the other; but the contraction of O, I, one inch, will produce extensive motion of the hand, while an inch contraction of the dotted line would raise the hand but one inch. When the muscle on the back of the arm is contracted, a lever of the first kind is represented. The elbow is the fulcrum, and is between the power and weight ; the action of the power, viz. the muscle on the back of the arm, draws the projecting part of the elbow up ; and the other extremity of the same bone, viz. the wrist, must be carried down. If the point of the elbow projected to A, and the muscla acted in the direction of the dotted lines (S, A), it would have greater " purchase p but if it contracted an inch, it would move the hand an inch only, while now, if it con- tract an inch, it will sweep the hand through great space, and of course, very quickly. The muscle also acts with greater power in the first part of its contraction, thin when its degree of contraction is near its limit. 171 . An example of the second lever is seen when a person attempts to raise a barrel of flour on to its head, by lifting at one end while the other is on the ground. The muscle acting upon 58 ORGANS OF VOLUNTARY MOTION. [CHAP. I. the heel (Fig. 32) is the power, the foot the lever, the ground where the toes rest the fulcrum, and the weight rests upon the ankle. Here, the greater the distance of the power from the weight, in proportion to the length of the lever, the great, er the effect. If the distance be short, the power must be the greater. The muscles which raise the weight of the body, when we stand on tiptoe, must be very powerful, and they are so, both by size (Lith. plate 1) and the reception of ner- vous influence. Fig. 32. Fig. 32. Represents the foot upon which the weight of the body rests through the oone (1), which may be called weight ; M, a muscle, is the power, for by contraction it raisea the weight ; 2, at the great toe joint, being the place of the fulcrum. 172. An example of the third lever is seen when we at- tempt to close a window blind by seizing it near the hinge ; the nearer the hinge the hand is applied, the greater the power required, but the less the motion. The part of the body most frequently described to illustrate this lever, is the forearm (Fig. 31). The muscle upon the front part of the upper-arm is the power, the joint is the fulcrum, the forearm is the lever, the hand is the weight. If the muscle had been attached at R, and been situated in the line T R, it would have been like putting the hand to the outer edge of the blind. The force required to raise the hand would be but slight ; it would have SEC. 2.] MUSCLES, TENDONS, ETC. 59 been raised, however, but slowly, and could have been raised but about one-third the length of T R. 173. Most of the muscles act disadvantageously as it re- gards expenditure of power, but the system is compact, beau- tiful, symmetrical, and the motions are performed with agility and to the extent required. In some cases the muscles act with the most complete advantage of position. 174. Some of the muscles, instead of acting between bones, are so situated as to act upon other parts to which they are attached. The " occipito frontalis " (Lith.) acts upon the skin of the head, moving the scalp, and is called a cutaneous or skin muscle. There are others of a similar character ; some act upon the fascia, as the Tensor vagina femoris (Lith.), rendering them tense. 175. The tendons of certain muscles pass through loops or pullies, in such manner as to produce motion in a direction quite different from that in which the muscle con- tracts ; the " superior oblique " of the eye is an example (Fig.67); the " digastricus," or " two-bellied muscle," is an- other instance one extremity is attached to the skull just below the ear ; it extends down to the side of the U-like bone at the top of the windpipe, where its central tendon is confined by a tendinous loop ; its front extremity is then attached to the inner side of the jaw near the middle. Its use is to de- press the lower jaw. 176. Bands confine the tendons of other muscles ; for in- stance, the one about the wrist called an annular ligament (Lith.). A similar one is found passing from the inside to the outside of the ankle, in front, confining the tendons that raise the toes. 177. Some of the tendons pass through or under each other. The muscle which bends inward the last joint of the fingers, is situated below the muscle which acts upon the middle joints ; the tendons of this last divide at their lower 00 ORGANS OF VOLUNTARY MOTION. [CHAP. I. extremities, one part being attached to one side of the bone, the other division to the other side, and the tendons for the last joint pass through between, whereby the fingers are neater and more useful. Again, the tendons of several mus- cles pass round certain bones, or are situated in grooves, as the tendon of the muscle on the outside of the fibula (Lith.), which passes down under the foot, and is attached just back of the great toe. Thus beauty and utility are every where combined. 178. Certain muscles pass across each other, as the tai- lor's muscle or sartorius, by which, with the action of others, the leg is drawn up, as when a tailor sits down on his board. The fasciculi of certain others are twisted, so to speak, and cross each other, as in the pectoralis major (Lith.). The contraction of the lower portion of this muscle would draw the shoulder down and forward, and the nearer it was at- tached to the shoulder, the more effectual ; while the contrac- tion of the upper part, would throw the arm across the chest, and the further from the joint, the more effectual. But the muscle must stretch down upon the arm but a short distance, or it would produce awkwardness. How ingenious, then, the contrivance which exists! 179. The position of the muscles is such, that motion is rarely produced by the action of a single muscle, but usually by the " composition of forces," which will be understood, if two boys attach two strings to a chair upon the floor, and then stand in front of it, some distance apart. If one only pull his string, the chair will be drawn toward him ; if each pull his string at the same time, the chair will move toward a point between them, which will be nearer to him who exerts the most force. If more boys be furnished with strings, the comparison will be more perfect ; and if one boy exert more force one moment, and another the next, the chair will de- scribe a variety of lines. SEC. 2.] MUSCLES, TENDONS, ETC. 61 180. The application of this principle in the action of the muscles is constantly required, but exceedingly difficult, as the force with which the muscle contracts must be almost constantly varying in the production of almost any motion. 181. The attachment of the muscles, except to the parts they are intended to act upon, is but slight, as can be seen, or felt rather, in the case of the neck cords, which hardly dis- turb the parts which surround them. They are, however, attached in the strongest manner at their extremities. Ob- serve the force with which the muscle upon the front part of the arm acta without in the least injuring its attachment. By its connection with the lever, if one hundred pounds be raised in the hand, the power exerted by the muscle must be twen- ty-two and one-half times as great, or sufficient to raise a " heavy ton.' 7 Other muscles exert greater power still. I have seen a man lie down upon his back under a cart, place his feet against the axle, and by straightening his limbs raise fifteen hundred pounds' weight from the ground. 182. The position of the muscles is such, that if one con- tracts another must relax. When, therefore, we consider the effects of contracting a muscle or class of muscles, we must also consider the effects of relaxation of its opponents ; and when we look for what will favor the contraction of muscles, we must consider what will favor the relaxation of its anta- gonists. 183. Contraction and relaxation of the muscles are attend- ed by a corresponding change of their substance. 184. This is proved by the change which takes place in the blood passing through a muscle, by the increased appetite and requirement for food attendant upon action of the mus- cles, or by an examination of the muscles of an animal which has been driven or hunted to death. 185. If the muscle undergo a change, two things are necessary ;. that the portion of the muscle which by its action 62 ORGANS OF VOLUNTARY MOTION. [CHAP. I. has become unfit for use be removed, and its place supplied by new material. Hence the necessity for a 186. Free flow of blood. By the current of blood through the muscle the decomposed substance is removed, and the substance to recompose the muscle is brought. 187. Pressure upon any part checks the flow of blood, and of course must be seriously injurious to the muscles ; to those of the young, for the muscles then need an extraordi- nary supply to cause them to grow, as well as to repair the effects of use, so do the muscles of all persons, that they may be endowed with the vigor necessary for the fulfilment of their duties. 188. Notice the muscles of the back (Lith.), and decide if the child can be gifted with a fine form, when the clothing prevents the free circulation of the necessary blood. Can the young lady be easy and graceful, when pressure upon the muscles of the chest, checks the flow of the repairing sub- stance, without which the muscles must be colorless, flabby, and weak, and incapable of performing their duties ? 189. Rubbing any part increases the flow of blood ; hence the benefit of rubbing the muscles. It causes the changes to take place in them more speedily, and gives relief to fatigue. 190. Fatigue is for the purpose of warning us, when the muscle has experienced so much decomposition as to render it proper to grant repose and time for its repair ; it is, there- fore, a friend whose hints should be regarded. The farmer who uses stimulating drinks, for the purpose of overcoming fatigue, does overcome the feeling of fatigue, but benefits not the muscle. If he go on to labor, he injures the muscle and profits not himself, as attacks of rheumatism and the stiffness felt in his declining years will fully prove. 191. Rubbing the muscles relieves from fatigue, by be- nefiting them ; hence why every laboring man should spend five, ten, or fifteen minutes, morning and evening, in doing SEC. 2.] MUSCLES, TENDONS, ETC. 63 for himself what experience teaches is so beneficial to the horse. 192. Rubbing supplies the muscles with blood, which shall increase their size ; hence why children should be tho- roughly and daily rubbed from head to foot ; for why should the colt, worth only a hundred dollars, be groomed so much better, that it may be fitted for the market, than the child, whose welfare is beyond price ? 193. Rubbing supplies to the muscles that blood, by the action of which a fine, healthy condition is preserved ; hence why those who wish to be graceful should rub the system from head to foot, at least once per day ; for why should the animal which the young lady rides, have daily attention paid to him in this respect, that he may prance with ease and make a fine appearance, while she, whose beauty is so much more attractive, is neglected ? 194. Rubbing supplies the muscles with the material which can restore their health and power of action. To the deformed, to the palsied, to those whose muscles are withered or shrunk from disuse, the hint is sufficient. To the posi- tively diseased by palsy it may do but little good it can do no harm. 195. Contraction and relaxation of the muscles has in one respect the same effect as rubbing, the blood-vessels being constructed, as hereafter described, so that the flow of blood must always be onward, and never backward. When a muscle contracts, its blood is pressed out from it ; when it relaxes, there is a rush of blood into it ; hence why the alternate contraction and relaxation are necessary ; for a muscle remaining long contracted, is undergoing decompo- sition without receiving blood to repair itself. The severest fatigue is therefore felt, to compel us to desist, or the muscle would be affected beyond restoration, as has sometimes oc- curred, when a feeble person has been called up, to save his 64 ORGANS OF VOLUNTARY MOTION. [CHAP. I. property from fire excited by the danger, he failed to heed, did not even notice the warning of fatigue, till exhausted, he was overcome, and years failed to effect a recovery. 196. In very rapid contraction of the muscle, a state ap- proaching continued contraction is produced. The blood has hardly time to gush through the muscle, perhaps does not visit every part, before it is sent on by re-contraction. Hence why a horse bears better to draw a heavy load slowly, than a light load quickly. Stage horses improve in " muddy go- ing," though longer on the road, their muscles contracting slowly, there is time allowed for their repair. 197. Exercise improves the condition of the muscle, by causing its bloodvessels to enlarge, both transiently and per- manently. There is a power operating in the healthy sys- tem, to adapt each part to the fulfilment not only of its ordi- nary, but extraordinary duties. 198. From what has been said, it is evident the muscles require more blood when in action than when in repose. The very exercise of the muscle answers the requirement in part; the increased action of the heart, as hereafter shown, is an advantage ; but the bloodvessels of the exercised mus- cles are enlarged for the time, and by repeated exercise the enlargement is made permanent, though an additional en- largement takes place at the time of action. 199. To strengthen the muscles, therefore, exercise must be gentle, repeated often, and very gradually increased. If it be violent at first, the muscle is injured. Those who speak, therefore, but once or twice per week, feel fatigue, while those who speak every day find it a pleasure. The person who is deformed from weakness of the muscles, exerts himself, and finds no relief, but harm to follow. 200. The sick must be especially careful, for the power referred to, as adapting all the organs to their exigencies, SEC. 2.] MUSCLES, TENDONS, ETC. 65 is feeble; and the muscles become strong very gradually in such a person, it is an exceedingly easy thing to overdo. 201. But rest seems as necessary as exercise. It is evi- dently so, for repose is eagerly sought after vigorous action, and a sound sleep follows. Slight repose is necessary after each contraction of the muscle, that the blood may be allowed to flow through it and communicate vigor by renewal, but yet the decomposition does not seem to be entirely compensated. 202. When the system is " growing," rest seems espe- cially necessary nature causes it to be sought, and follow- ing her hints, the system will not be subjected to very arduous labor, and a reclining posture will be allowed. Alarm will not be felt if, at such times, the chest and head fall forward somewhat. This will be "outgrown," if no force, supports, or tight clothing be used, and a plenty of exercise in the open air be allowed. The power which acts upon the muscle to produce all these results, is called the 203. Nervous influence. Whether this be of the same nature, when we see it exerted on the heart and causing it to beat, as when we see its effect in the contracting muscle of the arm, and when its action is seen upon the bloodvessels of the muscle enlarging or diminishing them, is not known. Whether there be one fountain or several from which it is derived, is not known with certainty. 204. Some of its effects are directly influenced by ttie mind, some only indirectly. The muscles are therefore di- vided into three classes ; those whicfc in health are contracted by the nervous influence under control of the will, such as the muscles of the arm, and are called the voluntary muscles ; those which are never directly acted on by the will, as the heart, and called the involuntary muscles ; those over which the mind ordinarily exerts no control, but over which within limited bounds it can, as the muscles concerned in breathing, and called mixed muscles. 66 ORGANS OF VOLUNTARY MOTION. [CHAP. I. 205. At present the muscles of the first class are under consideration. The nervous influence which acts upon them is derived from the brain through the nerves. To study these will therefore be the next step. But first, a view may be taken of the known effects of the nervous influence on the muscles. 206. Its first effect is to add immensely to the cohesive attraction of the substance of the muscle in one direction. Out of the body a muscle is separated by a small weight, but in life it is capable of exhibiting immense force without be- ing injured in the slightest degree. 207. The degree to which a muscle shortens and the power which it exerts, depends not on its size, merely, but on the nervous influence it receives.* 208. Whether the relaxation of the muscle is an active operation, or takes place by the withholding merely of the influence which caused its contraction, is uncertain. 209. The action of this influence depends much upon habit, as is seen by rotating the shoulder by means of the " trapezius " (Lith.) upward, backward, and downward, and then trying to rotate it downward, backward, and upward. The muscle is as ready to contract one way as the other, but we are in the habit of exerting the nervous influence upon it only in one way. How awkward the combined movement of the fingers when the first tune is attempted on the piano- by practice how graceful ! * * It has been somewhere stated, that if a small muscle be ordinarily called on to perform great labor, it is supplied with a large nerve. But we see every day, that a greater or less degree of nervous influence is exerted through the same nerve, and with the same instantaneous effect. Nor is there any proof or assertion, of which we are aware, that when a muscle increases to twice its former size and many times its former power, the number of nervous fibres passing to it from the brain are in- creased.' My own opinion is, therefore, that if a nerve be distributed through a muscle so as to be able to cause decomposition and contraction of all its parts, it is sufficient, and that any amount of influence may be transmitted through it. SEC. 2.] MUSCLES, TENDONS, ETC. 67 210. Many times indeed, muscles cannot act, because they have never been sufficiently exercised ^ but besides this, the perfection of gracefulness is the acquired ability to exert the nervous influence upon any muscle or part of a muscle, upon any class or parts of a class of muscles^ ; n- stantaneously. It is this which confers the power of singing any combination of notes, or speaking any combination of sounds, whether of our own or a foreign land. It is an al- most insurmountable task, but practice makes perfect. 211. The effect of habit is likewise seen in the muscles of expression, as those of the face (Lith.) are called ; though at times every muscle of the body exhibits the fervor of the mind. Almost any state of mind will, from habit, exhibit itself in the constant action of certain muscles, even when this is not desired, indeed when a strong effort is made to prevent it. The miser, who spends his time at home in counting his money, will betray his avarice in his face, even when dropping his hypocritical alms in the church box. 212. A lovely expression is to be obtained only by main- taining a lovely state of mind. Nature never supposed a man would be one thing and wish to appear something else, but judged he would be proudx>f showing himself as he is. 213. As all real beauty is in the mind, and matter is no- thing except as we associate the action of mind with it ; there is nothing so attractive, however bad the complexion or homely the features, as a face exhibiting an amiable disposition, a noble and cultivated intellect. The tinge of beauty on the cheek can be surpassed by the inanimate lily ; the dentist can supply the deficiencies of nature as perfect in beauty as her own works; the sculptor can give us perfection of features beyond reality : it is the mind only which makes the "human face divine." 214. The muscles being thus dependent on nervous in- 68 ORGANS OF VOLUNTARY MOTION. [CHAP. I. fluence and the action of the mind, if the nervous influence be diverted to other objects, the muscles cannot contract with vigor, nor can they, without the energetic action of the mind. Those, therefore, who hope to gain benefit from exercise by merely exercising the body, while the mind is deeply en- grossed with home or business affairs, will be disappointed. To labor or exercise in a way that engages the mind, and also produces a lively, agreeable disposition, is exceedingly important. A dull, compulsory walk, is not the thing. 215. The laboring man will also perceive that mental cultivation is important for him, if he would labor with suc- cess. He who reads two hours per day, and works eight, will accomplish more in a lifetime than he who labors ten, and does not devote any time to the improvement of his mind. 216. The voluntary muscles are also active involuntarily. That they can be so is evident from the twitchings seen in chorea or St. Vitus' dance, and in the convulsions of disease, lock-jaw, tetanus, &c. That they are is certain, as, if ft muscle be cut, the wound gapes ; if a bone be displaced, the greatest force to be overcome in "setting" it, -is the involun- tary action of the muscles of volition ; if a person walk, stand, sit, or recline, or evn repose in sleep, the constant in- voluntary action of the voluntary muscles is required to balance the system; many other illustrations might be used. 217. Some suppose a certain degree of power of con- traction resides in the muscle itself, which seems to be exhibited in the rigidity of the muscles after death. But, all things considered, every action of the muscle seems to be conferred by the nervous influence, and this I believe is the opinion of nearly all persons, and is proved by the ef- fects of tobacco, intoxicating drinks, fear and other emo- tions of the mind, and of disease of the fountains of nervous influence. SEC. 2.] MUSCLES, TENDONS, ETC. 69 218. The power and certainty with which the involunta- ry contractions of the voluntary muscles take place, seem dependent but very slightly upon habit, but upon the health of the system and its natural constitution ; things which affect the condition and energy of the nervous influence. The power of exercising this influence may be classed as an in- stinct. The power of balancing the system, seems to be rather dependent on overcoming fear and trusting to the power which has been spoken of, and on strengthening the muscles, than on perfecting the action of the voluntary in- fluence. 219. Habit has however its effect, either on the produc- tion of the influence or on its exercise ; for a disease having existed, its symptoms continue after it has disappeared ; as frequently a child cured of chorea continues to twitch, and other illustrations might be given. In such cases it is neces- sary to produce a powerful influence on the mind ; and many wonderful cures effected by pills of bread or something not as harmless, found in the recommendations with which quacks gloss their advertisements, may be accounted for in this way. 220. The action of the muscles is facilitated by cellular substance, bursse, and fat. 221. Cellular substance (Fig. 33) has been spoken of as found between the muscular fibres and fasciculi ; it is also found between the muscles, between those and the skin, and between many other parts of the body. 222. Sometimes it is condensed so as to form a thick fascia, but usually it has the appearance exhibited between the muscles, and which its name indicates ; viz., it is formed of very delicate membranes intersecting each other and form- ing cells, which communicate with each other and are moist- ened upon their inner surface, by a fluid very similar to sy- novial, but called serous fluid. From the fluid it forms, the cellular is also called a serous membrane. TO ORGANS OF VOLUNTARY MOTION. [CHAP. Fig. 33. Fig. 33. A small portion of cellular substance or flesh, stretched so as to show it cells. 223. This fluid is continually formed and removed, as is the synovial fluid, and like it sometimes is wanting or accu- mulates ; in this last case producing a kind of dropsy called anasarca, for which sometimes medicines, sometimes an ope- ration called tapping, is required. The result of this shows the communication of the cells with each other ; as an open- ing being made through the skin, the fluid from the entire limb is drawn off. It makes its way from one cell to another. 224. The rapidity with which this is formed is shown by the swelling of the feet, which will sometimes become quite " puffy " in a very short time, and again be reduced as quick- ly, though this is partly from the enlargement and diminution of the veins. 225. The cellular substance is seen and understood by the butcher who thrusts a tube into a piece of meat and blows the air into its cells, for the purpose of giving it a better appear- ance. The French, for a disease of the joints of horses, pass a tube through the skin and blow the air into the cellular sub- stance of the entire body.* When accident sometimes injures * One physiologist proposed to inflate the cellular substance of the body with hydrogen gas, that its buoyancy might enable a man to fly. A somewhat " flighty " idea. SEC. 2.] MUSCLES, TENDONS, ETC. 71 the side of the chest and lung, the air which we inhale finds its way into the cellular substance and the whole body is inflated. 226. Its nature and position is such that it is admirable as a " packing," and allows the muscles to move over each other with the slightest friction. 227. The bursae are bags, internally moistened with a fluid continually formed and removed, which is sometimes defi- cient, sometimes superabundant. In the first place, inflam- mation is soon produced ; in the last, a " weeping sinew " is the result, and weakness of the part is soon complained of. It should not be neglected as usual, as the remedy is simple and can be applied by any physician, though it may require repetition when done in the best way. Or a person may him- self lay the part affected, the wrist for instance, on his knee, and strike the bursse with the back of a firm, heavy book, with such force as to break the bag and allow the fluid to pass out. This is usually sufficient, but if the sides of the bag do not from inflammation unite, but again distend with fluid, the same operation is to be repeated. Some prefer to pierce the bursae and inject some irritating substance. Had I one, I should have it treated in this manner. 228. Being placed where there is liability to friction, their use is indicated. A large one is found at the elbow, beneath the skin ; several are found at the wrist ; one, of an hour- glass shape, is seen by pressing upon the edge of the palm of the hand, as the fluid from the front part is pressed back, and can be readily felt. 229. To the muscles fat serves as a packing, and to keep them warm when deposited between the skin and muscles ; in which position it also relieves from the rigid appearance which the contracted muscles would otherwise present. Its other uses will be spoken of hereafter. 72 ORGANS OP VOLUNTARY MOTION. [CHAP. I. SECTION 3. The Brain and Nerves. 230. The functions of the nervous system are numerous, but in this section will be considered only in relation to mus- cular action. 231. In this respect, the office of the nervous system is to produce nervous influence ; to transmit this to specific parts, and to cause it to act upon them. 232. The places where it is produced are called nervous centres ; the nerves are the means of transmission, and the extremities of the nerves, or an unknown apparatus at the extremities, are the means by which the nervous influence immediately acts upon the muscular substance. 233. First) The Nerves : These are white pulpy cords, reaching from the brain and spinal cord to every muscle of the body (Fig. 34). If minutely examined, every nerve is found to be composed, like a skein of silk, of threads, each of which might with propriety be called a nerve, but is usu- ally called a nervous filament. 234. Each filament is composed of a sheath, filled with a pulp or jelly-like substance. Two or more filaments, situ- ated by the side of each other and covered with a general sheath, constitute a nerve, which is, of course, larger or smaller, as it is composed of many or few filaments. The filaments are extremely minute, being finer than the finest thread of the spider. 235. As the destination of the filaments of any part is the same, they converge towards each other, forming the smaller nerves j which converging in the same manner, unite to form the larger ones. Thus are formed what are called branches and trunks. These are not, however, like those of a tree or stream, blended, or properly speaking, united, but in this wise : if ten branches be composed of ten fila- SEC, 3.] THE BRAIN AND NERVES, Fig. 34. 78 Fig. 34. In the upper part of the head is seen the large brain. In the lowerandbaek part, the small brain is represented. Below this, is seen the commencement of the 74 ORGANS OF VOLUNTARY MOTION. [CHAP. I. ments each, the trunk will contain one hundred in its entire length, or till it receive additions from other branches, which will increase its number. 236. The general neurilema, or nerve-sheath, envelopes the filaments of the trunk and branches, as the bark of a leaf- less tree incloses the wood. An inflammation of this sheath or membrane, is supposed by some to be the disease, neural- gia ; but it is probable, or even certain, that other conditions also produce that painful complaint. 237. In the course of certain nerves are found, what are called plexuses and anastomoses (Fig. 35). The lettered extremities represent the nerves coming from the neck re- gion of the spinal cord (Fig. 34). In the plexus, it will be seen that filaments from the various nerves pass across each other, and unite with those from a different nerve. The figured extremities of the plexus are therefore composed of filaments from each of the lettered extremities. An anasto- mosis is a small plexus, and not, as its name signifies, pro- duced by a genuine uniting of the nerves, or rather an open- ing of the nerves into each other. At either of these, the direction of the filaments is merely changed, and each one can be traced through the plexus or anastomosis. The object of such an arrangement seems to be, to allow a certain de- gree of influence to act upon any part, by uninjured branches, if a nerve be accidentally severed, and to allow the influence to act simultaneously upon different and perhaps distant parts, the harmonious action of which is required in accom- plishing any object. 238. That the nerves are the means of transmitting the nervous influence, is proved by the effects of sections and spinal cord, enlarged between the shoulders and in the loins. From this, the nerves are observed extending from either side in pairs, the large ones, in the region of the thighs called the sciatic, passing down the lower extremities, being especiallv worthy of notice. In the loins and vicinity of the shoulders, the nerves are observed sending branches to each other, thus forming a plexus. As the nerves unite to form the cord, it is also observed that their course is very much inclined vipward in the lower part of the back, and scarcely at all in the neck. SEC. 3.] THE BRAIN AND NERVES. 76 Fig. 35. Fig. 3o. This represents a plexus, and the fact that the nerves do not strictly unite with each other, but that the filaments of one pass to be inclosed in the sheath of an- other, their course and neighbors merely, being changed. compression of nerves. Experimental sections can be made in animals, and accident affords opportunity of observing the effects of section of human nerves. A lady in Concord, by falling upon a piece of glass, cut her elbow across what is commonly called the " funny " or " crazy bone," by which a section was made of the nerve which transmits influence to the muscles acting upon the little finger. She could no longer open it. If a divided nerve unite, as it usually will, in a longer or shorter time, control over the muscles is again restored. A section of any trunk exhibits an effect upon all the muscles receiving its branches. 239. The effect of compression, is exhibited when we strike the " funny bone " against the sharp corner of any piece of furniture. The little finger and side of the hand are not only numb in feeling, but are for an instant immovable by any influence we may try to exert upon their appropriate muscles ; but as soon as the nerve has recovered from the effects of compression, the muscles are again subject to our command. 240. A large nerve, " great sciatic " (Fig. 34), in a part of its course, is so situated that it is sometimes compressed between an unpleasant seat and the hip bones. The effect produced is described by saying " the foot is asleep."* The * This state of things is not produced by a stoppage of the circula- tion of the blood, as is usually supposed, 76 ORGANS OF VOLUNTARY MOTION. [CHAP. I. influence being to a great degree cut off from the muscles of the foot and leg, they are moved with difficulty, if at all. 241. A tumor sometimes grows in such a situation as to compress a nerve, exhibiting peculiar effects in the parts where the filaments of a nerve terminate. Removal of the tumor removes its effects. Disease of a nerve, and some- times disease of the part through which the nerve passes, produce like effects, exhibited in the parts where the nerve terminates. 242. When, from any cause, control over the muscles is lost, they are said to be paralyzed, when perhaps they are perfect, and ready to act, if the influence were only exerted upon them. Hence, sometimes rubbing the muscles, &c., will produce a favorable, and sometimes no effect, the cause of their inaction being far distant from them. 243. How the nervous influence is transmitted through the nerve, what effect it produces on the nerve, or the nerve on it, or whether the nerve rapidly undergoes changes while fulfilling its duties, is not known. Our present ignorance of the intrinsic nature of the nervous influence and its mode of action, precludes us from arguing very successfully, as to what is or ought to be the condition and manner of acting of the nerves. The nerves do not seem to undergo changes very rapidly, as they receive comparatively but a small sup- ply of blood. Hence they are seldom attacked by the in- ffammation which exists in parts which they traverse. This is another remarkable instance of the admirable arrangement which pervades the whole system. 244. Each nervous filament has the property of isolating, as the expression is, the influence transmitted through it ; that is, through any filament of a nervous trunk an influence can be caused to act upon its appropriate muscle or part of a muscle, without any influence being communicated to its nearest neighbor. SEC. 3.] THE BRAIN AND NERVES. 77 245. This exhibits a marked difference between the ner- vous influence and all those things to which it has sometimes been compared, and with which some have thought it iden- tical, viz., electricity, galvanism, magnetism, &c. These will pass from one filament to all the rest in the same nerve ; and if applied to a trunk, will exhibit effects in the muscles of all its branches. 246. There seems to be no proof that the filaments of a nerve increase in number or size by use. Nor does there seem to be any necessity for such increase. For aught we know, the most delicate filament is sufficient for the transmis- sion of ten times the nervous influence, if such an expression may be allowed, as is ever transmitted, when the most pow- erful exertions are made. Observe the almost superhuman force exhibited in certain diseases. Whether the influ- ence can be transmitted with any more facility or rapidity, when it is done frequently, is not known. Action of the muscle is produced with more precision, alacrity, and grace- fulness, when frequently and properly repeated ; whether this depend at all upon an improved condition of the nerve, is conjectural. 247. As, however, the development and preservation of the nerves must depend upon an adequate supply of blood, it is presumable that rubbing and general exercise, which increases the flow of blood through every part, would be highly beneficial to the nerves. This would be especially the case, when, from disease, the action of any part is torpid ; for then the restoration of the nerves thereof, must be very much hastened by accelerating the flow of blood, by fre- quent and brisk rubbing, particularly as the muscles of the part are incapable of effecting much by exercise. It is a general rule, that any part which receives but little blood in health, is very tardy in recovery when diseased, especially if the disease be of a low character. If, however, the dis- 78 ORGANS OF VOLUNTARY MOTION. [CHAP. I. ease be of an active character, and acute inflammation exist, so that rubbing produces acute pain, it should be dispensed with. 248. Second) The terminations of the nerves. The nerves are so exceedingly delicate, when they reach the muscles influenced through them, that the statements of au- thors in respect to their mode of terminating are very dis- crepant. Some suppose that the nerves arrive at a simple termination. Others suppose that the nerves terminate in loops, by which arrangement they suppose they can account for effects seen. Others again suppose that there is some peculiar arrangement at the extremities of the nerves, by virtue of which the influence derived through the nerve acts upon the muscle. Some suppose that a substance of a pe- culiar character may be discovered at the extremities of the nerves in the muscles. Others, and I believe correctly, think that when the filaments reach the muscles in which they terminate, they are connected with genuine branches, which are indeed parts of them, in such wise that the influ- ence acting through a filament, acts through all these minute twigs, which increase and diminish in number with the in- crease or diminution of the muscle. 249. There must be something peculiar in the extremity of the nerve, and different from its remaining parts ; as the muscles traversed by a nerve will remain entirely inactive, while those at the extremity are violently contracted. The influence must be caused to act through a certain distance from the extremities, as these do not touch each other ; while, on the other hand, the sphere of influence must be very limited, as one fasciculus of a muscle may be brought into action, while others in contact with it are uninfluenced. The darkness in which we thus sometimes grope, should not discourage the student, nor dishearten the confidence of the reader ; but en- courage the first to greater diligence in investigating a sub- SEC. 3.] THE BRAIN AND NERVES. 79 ject so interesting, the unfolding of which will prove so valu- able to mankind, and enrol his name among those of whom all men speak with love and reverence ; and assure the last, that much of the disease which the skill of the physician cannot prevent or cure, is owing, not to the inefficiency of science, but to our ignorance, which difficulty, we hope some day will overcome. 250. Third, The nervous centres : These will be found in the brain and spinal cord, as is proved by section and com- pression of nerves, reaching from those parts to the muscles, as before illustrated, and by the effects of disease of the brain and cord. 251. In the first place, the cord and its protections. The back-bone, in which the cord is situated, is its chief pro- tection. This is composed of twenty- four bones, called ver- tebrae, resting on the " sacrum," or sacred bone so called from its being offered by some ancient nations in sacrifice. 252. These bones vary in size and thickness, in different parts of the back ; in the loins they are very large and strong, presenting a great extent of surface for the attach- ment of parts. The front part of the bone (Fig. 36) is call- ed its body. This is very conspicuous in the loins, growing less and less so, till we arrive at the skull. Between each two of these, except the two upper ones of the neck, is found a cushion of elastic substance, called fibro-cartilage. This is very thick in the loins, quite thin in the chest, and inter- mediate in the neck, according to the necessities of the part where it is found. 253. The hole (Fig. 36) assists in forming a canal called the rachidien, which exists in the entire length of the spinal column. The diameter of the hole varies in different bones, as may be seen by examining Fig. 37. The hole in each vertebrae is greater at its upper and lower edge than in the middle, as in Fig. 38. By this arrangement, when the back 80 ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 36. Fig. 36. A vertebrae representing the body, the hole, the lateral (side) processes, and the spinous (spine-like) or posterior (back) process. is curved, the contents of the canal are not injured by pres- sure upon the sharp edges of the vertebral hole, as would be the case if the hole had been as represented by the dotted lines (Fig. 38). 254. The projection at the back of bone, Fig. 36, and which is so distinctly felt in the back of any person, is called the spinous or spine-like process. A remarkable difference is observable in the arrangement of this, upon different bones. In the loins it projects directly backward (Fig. 40) ; and when the back is erect, there is quite a space between the processes of adjoining bones. In the chest, the process in- clines downward very much, as seen by comparing Figs. 39 and 40 ; and when the back is erect, they almost or quite touch the bone below. In the neck, the inclination is less and less, as is also the size, till we ascend to the two upper ones, which are like those of the loins, but not as large, of course. 255. Two objects are gained by this admirable arrange- ment. Great extent of motion, forward and backward, is desirable, in the region of the loins and upper part of the Fig. 37. ORGANS OF VOLUNTAKY MOTION. [CHAP. I. Fig. 38. Pig. 38. Is an ideal representation of two bones with their intervening cartilage (2) of the back ; 1, 1, the bodies of the bone, through which a section has been made ; 3, 3, are the posterior (back) processes of the same ;" 4, 4, is the canal in the back-bone, the surfaces of the bones upon either side being full in the middle (opposite 4, 4), and re- ceding above and below. If the surfaces had been in the direction of the doited lines, the canal would have been of the same size at the top, middle, and bottom of the bone ; bat now there is opportunity for the bones to bend without causing any angles in the canal, or lessening it, prejudicially to the cord. neck ; while a forward movement of the vertebrae of the chest should be very limited, and is made so by the position of the ribs ; and backward motion, which would be still more deleterious, is properly restricted, by the inclination of the processes of the dorsal vertebrae. In the next place, the muscles attached to the spines, which are not inclined, have, as will be seen, a greater lever power, which is required for readily producing the desirable motions. The combination of great size, strength, and extent of surface ; the action of the cushions, thick and elastic ; the strong, perpendicular spines ; and the conspicuous and proper enlargement of the Fig. 37. Represents a front view of the brain raised up, and the spinal cord, the bodies of the vertebrae being removed. The black spots represent sections of the bone, between which the nerves are seen passing out. The greater distance of the spots from each other at different parts of the back, and the curve of the bone on the face toward the cord, exhibit the facility with which the back may be bent and the cord not injured. At the upper part of the cord, an enlargement represents the medulla oblon- gata (oblongated marrow) ; immediately above this, the cross lines show the pons Va- riolii (bridge of Variolius), as he suggested that the fibres of which it is composed might, like bridges, serve to connect certain parts of the two halves of the brain. Above thia is seen the crossing of the nerves of sight, called the optic commissure, and above this, the deep fissure, found between the two halves of the brain. The continuous lines upon each side of the centre, extending from the upper part of the neck to the sacrum, in front of which they are united by "cross lines, represent the situation of what are called the sympathetic nerves, upon the ribs upon each side of the back-bone ; in their course, several enlargements called ganglions are seen, and they are represented as connected by small branches, with the nerves coming out from the spinal cord. SEC. 3.] THE BRAIN AND NEftVES. 83 Fig. 39. Fig. 40. Fig. 39. Represents one of the vertebrae of the back (a dorsal vertebrae ). 2, The body of the bona. 3, The spinous process very much inclined down. 7, 7, The notches through which the nerves come out. Fig. 40. Represents a lumbar (loins) vertebras. 2, The body of the bone. 3, The epinous process not inclined. 7, 7, Notches for the passage of nerves. central hole or foramen at its upper and lower edges, in case of the lumbar (or loins) vertebree, is only one among a hun- dred instances of the perfection which reigns through the whole system. Is not such beauty and perfection decided proof that disease and premature death is not in accordance with the intentions of Nature ? 256. The prominences at the sides of the bone (Fig. 36) are called the lateral or side processes. They serve for the attachment of muscles, and in the region of the chest, afford support to the ribs. 257. Between each two vertebrae, at the sides, a hole is found, called the intervertebral foramen, or between the ver- tebrae hole This is partly excavated from the lower bone of the two, but mostly from the upper. Through these holes the appropriate nerves find a passage into the rachidien canal. 258. The second protection is found in what is called the dura mater (Fig. 41). This is a dense membrane, about one- sixteenth of an inch thick, which lines the rachidien canal, being connected with the vertebras at several points, but not very closely. Between it and the bones there is a portion of 84 ORGANS OF VOLUNTARY MOTION. [CHAP. I. oily or fatty substance, (during life it is between oil and lard in its consistence,) situated in its appropriate cells. This facilitates the movements of the internal cord. Fig. 41. Fig. 41. Represents the bodies (a, a, a) of three bones of the back, broken from the back parts (c, c, c), which are drawn away a little distance, that a view may be given of a perpendicular section of the spinal cord (5), and the parts (1, 2, 2, 3, 4) be- tween the cord and the inner surface of the bones. 1, Dura mater. 2, 2, The two lay- ers of the arachnoid represented as reflected at 6. 3, The coarse cellular substance occupying what is called the sub (under>arachnoid space. 4 5 The pia mater. 259. Another protection is found in the arachnoid or spider's- web membrane. As its name indicates, it is exceed- ingly de-licate. It lines and closely adheres to the dura ma- ter by one surface, at first appearing like a part of it, and is . reflected, as the expression is, so as to form another tube and cover the parts within it, to which it adheres. The two surfaces which are toward each other do not adhere, but are called free, and are moistened by a fluid called serous, exist- ing in health only in small quantities, as it is formed and re- moved in the most constant ratio by the action of the mem- brane itself. 260, The side of the more internal arachnoid, toward the cord is connected with a cellular substance, existing between this membrane and the one which directly covers the cord. The cells of this being filled with fluid, distend the internal SEC. 3.] THE BRAIN AND NERVES. 85 arachnoid, and keep the two surfaces of the two arachnoids in contact, affording admirable protection to the cord. 261. Still another protection is found in the pia mater, which is the name of a membrane which immediately covers the cord, closely adhering to it, indeed rather compresses it, as when the membrane is cut, the cord protrudes. 262. From the sides of the pia mater, a portion called a process projects, and from this certain points reach as far as the dura mater. These form what are called the ligamenta dentata (Fig. 42). These support the cord, or retain it in a central position, allowing it, however, a certain degree of mo- tion. The same purpose is subserved by a process, as it is termed, of the pia mater, which is attached to the lowest point of the rachidien canal. Fig. 42. Fig. 42. A represents (3, 2) a horizontal section of the cord and pia mater covering it, and at 1, 1, passing to the lining (4) of the bony canal. 1, 1, are called the ligamenta dentata, one of which is represented in B; which, by 1, represents a perpendicular section of the cord ; 2, 2, the pia mater ; 3, the ligamentum of one side, which at cer- tain places extends to the wall in the form of points or tooth-like ; hence the name deutata. 263. The cord extends from the skull to the lumbar ver- tebree, when its large divisions form the " cauda equina," or horse-tail (Fig. 34). The position of its lower extremity varies with the posture of the back. In a stooping postura it is not as low as when the attitude is erect. The cord ii 86 ORGANS OF VOLUNTARY MOTION. [cHAP. I, susceptible of being lengthened, and is stretched when the back is curved. Externally viewed, the cord is a white pulpy substance, so much resembling the marrow of the bones as frequently to be called the spinal marrow. It is not, however, a fatty substance, as the marrow, but is mostly composed of nervous fibres, like the nerves, many of which are indeed the same. 264. If a section of the back be made, as in Fig. 37, the nerves will be seen entering through the intervertebral fora- mina and the membranes of the rachidien canal, to unite with or form the cord. At the lower part, as in Fig. 37, or Fig. 34, the filaments of the nerve are seen inclining very much upward, after they enter the canal ; but the upper nerves unite more horizontally with the cord ; indeed, the upper pair rather incline downward. 265. If a transverse section of the cord be made, it will be seen (Fig. 43) to be composed of two halves, sometimes called two cords, united by a narrow band of white fibres, called a commissure. This accounts for the deep front and shallow posterior, dividing grooves seen in the entire length of the cord. Fig. 43. Fig. 43. Represents a cross, transverse, or horizontal section of the spinal cord, th dark half-moon shaped spots representing the gray substance. 266. Each half is composed internally of a gray sub- stance, differing in its arrangement in different parts of the cord ; its general appearance being that of a half-moon, with its convex side toward the other half, one horn reaching quite to the surface, and dividing each half into the smaller back SEC. 3.] THE BRAIN AND NERVES. 87 or posterior, and larger front or anterior columns, as they are called. 267. The gray has hardly as much consistence as the white substance. In great part, it seems to be composed of a granular substance, most nearly described by the word jelly ; while the white substance appears to be mostly fibrous. 268. The use of this gray nervous substance, whether found here or elsewhere, is not known. But as it is easy to form conjectures, this has been done. Some suppose that it is the generator of the nervous influence, distributed through the white fibres, and consider that there is a nervous centre wherever this gray substance is found, and speak of collections of it, as brains. To confess ignorance is, however, far more honorable than to support a fallacy ; beside that, it deceives ourselves ; for truth is so lucid and necessarily supported by such strong arguments, it is at once recognized by the mind unprejudiced by adherence to invented theories. 269. Some have supposed the white portions of the cord are composed of the nerves, which enter the canal to pass up to the brain. In this case, the cord would be a very simple thing to consider, viz. a great nerve the grand trunk of the body. But then, why such care in the arrangement of its protections ? Why the gray substance ? Why the enlarge- ments of the cord in the region of the shoulders, where the nerves of the upper extremities come off; or in the lower part of the cord, where the nerves of the lower limbs leava the spinal marrow ? 270. The best testimony and examination seem to prove that a portion of the nervous fibres commence at or in the cord, while another portion forms a part of the cord, being continuous from the brain ; while it is not impossible, but al- together probable, that nerves commence at the brain and terminate in the cord, as will be made more clear hereafter. 271. In fulfilling one of its duties, the cord may then be 88 ORGANS OF VOLUNTARY MOTION. [CHAP. I. considered as a mere nerve, transmitting influence from the brain. In fulfilling another duty, it may be considered as a nervous centre, or as a congeries of nervous centres, where nervous influence is produced, and from which it is transmit- ted to the muscles. 272. If the head of a turtle be removed, and a coal of fire placed upon his back, as soon as the heat affects the cord, with harmonized action the legs scramble off with the body as fast as possible. If, however, the cord be destroyed, by thrusting a wire down the canal, nothing of the kind takes place. If only the front portions of the cord be destroyed, the motions of the fore-paws only cease. To show that there are several centres in the cord, various illustrations might be used ; but space cannot be allowed to what may ultimately prove valueless. 273. In addition to what has been said, it may be well to exhibit in brief the opinions of the most eminent. Some sup* pose that the whole nervous system is continually charged with influence, which is continually passing to the muscles in a certain degree, and is increased when desirable. Others think the influence is produced at the end of the nerves, and is operated in some way, as yet incomprehen- sible, through the nerves ; by some thought to be accomplish- ed by a tremulous movement of the nervous filament, which nothing has proved to exist. Others think that a change is produced in the nerve, and propagated through the entire length of it ; some thinking that this consists in a mere pro- pulsory action from one particle to another, and some, that a decided change is produced in the particles forming the line of action. Most suppose that an entity is produced at the nervous centres, acting by certain, its own laws, through the nerves, with the quickness of lightning, and the perfec- tion of results which mark the works of the Creator only. Some of these last consider that the influence is produced in SEC. 3.] THE BRAIN AND NERVES. 89 the brain only, from which it is disseminated ; others, that it is produced in the cord only, from which it passes off*, some- times under the action of the brain, sometimes not. Some think there is but one grand centre in the cord ; others sup- pose there are several. Some again think that both the brain and cord are centres, and some that there are several centres, either in the brain and cord, or cord and brain, or in both. 274. It may seem strange that there are so many opinions upon so important a point, but the opinions are not more di- verse than the facts that can be advanced in their support ; and no theory upon this subject has been advocated, which is not opposed by some fact. A large part, however, of the suppositions under IF 273, and many more like them, are evi- dently fanciful, and have few supporters. There is also one apology to be made. Scarcely any dependence can be placed upon analogy, the source of many fallacious arguments, for all animals are not operated upon in the same way by similar experiments ; and a striking difference exists between effects upon other animals and man. 275. One theory is however worthy of more distinct no- tice. Sir Charles Bell supposed he had proved that the mid- dle portion of the sides of the upper part of the cord were nervous centres. In these he thought the influence was pro- duced which acts upon the respiratory or breathing muscles, and uncontrolled by the brain. My own opinion, and that of most, I believe, is in favor of the theory ; but some do not regard it as correct. 276. Diseases of the spinal cord are various and very perplexing to the physician, from ignorance of the nature of the nervous influence, its mode of production and action, and the effects which its production will have upon the appa- ratus producing or transmitting it. 277. Its diseases and injuries exhibit paralysis, convul- sions, cramps, lockjaw, shaking palsy, general weakness of 90 ORGANS OF VOLUNTARY MOTION. [CHAP. I. the muscles, &c. Some, perhaps all of these, may also be exhibited while the cord is, to all appearance, in a healthy condition. These exhibitions may be partial or general. One muscle, for instance, may be affected, or all below the injured point, or only the muscles of one side, according as a few filaments of the cord, the whole of it, or the half is af- fected. 278. One of the most simple ways of ascertaining the existence of certain common diseases of the back-bone or its contents, is to exert pressure along its extent, when pain will be felt if disease exist. In case it does, the earliest attention should be given, and the most assiduous care must be bestow, ed, for a long time, and in many cases it will be imperatively required. A person of real science, skill, judgment, and in- dustrious patience to investigate and apply, is the only one who can afford the assistance which nature requires, and even then failure must be expected. 279. To prevent the recurrence of such disease is worth trouble. The attention may therefore be drawn to one evil very generally prevailing. The clothing of females is fre- quently so arranged, upon the lower part of the cord, as to preserve a temperature too elevated for its health ; while in cool weather the upper part is too much exposed to suffer from a low temperature. This double cause acting upon the cord at the same time, and disturbing the circulation, must prove fruitful of the worst diseases. 280. That rapid changes of the cord are produced in ful- filling its duties, can only be inferred from the large quantity of blood which circulates through the vertebral canal, and the liability of the cord and its appendages to inflammation. From all that we know of its duties, we can only infer that it should be supplied with a sufficient quantity of good blood. 281. In the second place, the brain. Its outer protection is the hairy scalp ; beneath this is found a layer of fatty sub- SEC. 3.] THE BRAIN AND NERVES. 91 stance ; then cellular substance, muscles, tendons, &c., when we reach the skull. These parts serve the double purpose of preserving the temperature of the head, and lessening the effects of blows. A lady of my acquaintance was once thrown from a gig against the sharp edge of a stone, her bonnet and knob of hair were badly cut ; she was only stunned. 282. The general form of the skull has been demonstrat- ed (Arnott's Physics) to be the best possible for resisting the effects of weight or blows (Fig. 44). The figure exhibits the arch found at the summit of the head ; and any one may learn the strength of the arch, by observing the heavy bur- dens the arched bridge will support without yielding ; or still better, by observing his own head. The immense blows the negro's skull is capable of resisting is proverbial. Fig. 44 (A). 283. Concussion, or a severe jarring or shaking, seems to injure the brain more than cutting, or even contusion. Hence the impropriety of striking the head, even in the way of cuffing the ears. To prevent concussion, therefore, the ut- most care has been taken. The skull is supported upon a doubly-curved column, composed of spongy bones and inter- ORGANS OF VOLUNTARY MOTION. [CHAP. 1. Fig. 44 (B). placed cartilage, and attached in such a lateral manner to the hip-bones, that every advantage arising from a combination of the most perfect springs and an arrangement for the dis- persion of force, exists therein. 284. And not only is this column connected laterally with the hip-bones (if the thigh-bone had been placed di- rectly beneath the back-bone, every step would have been shocking) but the hip-bones are connected laterally with the thigh-bones. When the foot strikes the ground, these form an angle with the lower leg bones, which, with the arrange- ment of the joints of the ankle and foot, produce a perfection which leaves nothing to be wished. 285. The skull is composed of three layers ; the outer and inner are called tables, the intermediate one has the name of diploe. The outer table being tough, is broken with difficulty, while the diploe, being of a spongy or cellular na- ture, deadens the jar an inflicted blow might produce in the outer table. The diploe is not found in early life, when the soft state of the bones render such a structure unnecessary ; but as the bones grow brittle with advancing age, the diploe not only makes its appearance, but increases in thickness as the case requires. SEC. 3.] THE BRAIN AND NERVES. 93 286. The inner table is quite brittle and altogether averse to vibrating in harmony with the more external layers ; and of course unharmonizing vibrations tend to neutralize each other. 287. When the skull is removed, the first internal pro- tection is found in the dura mater, similar to that lining the spinal canal, indeed one is a continuation of the other. The dura mater of the skull, however, adheres closely to it, ex- cept when it dives down, as a separation between the halves or hemispheres of the brain, or where it comes forward un- derneath the back part of the upper brain, to serve as a shelf for its support. 288. In the first position it is called the falx, from its sup- posed resemblance to an ancient sickle (Fig. 45). It leaves the skull at the central line, and passes down nearly as far as the division of the brain exists, when it turns back, uniting with the first, till it arrives at the skull, when it goes on to line the rest of the skull. The falx is thus composed of two thicknesses, though at first it appears only one thing. 289. On the back part of the head is a ridge, extending from ear to ear. Corresponding to this, there is a ridge with- in the skull, from which the dura mater comes forward so far as to cover the cerebellum, when it folds back, adhering to itself, so to speak, to the ridge, from which it continues down upon the inner surface of the skull. 290. The dura mater is every where lined by the arach- noid membrane, which without close examination seems to be a part of it. As in the spinal canal, the arachnoid is reflect- ed upon the more internal membrane called the pia mater. The two surfaces toward each other are in health moistened by a glairy fluid, which prevents their adhering. Like other serous fluids, it is in health removed in the same ratio as it is formed. As there is no fatty substance between the dura mater and its bony cashier, as there is in the spinal canal, so ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 45. Fig. 45. Represents the fair (3), situated between the two halves of the large brain. Upon the under and upper edge are seen veins, called in this part of the body sinuses. 2, 2, Branches opening into the upper sinus. 6, 8, Branches which drain the lower portion of the large brain. 8, Space between the two veins into which the great sinua divides. 10, 11, Two large veins which have wound round to the side of the bottom ol the skull. there is no cellular substance between the arachnoid and all the upper parts of the brain ; for the fatty and cellular sub- stance are alike unnecessary. But at the bottom of the skull the cellular substance is very conspicuously developed, and supports the weight of the brain in a most admirable manner. The fluid contained in these cells communicates with that in the sub-arachnoid space about the pia mater of the cord, and as some thin*, affects the cord favorably, by adding its weight to the fluid of the canal. Not only the weight of the fluid in the skull, but a considerable portion of the weight of the brain, must be counted. Thus it is seen how beautifully the brain is placed, resting on the cellular substance and fluid of the sub-arachnoid spaces ; it is unconnected above, but is allowed, without any friction or danger, a certain degree of movement in the skull, at the free surfaces of the inner and outer arachnoid. SEC. 3.] THE BRAIN AND NERVES. 95 291. The delicate arachnoid being removed, the pia ma- ter is presented to view. This is a continuation of that in the canal, where it is quite strong and protective, as is re- quired for the support of the cord ; but at the upper regions of the brain it becomes exceedingly delicate, and seems com- posed almost entirely of bloodvessels of surprising minute- ness. It closely envelopes the brain, following all the wind- ings of its surface, and is much greater in extent than the outer membranes. 292. The Brain. What is usually thus called is com- posed of two parts, or as they are termed, the large brain or cerebrum, and the small brain or cerebellum. The last is found below the tentorium, in the lower and back part of the head ; the rest of the head is occupied by the cerebrum. 293. The consistence of the brains may be compared to jelly, the small brain being a little more firm than the large. The brains therefore flatten as soon as removed from the skull, and must be cut with a very sharp knife if an ex- amination be desirable. 294. The small brain, as seen in Fig. 34, is comparative- ly smooth on its external surface, and divided, as seen in Fig. 46, into, two halves, or hemispheres, by a shallow groove, whicK is apparent on the upper, back, and under surfaces. The color is in alternate stripes of_whjte_and gray. Its size differs in different persons, being usually largerln the female than in the male of the human species. 295. The large brain is composed of two hemispheres, separated by a deep groove, seen at 1, Fig. 37, which also passes forward from the back part, and backward from the front part of the brain, as seen in Fig. 47. In this groove the falx is situated. 296. The surface of the cerebrum is very uneven, being much like that of a peach-stone (Fig. 48). The prominences are called convolutions ; the indentations, anfractuosities. ORGANS OF VOLUNTARY MOTION. [CHAP. I. Fig. 46. Fig. 46. Upper surface of the small brain. These pass quite deeply from the surface in many places, as seen in Fig. 47 ; where it may also be noticed, that convolu- tions and anfractuosities exist in the groove which divides the hemispheres. They will also be found at the base of the brain. 297. As has been said, the pia mater follows all the windings of the surface ; while the arachnoid lies across, so to speak, from one convolution to another. 298. The color of the external portion of the cerebrum is very nearly like that of the ashes of " red-ash coal " a reddish gray, hence called the cineritious or ash-like part, the gray part, and is also called the cortical or bark part, because it surrounds the inner portion, as the bark of a tree surrounds the wood. 299. If a section of the cerebrum be made, Fig. 47, this arrangement will be conspicuous. The internal, white or medullary substance, is convoluted as the surface of the brain. It is indeed these convolutions, covered by the gray substance, which produce the convolutions of the surface The thickness of the covering varies from a sixteenth to a half inch ; differing in different parts of the same brain, varying still more in different brains : nor are its thickest or thinnest parts found in the same relative portions of different SEC. 3.] THE BRAIN AND NERVES. Fig. 47. Represents a section of the brain on a level with the bridge, or corpus callosum (d, e, d) ; a, the front ; 6, the back ; and c, the middle part of the white or medullary portion of the brain ; y, f, f, f, the gray, cineritious, cortical or outer part of the brain ; :r, a deep fissure extending from the front surface of the brain to the bridge ; t/, a similar fissure at the back part. brains, or indeed of the two halves of a brain. Neither does the size of the convolutions or the depth of the anfractuosities follow any rule. The depth or quantity of the white sub- stance varies as much. 300. Fig. 47, represents a section of the cerebrum on a plane with the grand bridge or commissure which unites the two hemispheres. It is called the corpus callosum. It seems to be composed mostly of white fibres like the nervous fila- ments. Many theories have been advanced in regard to its use probably all inventions. 801. If a section be made a little deeper, what are called 5 ORGANS OF VOLUNTARY MOTION. Fig. 48. [CHAP. t. Fig. 48. S represents the scalp, next to which is seen the skull or cranium (s, s). M, m, A part of the membrane lining the skull and covering the brain. L H, Left hemisphere of the brain. R H, A small portion of the right hemisphere seen beyond. F, The deep fissure in which the falx is situated. the ventricles will be brought to view (Fig. 49.) These are frequently spoken of as cavities, which expression is apt to convey a wrong idea as the sides of the ventricles are al- ways in contact, except they are separated by unhealthy collections, which sometimes are to be found within them. The ventricles are lined with what is like, and called, a serous membrane some consider it a continuation of the pia mater and arachnoid; some consider it has no connection with them. The ventricles have also several branches, called horns, leading off into different parts of the brain. 302. Forming the bottom of each ventricle, are found various parts of divers forms, sizes, and colors, helping to SEC. 3.] THE BRAIN AND NERVES. Fig. 49. 99 Fig. 49. Section of the skull, A, A ; the membranes, B, B ; the gray substance. C, C ; the medullary portion, D, D ; the posterior horn, E, and anterior part, F, of the ventricles. The cnoroid plexus ia seen at G. In the bottom and between the ventricles several parts are seen, but their use is not known. make up the entire cerebrum. To name them and specu- late upon their use, is all that science has yet done in respect to them. At the lower part of the brain, are also seen com- missures ; their utility is not known. 303. At the bottom of the skull, the brain is united with the spinal cord by an enlargement of it, called the medulla ob- longata, or oblongated marrow. They are here also connected with each other. But examinations hereabouts have, as yet, proved very unsatisfactory; for barren description is very bootless. We can only infer, that there is free opportunity for communication between all the parts connected with each other ; but how much influence they exert upon each other, and in what way, is unknown. 304. If a perpendicular section of the cerebellum be 100 ORGANS OP VOLUNTARY MOTION. [CHAP. i. made, a trunk of white substance is seen in the middle with branches extending on either side, from which smaller branches stretch to the surface. The inter-space is occu- pied by gray substance internally producing the appear, ance called arbor vitae, or tree of life ; and externally, the striped appearance of which I have spoken. 305. The white substance throughout the brain is fibrous for the most part. A great number of fibres radiate from the medulla oblongata, upward and outward toward the con- volutions. Some suppose that these arrive at the gray sub- stance, and then curve around and pass over to the other half, and become continuous with its fibres, thereby forming the corpus callosum. This is by no means certain. 306. The office of the cerebrum in producing motion, is unknown. The effects of experiments upon animals seem to prove, that the removal of large portions of the upper parts of the large brain, has no effect upon the production of motion frogs leap about, as if nothing had happened, and Magendie asserts, that carp swim as usual. But if certain of the lower parts of the cerebrum just in front of the upper part of the medulla oblongata be cut, the animal rushes forward or attempts to crawl if resisted, remaining in the attitude of onward motion. 307. The office of the cerebellum seems to be a little mole decided. It seems to exert an especial influence in .producing the involuntary motions of the voluntary muscles. Hundreds of these are performed, of which we take no notice. While addressing an audience, a person's mind seems to be abundantly occupied with the subject of his discourse and its delivery, and the balancing of the body which requires the constant action of hundreds of muscles, seems no more to be controlled by him, than in case of him who walks while asleep. In the case of every one there are many movements constantly produced, when he is reclining SEC. 3.] THE BRAIN AND NERVES. . 101 in the easiest position, and overcome by the soundest sleep. There is, also, awake or asleep, a constant action of the muscles, to a greater or less degree, as is evident from the gaping of a wound. That involuntary and unpractised influence may control the muscles, is certain as we see evidence of it in animals that walk as soon as born. 308. Flourens observed, that irregular motions were produced as soon as an effect was apparent in the cerebel- lum of birds, with transparent skulls, which he had forced to take alcoholic drinks. If injuries be inflicted on the small brain, the like irregularities will result. If the portion of the cerebellum on the right side, riear to the oblongata, be cut, the animal begins to revolve towards the left. If the similar part on the left side be cut, the animal revolves towards the right. Magendie says, he has seen these revo- lutions as rapid as fifty in a minute, and continue eight days. If the parts on both sides be cut at the same time, the animal is quiet, but unable to stand or walk. 309. If injuries be inflicted upon certain back and under portions of the cerebellum, the movements of the animal will be backward birds will attempt to fly backward. There seem, as Magendie thinks, to be certain parts from which influence is continually exerted upon certain classes of muscles, the action of which will produce certain motions ; but this is counteracted by the opposing action of another class. The effects of certain diseases, seem to prove the correctness of this opinion. Horses are sometimes so affected by disease that they will not, and apparently cannot, move backward. Most persons must have seen cats, when seized with what are called fits, fly with the utmost impetuosity round and round, or off in a tangent, regardless of obstacles. I have seen dogs, also, seized with the same impetuous and apparently involuntary influences. 310. By this time, the reader will perceive that no very 102 ORGANS OF VOLUNTARY MOTION. [CHAP. I. lucid description of the functions of the brain can be ex- pected. The results of apoplexy, and other diseases and irregularities of the brain, convince us that healthy, vigorous action of the muscles, cannot take place without a healthy condition of the brain exist. The debilitating effects of alcohol, tea, coffee, tobacco, &c., upon the nervous system are, among other ways, exhibited by tremulousness of the hands and general weakness of the muscular system. Parts at the base of the brain how numerous or how extensive we cannot tell exert, without doubt, a constant influence upon the muscles ; which, increased in frs power, produces what may be called active contraction of the muscles. These parts, or the whole brain, act likewise upon the cord, influencing its condition ; for in man the cord seems to be powerless, except connected with the brain : but influenced by this connection with the brain, the cord is the immediate source or centre from which the muscles are many times influenced. The office of the cord and brain, or of certain parts of them, seems to be different, or differently influenced, in man and animals; indeed, in different species of ani- mals. 311. Whether the frequent and proper action of the brain, in producing muscular contraction, increase its size, has not been shown. Apparently, no effect of that kind is produced. If the same cause produce rapid changes of the brain, cannot be positively asserted. We can only infer that it does, from the fact, that in case of muscular action there is an increased flow of blood, through the head. As this blood returns of a different color and quality from what it was, a logical deduction may be drawn that the brain has undergone corresponding changes. On the other hand, an increased circulation of blood, as when alcoholics have been taken, produces increased muscular activity ; so also in brain fever, or other diseases attended with active circulation of SEC. 3.] THE BRAIN AND NERVES. 103 blood through the brain. Apoplexy and opiates, attended with stagnation of blood in the head, not only produce stupor of the senses, but complete inaction of the muscles by any voluntary influence. 312. There seems to be no doubt, therefore, but a pro- per circulation of good blood, through the brain, is neces- sary for the accomplishment of its duties in producing mus- cular action. How admirable, that increased muscular ac- tion increases the rapidity with which the blood flows to the brain at the very time required! It hence follows, that rubbing the body and general exercise of the system must be highly favorable to the brain. Hereafter it will be seen, that cultivation of the mind increases the circulation of blood in the brain, and thereby increases its efficacy in fulfilling its duties in connection with labor. Nor less important will be a cheerful disposition, for a merry heart sends the blood coursing briskly through every organ. CHAPTER II. THE ORGANS OF SENSATION OR FEELING. General Observations. It is exceedingly difficult to give a concise, yet plain description, of the apparatus, by means of which a person feels. If, however, the reader will carefully follow me, step by step, I will endeavor to explain, clearly as possible, all that is known of the manner in which he sees, hears, smells, tastes, feels pain, or has any kind of feeling or sensation. It is evident to every one, that if his foot be hot, his mind knows it ; or if his foot be cold, his mind knows that ; or if the temperature of hia foot be comfortable and right, his mind knows that. If his hand be cold, or hot, or comfortable, his mind knows it ; but his mind is not in the foot or hand ; for if either be removed, he has the same mind as before. Other like arguments would prove that the mind has its seat nowhere, except in or at the brain. How then can the mind know if the foot be hot or cold 1 If the foot be pinched, the mind knows that ; if the hand be cut, the mind knows that, and if there be any thing, right or wrong, in any part of the body, the mind knows it at once. There must be something, therefore, which makes the mind know, at its seat in the brain, if the foot be hot or cold, bruised or sound ; which makes the mind know the state of every part of the body. The organs or apparatus for produc- ing sensations or feelings do this. They connect all parts of the body with the mind. Thus, no part of the body can be in any state, without pro- ducing an effect, through the organs of sensation, on the mind ; hence, 313. The organs of sensation or feeling are of use, in the first place, to cause every state or condition of the body to produce on the mind an effect called a sensation. 314. If a particle of dust fall into the eye, it produces a bad state in this part of the body, and this will produce an effect on the mind, called a sensation. If the stomach be overloaded with food, an effect GENERAL OBSERVATIONS. 105 called a sensation is produced on the mind ; if a finger be cut, a sen- sation is caused ; if the finger be pinched, a sensation of another kind is caused ; if the finger be cold, still another sensation is produced. If disease attack any part, it produces peculiar sensations, differing accord- ing to the disease and the part affected. Thus, by the different effects or sensations produced, the mind learns every thing it knows about the condition of the body, and of course, the more perfect the effects or sen- sations are, the better does the mind know the condition of the body. But again, it is evident to the reader that there is a book before him, his mind knows that there are letters upon its pages ; his mind also knows the color, form, and odor of a rose ; his mind knows that sugar is sweet and vinegar sour. How is this ? His mind is at the brain. Does he say that light comes from the book, and from its pages, and from the rose, into his eye, and thus he sees ? But this does not explain the whole operation. The light only comes into the eye, it does not go to the brain. Does he say, that he smells the odor of the rose, because it comes up into his nostrils ? But the odor does not act on the brain. How then does the odor produce an effect on the mind ? Does he say that he tastes the sugar, because it is put in his mouth 1 But the sugar dis- solves in the mouth and remains there, except he remove it by swallow- ing or otherwise. How does he know that the ice he touches is cold 1 How does he know his foot is tickled ? There must be means of con- necting all parts of the body with the mind. Thus, when light acts on the eye, there must be something which produces a corresponding effect on the mind. There must be something which makes the mind know when sugar is placed in the mouth, when ice touches the hand, or any part of the body. The mind knows these things by means of the organs of sensation. By the same means it knows all the effects which objects around us, both at a distance and near at hand, produce upon the body ; thus, 315. The second duty of the organs of sensation or feeling is, to cause surrounding objects to produce on the mind effects, called sensations. 316. The roll of thunder and the flash of lightning, produce effects on the organs of sensation ; and they then produce effects, called sensa- tions, on the mind which inform it of the approaching storm. Through the organs of sensation, or feeling, a piece of ice placed on the hand pro- duces an effect, called a sensation, on the mind which informs of its coldness : at the same time it produces another kind of sensation, which 5* 106 ORGANS OF SENSATION OR FEELING. [CHAP. II. informs of its weight, and still another kind, which informs of its color, size, form, &c. One person's voice produces one sensation, and the mind knows its friend ; another person's voice produces another sensa- tion, and the mind distinguishes its enemy. A rose produces a sensa- tion of smell, that informs the mind of its odor; another sensation informs of its color ; another of its delicacy, when touched. Camphor produces different sensations, of all these kinds, and thus reveals to the mind its qualities. Sugar produces sensations ; vinegar, different ones. Thus by sensations, the mind learns all that it knows of the objects surrounding us what and where they are. Indeed, knowledge of an object means, to know the kinds and degrees of sensations it is capable of producing in the mind, through the organs of sensation, and to this, is our knowledge of objects limited. The man born deaf, cannot know the important qualities or properties of the violin ; for its music has never produced a sensation in his mind. He has a mind, but there are no means of connection between the violin and his mind, such that it can produce sound. Some of the organs of sense are wanting, or in- capable of producing an effect on the mind. The portals of his ears are closed. 317. Objects surrounding us, do not therefore act directly on the mind ; and consequently do not produce any direct effect, or sensation on the mind. They produce an effect on some part, or parts of the body, viz., on some of the organs of sensation ; these produce an effect on the mind. The effect which objects produce on the organs of sensation, is called an impression. We so constantly say, we feel this, or that thing a piece of ice for instance that we often think we feel the ice. But the ice touches the skin, not the mind ; yet it is the mind that feels. What then does the mind feel, if it do not feel the ice ? It feels the effect which the ice produces or causes to be produced, on the organs of sensation. If a string that I pull, be fastened to a boy's finger, he says, perhaps, I pull his finger. This is well enough in common conversation. It is not, however, strictly correct : I pull the string, to be sure ; yet it is not I, but the string that pulls his finger. I make the string pull the finger. So the ice makes the body produce an effect on the mind ; yet the ice does not directly act on the mind. I may cause a pin to prick a person, and he may say 7 am pricking him ; but it is not correct. It is the pin that GENERAL OBSERVATIONS. 107 pricks him. A ball may hit a person. He cannot properly say, the person who threw the ball, hit him. 318. The effect or sensation produced by the organs of sensation on the mind, when the object acts upon them, will depend, therefore, in the first place, upon the nature or pro- perties of the object ; and in the next place, upon the condi- tion and nature of the organs of sensation. 319. That different objects would produce different effects on the body, is too evident to require remark. It would not be expected that boiling water and ice would produce the like effects on the body. But it is not so easily seen that the effect or sensation which the ice or boiling water causes the body to produce on the mind, depends on the nature and condition of the body, or of some of those parts of it, called organs of sensation. But if the hand be numb with cold, as on some winter's day, do things feel the same as when the hand is comfortably warm 1 If a person be sick, does not the weather feel more chilly to him than it would if he were well I Any person may try the experiment of putting one hand in hot and the other in cold water at the same time, and then plunging them in water neither cold or hot. This will not cause the same sensations to be produced through one hand as are produced through the other. But the water that acts upon one is precisely the same as that acting on the other. Why, then, the difference in the sensations ? Because the condition of that part of the body through which one sen- sation is produced, is different from the condition of that part of the body through which the other sensation is produced. If a person have a severe cold, a rose does not produce its ordinary effect ; not be- cause the rose is at fault, but because that part of the body through which the sensation of smell should be produced, is changed from healthy to unhealthy. If objects act upon the body when it is not in a healthy condition on any account, the sensations which result must, therefore, be unnatural. 320. But the nature as well as the condition of the parts through which sensations are caused, determine the character of the sensation. If a rose be put in the mouth, its odor does not produce any effect, because it is not the nature of the organs of sensation upon which the rose acts in the mouth, to cause any sensation of smell. If a bow be drawn on the back of a violin, it does not cause any music. To produce 108 ORGANS OF SENSATION OR FEELING. [CHAP. II. that, the bow must be drawn upon the strings, for they were made for the purpose. The odor of the rose must for the same reason be applied to the nose, for the organs of sensation which connect between the nose and mind have been made so as to act on the mind when the odor of a rose acts on them. If the eyes be shut and the mouth open, light can pass into the mouth, but yet a person cannot see, because the organs that connect between the month and mind, if acted on by light, have not been made so as to act on the mind when light acts on them. But the organs connecting betweeu the eye and mind are acted on by light, and are so constituted that when acted on by light, they will act on the mind. Certain parts of the body will produce the sensation of tickling when acted on in a certain manner, which other parts will not. Thus the effect or sensation produced on the mind, by the action of any object upon the body, will essentially depend upon the nature or constitution of the organs of sensation acted on. From this paragraph it is also to be inferred that there are several classes of organs of sensation, differing from each other in their nature. 321. Observe also, that any state of the body does not act on the mind directly, but on the organs of sensation, which act on the mind. An overloaded stomach does not act on the mind directly. To be sure we say this or that part, for instance a tooth, aches ; but this is not so. The tooth acts on the organs of sensation, and they cause the ache.* If a particle of dust be in the eye, we say the eye smarts ; strictly speaking it is not so ; the eye acts on certain organs of sensa- tion connecting between it and the mind; these produce an'effect on the mind. Thus, any healthy or diseased part of the body produces effects on the organs of sense, connecting between the part and the mind, and these organs produce an effect, sensation, or feeling on the mind. 322. The effect or sensation which any part of the body will cause to be produced on the mind, will depend on the condition of the part acting on the organs of sensation, and upon the nature and condition of these organs. * Perhaps the reader will object, that he really has felt the tooth ache ; that the ache was in the tooth and nowhere else. The reason of this was, that we are so made as to feel the ache in the part where, as a usual thing, the cause originating the ache first acts. Sometimes it is not so ; but this matter will be treated upon in its proper place. GENERAL OBSERVATIONS. 109 323. That a healthy condition of any part of the body would pro- duce a different effect on the organs of sensation, from that produced by an unhealthy state of the same part, or that two kinds of diseases of any part, acting at different times upon the organs of sensation, would pro- duce different effects or impressions upon them, is too evident and too often experienced to require proof or remark. But it is important that it be as clearly seen, that the effect produced upon the mind depends also upon the nature and condition of the organs of sensation. Thus, in case of disease, when a person has chills, as they are called, he stands before the fire, but gains no comfort, though his body be heated. The dis- eased condition of the organs of sensation prevents them from produc- ing the sensation of warmth in the mind, though they are acted on by heat. A person afflicted with neuralgia has a tooth drawn, in hopes of stopping the pain, but finds his hopes vain. ' It is the diseased condition of the organs of sensation which produces the painful sensation upon the mind. This is proved by the fact, that as soon as the condition of the organs of sensation is changed for the better, the painful are ex- changed for agreeable sensations. 324. But the nature of the organs of sensation is still more worthy of notice. If the skin be pricked, pinched, bruised, burned, or the like, when in a natural or healthy condition, the organs of sensation, connecting between the skin and mind, will be acted on, and will also act on the mind, producing sensations. If, however, the tendon on the back of the hand, or any other tendon be exposed, it will be fouud by experiment, that it may be pricked, pinched, bruised, and even acted on by burning heat, and the person not know it. The organs of sensation, connecting between the tendons and the mind, may be acted on, for aught we know, but their nature is such that they produce no effect upon the mind. But if the tendon be twisted a very little, the mind will know it, for the organs of sensation connecting between the tendons and th", mind have been made so as to be acted upon, and to act on the mind, under such circumstances. If a healthy bone be cut, the mind does not know it ; because the organs of sensation connecting the bone with the mind have been so made, that if acted on, when the healthy bone is cut, they produce no effects on the mind. If, however, the bones be diseased or broken, the organs of sensation produce effects on the mind if the bones are moved in the slightest degree ; for this is their nature or constitution they have been so made. Persons have sometimes died of diseases of the heart, which they have had for years, and yet no one knew it till it was learned by post mortem (after death)' examination. IK) ORGANS OF SENSATION OR FEELING. [CHAP. II. The organs of sensation, connecting between the heart and mind, were not so made as to act on the mind in such cases. Reasons why these things should be so will be hereafter given. Thus the effect upon the mind, which any part of the body will cause to be produced, will depend in the first place on the condition or state of the part ; in the second place, upon the condition of the organs of sensation, and in the third place, upon the nature of those organs. From the facts adduced in this paragraph it is also to be inferred, that there are several classes of organs of sensation, each gifted with different powers, by which each one be- comes efficient in its own way. 325. The next question to answer, is, How do objects act on the organs of sensation, and how do they act on the mind ? This is not known. But to form as reasonable a conjecture as possible, we must first notice, what is necessary to produce a sensation in the natural course, viz., mind, brain, a nerve, an organ of sense, and an object. 326. It is thus seen that several parts are necessary to form the organs of sensation, viz. the brain or nerve, and organ of sense ; and in the order in which they stand in the preceding paragraph, they are be- tween the object and mind. The mind is to be acted on, the object is to cause the mind to be acted on. It does cause the mind to be acted on, by acting on the organ of sense* which acts on the nerve, which acts on the brain, which acts on the mind. Thus it will be seen, that if the organ of sense be wanting as in Fig. 50, the object cannot pro- duce an effect on the nerve, or if the nerve be wanting, an effect can- not be produced by the organ of sense on the brain, or if the bi*ain be wanting, an effect cannot be produced on the mind, and of course, if the mind be wanting, no effect can be produced upon it. These things are proved in various ways. In the first place, to produce a sensation, 327. The mind is necessary ; for if the mind be entirely occupied with any business, a friend may speak and his voice is not heard. Of course, it produces an effect on the organ of sense, and that produces an effect on the nerve, which produces an effect on the brain, but that causes no effect, which acts on the mind and is perceived. 328. The brain is necessary, as is evident when any derangement of it is produced by accident, disease or medicine. An insane person walks * This has nearly the same name as organs of sensation, but is only one of the organs of any sensation. GENERAL OBSERVATIONS. Ill barefooted on the frozen ground, and though frostbitten, teels no tion. Opium, and its like, act on the brain, so as to prevent it from acting on the mind. The physician takes advantage of this quality of various medicines, to lull pain, as the expression is. Perhaps, and probably, an effect is produced on the nerves at the same time which prevents them from acting on the brain, as when pain is produced. 329. A nerve is necessary, as is proved by cutting the nerve, experi- mentally, in case of animals, and accidentally in case of man, and by compressing the nerve. A sensation is not then produced by any thing applied to the part, where the cut nerve commences ; e. g., the lady with the elbow cut, &c., mentioned in a former paragraph. 330. An organ of sense, is the name given to the part in which the nerve commences, and is of course necessary. It is sometimes necessary, as hereafter seen, to direct in a proper manner, the action of an object upon the nerve. 331 The necessity of an object, to produce an effeet on the organ of sense, or through the organ of sense upon the nerve, is too obvious to require illustration. 332. It is important now, to observe, that if any of the organs of a sensation be diseased, the kind of sensation which an object will cause to be produced, will be affected thereby. If an organ of sense be dis- eased, an object will not produce the same effect on it as if it were healthy. If the organ of sense be healthy, but the nerve, or any part of it, unhealthy, the effect produced on the brain will be different from what it would be if the nerve were healthy; and if the effect on the brain be different, the effect the brain will produce on the mind will be different. So, also, will the sensation be unnatural, if the brain be diseased. That is to say, if the condition of the organ of sense, the nerve, or the brain, be changed, a corresponding effect will be produced on the sensation. When sick, therefore, things do not taste, smell, or feel as before ; a very little light pains, or a very low sound distresses. It is very important, as hereafter seen, that the truths of this paragraph be fully appreciated and understood. 333. A sensation is usually produced in the manner shown in the preceding paragraphs, but it is evident that if the brain act on the mind, a sensation will be produced, even if a nerve have not acted on the brain. So likewise, a nerve can act on the brain, and the brain will then produce an effect on the mind if the organ of sense have not acted on the nerve ; and with like results the organ of sense can act on the nerve, if an object have not acted on it. In all these cases, when the mind perceive* 112 ORGANS OF SENSATION OB FEELING. [CHAP. II. a sensation, it will believe some object has acted on the organ of sense, because it is usually the case, and because it has been so made as to think it is so. Thus, by some disease of some part of the organs of sensation, a sensation is produced, and a person thinks a tooth is the cause, because the pain is like toothache, but when the tooth has been pulled, he learns that his idea was wrong. From a disease of some of the organs of sensation, a person will feel as if some animals, e. g. ants, were creeping on the skin, but it is not so, as he finds by examination ; thus 334. The existence and character of sensations will de- pend, on the properties of acting objects, on the nature and condition of the organs of- sense, nerves, brain, and on the mind. The divisions of this chapter are therefore obvious. SECTION 1. Sensations. 335. Any effect produced on the mind, by or through any part of the body, is called a sensation. Sensations are of many different kinds : of hunger, of thirst, of pain, of touch, of heat, of cold, of tickling, of nausea, of suffocation, of fulness, of sweetness, of sourness, of a rose, of camphor, of weight, of the various colors, of sounds, &c., &c. Sensations of the same kind vary greatly in intensity. When of such a degree, as to be quite noticeable, they are called feelings. If the weather be perfectly agreeable, it is usual to say it produces an agree- able sensation, but if it be cold or hot, the usual expression is, it feels cold or hot. That is to say, a strong sensation is called a feeling. 336. Sensations may be divided into two grand classes, pleasurable or delightful, and unpleasant or painful. 337. Pleasurable sensations, when of a high degree, are called delightful feelings. They are for the purpose of re- warding the mind, for the care it has taken of the body, and inducing a continuance of the same care. 338. Pleasurable sensations are produced by the healthy condition and by the proper action of any part of the body. SEC. 1.] SENSATIONS. 113 A healthful condition of any part of the body, causes the organs of sensation to produce in the mind that peculiar and desirable sensation, difficult to describe, but which every one has experienced, when he says I feel well. The healthy exercise of any part increases the same sensa- tion. The healthy exercise of the muscles is productive of great plea- sure. He, therefore, who pursues a sedentary life, fails to enjoy all that class of delightful sensations which make happier the life of him who, by daily exercise, improves his muscular system. He not only, day by day, enjoys the sensations attendant upon the action of his muscles but fits them to increase the pleasures they are bestowing. For a full, healthy, daily exercised muscle, causes much more pleasurable sensations, and for a longer time, than the inefficient, feeble muscle. There is, therefore, pleasure in labor ; not in the fatigue of laboring too long, but in labor, such as a man ought to do. The often exercised ear, adds a double charm to existence. The sensations it wakes up, thrill the soul, almost to ecstasy. The sensations caused by light, acting on the eye, are highly pleasurable. The mind, imprisoned from the action of light, and shut out from all the delightful sensations it causes, soon feels a gloom all other sensations cannot entirely remove. The balmy air of spring time or summer, wafted around us, and bearing to our nostrils the sweet fragrance of the scented fields, acts so genially upon the body, that the mind is satisfied with the delicious sensations it produces. The organs of digestion, while acting to prepare the food in the mouth, or after it is swallowed to the stomach, add much to the gratifications of life. Nor is there a small degree of pleasure felt, when, after proper action, the exercised organs are allowed proper repose.* * I cannot help transcribing from a book, so common, on account of its value, that perhaps a reference will be thought sufficient ; but Parker's Exercises may not be known to every one, and the passage will bear more than one reading : " The words commonly used to signify diversion are these three, namely, relaxation, amusement, and recreation ; and the precise mean- ing of these words may lead us to very useful instruction. The idea of relaxation is taken from a bow, which must be unbent when it is not wanted to be used, that its elasticity may be preserved. Amusement literally means an occasional forsaking of the Muses, or the laying aside our books when we are weary with study ; and recreation is the refresh- ing or recreating of our spirits when they are exhausted with labor, that they may be ready in due time, to resume it again. " From these considerations it follows that the idle man who has no work can have no play ; for, how can he be relaxed who is never bent ? How can he leave the Muses who is never with them ? How can play refresh him who is never exhausted with business ? 114 ORGANS OF SENSATION OR FEELING [CHAP. II. 339. Pleasurable sensations dissipate melancholy, remove oppressive feelings, excite the action of the system, assist di- gestion, tend to improve health, and lengthen life. The physician recommends to the low-spirited to travel, where new and pleasurable sensations and a variety of them will be produced. " The smell of the fresh air," says the invalid, " makes me feel better." The odor of the preparing food, if agreeable, excites the appetite ; the taste of relished food causes a free flow of saliva into the mouth, and a free flow into the stomach of fluids necessary there, for a further prepa- ration of the food. It is important, therefore, that we cultivate an appe- tite for wholesome food, and by exercise produce a relish for it ; for the agreeable sensations then caused, will cause the food to be more readily and perfectly digested. Indeed, it is important that we cultivate all our organs, so as to realize the greatest possible variety and the highest pos- sible degree of pleasurable sensations. 340. It must not hence be inferred that all causes of pleasurable sensations are productive of health. Some things cause pleasurable sensations at first, but afterwards very un- pleasant sensations. Man has been gifted with reason and intelligence, the cultivation of which is attended with a far higher degree of pleasure than is produced by exercise of the body. If he cultivate these by acquiring knowledge, " When diversion becomes the business of life, its nature is changed ; all rest presupposes labor. He that has no variety can have no enjoy- ment ; he is surfeited with pleasure, and in the better hours of reflection would find a refuge in labor itself. And, indeed, it may be observed, that there is not a more miserable, as well as a more worthless being, than a young person of fortune, who has nothing to do but find out some new way of doing nothing. " A sentence is passed upon all poor men, that if they will not work, they shall not eat ; and a similar sentence seems passed upon the rich, who, if they are not in some respect useful to the public, are almost sure to become burthensome to themselves. This blessing goes along with every useful employment ; it keeps a man on good terms with himself, and consequently in good spirits, and in a capacity of pleasing and be- ing pleased with every innocent gratification. " As labor is necessary to procure an appetite to the body, there must also be some previous exercise of the mind to prepare it for enjoyment ; indulgence on any other terms is false in itself, and ruinous in its con- sequences. Mirth degenerates into senseless riot, and gratification soon terminates in satiety and disgust." SEC. 1.] SENSATIONS. 115 he will learn what things he may use, and how he may use them, so as to promote his immediate and ultimate happipess. The child, finding the seeds of the thorn-apple, and being ignorant of their quality, eats many of them and dies. A person ignorant of the nature of henbane, culti- vated the plant by his door, because he thought " the berries so pretty." They were equally attractive to his child, which not only looked at them and picked them, but ate them ; it was made very sick. A child cries for sweetmeats, which the mother, not regarding sufficiently the ultimate good of the child, allows it to have ; sickness, fits, convulsions, &c., fol- low ; while those of more knowledge, know it their duty, but still more feel it their pleasure, to watch the child till old enough to heed instruc- tion, when they carefully teach it to avoid trouble -causing things. The young man who sips the enticing wine, wishing to enjoy the hilarity it will produce for the moment, will learn, when the poor-house is his pros- pective home when his constitution is broken down, health and friends gone, and he a disgrace to himself and mankind that many times " present pleasure is future pain." The oyster or other supper may make the passing hour more convivial ; but a disturbed sleep and break- fast without appetite, and ere long a dyspeptic stomach, will teach a per- son that man cannot long be affected with pleasurable sensations, with- out he gain knowledge, and practise accordingly. 341. Pleasurable sensations tend to improve the disposi- tion. The child's mind should therefore receive a great variety of sensa- tions all those kinds which will not prove harmful in the end. It should be taught to love the flowers, for then* beauty and then* odor, and to be charmed with the scenery of nature. When very young, its mind should be occupied and its attention taken up with all the sensations produced by exercise, by new sights and sounds, by playthings, by songs and mu- sic whatever will interest it, without producing any harm. Its mind is almost a blank, has scarcely a thought, is almost wholly dependent on sensations produced through its organs of sensation, and they have not yet become full and perfect. If it have no other sensations, it will desire those which are produced by eating or tasting ; for from the first moment the infant mind wakes to intelligence, it will not be satisfied, without its attention be occupied with something. If the child desire to have some sensation produced which is harmful, its attention is to be occupied with some other sensation which will make it forget its desire. If the child's desire be denied, without its attention being occupied, it will fret, and its 116 ORGANS OF SENSATION OR FEELING. [CHAP. II. disposition will be injured ; but if its attention be called off by some new sensation, which is not harmful, no fretting is produced, e. g. t if a child desire sweetmeats, and they are put out of its reach and left where it can see them, and nothing more done, it will have a cry ; while if some plaything be presented before it, or it be asked to go and walk, or in any other way, if its attention be occupied and sensations produced, while the sweetmeats are put out of its sight, the child will remain pleasant. It is hence seen how judicious it is to cultivate our physical systems in such a manner, that all proper sensations shall be produced in an intense degree ; for though the pleasure of taste and smell, of touch and muscu- lar exercise, of sight and hearing, may not rate with the results of men- tal cultivation, they fit the body to better serve the uses of the mind ; they soften the disposition, and make us love better, ourselves, our fellow- men, and the world around us, which is so pleasure-giving to the healthy mind in a healthy body. 342. Pleasurable sensations produced by objects, render them attractive to the mind. Hence persons may not only produce a very favorable first impres- sion, but continue to render themselves agreeable, by dress and graceful manners, and by ministering to the sense of hearing, taste, and smell. The ear is beguiled by the silver tones of the voice. The good house- wife retains the love and affection of her husband, by always meeting his appetite with delicious food. Many a heart has been ensnared by the fragrance exhaled from a bouquet of beautiful flowers, arranged by still more beautiful hands. Let not these little things be spurned. We may love a person for his good-nature, and admire his intellect, who is clown- ish. The careless woman may be the idol of her husband, for she may have excellent traits. But sensations must be produced on every mind, and they must please or displease. True, habit effects much ; but God has intended that every class of the organs of sensation should be pro- ductive of sensations, and he will not allow his laws, even of the most minor character in our eyes, to be trampled upon with impunity. If one sensation only, displeases, it is so much for the other sensations to over- come. It will not be fruitless, therefore, to study the means by which sensations are produced and perfected, as we may thereby be able to make ourselves happier, and capable of rendering others happier. 343. Unpleasant sensations. When these are intense, they are called painful. They are for the purpose of warn. SEC. 1.] SENSATIONS. 117 ing the mind when the body is exposed to danger, or is actu- ally injured. The causes which produce them may be con- sidered under three heads. 344. First. Unpleasant sensations are produced when any part of the body is not used or exercised as much as it should be. If the muscle be not exercised, an uneasiness, a discontentedness, a dissatisfaction with one's self, with the world, and with everybody in it, is produced ; sensations difficult to describe, and still more difficult to bear with a pleasant spirit. It may be called an appetite for the exercise of the muscles. The lover of music has often felt the unpleasant sensations produced by want of exercise of those organs which cause sensations of musical sounds. He has often exclaimed, " I feel hungry for music." This feeling is not altogether of a physical nature, if I may use such an expression. These unpleasant sensations are felt, because it is harmful to a person to have the organs causing such sensations, remain longer without exercise. 345. Second. Painful sensations are felt when any part of the body is over-exercised or over-tasked. If the muscles be over-exercised, they first produce weariness, then fatigue, then exhaustion. The slightly unpleasant sensation of weariness is to warn when the muscles have acted as long as is for their good, and require rest. This sensation ought never to be increased to fatigue, much less to exhaustion ; for then the muscles suffer, and sometimes be- yond restoration. Persons have been so much excited by a fire, which was destroying their property, as to work on without heeding, or indeed feeling the sensations which would have warned of danger, till exhausted by labor, they have sunk down, never more to recover perfect strength. Whoever, therefore, takes alcoholic drinks or other poisons, that they may act on the brain and prevent the sensation of weariness from being pro- duced, does himself harm. He ought to feel that he has done enough. The poison does not improve the muscle, and if he go on to labor, he will lay the foundation for rheumatism, and many other complaints. The housekeeper, who, tired, thinks to relieve herself by a cup of tea, and then go on, and finish her work, exhausts the system, and if she do not feel the exhaustion, produces at last a sick headache or like evil, lasting for days, perhaps. Too long-continued action of any organ, exhausts its power : an approach to this is notified by unpleasant sensations. 118 ORGANS OF SENSATION OR FEELING. [CHAP. II. 346. Third. Painful sensations are produced, when any part of the body is affected by accident, or is suffering from T.n ; V "',"<** J'c v 4rtCr^'i:/-" i U , ..-"III .fenii'>i . When the body is in the immediate vicinity of danger, a strong sen- sation of alarm seizes the' mind, and impels it "to caW fof the body. Some might say that this was wholly the operation of the mind. But if a very young child be raised, and then brought down c^ickly, as if it were falling,^ it will ..be seen, by its outstretched arms,-to be jin alarm. It has never yet fallen, and knows aot that harm will follow, bftt a sensation is produced by certain organs of sensation* -which .have been made to act under such circumstances. It has also been, shown that some parta did not produce pain under those circumstances, that caused others to produce pain. The reason for this is now seen. The skin produces pain when it is acted upon in any injurious way, because it is the out- post of the body ; but why should the parts within, be painful when pricked, cut, etc. ? The skin must be injured before they can be, and if it give warning that is sufficiei, But the tendons are exposed to the danger of being twisted, without the skin being injuriously acted on ; it cannot give warning therefore. Hence the tendons do. The bones become painful as soon as broken or diseased, because the splints and bandages of the surgeon cannot be applied so tightly without stopping the circulation of the blood as to keep the bones perfectly quiet ; the person would many times use the bones before they had fairly recovered, if they were not painful. When they are not so, the surgeon is usually under the necessity of making them so, that the pain may assist his splints and bandages, loosely applied, in keeping the bones quiet and the person from using them. If an ulcer be upon the hand, it can be covered, and allowed rest, but if disease affect the lungs or heart, they must be kept in action, that life may be preserved. If they were painful, as it is best she hand should be under like circumstances, the pain would wear out the life of a person, much before it now terminates. When pain does exist, the kind of pain and degree of it, is very useful also in enabling the experienced physician to determine where and what the disease is. Hence the difficulty of determining with accuracy the disease of any part, when it is not the cause of any pain, and the diseases of children who cannot describe the pain felt ; more especially when so young that their countenances do not at all express the kind of pain they are suffering. Thus pain is a great blessing ; and when it does SEC. 2.] OBJECTS PRODUCING SENSATIONS. 119 not exist, as it should, instead of rejoicing, the physician sets himself to produce it, by, for example, rubbing the bones together, etc. It is to be noticed, however, that sometimes, as far as we can now see, pain is produced without a good result, since it is very exhausting and without any apparently good effect, and the physician finds his art serves him greatly, by enabling him to minister medicines, which shall prevent the painful sensations, without interfering with the curative process ; for if he do nothing but check the pain, nature will be able to cure the disease, when otherwise she would have failed. I see, however, so much perfection in the human system, that I am always inclined to adopt the expression of the poet, " whatever is, is right," and to think the reason why I cannot see it so, is owing to my short-sightedness, and fear if I should change any thing, I should be hanging the " pumpkin on the oak," only to fall upon my head and fell me to the ground. 347. Painful or unpleasant sensations quite opposite to pleasant or delightful ones tend to produce melancholy, to depress the spirits, to lower health, and shorten life ; to ren- der the disposition fretful, and make objects repulsive or dis- agreeable. It is to be expected, therefore, that the sick will be less amiable than when well ; and allowance must be accordingly made. Every thing which will tend to cause disagreeable sensations, must be avoided ; and the attention of the mind so occupied with sensations which will not prove hurtful, that painful sensations will not be produced. When chil- dren are sick, this is especially important. And sick or well, we should aveid all those causes which produce unpleasant sensations. SECTION 2. Objects producing Sensations. 348. An object is any thing which is the first acting cause, that produces a sensation. This object may be external as when ice produces a sensation of cold ; a pin, a sensation of pricking ; a rose, a sensation of smell, &c., or it may be internal, as when any diseased condition of any part of the body produces, or causes to be produced, any sensation. 120 ORGANS OF SENSATION OR FEELING. [CHAP. II. 349. Different objects tend to produce different sen- sations. This truth hardly needs illustration ; for the reason why objects are called different, is because they produce different sensations. If one object were precisely like another, and without our knowing it should be put in the place the other occupied, we should believe it was the same. There are twins so closely resembling each other, viz., produce such similar sensations, that people do not distinguish them, except they are near together, viz., produce sensations, at the same time, when if the sen- sations are similar in all other respects, they are different in this, that the objects appear to, and do, occupy different places. Thus two objects will differ, at least in this, that they cannot occupy the same place at the same time. 350. Different objects produce different sensations of cer- tain kinds, and similar sensations of certain other kinds. Thus a piece of ice produces a sensation of coldness, and a piece of heated iron a sensation of heat in which respects they differ ; but the ice produces a sensation of weight, and the iron produces a sensation of weight in which respects they produce similar kinds of sensations. Sugar produces a sensation of sweetness, and honey produces a sensa- tion of sweetness in which respects they agree ; but sugar is a solid and honey a liquid, in which respects they differ, and produce corre- spondingly different sensations. Hence objects are classed. All those which produce similar sensations of any kind, in respect to that kind of sensation, are classed together, and called by the same name, e. g., all those objects which produce a sensation of sweetness, like sugar, are called sweet : all those which cause a sensation like vinegar, in respect to sourness, are called sour ; those producing sensations in respect to coldness, like ice, are called cold. Thus sugar, molasses, honey, are called sweet and in this respect not classed with vinegar ; while vinegar, honey, molasses, water, &e., are classed together in certain respects, and called liquids while sugar, ice, &c., are classed together in one respect, and called solids. Honey and molasses fall into two classes together they are sweet and they are liquids : that is, they produce similar sensa- tions of two different kinds. Thus, 351. The more kinds of similar sensations any objects produce, the nearer are they considered to be of the same nature ; till at last, when the only difference of sensations is SEC. 2.] OBJECTS PRODUCING SENSATIONS. 121 in respect to the places they occupy, they are considered to be of the same identical nature. 352. The same objects may be said to produce different sensations under different circumstances. But this is not strictly correct ; for if it be said, that boiling water produces a different sensation from water of a low temperature it is not, properly speaking, the water in either case, but the caloric (commonly called the heat) which produces the sensation. Thus when any different sensation is produced by an object, it would be proper to speak of it as a new object ; but for present purposes, it will confuse the mind less to adopt the common expression and draw the mind to the next very im- portant proposition, viz. 353. That every object has a tendency to produce, under similar circumstances, a similar effect. This must be so, or we should be unable to place any confidence in sensations ; they would be of no use to us. But when we feel a certain sensation, we say without hesitation, it is produced by sugar, by a rose, by ice, etc. If it be argued that the same objects do really produce, or cause to be produced, different sensations, it is granted. Indeed, that ia what I wish to prove, and at the same time, that this is not owing to any change in the nature of the objects acting, but in the organs of sen- sation acted on. If an article produce a different sensation from what is usual, for instance, if it taste differently, it is easily proved that this ia not on account of any change which has taken place in the article, for other persons will say they do not notice any change in the sensation it produces. If wine be tasted after sweet things have been eaten, it will taste flat or insipid. If it be tasted after cheese, its flavor is said to be improved. Now the wine cannot have changed its nature while a person has been eating a piece of cheese, because, to those who have not eaten any its taste is not altered. Sensations caused by an object are oftentimes at first unpleasant, but after frequent repetitions, the sensation is different and pleasant. The same world is around all : to one it ia full of beauty every sight is charming every sound melodious ; to another it is so dull and prosy as to be hardly worth living in it ia fruitful in nothing but faults every object creates ugly sensations. Why the difference 1 It cannot be owing to the different action of the same objects upon persons, but to the action of objects upon different persons. The things are the same, acting under similar circumstances our con- 122 ORGANS OF SENSATION OR FEELING. [CHAP. II. Btitutions must be different. When, therefore, an object is called un- pleasant it is not using language correctly. It may produce pleasant sensations in another constitution. By such language we attribute to an 'inanimate thing, an ill disposition and a versatility of character not belonging to it. 354. It should be inferred, then, that, as beauty is in the eye, the music in the ear mental as well as physical, as the nature of things is inflexible and will not adapt itself to us, and as by the power of the Creator it has been made right, and as we are susceptible of change and our organs of adaptation, if the sensations we experience are agreeable all change should be prevented ; but if in a world so perfect, so lovely, gloomy and disagreeable sensations are felt, a change should be wrought in the system. To do this a person may feel encouraged by his own and others' ex- perience of the facility with which changes may be produced. If it be desirable to know what course to adopt, it may be learned by giving attention to the organs of sensation, and the condition of them, neces- sary to produce pleasant or unpleasant sensations. By the knowledge thus gained, he will be able to produce a state of proper relation between his organs and the objects of nature, which will result in delightful, or if painful, yet profitable sensations. SECTION 3. The. Organs of Sense. 355. These are those parts of the body in which the nerves of sensation commence, and by means of which objects are caused to act in a proper manner upon the nerves. The most important part of any organ of sense is, therefore, the commencing point of the nerve. 356. These organs of sense are also sometimes the objects which produce the impression upon the nerve. The skin is an organ of sense j when it is diseased it, like an object SEC. 3.] ORGANS OF SENSE. 123 % without any thing acting on it, acts on the nerve. In the same manner other parts of the body produce effects upon the nerves commencing in them. 357. Not only is every part of the body an object produc- ing sensations, but it is also an organ of sense, as I presume there is not any part of the body in which nerves do not commence. 358. It is also evident that within the body, the parts producing effects on the nerves come directly in contact with the nerves, and act upon them without any thing inter- vening. As in case of diseases of the skin, the part diseased, which in this case is the object, is directly about and upon the nerves through which an effect is produced on the brain. 359. But in case of those nerves through which external objects cause effects to be produced on the mind, it would not be allowable to have the objects act directly, as the nerves would be injured by exposure. Such nerves have, there- fore, been covered. As in case of the nerves commencing in the skin, they will be found a short distance below the outer surface, as in Fig. 50. Also in case of the nerve of taste, commencing in the mouth, and in case of the nerve of smell, commencing in the nose, the points of the nerves will be found just below the surface. 360. In case of the eye and ear, it is necessary that the objects producing the impression upon the nerve should be acted upon in a peculiar way, that effects or impressions may result. Here, therefore, the nerve is found at the bot- tom of an apparatus adapted to fulfil its duties perfectly. 361. It is evident, therefore, that there are several kinds of organs of sense. Those parts of the body through which any kind of sensation is produced, and which cannot be pro- duced by or through any other part, are considered to belong to the same class. We have six classes : the ear, the eye, the nose, the mouth, the muscles, and to avoid too much sub- 124 ORGANS OF SENSATION OR FEELING. [CHAP. II. Fig. 50. Fig. 50. Represents one half of the cerebrum, A, and cerebellum, B, and medulla oblongata, C An enlargement called a ganglion is seen at D. 1 is a nerve represented as terminating in a, b, c, rf, e, just below a at the surface of b, in the little eminences or papillae there found, a, 6, c, d, e, is an ideal representation of an organ of sens*, and whatever acts upon the surface of a will affect the. commencement of the nerves. 1, 2 represents nerves commencing in any part of the body below the surface. 3 re- presents a plexus by which it is seen that disease may exist at certain parts and not affect all the fibres passing between any point and the brain. 4 represents the sec- tion of certain nerves. If the cut end at 4 be touched, a sensation will be supposed to be produced where the ends of 4 naturally are. division, all the other parts of the body are grouped together and called organs of common feeling. Though some distinguish the skin as the organ of touch, and all other organs as organs of common feeling or sensation, others make SEC. 3.] ORGANS OF SENSE. 125 other subdivisions still, calling the stomach and throat organs of the sense of nausea ; certain parts through which tickling, etc., are produced, organs of the sense of tickling. A. The Organs of the Sense of Common Sensation, or Common Feeling. 362. 1st. The Skin. This includes the lining of the eyes, nose, and mouth, and in a certain sense the lining of the stomach, and the whole or a part of the remaining portion of the digestive canal. It is distinguished as the organ of touch, and may be considered as including all those parts of the body which will produce the sensation of contact when merely acted on by an object neither hot nor cold, nor in any way injurious. The sensation referred to is that indefinite sensation, not pleasurable or unpleasant, which merely informs of the presence of an object in contact with, or touching us, but gives no other definite idea. It is such as is produced by a tasteless substance in the mouth, or by food as it is being swallowed. It is entirely different from the sensation produced if the food be swallowed " the wrong way," and pass into the wind-pipe ; there is then a tickling, an unpleasant sensation. Some have supposed that the sensation of contact or touch, was produced by the difference in temperature, of the object and the surface touched ; but the saliva in the mouth produces a sensation of touch, and if an object be of the same temperature with the body and brought ever so gently in contact, a sen- sation will yet be instantly perceived. 363. The skin, as an organ of sense, is of use merely in affording to the nerves a proper commencing place, and in protecting them from exposure. 364. For this purpose a thin layer of skin, and but a thin layer, as in Fig. 50, is overlaid upon the nerves, while the layers below serve as a support to the nerves, and allow of their proper arrangement. How the nerves commence, is not known. Some think that they commence by loops, while others think they commence by points. There is, doubtless, an arrangement of loops to be seen, but it seems 126 ORGANS OF SENSATION OR FEELING. [CHAP. II. to me these are not the commencements of the nerves, which I am in- clined to think commence by points, and form the loops by uniting with each other in a plexiform manner. I shall therefore speak of the nerves as commencing by points, as there is a particular point of the nerve where it is acted on, where the impression is produced, and where the mind always considers that the impression is made. For instance, if the nerve connecting between any point of the skin and the brain be pricked, at any place between the skin and brain, we are so constituted as to believe the point of the nerve in the skin has been pricked. If a man's arm have been removed, and the nerves which commenced ia the hand be pricked at the stump, it will seem to him that the hand is pricked, though the hand has been lost for a long time. If the nerves be acted on by cold, it will seem to him that his hand is cold. Thus also if disease affect any nerve in any part of its course, and cause pain- ful sensations, we are so constituted that the mind believes the disease exists where the nerve commences but on farther examination no dis- ease is found at that place, and the experienced physician knows ; as a general thing, that disease exists at some point in the course of the nerves connecting that part with the brain. Thus, if the foot be cold, no mat- ter how warm the central parts of the body are in which the interme- diate portion of the nerve is situated, the nerve is so made, that, if healthy, it acts on the brain, or on the mind, only according to the impression produced on its commencing point in the foot, and receives no impression from the warm parts, acting through its sides. This is to me one of the most wonderful phenomena to be observed in the whole economy of the system : but to return to the skin. 365. That the nerves may be properly acted upon, the under layer of the skin is formed into a great number of em- inences called papillae (Fig. 51). They may be seen at the ends of the fingers, in rows, beneath the delicate layer which protects them. In those places they are very near each other, in other places they are more remote. In these papillae the nerves commence. 366. The more numerous these are, the more acute is the power of producing sensation in any part, and the more per- fectly can objects be distinguished. Any one can try the experiment mentioned, by Weber I think, of SEC. 3.] ORGANS OF SENSS. 127 r.51. Fig. 51. 1, The cuticle. 2, The rete-mucosun. 3, Two of the papillse. 4, The deep layer, or dermis true skin. 5, Fat cells, magnified very much. 6, Perspiratory gland with spiral outlet. 7, Another perspiratory gland with a straight tube as seen in the scalp. 8, The roots of two hairs inclosed in their sacs or follicles. At 9, is seen th short tube of several cryptae, forming a gland, and which form the oily or sebaceous substance which oozes upon the surface of the skin, to preserve it in a good condition. immersing the finger, and then the hand, in very warm water. The heat of the water will become apparently more intense, the greater the surface upon which it acts. The heat of the water does not, however, increase, but it seems the sensations become more powerful the greater the number of nerves acted upon at the same time. Thus when the papillae are thick, the same object will act on a greater number of nerves, than when the num- ber of the papillae is less. It has been found also that if the points of two needles, at certain distances, touch the skin of one part of the body, e. g. the ends of thr fingers, they will be distinguished as two things, while, if they touch certain other parts, they will appear as but one thing, and the distance of the points from each other must be increased, that they may appear as two things. 367. The structure of the skin differs in its protective character, in different parts of the body. Wherever, by use, it is frequently pressed upon, its external layer 128 ORGANS OF SENSATION OR FEELING. [CHAP. H. becomes tnick, callous, almost homy at times, as upon the soles of the feet, in the palms of the hands, etc. 368. lu other respects, as an organ of sense, it does not appear to differ throughout its entire extent. Yet through different parts of it, the same causes produce different effects, which seem, therefore, to be owing not to any difference in the structure of the skin, but a difference in the constitution of the parts, connecting between the skin and mind. Through one part of the skin, the sensation of tickling can be pro- duced, through another part it cannot. A similar effect is produced upon the skin, in one case, as in the other, bat a different effect upon the nerves, because they are differently made. If the odor of the rose be drawn through the nose, it produces a sensation, but if it be drawn through the mouth, when the nose is closed, it does not produce a sen- sation. The skin, lining these parts, does not seem to materially differ in its structure. The reason for the difference must, therefore, be in the constitution of the nerves, connecting these parts with the mind, as will be hereafter substantiated. It is important to notice this point, viz., the proof that the nerves are differently constituted. I will therefore mention one more illustration. Different parts of the body, are of different tem- peratures, naturally. The feet are naturally the coolest parts of the body, the head much warmer, but not as warm as the heart, lungs, etc. The hands are warmer than the feet ; hence if the hand touch the foot when both, in themselves considered, are perfectly comfortable, the foot will feel cool to the hand, and the hand feel warm to the foot ; because the natural heat of the hand, acting upon the nerves of the foot, is too much for them, and vice versa. The comparative warmth or coldness natu- ral to any part, depends on its distance from the heart and the quantity of blood it receives, as will hereafter be proved. The nerves therefore commencing in any part, must be acted on by a degree of temperature, a shade different from that acting on the nerves of any other part, and fet they all produce one sensation a sensation of comfort. Is it not astonishing that the temperature acting on the nerves of the foot, should produce the same sensation of comfort as the different temperature act- ing on the nerves of the hand ? And if the temperature of the foot rises to the temperature of the hand, and which through the nerves of the hand produces a feeling of comfort, it should, through the nerves of the foot, produce an uncomfortable sensation, of too much heat. There- SEC. 3.] ORGANS OP SENSE. 129 fore the nerves of the two parts must be differently constituted ; and the millions upon millions of nerves connecting the various points of the surface of the body with the mind, must be constituted with almost as much variety as there are nerves, and in such manner that each nerve will be acted upon so as to produce an agreeable sensation, by the natural temperature of the part in which it commences, and produce a disagreeable sensation when the slightest change in this natural tem- perature takes place. It is a wonderful thing that we are made as we are, and almost as wonderful that we know so little how we are made. When the poet sung, " It is a harp of a thousand strings," he had but a feeble conception of his subject. Indeed, the eloquence of man must be dumb, when the perfection of the Creator's works is before us. 369. The uses of the skin, as an organ of sense, may be considered under three heads. In the first place : 370. It may be considered as producing negative sensa- tions ; that is, those which cause neither pleasure nor pain. It produces such sensations when any thing comes in contact with it, if the thing be neither profitable nor harmful. There is no reason why, in such a case, pleasure or pain should be produced ; it will do us no harm if the object touch us, it will do us no particular good. The instant it becomes harmful, the skin produces an additional sensation of pain ; and when necessary for our welfare, it produces a sensation of pleasure. This negative sensation, is called the sensation of touch. Some suppose sensations of touch inform the mind of the solidity of an object by the depth to which the object acts ; that is to say, if the finger be pressed upon any thing, which is soft or yielding, it will produce an effect only on the nerves, commencing near the surface if the object be more solid, it will act on nerves commencing deeper. Some also think, that the form and size of many things are determined by the number and position of the nerves through which the sensation of touch is produced ; that is, if an object one inch long be touched, it will affect only half as many nerves as if it be two inches long. Some think the smoothness of an article is determined by similar sensations ; as, if an article be rough, it touches only a few nerves, the commencements of which are not near each other while, if the article be smooth, each nerve is acted on. But it would seem, these things are determined partly, if not wholly, by muscular sensations, as hereafter shown. 6* 130 ORGANS OF SENSATION OR FEELING. [CHAP. II. 371. Second. It may be considered as producing posi- live sensations of pleasure or pain. Its duty is, to produce such sensations, especially when acted upon by prpper or improper temperatures. Preserving a certain temperature is so important to health, that it is rewarded with the most pleasurable sensations ; while the slightest deviation is noticed by corresponding un- pleasant sensations. And as the whole duty of guarding the system, in this respect, depends on this organ of sense, it might pre-eminently be called, the organ of the sense of temperatures. How much it adds to the enjoyments of life, every one has appreciated when walking in the field or resting in the shade, quite satisfied with the delicious sensations of a summer's day. Still more was it our friend, if perspiring and ex- hausted, we thoughtlessly threw ourselves down where the temperature of the body was reduced too rapidly. The cold chill that ran through the frame, aroused us to safety. All injuries from which the skin suffers, will excite it to cause unpleasant sensations. It is thus our never sleep- ing guard. 372. Third. It may be considered as the organ of the sense of tickling, and many other such sensations which are worthy of merely a notice. The particular characteristics of the skin, as an organ of sense in the mouth and nose, will be mentioned hereafter. 373. To fit the skin for fulfilling its duties as an organ of sense ; in the first place, it will be necessary that the ex- ternal protecting layer, called the cuticle, scarf-skin, epider- mis, &c., be flexible, delicate, and as thin as the position it occupies will permit. 374. To preserve these good qualities, it is constantly lubricated with an oily fluid, formed in little pouches or bags, called cryptae or follicles (Fig. 51), and poured out upon the surface through their open mouths. As this fluid is of an oily nature it must be constantly removed from the skin, otherwise a collection of it will take place, which becoming gummy, will prevent the existence of that delicacy which it is intended to preserve. That it should be oily, is evident enough, as it was neces- sary it should protect the skin from the action of water and other things; SEC. 3.] ORGANS OF SENSE. 131 which are decidedly injurious, as is seen when the oil has been removed from the skin, not only, but drawn out from it by the continued applica- tion of hot water especially if assisted by soap, e. g. the hands of the washerwoman. The skin is not then delicate and well adapted to act as the organ of touch. A proper application of water, perhaps, assisted by soap, is to be recommended ; not such that the oil shall be exhausted from the skin, but merely rerrroved from its surface. To assist this, the skin may be vigorously rubbed with a towel, more or less harsh, as the case may require, and as may " feel comfortable." 375. The fluid being formed from the blood, a plentiful supply of this is necessary. This is obtained by general exercise, for that action of the muscles which urges the blood along through themselves, assists in circulating it through the skin ; by briskly rubbing the skin, for the efficacy of this may at any time be seen, the skin glowing with the life-giving blood that is brought into it by rubbing any part ; and by proper clothing, for without this, the blood cannot be long retained in the skin. 376. To fit the skin for fulfilling its duties; in the second place, it will be necessary to preserve a free circula- tion of blood, through the deep layers of the skin ; for on the reception of blood in ample quantities, depends the life and energy of the nerves. If a person be exposed to the cold, which contracts the bloodvessels and shuts out the blood, the part affected becomes numb. On the other hand, if the bloodvessels are overloaded with blood, and its circulation thus checked, sensations are equally indistinct and vague. The same means which will supply blood for the formation of the oily fluid, will supply it for the good of the nerves at the same time. This illustrates what will often be noticed, that what is for the good of a part, in one res- pect, is good for it in all, and never injurious. 377. 2d. We may now consider the remaining organs of common feeling. All parts of the body are thus grouped together, not because they produce similar sensations, partic- ularly speaking, but because the sensations they produce are for the same general purpose, viz., to inform the mind of the good or bad condition of any part of the body, of a good 132 ORGANS OF SENSATION OR FEELING. [CHAP. II. condition, by producing pleasurable sensations of a bad con- dition, by painful or unpleasant sensations ; and because the arrangement for acting on the nerves is similar in all these parts, viz,, the parts or organs act directly on the nerves, which commence in them. If each part which produces peculiar sensations were considered as an organ of sense, this group would be very much subdivided. The sen- sations caused by the windpipe, when any thing falls into it, are dissimi- lar to any others, and the lining of the windpipe might be distinguished as an organ of sense. A decayed tooth produces a peculiar pain, and that might be called an organ of sense ; and so every other part, which con- stantly produces peculiar sensations, might be looked upon as an organ of sensation ; but this subdivision would be useless. By nature or by experience we learn the meaning of the various sensations ; that is, where and how they are caused ; and are thus able to give attention to the cause of the evil, and what is still more important, to the prevention of its re-occurrence. B. The Muscular Sense. 378. Before the time of Sir Charles Bell, the rnusclea were not considered as organs of a particular sense, but were included among the organs of common feeling. He called attention to the importance of distinguishing the muscles as organs of a peculiar sense, and was the means of exalting them to their proper station. 379. The nerves which connect between the muscles and the brain are acted on immediately by the contracting mus- cle, different sensations being produced by different degrees of contraction. Thus, if the muscle contract or shorten one inch, one sensation will be produced ; if the muscle contract two inches, or more, or less, a dif- ferent sensation will be produced. Hence 380. The mind knows the degree of contraction of the muscle, by the sensation produced. And as the contraction of the muscle produces correspondent motion of some part of the body, SEC. 3.] ORGANS OF SENSE. 133 381. The mind knows the amount of motion produced, and also the kind, by the sensations produced. Thus the mind is able to guide the motions of all parts of the body ; e. g., if a person wish to raise the hand in a straight line, the mind, from previous experience, knows the sensations the muscles should cause, when contracting in such a manner as to produce the desired motion ; as soon, therefore, as any other sensation is felt, the mind checks the action of the muscle or muscles producing the wrong sensation, and causes the proper contraction to take place, thus regulating the motion. 382. Another kind of sensation is at the same time pro- duced, viz., a pleasurable sensation, of a character peculiar to the proper action of the muscles. The reason for this is quite clear : the action of the muscles is so es- sential to man, that it is important they be always kept in a healthy con- n^on. This cannot be without exercise. If it be not necessary to use them to-day, it may be to-morrow, or the next day, or the next. It is essential that they be exercised to-day, and every day. A pleasurable sensation has been therefore wisely caused to attend the exercise of the muscles, as a reward, and also 383. Another sensation of an unpleasant character is produced, when the muscle is not exercised, to punish us for not doing our duty. 384. Another sensation is produced, when the muscle has been over-exercised. This is to induce us to allow it repose, that it may recover that strength, healthy condition, and per- fection, it has in a measure lost by action. Some suppose that rest, after muscular action, is necessary, rather for allowing the nervous system, than the muscular, to regain vigor. But as the sensation of weariness or fatigue is felt only in the muscles exercised, the supposition seems to be gratuitous. When the nervous system is ex- hausted, the person is apt to express himself " I feel tired all over." 385. Another sensation is felt when repose is given to the muscle. This is of a pleasurable character, and is to reward a person for care, and to induce it on other similar occasions. 134 ORGANS OF SENSATION OR FEELING. [CHAP. H. 386. Still another sensation is felt, when the muscle is cut, bruised, &c., or diseased. This sensation seems to be of the same character as those produced by the organs of common feeling or sensation ; and in this respect the muscles might be included in the same category with them. 387. The sensations produced by the action of the mus- cles, enable us to determine the hardness of an object, its form, its size, and to a degree, if not wholly, its smooth- ness, &c. For if the muscle be contracted to a given degree, and motion is yet resisted, the object would be considered correspondingly solid ; e. g., if the finger be placed upon dough, and the muscles of the arm which move the finger be contracted to a certain degree, motion of the finger is produced ; while, if the finger be placed upon the table, no motion of the finger takes place, with a similar contraction of the muscles. The table is then called harder than the dough. The form of an object is determined by the contraction of the muscles as the hand is laid upon its surface. For instance, if the musc.es contract so as to draw the fingers perpendicular with the palm of the hand, the object is considered to have a square edge. If the muscles contract, as when the fingers grasp a ball, the ob- ject is considered spherical. Of course, in this case, the sensations pro- duced by touch assist and are essential ; for the form of an object is de- termined by the contractions of the muscles necessary to cause its surface to be touched by the body more commonly by the hand or fingers. In the same way, the size is determined. For as a greater or less contrac- tion of the muscles of the arm is necessary, to sweep the hand over the object, so is the object regarded as larger or smallej: ; and as the muscles meet with more or less opposition, so is the object regarded as smooth or rough. C. The Sense of Taste. 388. The tongue and back part of the sides of the mouth are the organs of the sense of taste. The skin lining the entire mouth is at the same time the organ of the sense of touch and common feeling. A bit of sugar placed any where in the mouth produces a sensation of touch, but only in certain parts, the sensation of taste. The sensation of taste is not caused through the same nerves, therefore, as the sensation of touch ; this is SEC. 3.] ORGANS OF SENSE. 135 also proved by the effects of disease, which sometimes takes away the power of tasting without affecting the power of touch, and vice versa. That is, by disease a person is unable to taste sugar placed upon the tongue, though the sugar produces the sensation of touch the same aa ever, or in other cases he tastes the sugar when it produces no sensation of touch. 389. The organs of taste may be considered as double, the central line on the surface accurately dividing the tongue into two tongues, so far as tasting is concerned. This is proved by dissection, and by disease, which sometimes unfits the nerves of one side for performing their duty. 390. The nerves of taste commence in the lining of the mouth in the same manner as the nerves of touch. The papillae in which they commence are much more numerous at the tip of the tongue than elsewhere, hence that is the part which produces the most lively sensations. It is proper it should be so, for that part can be thrust from the mouth, and with it articles can be tasted before they are allowed to act on so great a number of nerves, as when taken into the mouth. 391. By some it is thought that all the nerves of taste are not of the same quality; that is to say, that the same things produce one kind of sensation through the nerves connecting between the tip of the tongue and the mind, and another kind of sensation through the nerves connecting be- tween the sides of the mouth and the mind. They illustrate the idea by what every one may notice, viz., that some articles taste differently after they have been in the mouth a little time, which these persons suppose to be owing to the opportunity they have had of reaching the nerves farther back in the mouth. Others explain this phenomenon, by supposing that after some substances have acted for a little while upon the nerve of taste, they alter the nature of the nerve in such a manner that it produces new kinds of sensations. One thing is certain, 392. The nature of the nerves of taste is very easily changed, both transiently and permanently. In proof of this, the common fact need only be mentioned, that food 136 ORGANS OF SENSATION OR FEELING. [CHAP. II. which it is very disagreeable for us to taste at first, becomes delicious in a short time, not more because we become accustomed to the taste than because the taste is changed. The taste of an article depends much, also, upon what articles are combined with it, and what articles have been eaten previously. A variety of articles by themselves, produce such sensations we cannot relish them at all ; when mixed in proper proportions they produce exceedingly agreeable sensations. In this lies the great secret of cooking, viz., to combine articles in such a manner as to cause them to relish. Another secret consists in this, viz., to place articles before a person in such order, that eating one shall increase the relish for another, and improve the sensations it produces. By breaking both these rules, some housekeepers with the greatest abun- dance, never have any thing fit to eat, or one thing, if good, spoils the taste of another good thing which follows it ; while by giving attention to these principles and learning how the taste is generally acted upon, or particularly acted upon in particular cases, a housekeeper with very small means will always have a delicious table. I have known persons to be so unskilful as to put on the table, to be eaten with meats, richly preserved fruits, perhaps thinking they must be nice, because expensive, while with meats, being more or less of a fatty nature, something acid is agreeable ; plain apple or cranberry sauce would have improved the meat, and the meat the sauce ; thus the old proverb is true, " one person will prepare a better dinner with a shilling than another with a pound." A Frenchman will make a delicious soup with what ordinary cooks will throw away. In this, as in every thing else, it is not the outlay of money, but mental application, which will gain the desirable end. 393. The use of this sense is to give pleasure while eat- ing, that we may be induced to chew the food thoroughly, and allow it to be mixed with a good supply of saliva ; two very important things in the digestive process. It also facil- itates digestion, by causing a free flow of saliva. " The mouth waters," is a frequent description of the effect of food before it is tasted. Much more powerful in the same way is the action of the food when taken into the mouth. A some- what similar influence causes a free flow of digestive fluids into the stomach, as shown hereafter. As previously shown, it is very important that we cultivate a relish SEC. 3.] ORGANS OF SENSE. 137 for wholesome food, and then that we eat it only when it is highly relished, and that we enjoy it to the full, by the allowance of proper time, etc. 394. That substances may produce an effect on the nerves of this sense, it is necessary that they be dissolved. For this purpose the constant flow of the saliva is well adapted. 395. When the mouth becomes dry, as well as when the organs of sensation are diseased, the sensation of taste will be wanting or very much changed. This sense in animals serves them instinctively to distinguish between wholesome and unwholesome food. Some have thought that it would be the same with man in the uncultivated state. One thing is certain, the taste of animals, as well as of man, is easily changed, and as the taste of animals can be preserved, so can that of man without change. If a child be always fed upon milk, it will, when young, desire nothing else, for why should it desire to taste something it never tasted ? If we, when mature, find any new thing, we have so little desire to taste it, that we use great caution, and at first taste but a bit ; indeed we have no desire to taste it. The child who has never had a bit of sugar or sweetmeats placed in its mouth will never desire it, and, therefore, never cry or fret because it does not receive it. A child should never, there- fore, receive the least thing except its wholesome food, until it is old enough to understand why it should have but little of certain things, and only at certain times. Thus will the mother save the disposition of the child from a great source of injury, and save herself much trouble, while certainly, the health of the child will be much the better. I have known, as every one has, a mother to give a child a bit of sweetmeats which has been the means of a hundred crying fits ; for every time the child saw the like, it would wish to eat, and the mother would not dare to give what the child wished. D. The Sense of Smell. 396. To understand this sense we must, in the first place, give atten- tion to the objects which act upon its organs. The rose may be at a distance from us, and yet we perceive its odor. The whole air is some- times filled with the fragrance of the fresh-blown clover field. The rose itself does not, of course, affect us. The usual opinion is, that exceed- ingly minute particles of the rose and all odorous bodies, are continually 138 ORGANS OF SENSATION OR FEELING. [cHAP. II. coming off from them, and that these act upon the nerves. Of course, if this theory be correct, the greater the number of particles acting on the nerves at the same time, the more powerful would be the sensation ; and it is usually found that the most odorous articles are very volatile (fly- ing). But some articles have been said to render a large space fragrant with their qualities for years ; and yet without losing weight appreciably. We can hardly conceive of particles so minute as this would require and a variety of arguments have induced me to suppose the ordinary philosophy was not quite correct ; but it explains most phenomena well enough, and I shall adopt it. Suppose the air then to contain particles of a rose or any thing else, it will next be necessary to have the air pass over the nerves ; and the greater the number of nerves it passes over, the greater the probability that many of the nerves will be affected by the particles, few or many, which the air contains and the greater the quantity of air passing over the nerves, the greater the probability that many nerves will be acted upon, and an intense effect be produced therefrom. 397. The nose is exceedingly well adapted to be the organ of the sense of smell. The lining of the nose is also the organ of the sense of touch and common feeling ; as substances may produce the sensation of touch or pain, without causing that of smell. By disease, also, a person may be devoid of either the sense of smell or touch, without the other being lost. There must, therefore, be two kinds of nerves connecting between the nose and mind which is found to be the case. 398. It is composed above of a bony framework, which is lengthened down by cartilage. The yielding nature of this, prevents the prominence of the nose from being objectionable on account of its liability to accident ; while the elasticity of the cartilage, preserves a free passage to the air. The yielding nature of the cartilaginous portion also allows the passage to be closed, if the air.be unpleasant, or narrowed when it is desirable to in- hale the air with increased force. 399. The nose is divided above by bone, which is also lengthened down by cartilage. This increases the extent of surface in either half of the nose, and in fact divides, for all the purposes of smell, the nose into two noses ; for SEC. 3.] ORGANS OF SENSE. 139 the sense of smell may be lost in respect to one nostril, and may remain in respect to the other. And the nature of the nerves connecting be- tween the nostrils are sometimes different ; so that, as some persons have one sensation when a substance acts on one side of the tongue, and a different sensation when the same substance is moved on the other side of the tongue so some persons have one sensation produced when odor acts through one side of the nose, and another sensation when the same particles act through the other side. 400. Several bones, called turbinated (coiled) or spiral (Fig. 52), are attached by one edge to the outer and upper side of the inside of the nose. The other edge hangs down into the nasal passage, and is somewhat coiled ; though not as much in men as in many animals. Fig. 52. Fig. 52. Is a perpendicular section of the face-bones, through the nose and across its passages. The figures 7, 7, are placed in the sockets of the eyes ; 12, is the cheek- bone, within which is seen the antrum with a small bit of its lining raised up. In the antrum of the other side, a bristle is represented, thrust up through an opening into the nose, the cavities of which are divided by the vomer 11, and partially divided by the lower spongy bones 10, 10, and middle spongy, to which the lines from 7 lead ; 18, the roof of the mouth. By this arrangement, two objects are gained. In the first place, the lining of the nostrils presents much more surface to the action of the air, and in the next place, the nasal passage being narrowed, there is much more probability that the odorous particles, which the passing air contains, will act upon one part or another. 401. The nerves of smell commence in papillae, found beneath the surface of the delicate lining of the nasal passages. 140 ORGANS OF SENSATION OR FEELING. [CHAP. II. Thus, as the air, by the action of the breathing apparatus, is swept through the passages of the nose, the odorous particles of one substance produce one effect, those of another substance produce another effect. The question might be asked, if a particle of substance, after it had acted on one nerve, could be carried on to act on another 1 This is not known, probably it could not. 402. To facilitate the action of odorous particles, it is ne- cessary that the lining of the nose should be kept in a proper condition by a substance, serving the same purpose as the oily substance poured out constantly on the skin. It is formed in a similar manner, and differs in its nature, only to be better adapted to the wants of the part to which it is supplied. It is very similar to the substance which is supplied to the lining of the mouth, and readily seen, looking like the white of egg, if a spoon or knife be scraped gently down upon the surface of the tongue. 403. The lining of the nose is also kept in a proper con- dition by the fluid which has already served a similar pur- pose in the eyes. When therefore either of these fluids is wanting, the power of the sense of smell is correspondingly deficient. So on the other hand, when the supply is too abundant the sense of smell is injured. Both of these things are frequently illustrated by the effect of colds. 404. In man, this sense seems to be chiefly useful by in- creasing the pleasures of existence. It prepares and increases the appetite for the preparing food. This sense is so seldom wanting at birth, (I never knew but one case,) that it may be of much more use than at first appears. In case of animals, it appears of great use in distinguishing their food, and won- derful things are told by travellers and naturalists of the acuteness of smell of certaid birds, etc. But I do not place confidence in them, as there is no reason it should be so. The acuteness of smell in case of the hound is owing, in great part, to the great extent of lining surface of his nostrils, by which a large number of nerves can be presented to the action of air which he snuffs. 405. The sense of smell seems to affect the sense of taste, or rather certain sensations which we call sensations of taste, SEC. 3.] ORGANS OF SENSE. 141 seem to be made up of effects produced through the organs of smell and through the organs of taste. For if the nostrils be closed, certain articles produce little if any taste. An idea to be taken advantage of, when a person must swallow un- pleasant things. The near alliance of the nerves of taste and smell is also seen by what everyone has noticed, that one thing tasies as another one smells, or vice versa. That is, the sensation which one thing pro- duces through the nerves of taste, is similar to the effect another thing produces through the nerves of smell. 406. There are various cavities connected by small open- ings or tubes with the nostrils. 1st. There is one within each cheek bone, called an antrum, with a tube opening into the side of the nostril. There is one within the ridge of bone felt beneath each eyebrow, called a frontal sinus, with a tube opening into the upper part of the nose. The inner end of this sinus sometimes almost meets that of the opposite, its other end being found within the outer end of the eyebrow. Sometimes they are a little distance from each other at their inner ex- tremities, and short or long as the case may be. Sometimes they are broad, either up and down or from forward back, being large or small as the case may be. Sometimes their size is indicated by an external prominence, sometimes not. There are other small cells or cavities in the bones forming the roof of the nose ; their tubes open into the top of the nose. 407. The skin or membrane lining these cavities is con- tinuous with that Iming the noe. It forms and pours upon its surface a similar substance, though not in so large quan- tity. The tubes heretofore mentioned are the outlet of this fluid. Colds sometimes increase, sometimes diminish the quantity of fluid formed, and sometimes at the same time cause a closure of the outlet. A collection then takes place in the cavity. Severe consequences usually follow in a short time. Similar disease of the membrane, though not the re- suit of colds, will produce like results. 142 ORGANS OF SENSATION OR FEELING. [CHAP. II. E. Sense of Sight. 408. The eye is very admirable, both on account of its beautiful structure, and the perfect manner in which it fulfils its duties. But it is exceedingly difficult to render its mode of action perfectly clear. With the aid of lithographs, however, if the reader will assist with his imagi- nation, and give his undivided attention, the task may perhaps be ac- complished. He must, however, pardon the author, if, in the earnest attempt to render the subject clear to every understanding, the descrip- tion should appear, by the homeliness or simplicity of expression or illus- tration, to fall below the dignity of a book treating upon op.ics. If he be in the habit of reading upon these subjects, he will confer a favor on the author, and perhaps on himself, by reading as if a beginner, follow- ing step by step, without anticipation, as explanations may then appear proper, which otherwise would seem unnecessary ; and the language used is intentionally different from what is usual ; some very familiar expressions will carefully be avoided, nor should the reader allow his mind to suggest them. The eye is neither a telescope nor a micro- scope, but an apparatus with which to see. How do we see 1 is the question to be answered. And if, in following the author, the reader ar- rive at the same conclusions he has often before, as it is expected he will, it will perhaps be by a way somewhat new, except to physiologists, and free from many sources of confusion to which descriptions of this sense are usually liable. 409. If the eye be directed toward yonder tree, it apparently produces a sensation ; that is, it is seen. If the eye be closed, the sensation ceases. 410. The eye is, therefore, the organ of sense through which the sensation is produced. It is the organ of the sense of sight. It will by this time be easily remembered, that when an effect is pro- duced on the nerve commencing in the organ of sense, that effect ia called an impression. This effect or impression acts through the nerve and brain upon the mind, causing a sensation. It will be convenient in this division of the section, to make free use of the word impression. 411. If the tree be removed, the sensation will cease. 412. The tree must therefore be one of the causes of the impression made upon the eye. SEC. 3.] ORGANS OF SENSE. 143 413. But the tree is at such a distance that it cannot itself act on the eye. Yet something must act on the eye, and something must be caused to act on the eye by the tree. That something is called light. 414. Light, therefore, is that something which objects more or less distant cause to act on the eye and produce impressions. Some think that light is composed of very small particles, which ob- jects cause to act on the eye. Others think that there is a substance very much more subtle than air, existing throughout the universe. This fluid, as it is sometimes called, or ether, as it is also called, is supposed to be thrown into waves by the action of objects, and these waves caused to act on the eye. It will make no difference at present, in any practi- cal respect, which theory is adopted ; but as the language used in con- nection with the first mentioned is more easily understood, light will be here considered as composed of exceedingly minute particles. These always move in straight lines till they meet some object which turns their course, when they again move in straight lines. A series of these particles of light following each other, is called a ray or beam of light. Whether in a ray of light the particles are very near each other, or at considerable distance, is not known ; nor is it known whether they are nearer in some cases than in others. The quickness or velocity with which they move is almost incredible. 415. But in a few hours the sun will set, and leave the world in darkness. The tree will remain, and the eye may remain, but the tree will not produce any sensation. The action of the tree, therefore, de- pends upon the sun. But the sun does not touch the tree. The sun must, therefore, cause something to act upon the tree, causing the tree to cause the light to act upon the eye. 416. How this is, is made known by examining the nature of light. The particles of light, when striking against certain objects, bound off like india-rubber balls. If a handful of these be thrown against the wall, some would bound off or be reflected (turned back) in an upward direc- tion, some downward, some to one side, others to the other side, and thus be scattered over the entire room. Thus is it with light. 417. The idea, therefore, is this, viz., that the sun acts upon the tree by means of light, the particles of which pass from the sun to the tree upon which they strike ; it then reflects or bends them in various directions, and some of the particles being bent or reflected so as to 144 ORGANS OF SENSATION OR PEELING. [CHAP. II. come in a straight line to the eye of the observer, an effect or impression is produced. Hence 418. Various objects produce an effect through the eye by reflecting light upon, or rather into it. 419. But yonder house by the side of the tree also produces an effect or impression upon the eye. The light of the sun must also strike upon that and be reflected to the eye. But the sensation produced is different from that produced by the light coming from the tree. The impression must of course be different, and the light producing the impression must be different, therefore the light coming from the tree must be different from that coming from the house. But the light coming from the sun to the tree is precisely similar to that coming from the sun to the house. These objects must, therefore, do something more than merely bend the light; they must change it so that it will cause different impressions after it has left them, for the light is similar before it comes to them, but different afterwards. How this is will be understood by noticing, in the first place, that 420. The light coming from the sun is composed of three kinds of light. 421. When all three kinds act on a single nerve at the same time, they produce the same sensation as when light from the sun acts on it. It is called the sensation of white light, or whiteness. If one kind act by itself, it produces the sensation of red. If a second kind act by itself, it produces the sensation of yellow. If the third kind act by itself, it pro- duces the sensation of blue. If the first and second kinds, in proper proportions, act at the same time upon the same nerve, they produce a sensation of orange. If the first and third kinds in proper proportions act, they produce a sensation of purple. If the second and third kinds in proper proportions act on the same nerve, they produce the sensation of green. Thus every variety of sensation of color is caused by the action of one or several kinds of light at the same instant on the same nerve. When the nerves are not acted on by light of any kind, they cause a sensation of blackness, as when a person goes into a perfectly dark room. Sensations produced by the action of any kind of light singly, are called simple sensations. Sensations produced by the action of more than one kind of light, are called compound sensations. If it be asked, How are all these things known ? The answer is, by the use of proper apparatus the light of the sun can be separated into three SEC. 3.] ORGANS OF SENSE. 145 kinds, either of which, or any combination of them, can be made to act on a nerve of the eye at the same instant. We are now prepared to notice, in the second place, that 422. Some objects absorb (drink up) all the light that falls upon them, while others reflect all that falls upon them ; while other objects again, absorb one kind, or two kinds, or part of one kind, or two kinds, as the case may be, and reflect the rest. 423. The reason is now instantly seen why objects produce different impressions. Yonder house absorbs the yellow and blue light and re- flects the red, and hence produces a sensation of red. The tin upon the roof does not absorb any, but reflects all kinds just as they come from the sun, and the same effect is, of course, produced as if the light came from the sun directly to the eye ; a sensation of dazzling whiteness. The posts in the yard absorb all the light and do not reflect any, nor produce any effect on the eye, and the want of this effect causes the sensation of black, and we say we see the posts to be black. The leaves of the tree absorb the red light and reflect the yellow and blue, which together, acting upon the eye, cause the sensation of green. But when the frosts of autumn shall change the nature of the leaves, some of them will absorb the red and the blue, reflecting only the yellow, and producing, therefore, the sensation of yellow, while others will absorb the blue and yellow, and reflect only the red. Thus by the change in the nature of the leaves, and their power of absorption and reflection of light, which falls upon them, is produced all the gaudy beauty of our autumnal forests. For when night comes on and there ia no light to be reflected, all things alike want the power of producing sensations, and as the eye strives to pierce the darkness of the forest, it causes only the sensation of blackness. 424. Some objects produce light, which passing directly to the eye, causes sensations. Thus objects are of two kinds. 1st. Those which produce sensations by their own light, and 2d. Those which produce sensations by reflecting light pro- duced by other objects. The sun, candle, the fire, and the like, are examples of objects causing sensations by their own light. The kind of sensation they will produce, will depend on the kind of light they produce. The sun, " the great 7 116 ORGANS OF SENSATION OR FEELING. [CHAP. II. fountain of light," produces all three kinds of light at the same time. Some other light-giving objects, however, produce but one kind of light ; most objects, however, produce several kinds. It is now desirable to state distinctly an important proposition. 425. When different kinds of light act at the same time on the end of the same nerve, a compound sensation must be produced. In order, therefore, to have the light coming from different objects produce distinct sensations, it must act on the commencing points of different nerves, and the more perfectly this is accomplished the more distinct will be the resulting sensations \ this is the great office of the eye. Yonder now is the house, which produces the sensation of red, and the leaves of the tree, which produce the sensation of green, because the red light is reflected by the house, and the yellow and blue by the leaves. If the light from these two objects acted on the end of the same nerve, at the same time, the sensation would be that of white, because all three kinds of light would be acting at the same time on the same nerve. But the red light from the house does enter the eye at the same time with the yellow and blue light coming from the leaf, and yet a distinct effect is produced. Therefore there must be more than one nerve in the eye, and the eye must be so made as to cause the light coming from the house and entering it, to act on one nerve, and the light entering it from the leaf to act on another nerve. It must be the same in respect to the light coming from any and every object we see ; thus, 426. The number of objects which we can distinguish being very great, the number of nerves commencing in the eye must correspond (Fig. 53). That the reader may comprehend how the different nerves are acted upon by the light coming from different objects, at the same time, and in such manner that each nerve acted on shall be affected only by the light coming from its own object ; let him try the experiment of placing several candles near each other. Then having made a pin-hole in a sheet of paper or pasteboard, hold it in such a manner within a few inches of the candles, that the light from all of them will shine through the pin-hole ; let then some object be held a little distance from the pin-hole, upon the side of the paper opposite the candles. He will thus see that light moves in straight lines, for the light goes directly on from the pin- SEC. 3.] ORGANS OF SENSE. 147 Fig. 53. Fig.53. 3, Represents the outer coats of the back part of the eye. 1, The optic nerve composed of millions of fibres. 2. An ideal respresentation of the commencement of the fibres. Between the nerves and outer coats 13 seen the pigmentum nigrum. hole in the same direction it had while coming from the candle to the pin-hole, and he will quickly see which spot the light from any candle produces, by blowing out a candle, for its spot will instantly vanish, and reappear if the candle be lighted. He will also see that the light from one candle crosses that from another at the pin-hole, without any interference. How or why this is, cannot be told, but it is an evident fact. If now he look at lithograph Plate 5, Fig. 1, he will notice a repre- sentation of the eye in outline, as a box of a spherical form, with an open- ing in front ; just back of this is a partition with a hole in it correspond- ing to the pin-hole in the pasteboard, and in the back part is seen the commencing extremities of a great number of nerves, each one of which extends back to the brain. In front of the eye are placed three candles, producing red, yellow, and blue light. When the light coming from each is mingled, as it is in passing through the hole in the partition, a, it would cause the sensation of white light, if a nerve were there to be acted on ; but when the red light has gone through the hole, it, like the others, pursues its straight course, and therefore acts on its own nerves at the same time the blue and yellow light act on their nerves. 427. The more light there is acting on any nerve at the same time, the more intense will be the sensation produced. This is almost self-evident. When we go into a nearly dark room, there is so little light acting on the nerves, that objects can hardly be discerned ; while if we go out doora, of a bright winter's day, the light 148 ORGANS OF SENSATION OR FEELING. [CHAP. II. reflected from the snow, painfully dazzles. Under some circumstances, therefore, it will be desirable to have as much light as possible enter the eye ; while in other cases, it would be desirable to shut out the light. It is evident such an end could be gained by enlarging or lessening the hole in the partition a. For if it should be enlarged, more light would be admitted ; while if it were lessened, so much light as now could not reach the nerve. 428. If the reader take the pains to hold a candle near to the eye, and remove it and re-bring it towards the eye of another person, he will perceive an enlargement and lessening of the hole, called the pupil, seen in the colored part of the eye, called the iris, which corresponds to the partition (Lith. PI. 5, Fig. 1) a. It would now seem that all the requirements for seeing are obtained; but the most difficult part of the matter yet remains. It is seen that the light from three candles (Lith. PI. 5, Fig. 1) acts upon a large portion of the nerves in the eye. But with the eye we can distinguish a thousand candles, which could not of course be, if no other arrangement existed than that already described. If the hole in the partition a be made very small, then only a little light from each object would pass through, and act on a correspondingly small space, in the eye ; and there would then be room for the action of light from a great many different objects. It has, however, been seen, that in a dimly lighted room, where only a very small amount of light acted on the nerves, but a slight effect was produced. With so small an amount of light as would pass through a pin-hole, acting on the nerve, the effect would not be so powerful as necessary ; more light must, therefore, be allowed. But when the open- ing is large, it is seen in Lith. PI. 5, Fig. 1, that the light acts over many nerves ; so that no more light acts on one nerve, than if the hole in partition a were smaller. Though in this case the sensation would be stronger, it would yet be feeble. If, however, any thing can be done by which the light passing through the hole in the partition, which I will now call the pupil, can be concentrated (brought to a centre or point) that is to say, the red light be brought to a point by itself, and the blue and yellow light brought to points each by itself the desired end will be gained ; for then all the light from one object passing through the pupil will be made to act on a single nerve and there can be as many different sensa- tions as there are nerves, if there are only as many objects to cast their, light through the pupil. To understand how this is accomplished, we must notice a third effect, which is produced upon light by some objects. SEC. 3.] ORGANS OF SENSE. 149 429. Some objects transmit (send through) the light fall ing upon them as window-glass transmits the light of tht sun. Such objects are called transparent. Some objects transmit one kind, and reflect the rest ; or transmit a part of all, and reflect a part of all. There are very few, if any objects, which transmit all the light falling upon them. 430. If a ray of light fall perpendicularly upon the sur- face of a 'transparent object, as C, D (Fig. 54) falling on the surface S, I, the light will not be bent out of its course. Fig. 54. R, S, T, U, represents a ray of light passing obliquely from the air S, I, into the glass A, B and from that into the air P, T ; R, O, would be the direct line S, P ; I, T, perpendiculars ; C, D, a ray of light entering the glass perpendicularly, and of course not bent. 431. If a ray of light fall upon the surface of a transpa- rent object in an oblique or slanting manner, the light will be bent just at the surface of the object it is entering, as shown by R, S, T, U, Fig. 54. An experiment illustrating this can be tried by putting a quarter of a dollar in an empty bowl. Then place the bowl in such a position that the light coming from the money over the edge of the bowl will not enter the eye, but pass a little above it as in (Fig. 55) the line of light a, b. If water be poured into the bowl, the light which passes from the money perpendicularly into the air at c, a, will not be bent, but pass the same as before the water is poured into the bowl ; but all the light pass- ing from the money through the water and entering the air in a slanting direction, will be bent, and the light which passes in the line from the 150 ORGANS OF SENSATION OR FEELING. [CHAP. II, money to the edge of the bowl, when there was no water in the bowl, passes in the same line as far as the surface of the water, but as soon as it enters the air it is bent and strikes against the bowl, while the light which left the money in the line a, b, before the water was poured into the bowl, follows the same course as far as the surface of the water, when it is bent so as to take the line a, d, e, which passes into the eye and produces an impression. This is the reason why pouring water into the bowl enables a person to see the money, though the bowl and eye are not moved. Fig. 55. 432. The more slanting or obliquely the light enters from one object into another, the more is it bent. This is represented by the lines in Fig. 55, between a, b, and a, f. 433. It is also seen that the light passing from the water into the air, in Fig. 55, bends from the perpendicular c, a, to the surface of the air. This is true of the light passing out of the water on each side of the perpendicular. Now the air into which the light passes, is not as dense as the water out of which the light passes into the air. There- fore as this is always the case, 434. It is a rule or principle that light passing from a denser or more solid object into a less dense or less solid ob- ject, is bent from the perpendicular to the surface it is enter- ing. 435. In Fig. 56, light is represented as passing from air into water, thence into glass, thence into air again. In passing from air into the water, the light is seen to be bent, but is now bent towards the SEC. 3.] ORGANS OF SENSE. 151 perpendicular to the surface which it is entering, because the object, viz. the water which it enters, is more dense than the air which it leaves. As it enters th" irin.-s. it is observed to bend again. This time it also bends towards the p-.^pendicular to the surface it is entering, because the glass is more tU n. -e than water. But after passing through the glass it passes into the less dense air, when it bends from the perpendicular, and bends much more than at either of the previous times, because the re' is much more difference between the density of the glass and air, than between the air and water or water and glass. Fig. 56. Fig. 56. A, D, is a ray of light passing from air into the more dense water at D, where it is bent towards the perpendicular C, D. E, H,is the continuation of the same ray through the denser glass which causes the light to bend at E towards the perpen- dicular E, F. H, R, is the continuation of the same ray through the less dense air which causes the light to bend from the perpendicular H, G, and to a great degree be- cause of the great difference in the densities of air and glass. 436. It is a rule of universal application that light in passing from a less dense into a denser object, is bent towards the perpendicular to the surface it is entering. 437. It is also a rule that the more the density of bodies differ, the more is light bent in passing from one object to another. 438. There are therefore two things which influence the bending of light. 1. The direction in which it falls upon an object. 2. The density of the object. 152 ORGANS OF SENSATION OR FEELING. [CHAP. II, 439. If now light pass in straight lines through the flat piece of glass C (Fig. 57), it does not change its course because it falls upon the glass perpendicularly to the surface, but when the light passes to the piece of glass L, made with rounded surfaces, the light will be bent as it enters the glass, because it does not strike upon the glass L, perpendicularly to its surface. It will of course be bent towards the perpendicular to the surface it is entering. When it has passed through the glass and enters the air it will be bent from the perpendicular, because it is entering a less dense object than it is leaving. The result is seen from the figure. Fig. 57. Fig. 57. a, 6, c, represent rays of light which pass through the piece of glass c, without being bent as they fall perpendicularly upon the glass c. But as they fall upon the lens L, in a direction not perpendicular to its surface, they are bent in such a man- ner that they all cross each other at the point ra, which is called the focus, beyond the focus the rays spread farther and farther from each other. 440. The principle is perhaps better illustrated by Fig. 58 : a rep- resents a candle, with the ray of light (a, d) passing to a piece of glass (d, k) called a lens. As soon as the light enters the lens, it is bent towards the perpendicular (e, d) to the surface it is entering. When the light passes from the lens, the light is again bent, and is now bent from the perpendicular (h, g~) to the surface of the air it is entering, and passes on in the straight line (h, i) until it shall meet some object which will absorb it, reflect it, or transmit it. Again, the light (c, k), as it enters the lens, is bent toward the perpendicular, and when it leaves the lens is of course bent from the perpendicular, and goes on in the straight line (k, i) till it meet some object. Observe now an important thing : the light (a, d, h, i) crosses the light (c, k, i) at a point (i), which is called a focus ; and it will be seen by Fig. 57, that all the light passing to the lens between the outer rays (a, and c) will, by the application of the principles just mentioned, be bent so as to cross at the same point or focus (m). Fig. 53. , 6, c, are three rays of light falling upon a lens; (6,/) falling per- pendicularly upon its surface is not bent upon entering, and as it leaves in a line per- pendicular to the surface it is not bent. The line a, falling at d upon the lens to which e, d is perpendicular, is bent toward that part of the perpendicular within the lens which the light is entering. When the light leaves the lens at A, instead of passing to f, it is bent from the perpendicular /, g, to the point i. It is understood that the light is passing from the lens into a less dense substance. 441. The problem is then solved, viz., if the light coming from any point be made to pass through a substance of proper nature and form, it will be gathered to a point. In proof of this, let the reader try the effect of a sunglass, which is a simple lens, the surfaces of which are rounded or convex. If the light of the sun be allowed to shine upon the sunglass, and a piece of 'paper or any object be held upon the other side of the lens, by moving the ob- ject nearer or farther from the lens, at last it will be seen that the lens bends all the light falling upon it in such manner that the light crosses at a point. For if an object should be held in the light at the points 1, 2, 3, Fig. 57, it would make a smaller spot at 2 than at 1, and a smaller one still at m, and a larger one again at 4, just as the light passing through the lens does upon the object held in its course ; for if this be held quite near to the lens, and then withdrawn slowly, the light will produce a smaller and brighter spot, till at last there is a mere point, when the spot will in- crease in size and dimmish in brightness. If the experiment be tried with the light of a candle and sunglass, the result will be the same. 442. Suppose now, there are two points at a little distance from each other, as in Fig. 59, A, B, from which light is passing to a lens. By the application of the before-mentioned rules, the light will be found mingled on the front surface of the lens, but so bent as it enters the lens and passes from it, that all the light from A, which falls upon the lens, crosses at the point b, and all the light from B crosses at a. If an ex- periment be tried with a sunglass and two or more candles, the same thing will be proved, for it will be found that all the light from each can- dle will cross at the same spot it will if that candle only be lighted. Of 7* 154 ORGANS OF SENSATION OR FEELING. [CHAP. II, course, if the object receiving the light be held in the right place, the light passing through the lens will produce as many spots as there are candles. Fig. 59. Fig. 59. A, B, repres the light falls upon the c< iris ; E, E, the lens, the >. A, B, represent two points, of which there may be millions. From A, B, ' cornea, c, c, and is bent as it is passing into the eye. D, is the te small spot at which the central rays or axes from A and B pass, being called the centre of the lens. After the light leaves the lens it is observed to cross at the retina (a, d), while if the retina had been as far distant as G, or only as far distant as H, the light would have acted over considerable space. 443. If, now, we go back to the subject of IT 428, we shall readily see how to gain the desired end, viz., by placing a lens, as in Lith. PI. 5, Fig. 2, so that all the light passing through the pupil of the eye shall pass through the lens ; for by that means the light coming from any point of an object will cross at a certain point within the eye, and if the nerve be there, it will be acted upon by all the light coming from the given point of the object, and entering the pupil. 444. There are now two difficulties to overcome ; the first is, what is called the " spherical aberration." It is produced as explained by Fig. 60 ; the light falling upon the surface of the lens near its edges, is bent more than the central light, because from the shape of the lens the light falls more obliquely or slanting upon the surface near the edges than upon the more central parts of the lens. Of course, the light passing through the outskirts of the lens will cross at a point or focus nearer the lens than the central light will ; but it is desirable to have all the light cross at the same point, and it must be so arranged that all the light coming from any point of an object, and falling upon the lens, may act upon the nerve. This end is gained in three ways : 445. 1st. The iris (rainbow), or colored part of the eye, SEC. 3.] ORGANS OF SENSE. Fig. 60. 155 Fig. 60. Exhibits the fact that A, O, falling perpendicularly on the lens, is not bent. B, 6, are bent somewhat, and cross at o. C, c, are bent still more, and cross at h ; while D, d are bent most of all, and crost at H. represented by the partition a, in Lith. PL 5, Figs. 1, 2, pre- vents light from falling upon the edges of the lens. 446. 2d. The form of the lens, as found in the eye, is peculiar, and such (Fig. 61) as is adapted to the purpose desired, being more round, or more convex on the back or posterior surface than on the front surface. 447. 3d. By the peculiar structure of the lens, it is adapted to its purpose. It is composed of layers like an onion, and as represented in Fig. 61. The outer layers are almost liquid, the next like jelly in consistence, the middle of the lens being almost like gum-arabic for density. The light, therefore, which passes through the central part of the lens, will, on account of its greater density towards the centre, be bent more than otherwise, and cross at the same point as the light passing through the outer parts of the lens. 448. The second difficulty to overcome is this : the different kinds of light are not bent equally by the same substance. If the light passing from the point a, Fig. 62, be white light, that is, composed of the three kinds, red, yellow, and blue, as it passes through a common 156 ORGANS OF SENSATION OR FEELING. [CHAP. Fig. 61. Fig. 61. Cornea fitted into the sclerotic coat. A, Choroid. B, Pigmentum nigrutn- C. Retina, lined by the hyaloid membrane, containing (K) the vitreous humor. D Tne optic nerve. I, The lens. G, Iris, coated on the back side with pigment, (paint)- H, Ciliary processes. F, Aqueous humor. lens, it will be found that the blue light is bent the most, and crosses at a point nearer to the lens than where the yellow crosses, which is also nearer than the focus of the red light. But in the eye under ordinary circumstances, this does not take place. How it is prevented is not known. We may now pass to consider the structure of the eye, and it3 appendages, after which we shall be able to sum up the abilities of the eye, and have a clear view of what seeing is, and how it is accom- plished. 449. First, the external appendages of the eye. The eye is placed in a deep and large socket. In this the eye is protected by a cushion of fat, in and upon which it is situ- ated. It is also well protected from blows by the jutting forehead, the prominent nose and cheek bone; indeed, it is shielded in every direction, except directly in front and to the outside, where it can easily see, not only to take care of itself, but also the body. 450. The eyebrows also shield the eye in a measure SEC. 3.] ORGANS OF SENSE. Fig. 62. 157 Fig. 62. Shows that some of the light is bent more than the rest. from the dazzling rays of the sun, and from the perspiration flowing from the forehead. They are nourished and caused to grow by the blood which flows around their roots. To insure a good supply of this, the skin at the eyebrows should be daily rubbed. 451. The eyelids close over the eye to exclude dust, to wipe off the dust which has been admitted, and to spread the fluid, called tear-fluid, over the eye. The movement of the lids is accomplished by two muscles. One is called the an- nular, orbicular, or ring muscle of the eyelid. It passes around the opening of the lids, as in Lith. Fig. 1, PI. I. When it contracts, it gently closes the eye. When forcibly contracted, it slightly draws inward the outer corners of the eyelids, as the muscle is connected to the edge of the orbit near the nose. The eyelid is raised by a muscle which commences at the back part of the eye socket, and passing over the eyeball, terminates in the upper lid just beneath the skin, and above the edge of the lid, as seen in Fig. 63. The form of the edge of the lid is preserved by cartilages, called the tarsi. They are curved to the form of the eyeball, but 158 ORGANS OF SENSATION OR FEELING. [CHAP. II. keep the lids stretched from corner to corner. At the outer edge of the lids the eyelashes are found beautifully curved, in such way that when the lids are closed they may inter- lace, yet their ends be never entangled, as is seen in Fig. 64. Sometimes an eyelash will perversely grow into the eye. It should be drawn out of the lid at once, and if the one which follows it shall take the same course, as it probably will, that is to be treated in the same way. The lashes sometimes come out, and either the disease which causes them to come out, or their coming out, produces very bad results. The physician should be consulted in good season. The edges of the lids when closed, do not leave a groove at their back edge, as sometimes said, and as represented by Fig. 65. The lids meet at the back edge, but not at the front, as any person may satisfy himself by looking at the closed eye. Near the inner edge of the lids there are many small openings of tubes, which lead up into the lid and terminate in minute pieces of apparatus, consisting of coiled tubes, called Meibomian glands. In these is formed a kind of fatty substance, which, oozing down upon the edges of the lids, serves to prevent the tear-fluid from running over upon the cheek. 452. The tear apparatus consists of a small organ, about the size and form of a sparrow's egg, of a whitish-yellow color ; situated above the eye, a little outside of the middle of the socket, and near its front edge. In this, the tear-fluid is formed from the blood. From this, which is called the lachrymal or tear-gland 1 ! from ten to fifteen very minute tubes lead down, and open into the eye through the inner surface of the upper eyelid, just above its inner edge. Through these, the eyes are moistened. 453. The tear-fluid is led off from the eye into the nose, through appropriate tubes. If the prominent point of the lids, seen near the inner corner, be turned out, a black speck SEC. 3.] ORGANS OF SENSE. 159 Fig. 63. Fig. 64. Fig. 64. The left eye with the muscles of itself and lids, exposed by removing the outer "part of the socket, a, The elevator of the eyelid (levator palpebrarum). b, The superior, e, The external, and c, the inferior recti (straight) muscles, a, The inferior oblique. Fig. 04. Represents the eyeball with the entering nerve at the back part. The curved lids are seen in front, and the skin covering the lids is observed to continue round the edges of the lids to line them, and then is reflected back, as it is called, upon the eyeball, over the cornea, and is continuous with the lining of the lower lids. Fig. 65. will be readily noticed. Upon further examination, it is found to be the opening of a minute tube, which curves around, and with its fellow from the other lid, opens, as seen in Fig. 66, into a large tube or canal, called the lachrymal or tear-duct. This opens into the nose. 454. The tears are of use, ordinarily, to moisten the eye, and after- wards the nose. When horseradish, mustard, and such things, " fly up into the nose,*' the flow of tears is increased in such a degree that they cannot be carried off into the nose, but gush over upon the cheek. The intention in this case is, that by flowing into the nose they shall remove the substances producing the trouble. The flow of tears is often increased by the emotions. Their use in these cases is not evident. 455. The tubes leading from the eye to the nose, are sometimes closed ; the tears then constantly flow over upon the cheek, and the person by constantly wiping them away brings on soreness of the eye, which, in a little time, becomes very distressing and serious. A slight operation of inserting a small silver tube will remedy the whole evil. It 160 ORGANS OF SENSATION OR FEELING. [CHAP. Fig. 66. ^-rz A, Fig. 66. A, represents, but not correctly as it respects form, the lachrymal or tear- gland ; B, the ducts or tubes leading from A, into the eye ; C, C, the puncta lachry- malia, or the openings through which the tears flow from the eye into D, the lachrymal or tear-sac, which opens at E, into the nose. may result from a cold, and pass away when the cold is removed. If it do not, let it be early attended to. 456. The lining of the eyelids and the covering of the eye- ball, are very similar in their nature to the lining of the nose ; indeed, may be considered as a part of the same thins; extending through the tubes which connect the eyes and nose. It is therefore seen, how liable the lining of the eye will be to dis- ease, if a person take cold ; both on account of its similar structure with the lining of the nose, and from its intimate connection with it. In ordinary, slight inflammation of the eye, experience has long proved there is nothing so generally good, as washing the eyes frequently with cold water. From the similarity of structure, it might be assumed that similar benefit would ensue from bathing the nostrils with cold water, by snuffing it. This is found to be the case in colds, catarrhs, &c. All those eye-washes, lauded so highly by their cowscienceZess-compounders and venders, should be carefully avoided. If good for any thing, they can- not be worth what will be charged for them, and many a man has lost his eye-sight by the use of them, when he thought if they did no good, they would do no harm. An inflamed, or sore condition of the eye, SEC. 3.] ORGANS OF SENSE. 161 should not be neglected as it is, too frequently, but attended to by some one who is responsible. 457. At the inner corner of the eye, and, as it were, be- tween the ball and the inner corner of the lids, is a substance or part small, but somewhat prominent. It is of a pale red in ill health, and a bright red in health. Upon its surface are the openings of small tubes, leading to an apparatus like the Meibomian glands, forming in considerable quantities a simi- lar substance, which at times is seen collected at the inner corner of the eye. On the surface of this is seen, upon examination, a number of very minute hairs ; which some- times become large, and prove very troublesome irritating the eye, &c. This must be prevented by drawing them out, and repeating the operation as often as necessary. From the inner corner though not from the part just described a fleshy substance sometimes grows, and extends up over the ball of the eye. If this growth be very slow, hardly observable from year to year' and cause no soreness, it may be let alone. But if it grow fast, and extend up to the transparent part of the ball, and threaten to cover " the sight " or any part of it, it should be removed at once ; and if it grow again, as is probable, it should be again removed. 458. The ball of the eye is moved - by the action of six muscles. Five are attached (Fig. 67) by one extremity, to the deepest part of the socket ; four of the five, called recti or straight muscles as their name would indicate come forward in a straight direction and are attached to the white of the eye, just back of its front edge. One muscle is attached above ; one beneath on the outside, and one on the inside. The contraction of these muscles draws the eye either upward, downward, outward, or inward ; and two muscles acting at the same time, direct the eye in the intermediate direction while the suc- cessive contraction of the muscles, will produce a rotary motion of the eye. 459. The fifth muscle, called the superior oblique, passes forward (as seen in Fig. 67) to near the upper edge of the socket, and nearer the nose than the centre of the socket, 162 ORGANS OF SENSATION OR FEELING. [CHAP. II. Fig. 67. Fig. 67. 1, A small portion of the bottom or back part of the socket of the eye. 2, The optic nerve. 3, The eyeball. 4, The levator of the eyelid, with eyelashes at- tached. It is raised up from its natural position to show, 5, The superior oblique passing through the tendinous loop 6. 7, Being a continuation of the tendon 5, and is attached to the eyeball near 3. 8, Is the tendon of the inferior oblique, attached to a piece of bone which forms part of the eye-socket near the roots of the nose. 9, The superior rectus. 10, The internal rectus. 11, 12, The external rectus, with a portioa cut out that other parts may be shown. 13, The inferior rectus. 14, The edge of the eclerotic, where it is joined to the cornea. where the tendon of the muscle passes through a tendinous loop, when it turns back and becomes attached to the upper, outer, and back part of the eyeball. When this muscle contracts, therefore, it rolls the eye inward and down, as when the eye is directed to the tip of the nose. 460. The sixth muscle, called the inferior oblique, is at- tached by one extremity to the front and lower part of the socket near to the nose. It then passes under the eyeball and becomes attached to it at its lower, outer, and back part. When it contracts, it tends to roll the eye upward and out- ward, causing it to look toward the outer end of the eyebrow. 461. It is thought that the contraction of the inferior and superior oblique muscles would tend to draw the eye forward, while the recti muscles by contracting would tend to draw the eye backward, thus sus- pending the eye as it were, and causing it to be moved with the greatest ease. 462. Sometimes one eye or both are drawn inward, sometimes out- ward. At one time it was thought that this was owing to the inner or outer muscle being imperfect too short. Very many operations were therefore performed of cutting the muscle, supposed to be too short. But it was found to remedy the evil in only a few cases. The cause SEC. 3.] ORGANS OF SENSE. 168 of the evil was discovered, upon examination, to be a defect in the power of seeing, with the eye which was turned out of its natural position that it might not interfere with the vision of the other. Sometimes this defect is removed by the operations of nature, when in some cases the eye re- turns to its natural action, but in some cases does not. In these cases, and in those where the muscles are naturally too short, it will be proper to operate by cutting the muscle, the cut ends of which will be in a short time connected by an additional quantity of substance, which will make an addition to the length of the muscle. But if the eye be defect- ive, the muscle, true to its duty, will again direct the sight of the eye inward. If a child be cross-eyed, the eyes should be examined, and if the vision be defective, let the mother remember that a good disposition and a cultivated mind will make her daughter more happy and more loved, and the means of more happiness to others, than if, without these, she were gifted with the fabled beauty of the Houries. 463. The eye. The outer part of the eyeball, from its color, is called the " white of the eye," and from its firmness is called the sclerotic (hard) coat. It has two openings, a large one in front, to admit light, and a much smaller one, a little to the inside of the back centre, to admit a bundle of nerves, called collectively the optic (to see with) nerve. From the form and structure of the sclerotic it yields but slightly, except to great pressure. It is about the thickness of common pasteboard, thicker, however, at the back than the front part. The use of this spherical box, is to allow the attachment of muscles, the action of which properly direct the " sight of the eye ;" to allow the nerves to enter from the brain, and the light which is to act upon them, to enter from the world ; and to preserve from harm the delicately adjusted apparatus, which causes the light from any point of an object to act on the point of a single nerve. Sometimes the sclerotic is misshapen, for it is seen by Lith. Fig. 2, PI. 5, that a certain size of box is necessary, that the focus of the light passing through the lens may be on the end of a nerve, found in the back part of the box. Sometimes the sclerotic is too deep, sometimes not deep enough. The remedy for this is wearing glasses, as hereafter shown. Sometimes the back part of the sclerotic is not perfectly well shaped, being irregular, in which case vision will be confused for this there is no remedy. 164 ORGANS OF SENSATION OR FEELING. [cHAP. II. The sclerotic is rarely subject to disease, but is frequently the cause of much pain when the parts within it are diseased. It is painful when pressed upon, for this is a danger to which it is exposed, and which it is to resist. It does in one way resist by the pain it produces, thereby calling the assistance of the mind to its relief. This may be tried by making pressure with the ringer upon the eye. When the eye from disease is unnaturally full, as it would usually be in case of inflammation of any portion of the interior apparatus, the pressure made upon the scle- rotic Will cause a deep ache, becoming more severe as the cause acts more powerfully. To avoid using the eye, and to make application of cold, will be advisable. But the attention of the experienced physician had better not be neglected too long. 464. Lining the sclerotic, but scarcely adhering to it, and not reaching as far forward as it does, will be found a more delicate coat, or layer, called the choroid, the explanation of which conveys but little if any idea of the thing named. It is not half as thick as the outer coat of the eye. The sur- face next the sclerotic is a rich chocolate brown, while the inner surface is a deep black, that is, absorbs all the light falling upon it. The use of the choroid is to form a support to the bloodvessels, some of which extend forward to nourish, and supply the wants, of the front parts of the eye ; and to form the coloring matter, of especial use upon its inner surface. Being the seat of many bloodvessels, it is es- pecially liable to diseases of an inflammatory character, the treatment of which depends upon so many circumstances, that the most skilful physi- cian will sometimes be in doubt. Ignorance only, will feel assurance, and promise uniform success. 465. The coloring matter upon the inner surface is so conspicuous, it is many times considered as constituting a dis- tinct coat, called the pigmentum nigrum (black paint). It is very much thicker as it is examined at the middle and front part of the choroid and its appendages, than at the back part. The use of this part is supposed to be to absorb the light, which might be reflected from one part of the eye to another, and produce indis- SEC. 3.] ORGANS OF SENSE. 165 tinct vision, as is evident would be the case if the light coming from one point of an object, were allowed to be reflected about till it should fall upon the domain of another object. 466. Within the last mentioned coats is found the nervous coat called the retina (net-w&rk, from the supposed arrange- ment of the nerves when the name was given, a wrong idea, however). This is merely the divisions and terminations of the optic nerve, or rather it is the commencing points of the optic nerve, which as it leaves the eye, is doubtless com- posed of all the filaments commencing at the millions of nervous points presented in the eye, to the action of the light. A few of these are represented ir\ Fig. 53. The retina is composed of a slight amount of other substance, serving to connect the nervous substance. The use of the commencements of the nerves is to receive the action of light, the different kinds of which, by producing different effects, cause different sensations. The use of such a form as exists in case of the retina will be seen if the experiment of the sunglass with several candles be tried. The candles may be in a line, but the foci on the other side of the lens will not be found in a line, but it will be necessary to curve the objects upon which the foci are caught. It is also seen in Lith. PI. 5, Fig. 2, that the foci produced by light passing through a lens, are not in a straight line, but in a curve. The peculiar form of the eye in respect to all its parts, is, of course, explained in the same manner. Thus, there must be the most beautiful and perfect adaptation of the various parts of the eye, both in their absolute and proportional size 467. Within the retina, and filling nearly two-thirds of the cavity of the eyeball, is found what is called the vitreous (glass-like, not from its being as solid, but from its being transparent as glass) humor. It is composed of a membrane called hyaloid, (glass-like, from being very pellucid) which covers it entirely, and is arranged through it in the form of cells, which are filled with a very limpid fluid. The mem- brane does not adhere to the retina at all, but is connected with the choroid at its front part, by processes adapted to the 166 ORGANS OF SENSATION OR FEELING. [CHAP. II. purpose. At its front part, it is hollowed out, or concave, to receive the back part of the lens, as represented in Fig. 61. Between the hyaloid and retina, but belonging to the retina, is found a network of bloodvessels, formed by the divisions of a bloodvessel, which enters the eye through the centre of the nerve. One branch of it extends through the centre of the vitreous humor. The network upon the retina is represented by Fig. 68, and may be seen by closing one eye and directing the other immovably upon some object like a white wall, and moving a candle up and down near to the eye, upon dther side. Fig. 68. Fig. 68. The artery and its coarser branches found at the back part of the eya upon the retina. The use of the hyaloid, and the fluid it contains, is to fill the back part of the eye with a substance which shall act in such a manner upon the light leaving the lens, that it shall produce a proper effect upon the nerve. But as light is acted upon differently by objects differing in their density, the proper action of the vitreous humor will depend upon its being of a proper density. If it be too dense, it will bend the light too much, and its focus will not be on the nerve, but near to the lens. If the vitreous humor be not sufficiently dense, the light will not be bent enough, and the focus will not be at the nerve, but the light will fall upon the nerve before it has arrived at its focus. In either case, vision will be indistinct. The density of the vitreous humor depends upon the hyaloid membrane forming the cells, and the fluid filling them. Either of these parts may vary in respect to their density. The evil of either kind is to be corrected by wearing proper glasses. But either the mem- brane or the fluid may lose its transparency in whole or in part, in which SEC. 3.] ORGANS OF SENSE. case, as the light cannot pass through perfectly, more or less indistinct- ness of vision will be the result. Sometimes this state is lasting, while in other cases, a proper attention to health and the means for improving it, will be effectual. Most usually all attempts to improve vision, in such cases, will fail. 468. What has been said of the lens need not be re- peated. It is situated in front of the vitreous humor, a pait of it sinking into the concavity of the humor. It does not, however, adhere to the hyaloid membrane, but is kept in its place by appendages connecting it with the choroid, similar to the appendages which connect the hyaloid with it. They are called ciliary (like the eyelashes) processes. They do not, however, resemble them, but more resemble a plaited, narrow ribbon. The lens is composed of a capsule, or covering, and the substance contained within, differing in density as the centre is approached. The use of the lens has been already set forth. But its use has been somewhat exaggerated, as it has been made to represent the entire ap- paratus, which causes the light to be properly bent. It does not per- form all this duty ; indeed, it does not perform the most important part of it. It bends the light somewhat, but its greatest probable use is owing to the different densities of its parts, as it thus corrects the sphe- rical aberration. Its form, also, assists in the same matter. As the utility of the lens is, however, to bend the light, to a greater or less degree, a greater or less density of the lens must affect its mode of action. If more dense than it should be, it will bend the light more than it should ; if less dense than it should be, it will not bend the light enough. In either case, as seen in the case of the vitreous humor, the focus will not be at the nervea The evil must be remedied by the use of glasses. If the different densities of the parts of the lens from the circumference to the centre are not what they should be, vision must be indistinct. If the central part be not so dense as it should be in propor- tion to the outskirts of the lens, the light passing through the centre will not be brought to a crossing point so soon as the light passing through the outskirts, and vice versa, as seen in Fig. 62. The capsule of the lens is liable to diseases of various kinds, by some of which it becomes thickened, or loses its transparency. The same is 168 ORGANS OF SENSATION OR FEELING. [CHAP. II. true of the substance of the lens. A thick, milky appearance of the lens, produces what is called a cataract. In these cases, the light not passing through the lens, vision is impossible or very imperfect. Some- times the physician is able to remove the diseases of these parts ; but to restore sight, it is usually necessary to remove the lens. This is called an operation for the cataract. It is not very painful, and almost always has a favorable termination. Glasses must be worn, as it is necessary for a lens outside the eye to do that for which the removed lens was in- tended. 469. We will now pass to the cornea. This is fitted into the sclerotic coat much as a crystal of a watch is fitted in its case, as seen in Fig. 61. It forms the front part of the eyeball. It is more prominent than the sphere would be, to which the sclerotic belongs, as is easily felt. It is perfectly transparent, as is the delicate skin or membrane covering it, and which is a continuation of the skin lining the lids and covering the front part of the sclerotic, as seen in Fig. 64. If put in alcohol, the outer part of the cornea becomes milky in color, while the inner part remains clear as before. This shows that the cornea, though it be thin, is composed of seve- ral layers, differing in their nature. It may be, that in this way the eye obtains its " achromatic " properties. The use of the cornea is almost evident. It serves as a window to admit light. But as light must, from the convex surface of the cor- nea, enter it for the most part in a slanting or oblique direction, it will bend the light, and very much likewise, because the difference in the den- sity of the cornea and the air from which the light comes is great. It is here indeed that the bending, or refraction, as it is called, of the light, is greater than any where else in the eye. But the density of the cor- nea may vary, when the effect it will have upon the light will be corres- pondent, and cause its focus to fall somewhere besides on the nerve. The bending of the light will depend also upon its form. The more round or convex it is, the more will it bend or refract the light. The cornea, or the membrane covering it, may be affected with vari- ous diseases, in the course of which their transparency may be in. part or wholly lost. It can sometimes be regained by proper treatment ; some- times it cannot. The covering of the cornea is so delicate, it is very SEC. 3.] ORGANS OF SENSE. 169 hazardous to operate on it with carelessly made eye-washes made only to sell, and generally by irresponsible persons. 470. Between the cornea and lens is a space filled with fluid of a very limpid character, called the aqueous (water- like) humor. It is less dense than the cornea, and of course an effect will be produced on the light entering the humor, but the difference is very slight, and the effect also. The difference between it and the lens is greater, and of course the light is acted upon accordingly. The particular use of this fluid is not evident, except it be to fill the space with a fluid in which the iris could act with perfect ease, and which by its nature was perfectly adapted to receive the light from the cornea, and pass it in a proper manner to the lens. It is liable to become more or less dense than natural, when its defects must be supplied with glasses. It also sometimes loses its opacity, which it can regain, as a general thing. Its loss, as when the eye is cut, is very quickly restored. 471. The iris corresponds to the partition a in Lith. Fig. 1, 2, PL 5. It is the colored part of the eye. The opening is called the pupil ; circular muscular fibres about the pupil, by contraction lessen the size of the pupil, (Fig. 69). Ra- diating fibres, by contracting, enlarge the pupil, (Fig. 70). The iris divides the front part of the eye into two chambers, which communicate with each other through the pupil. Fig. 69. Fig. 70. pig. 69. A front view of the iris, showing the circular fibres about the pupiL Pig. 70. A back view of the iris, showing the radiated fibres. Th us of the iris is to admit a greater or kss number of rays of 8 170 ORGANS OF SENSATION OR FEELING. [CHAP. II. light, and to prevent light from passing through the lens too near its edge. Sometimes at birth, there is no opening through the iris. In this case it is but a slight operation to make one. Sometimes the power of enlarging or diminishing the pupil is lost. This evil can usually be remedied by the physician. Sometimes the iris is injured or affected by disease, or naturally is in such a state that an artificial pupil must be worn upon the eye. There are various diseases of the iris not worth while to mention, as they occur but seldom, and can always be best managed by the skilful practitioner. 472. Thus it is seen that all parts of the eye, from the cornea to the retina, and also the sclerotic, by its form and size, have an influence in producing the grand result, so frequently stated as necessary to be accom- plished by the eye, viz., to cause all the light coming from any one part of an object to fall upon a single nerve and produce an impression, un- influenced by light coming from any other point ; for the instant the light from any two objects falls on the same nerve, that instant they become one object, for all power of distinguishing them is lost. For if (Lith. Fig. 6, PL 5) the light from r, b, act on two nerves, the light from r being red, and the light from b being blue, will each produce its peculiar sensation. But if the nerves be considered as one, the effect on it will cause the sensation of purple, and the light will not then appear to come from two objects, one yellow the other blue, but from one object entirely purple. 473. Suppose, however, the objects r, b, be brought so near each other as to act on the end of the same nerve, when small, as first sup- posed, or as represented in Lith. PI. 5, Fig. 5, that instant they will ap- pear but one, and cause the sensation of purple. This is what occurs when paints are mixed suppose red and blue. The light falls upon them and is reflected, and the particles of red and blue are at a dis- tance from each other when the mixing is commenced ; the light from the different particles is reflected into the eye, and acts on the end of different nerves ; but as the particles are brought, by the process of mix- ing, nearer and nearer to each other, the light from two different parti- cles falls on the same nerve, and the two paints produce the sensation of purple. If now, the nerves of a person should be comparatively large, the Tight from the particles of blue and red paint would act on the same nerve before they were as near each other or were as thoroughly mixed, as in case of a person whose nerves were finer. Without doubt, SEC. 3.] ORGANS OF SENSE. 171 the nerves of some persons are coarser than those of other persons, and this is one way in which we may account for the difference of colors which different people experience when looking at the same thing. 474. Again, suppose the light from any part, on account of some wrong state or form of the sclerotic, vitreous humor, lens, aqueous hu- mor, or cornea, which as before set forth may exist, arrives at the retina just before it crosses, as in Lith. PI. 5, Fig. 3, then the light from y, which we will consider yellow, will act on some of the same nerves as the light from b, which may be considered as blue, and the light from r, which may be considered as red, will act on a part of the same nerves as the light from y. In this case, there must be two causes of confusion : 1st. The light from y, which should act on a single nerve, and would thus produce an intense effect, acts over several nerves, and produces but a slight effect upon any one. 2d. The light from different objects acting on the same nerves, distinct sensations cannot be caused. 475. Again, suppose from some wrong state of some part or parts of the eye, the light is bent so as to cross before it reaches the retina, as in Lith. Fig. 4, Pi. 5. It is seen that the same results are produced, the same indistinctness of vision as described in the preceding paragraph, but the causes are quite different. 476. Where the light reaches the retina before it crosses, the eye is called long-sighted. In this case it is necessary to do something which will cause the light to bend to a greater degree, and reach its focus at the same in- stant it reaches its nerve. A convex lens is required for reasons hereto- fore seen. If this be placed before the eye, the light will be bent before it enters the eye, and the contents of the eye will do the rest, as seen in (Fig. 71). The convexity of the lens required, must depend upon how much the eye fails to fulfil its duty, for the less the eye bends the light, the more must the lens be called upon to do. 477. Where the light crosses before it reaches the retina, the eye is called short-sighted. In this case a lens called concave will be required, and which oper ates to bend the light from the axis of the lens, instead of towards it, as in the case of the convex lens. Thus the light being bent out, if the expression may be used, as in (Fig. 72), the eye will bend it back again, and in such manner that it will cross at the instant it reaches the nerve. The degree of concavity of the lena must depend, of course, upon th 172 ORGANS OF SENSATION OR FEELING. [CHAP. II. Fig. 71. Fig. 71. A, represents a lens causing the light to bend before it enters the eye, whien Is able to bend the light in the direction of the dotted lines, so as to produce foci at the back part of the eye instead of at B, as represented by the continuous lines in which the light would pass if there were no lens in front of the eye. The situation of the dotted lines is not correct, except in the fact that the foci are at the retina. The light is here represented as converging when it falls upon the lens ; thi-3 is sel- dom the case. It usually is diverging when it comes from any object to the eye, as in Fig. 72. When an object is very far distant, the light is generally considered as coming in parallel rays, as represented by Fin. 57, but it is seldom if ever the case that it is so. If it should be so, why should the light from different points of an object falling upon the entire surface of the lens, be brought to different foci ? That different foci may be formed by the light coming from different points of an object, it is necessary that the rays of light from the different points should fall upon the lens with different degrees of obliquity, when, though they may fall upon the same point of the lens, a different di- rection corresponding to the obliquity will be given to them, and they will produce foci at different points. degree of short-sightedness of the eye. The kind of glasses adapted to the eye is ascertained by trial. 478. Another matter may now come before the mind. If an ex- periment be tried with the sun-glass and candle, it will be found that the distance of the focus from the lens will vary with the distance of the candle, to wit, when the candle is carried to a distance from the lens, the focus is nearer the lens than when the light is placed near the lens. The reasons for this it is not necessary to discuss ; the experiment proves the fact, as represented by (Fig. 73). If therefore, a nerve were at the focus of a distant object, it could not also be at the focus of a near object at the same time. But objects which are distant, and those which are near, produce distinct sensations in the eye if it be perfect in every respect. Yet the apparatus of the eye which bends the light, acts in the same manner as . the lens used with the candle, as is seen in the case of long-sighted and near-sighted persons. For near-sighted persons bring an object which they wish to see, quite close to the eye, because when it is at a distance, the light coming from it crosses or forms its focus before it arrives at the norve ; but the nearer the object is brought to the eye, the farther from the lens is the focus formed, until it is formed at the nerve, when near-sighted persons can see. In case of long-sight- ed persons, th fena would be formed too far from the lens ; and they SEC. 3.] ORGANS OF SENSE. Fig. 72. 173 pjcr. 72. B, C, concavo-concave lens. Light in passing through it is observed to b bent from the axis A, E, as in case of A, D, A, F. therefore remove an object from the eye, till at such a distance that its light will form a focus at the nerve. Fig. 73. Fig. 73. A, A, a lens by which the light passing from o, is bent to a, while if th object producing light be moved to d, the light coming from a more distant point is bent to a nearer point on the opposite side, as shown by the dotted lines. 479. It cannot be, therefore, that the eye remains the same when looking at a near object, in case of one who sees equally well objects at a distance. How the eye is altered is not however known. There are many hypotheses. If 'an experiment be tried with the lens and candle, such that the object upon which the focus falls remains perma- nent, as does the retina in the eye, and while the candle is removed from the lens, the lens be also removed towards the retina, if I may call it so. 174 ORGANS OF SENSATION OR FEELING. [CHAP. II* the focus will be seen to remain always at the retina. When the candle is brought again towards the lens, the lens must be removed from the object. This, of course, is the same thing as if the lens should be perma- nent, and the retina should be caused to change place with the motions of the candle. On account of the results of this experiment, some have thought the apparatus which bends the light, is moved forward or back- ward, as we look at near or distant objects. Some have thought that the eye was made deeper by the pressure of the muscles when we look at near objects, by which means the bending or refracting apparatus of the eye would be made more distant from the retina. There are many ob- jections "to this. The sclerotic is very unyielding, and causes unpleasant feeling when pressed gently. Some think the lens of the eye is drawn forward when we look at near objects, and moved back when we look at distant objects. But there does not seem to be any means for accom- plishing this duty, for it must be moved very much to accomplish the desired end. Others, again, have suggested that the adaptation of the eye was produced by the increased and diminished density of certain parts of the eye. Others have thought a change in the position of the lens in its place would give the desired result. Others, again, have said that the object was gained by the change in the size of the pupil, which will be noticed to diminish when near objects are observed. None of these three opinions can be correct, as is quite evident without remark. Some again have thought, that light coming from an object produced a variety of foci, to wit, that passing through the outskirts of the lens one focus, that passing through the central portions of the lens other foci. This is not so, as heretofore proved ; but if it were, the conclusion would not be correct, which is this, that the light from a near object passing through the outskirts of the lens produces a focus at the nerve, at the same time uld be of the same size as those waves which had gone in another direction, and found nothing to obstruct them when they were four feet from where they were produced. Thus it is with waves of the air ; if a person fire a pistol, the waves it produces striking against a steep hill, bank, ledge, house, or the like, will be sent back ; by the time they reach the person's ear, however, they will be very small, and pro- duce but a slight effect or impression. As this is feeble, the cause of it, viz., the pistol, will appear to be a long distance off. This is what is called an echo. It seems to a person as if a pistol were fired a Icng djs- SEC. 3.] ORGANS OF SENSE. 185 tance off, and in a certain direction, viz., in that direction from which the waves come to the ear. 509. We judge any sound-producing object is in the direc- tion from which the waves of air it produced came to our ears. 510. The states of the air affecting the character of its waves, depend upon its temperature, its degree of moisture, and its density. Upon these it will not be"worth while here to speak, farther than to say, these different states of the atmosphere modify considerably the ef- fects which vibrating objects produce upon it, and of course modify the effects it produces upon the ear. Before passing to consider this organ, I cannot forbear expressing the astonishment that almost confounds me, when I think of the innumerable variety of waves which may be pro- duced in the air the simple air. It sometimes seems as if it could not be so. 511. The ear is a complicate piece of apparatus or me- chanism, for the purpose of causing the air-waves to act in a proper manner upon the commencing points of the nerves of hearing. 512. The external ear is so well known as not to need description or remark, except that it is uncertain whether it is of much assistance in hearing or not. Some persons, who have lost it by accident or disease, have not felt its loss. By o.thers, it is thought of much importance. 513. From the external ear, a tube leads into the head, from half an inch to an inch and a quarter, when it is closed by what is called the membrane of the tympanum (drum), or sometimes, the outer drum-head. 514. This tube is protected by hairs found at i*<3 commencement, and by what is called ear-wax. This is found in follicles or cryptse, viz., little pouches with openings upon the surface of the tube. They are similar to those forming the oil upon the skin, and the mucus of the mucous membranes. It is sometimes formed very rapidly, collects in the ear- tube, hardens, and causes a greater or less degree of deafness. When deafness is produced by this cause, it can be removed by dropping into the ear a few drops of sweet oil, and retaining it a short time with a bit tf cotton, chewed paper, or the like, when the oil and any collections 186 ORGANS OF SENSATION OR FEELING. [CHAP. II. in the ear are to be removed by a thorough syringing with castile soap and warm water. It is said that many cases of deafness are thus cured, and many others very much relieved. It is here seen how much people are imposed upon, who are induced to buy at great expense a small bot- tle of ear-oil, which cannot be better than sweet oil and probably is not as good, while the chief good is all the while to be derived from the syringing with soap and water, viz., from cleanliness. 515. The membrane which closes the end of this tube, passes downward and inward slightly, as seen in Fig. 76. Its utility depends upon its flexibility. It is necessary it should be acted on by the slightest wave of air which comes down the tube. 516. Passing through the membrane of the tympanum (drum), we arrive in the tympanum (B, Fig. 76.) This is about the form and size of a kidney bean ; it is filled with air. Opposite the outer drum-head are what are called the inner drum-heads, viz., two openings (2, 3) closed with mem. branes ; one is of an oval form, and called the foramen ovale (oval hole) ; the other is called the foramen rotunda (round hole). They will again be noticed. At the back part open, ings are found, leading into what are called the mastoid cells, viz., cells in the mastoid bone, which is found and may be felt just back of the ear. The use oFthe cells is not known. They are supposed in some way to facilitate the power of hearing. At the lower part, the drum of the ear terminates in a small tube, called the Eustachian tube, which leads down /nto the back and lower part of the nose, or into the upper and back part of the throat. Through this the air has a free passage to and from the ear, and any substance can pass this way from the ear-drum. 517. The lining of the nose extends up through the Eustachian tube, and lines the drum of the ear, and of course the drum-heads, and also lines the mastoid cells. 518. Any disease, therefore, affecting the throat or lining of the nasal cavity, would easily extend to the Eustachian tube, and through SEC. 3.] ORGANS OF SENSE. Fig. 76. 187 Fig. 76. Is an ideal representation of some of the principal parts of the ear. The dark dotted part corresponds to the bone. A, represents the tube leading inward from the external ear. The skin which covers the ear is seen lining the passage, the mem- brane at the bottom of the ear-tube, and also the pouches, sacs, or cryptae, on either side. The sacs are not, however, in the bone as here shown, on account of being so much magnified. The sacs are thousands in number, and form the ear-wax. B, rep- resents, but not in form or size, the drum of the ear. At the lower part a tube, repre- senting the Eustachian, is seen leading into the nose, and lined with a continuation of the lining of the nose, a, 6, c, d, The four bones connected upon one side with the ex- ternal membrane, and on the other side to the membrane (2) leading into the labyrinth. y, is a muscle, the use of which is not well determined. C, may be taken to repre- sent the labyrinth rilled with fluid and containing the sac D, which is also filled with fluid. The nerve of hearing is seen coming through the wall of bone surrounding the laby- rinth, and dividing and subdividing with its points towards the inner surlace of the uac, as seen at the extremities of the lines with which i is connected. 188 ORGANS OF SENSATION OR FEELING. [CHAP. II. that to the lining of the ear-drum and produce derangement of the hear- ing apparatus, and hardness of hearing. Hence why colds, catarrhs, scarlet fever, attended with soar throat, and the like, are so apt to pro- duce transient or permanent deafness. 519. In the first place, the tube is so small that any little thickening of its lining will close it. This may take place and the sides of the tube not adhere, or they may grow together. To know if the tube be closed, compress the nostrils and shut the mouth, then blow with force. If the tube be open, the air will be forced into the drum B, and distend the membranes outward. This will produce a sensation of feeling, and usually a crackling, or a rumbling sound. If *he tube be closed, nothing of the kind will take place. To know if the tube be permanently closed, it will be seen by Fig. 77, that a probe may be passed along the floor of the nasal cavity to its back part, when the probe, if turned inward and downward at the outer extremity, will be turned upward and outward at its inner extremity, and enter the tube. This by the skilful physician can be readily done. If the probe can be passed into the ear-drum without causing pain, time after time it can be done, and with the use of larger probes, till at last the opening will remain when the probe is removed, and the air is again allowed a passage into the ear, and the collections of the ear a passage out. In such a case, very great care must be taken to avoid colds, as the slightest causes will tend to close the tube again. Fig. 77. Fig. 77. Represents a section of the nose upon one side of the division or vomer, the turbinated (coiled) bones are seen with a portion removed. The line A, TO, extends to the' opning of the Eustachiau tube, m. SEC. 3.] ORGANS OF SENSE. 189 520. If the tube be permanently closed, it has been sometimes pro- posed to make an opening through the external membra "ic. By this means, air of course would be admitted to the drum of the e&r, but there would be no chance for the collections of the ear to pass off, and the result of such experiments has proved unsatisfactory. 521. The membrane lining the ear-drum, and also the mastoid cells, is subject to a variety of diseases. Its lubricating fluids are not formed in sufficient quantity at times, and the membrane becomes dry, and where* it covers the drum-heads, it would, of course, diminish their flexibility. Again, at times the fluids of the ear-drum are formed, in superfluous quantities, and injury ensues. " The lining of the drum is thickened and the consequences are bad, etc. If hardness of hearing depend upon want of flexibility of the membranes, it can be determined, many times, by the history of the case, and by the kinds of sounds heard most distinctly. If a child's voice be heard readily, while the low voice of manhood is heard with difficulty, the hardness of hearing may be attributed, in many cases, to inflexibility of the membranes. The physician can, in many cases, by proper injections and attention to the general health, restore health to the lining of the ear-drum. It is some- times very beneficial where the membranes are inflexible to close the nose and mouth, and then -alternately blow the air into the ear-drum, and allow it to return. This will throw the membranes into motion, and by frequent repetition tend to give them suppleness. If, however, the slightest pain is thus produced, the course should not be pursued. 522. An arm of a small bone called the malleus (hammer), a, is attached to the membrane, just below its centre, as seen in Fig. 76. The head of the hammer is attached to another bone called the incus (anvil). This has by some been thought to resemble a tooth with two fangs, one larger than the other, and considerably separated from it. To the longer branch or arm of this bone, a very small bone, called the orbicularis (round bone), c is attached. By some it is considered as a part of the anvil-shaped bone, as it is inseparably attached to it after the period of childhood. It is only about as large as the flattened head of a pin. The fourth bone from its form, called the stapes (stirrup), d, is attached to the round bone by one part, and exactly covers the oval hole (2, Fig. 76). 523. The bones are jointed together in such a manner as to move upon each other. When, therefore, the slightest movement is produced in the first membrane, it will be communicated to the chain of bonea 190 ORGANS OF SENSATION OR FEELING. [CHAP. II. Fig. 78. IIIIIIB '..'" !! iI|Sliilllllf!iIili JF Fig. 78 The bone of the ear, 1, malleus (hammer), 2. The upper one is called incus (anvil), the lower one orbicularis (round). 3, Stapes (ptirrup). Fig. 79. Fig 79. Represents a section of the bone containing the drum of the ear in which the bones are seen. stretching across to membrane 2. Each movement of the first membrane will, therefore, act upon membrane 2. 524. It is, however, certain that persona have lived and enjoyed their hearing well where the bones were wanting. They are not, there- fore, absolutely essential. By some it is thought that hearing is usually SEC. 3.] ORGANS OF SENSE. 191 produced by the communication that takes place through the air, between membranes 1 and 3. Others think that communications will always be made through the air between 1 and both 2 and 3, and that the bones are merely of use to produce a proper state in the membranes, in respect to tensity, etc. Others again think that communications are made from 1 to 2 by the bones, and from 1 to 3 at the same time by the air. Others think that, ordinarily, communication is established by the bones, but when the bones are wanting the air is the medium. It is, therefore, by no means certain how beneficial or necessary the bones are. There is no doubt in my mind that they are of use, and that want of proper motion at the joints where they are united} renders hearing indistinct ; and to preserve facility of motion between the bones, the same things may be recommended as in case of inflexibility of the membranes. 525. A muscle, worthy of note, extends from the vicinity of the Eustachian tube to the hammer. By contraction, it can make the membrane 1 more or less- tense. Some suppose that the membrane must be tuned, so to speak, to the various waves acting upon it for instance, that the waves producing an acute sound, are met by a tense state of the membrane ; while a wave producing a low or gruff sound, is met by a lax or slackened state of the membrane. It is uncertain. 526. The membranes covering the oval and round holes, called also fenestra (windows), separate the ear-drum from the labyrinth. This is worked out of the very solid bone, and consists of three parts, called the vestibule (porch), semi- circular (half-circle) canals, and the cochlea (snail-shell) (Fig. 80, and Fig. 81). The particular use of these parts is not known. The general princi- ple by which hearing is produced, can be better obtained from Fig. 76, where a circular box represents the entire labyrinth. 527. The labyrinth is lined throughout with a skin or membrane, adhering closely to the bone by one side ; but very smooth and delicate upon the other, like the free surfa'ce of a serous membrane. Upon this surface is poured out a limpid fluid, called the aqueous (watery) humor of the ear. It fills the labyrinth. 192 ORGANS OF SENSATION OR FEELING. [dlAP. II. Fig. 80. ^e&=^ X. Fig. 80. The labyrinth; V, ventricle ; O, foramen ovale; R, foramen rotundum; A, A, ampullae ; z, z, semicircular canals ; K, cochlea. 528. la the midst of this fluid, in the vestibule and semi- circular canals, is formed a membranous bag or pouch, taking the form of the parts in which it is found ; but not touching the sides of the labyrinth, except at certain parts, as at ?/, Fig. 76, where the lining of the labyrinth is reflected, as it is said, to form the external layer of the bag. The bag is filled by a fluid similar to that outside of it, and formed by its inner coat or lining. The sac, however, is exceedingly delicate, and has been compared to the retina of the eye for delicacy, but is more firm. 529. Jn this sac sometimes, and in the fluid outside of it, a powder, like powdered bone, is found. Sometimes it is so coarse as to resemble sand, or collected so as to form tiny stones. Its, or their use, is not known. 530. The nerve of hearing passes to the bag and also to the lining of the labyrinth in the cochlea, where it divides and subdivides, terminating, as some say, at the very surface or perhaps, as others say projecting a little into the fluid, SEC. 3.J ORGANS OF SENSfi. Fig. 81. 193 Fig. 81. Section of the labyrinth, drum of the ear, and external tube a closed by a membrane, to the inner surface of which the hammer c is attached ; cf, the anvil ; c, the round bone connecting the anvil with the stirrup ; g-, the semicircular canals ; h, the cochlea ; f, the passage of the nerve. and as it seems very near the surface, in delicate papillae, represented by x, in Fig. 76. 531. The movements of either or both membranes, will produce waves in the fluid of the labyrinth and its inclosed bag ; which dashing upon the surfaces containing the points of the nerves, will cause impressions as various as the pro- ducing causes. 532. The minute circumstances to be regarded in producing perfect hearing, are not understood. It is however evident enough that a proper supply of prpper fluid is necessary. It is probable that this, like most if not all other fluids in the body, is undergoing constant change by fre- quent removal and as frequent formation by the lining of the labyrinth, and the covering and lining of the bag. If it be either removed or 9 194 ORGANS OF SENSATION OR FEELING. [CHAP. IT. formed too rapidly, defective hearing must be one of the consequences. It may likewise become too thick, or by some disease of the inclosing bones or membranes, it may be allowed to flow out, when hearing would of course be lost. The membranes also, in which the nerves are distrib- uted, may become thick and affect hearing. 533. To know whether the contents of the labyrinth be affected, a watch may be placed in several positions on the affected side of the head. If the ticking be heard distinctly, assurance is bad, that the laby- rinth and its contents are not affected, for the bones of the head conduct the vibrations of the watch to the labyrinth. But if all be silent, hope is lost. Hearing, as dependent on the condition of the nerve, will be spoken of hereafter. 534. With such a multitude of causes to affect hearing, it is no won- der that we find many people deficient in this respect, or that deafness often baffles the skill of the most skilful, or that the ears which hear well should yet have such imperfection, that there should be a slight difference in the sounds produced through the different ears of the same person. The wonder is, that the ears should be so generally perfect. The most hasty glance at this subject will convince any one, that as there are so many causes of deafness, those who warrant or advertise their oils as sure cures for deafness, are uripardonably ignorant or most arrant scoun- drels, or probably something amphibious in this respect. 535. I cannot better conclude this sketch of the ear, than by quoting from Le Cat's most excellent treatise on the senses. " Life, deprived of sensations as valuable as those of hearing, would be a kind of prema- ture death. The deaf man is necessarily a dumb man, and who can compute hia loss? His never-sleeping guard* that warned him of a thousand dangers is dead. And now, the crash of the falling tree, the scream of the drowning child, the tread of the midnight thief, and the mutterings of the coming storm, fall on his ear as vainly as the tear of sorrow on the brow of death. Who can compute his loss ? The sweet echoes of the valley, the voice of friendship, the hallelujahs of the Sabbath, and the loud artillery of heaven, are alike condensed into barren nothing- ness, and in the very excess of stillness he loses all the pleasures of soil- tude." * Not quite correct, for the sense of hearing is at times " hushed *a death-like sleep." SEC. 4.] THE NERVES OF SENSATION. 195 SECTION 4. The Nerves of Sensation. 536. These are white pulpy cords extending from the organs of sense to the brain. They look very much like the nerves of motion, heretofore described. Some think the nerves of motion terminate in the nerves of sensation forming loops and a circuit with them. But, as often said, the commence- ments of the nerves are so minute, it is impossible with present means, to learn how they commence. The word commence is used, because in ordinary cases, the portion of nerve found in the organ of sense is the part first acted on. 537. It is the duty of the nerves to be acted on by cer- tain causes, and then to act on the brain and cause sensa- tions. When the right kind of objects act on the organs of sense in a healthy condition, an effect is produced at the brain, if the nerves be entire, healthy, and not compressed ; but the instant the nerves extending from any organ of sense to the brain are cut, or compressed, or diseased in certain ways, no effect can be produced by acting on that organ of sense. This shows that nerves are the agents through which effects are produced on the brain, and will also teach what particular nerves are agents in the production of any particular sensation. For instance, there are two nerves extending from the lining of the nose to the brain. If one be cut the animal cannot smell, but feels pain if the lining be pricked, while vice versa, if the other nerve be cut while the first remains entire the animal cannot feel pain if the lining be pricked, but can smell as well as ever. This teaches that one nerve is the nerve of smell, and that the other is the nerve of common feeling. 538. Some causes act only on certain nerves, while other causes act on other nerves. For, as just shown, the nerve of smell produces no effect when it ifl pricked ; so the cause, which through some nerves produces tickling, pro- duces no apparent effect on other nerves. Light can and does act through the outer layer of the skin, but without producing an effect of sensation. 539. Some causes act upon all the nerves, or upon 198 ORGANS OF SENSATION OR FEELING. [CHAP. II. several, producing different effects and causing different sen- sations. Electricity, as it is called, will act upon the nerves passing from the organ of taste, and the sensation caused is the same as if a person were tasting something. If it act on the nerve of smell, a sensation of smell is perceived. If it ac. on the nerve of hearing, a sensation of sound is produced. If it act on the nerve of sight, the sensation of light is pro- duced. If it act upon other nerves, other sensations will be produced. If a person falling, strike the head violently, the jar acts on several, per- haps all the nerves, so as to produce sensations, differing in case of the different nerves ; thus a person " sees stars," hears a sound, perceives a smell, and through other nerves has sensations of pain, of "jarring," &c., produced. From the previous paragraph as well as this, it follows, that as some of the nerves are acted upon by causes having no effect on other nerves, and as, when the same cause does produce effects through differ- ent nerves the effects are different, 540. The different nerves are differently constituted, and are intended to produce certain kinds of sensations, whatever may be the causes acting upon them. This is an exceedingly interesting and important proposition, and a few more illustrations may be brought forward. If a nerve in the finger be pricked, it produces a sensation of pain ; but if the nerve of smell be cut, it causes a sensation of smell ; if the nerve of taste be pricked, it causes a sensation of taste. If the nerve of sight be cut, as is sometimes necessary in extirpating the eye, a sensation of a great flash of light is caused. If the eye be pressed, two sensations are at once produced through two different nerves. Pressure through the eye on the nerve of sight produces a sensation of light, while pressure on the nerve of com- mon feeling, extending from the eye to the brain, produces an unpleasant or painful sensation.* * Thus it is seen that the nerves are so made, that the sensation of light can only be produced through the nerve of sight, and through its agency only can a person see. It has been seen in a previous section, that a person distinguishes objects only by the color of the light they cause to act on the nerves, and by the direction in which the light comes, for which purposes the eye is necessary. Since the eye and nerve of sight are both necessary that a person may see, how absurd it is for persons to pretend to see through the pit of the stomach, their fingers' ends, the top SEC. 4.] THE NERVES OF SENSATION. 197 541. There is one other respect in which the nerves are peculiar. Some causes act only at the commencement of the nerves, other causes act upon any part brought within the sphere of their influence. If any peculiar temperature act on the commencement of a nerve it produces effects, but only by acting on the commencement. For instance, the temperature acting on the foot produces an effect on the brain, but the nerve extending from the foot to the brain is acted upon by a great va- riety of temperatures at different points, but they produce no effect. How wise this provision is! Had it been otherwise, the variety of sensations produced through any nerve would have entirely confused the mind, and no idea of the state of the foot could have existed. If, however, the same nerve be cut, a sensation will be produced similar in all cases, whether the nerve be cut in the foot or in some other part of its- extent. It is thus with all the nerves ; viz., cut them in any point of their course, and they will produce like results as if cut at any other point. If elec- tricity act on the nerve at any point of its course, it produces the same result as if it acted at any other point of it. To sum up the whole matter, therefore, it is seen that some objects act on one nerve and some on another, while some things act on all the nerves ; that some causes act on the nerves at their commencement only, while other causes can produce effects if they act on any part of the nerves ; and that, 542. The kind and degree of effect produced on the brain of the head, &c., as some impostors assert they do. Says Muller " So long as a magnetic patient manifests merely, the ordinary phenomena of nervous action that are seen in other disorders of the nervous system, it is all credible enough ; but when such a person pretends to see through a bandage placed before the eyes, or by means of the fingers or the epi- gastrium (upon the stomach), or see round a corner and into a neighbor- ing house, or to become prophetic, such arrant imposture no longer de- serves forbearance, and an open and sound exposure of the deception is called for." That such things may be done, it should be remembered, not only must a person be magnetized, but also the laws by which the Cre- ator has ordained that light shall be governed. It is to be hoped as we attribute the ignorance of our ancestors to the times in which they lived, and pardon them for believing in witches, and hanging those who were " plainly proved to be leagued with the Prince of Darkness," that a more enlightened future generation will not reflect too severely on their fore- fathers for their credulity in respect to clairvoyants, quack pills, &c., of the present day. 198 ORGANS OF SENSATION OR FEELING. [CHAP. II. ty any nerve, acted upon at any point by any cause, depends on the NATURE and STATE of the nerve acted on. 543. The nature of the nerve determines the kind of effect produced when action of the nerve is produced. For instance, the nerve of hearing cannot produce a sensation cf light, neither can the nerve of sight cause a sensation of sound, and the other nerves are by their nature able to produce only their peculiar kinds of sensation. Each nerve of any class of nerves can of course produce a variety of sensations, but all of one kind ; that is to say, every nerve ot the class is able to produce any sensation that any other nerve cf the class can, for the instant any nerve produces any sensation or is the agent in producing any sensation, which another nerve cannot produce, it must be classed separately from the other nerve. For instance, all the nerves of sight can produce the sensation of light and all the varieties of that kind of sensation, but cannot produce the sensation of sound ; while all the nerves of hearing can produce the sensation of hearing, but cannot cause the sensation of light ; and though the nerve may have its condition altered so as to produce different varieties of sensations of its own kind, and with different degrees of intensity, if a nerve act at any time it must produce sensations of its own kind. 544. The state of the nerve will determine the degree and variety of effect it will produce on the brain. 545. The state of the nerve is either natural or culti- vated. 546. Natural. The state of one person's nerves is naturally such that a slight cause produces a powerful effect The state of another person's nerves is such that a powerful cause will produce only a slight effect. In other persons slight causes act through some nerves and produce intense sensations, while powerful causes act through other classes of nerves with- out much effect. Persons do not, therefore, perceive similar sensations under the same circumstances. 547. Cultivated or artificial. Disease will alter the state of the nerves to such a degree that sometimes they produce sensations without the action of any other cause. For to produce a sensation it is not necessary that any thing act on the nerve, only a certain state of the nerve. Usually, to be sure, some cause acts on the nerve and produces the state which causes the nerve to produce an effect on the brain ; but if disease pro- SEC. 4.] THE NERVES OF SENSATION. 199 duce the same or a similar state of the nerve, the sensation will be pro- duced. To illustrate ; wood, coal, oil, spirits, slaking lime, or aught else may be used to cause water to boil, it matters not. The water boils when it is in a certain state, viz., when it is hot enough, and whatever brings it into that state will cause it to boil. So a disease, a cut, electri- city, or the more usual cause, may cause a nerve to produce a sensation ; if acting on the nerve any where, they produce a certain state. Some- times disease does not produce such a state that sensations are produoed, but such a state that a slight cause will produce sensations. To illus- trate again ; if the water be very hot, only a little wood will be neces- sary to cause it to boil. Thus a student by much study and neglect of exercise, many times produces such a state of the nerves of sight that the action of only a little light proves very unpleasant. Diseases in some instances produce such a state of the nerves, that very powerful causes produce only slight effects. Diseases are so peculiar in their effects, that the state of the nerve necessary to produce certain varieties of sensation is very easily produced, or with great difficulty. That is, the nerve of sight is very easily acted upon by causes of certain colors, the nerve of hearing by causes of certain sounds, certain kinds of odors easily produce a powerful effect, or vice versa. These nerves are deficient only in respect to certain varieties of sensations of the kinds peculiar to each. Some per- sons are thus affected naturally or by disease, very early in life, and to such a degree that certain colors do not produce any or at least not a usual effect, and they ** see things differently from other folks." Others are affected in such a way they do not hear certain sounds at all, or smell certain odors, etc., etc. 548. Medicines produce like effects with those just des- cribed. Some medicines will produce such a state of the nerves that the slightest cause will excite sensations, or, perhaps sensations will be produced without any other cause, or, on the other hand, produce such a state in the nerves that no effect, or but slight effect, can be produced by the most powerful causes. This is, of course, highly beneficial when it can be done without retarding nature in her efforts to produce a cure. The slamming of doors, and all the like aggravations of disease, of course are comparatively harm- less when the state of the nerves is such that but a slight sensation can be produced. 200 ORGANS OF SENSATION OR FEELING. [CHAP. II. 549. Various kinds of food, and indeed, the whole manner of living, will either exalt or depress the state of the nerves in such manner that the sensations will be easily or with difficulty produced. Thus it is in our power to produce, within limited bounds, such a state of the nerves, that the causes acting upon them shall produce such sensations as are desirable. Let us now give our attention to the kinds of nerves, viz., those which produce similar sensations. 550. a. The first pair of nerves of sensation is called the olfactory. They extend from the brain forward over the nose, where little branches pass down through the sieve- like holes in the bone forming the roof of the nose, and ter- minate, or rather commence in the lining of the nose, as heretofore described, and represented at Fig. 82. Fig. 82. Fig. 82. Represents a section of the nose parallel with its natural division. From 4, a line reaches down to the olfactory nerve, or what is sometimes called the olfac- tory lobe of the brain. From it the nerves are seen passing thiough the cribriform (sieve-like) portion of the ethmoid bone. The other portions do not need mention. Properly speaking, however, that which extends from the brain over the roof of the nose, should be called a part of the brain, or the olfac- tory lobe of the brain. It is in fishes the largest portion of the brain. The branches which come down into the nose should be considered as the nerves of smell. 551. b. The second pair of nerves of sensation, are the nerves of sight, called the optic nerves. When they leave SEC. 4.] THE NERVES OF SENSATION. 201 the eyes, they seem as if composed of millions of fibres col- lected in one bundle, and covered with a sheath, which is con- tinuous on the one part with the dura-mater of the skull, and on the other extremity with the white of the eye. It is supposed that every nervous point in the retina is the commencement of a nervous fibre, which assists to compose the optic nerves. 452. A little back from the eyes, the nerves from each eye meet, and a part of the fibres from each pass across, viz., that half of the fibres towards each other oass acvss between each other, when the nerves go on to the brain, with which they do not immediately unite ; but as if there were a neces- sity for them to produce effecte at a certain part of the brain, they wind around and terminate at the inner, middle and lower parts of the brain (Fig. 83). Fig. 83. Fig. 83. 1, The external or sclerotic coat of the eye with the cornea at the front part. 2, The choroid coat with the ciliary processes at the front part. 6, The com- missure of the optic nerve, showing the crossing of the nervous fibres. The lower portion of the brain the commencement of the spinal cord, and the roots of tha nerves, are easily recognized. Q* 202 ORGANS OF SENSATION OR FEELING. [CHAP. II. 653, c. The third pair of nerves of sensation commence at the ears, and are immediately brought in contact with the nerves called facial, which are nerves of motion ; by the side of these they pass back to the brain. 554. d. The fourth pair of nerves of sensation are called the nerves of taste. But at present it is not determined which nerve is the nerve of taste. Some suppose one, some suppose another ; there being several nerves commencing in the tongue, which extend to the brain, and experiment has not yet decided to which to give the preference. 555. e. The nerves of the muscular sense are very numerous, and are so combined with the nerves of common feeling, that they may be considered as part of them, so far as it regards their structure, arrange- ment, and terminations at the brain. 556. /. The nerves of common feeling. These are very numerous, and in fact embrace several kinds of nerves, which are called by the same general name, either because their duties are not worthy of par- ticular notice, or because they are so blended with other kinds of nerves that it is not possible to distinguish them by experiment or examination. Indeed, in most cases they are so similar to the nerves through which motion is produced, and so blended with them, that it is not possible to distinguish in the greater part of their course, the nerves of feeling from the nerves of motion. Indeed, till within a few years, it was thought that the same nerves fulfilled two agencies at once, viz., that they were the agents for producing motion, and also sensation. 557. The nerves of common feeling including the nerves of the muscular sense commence, so far as can be judged, in every part of the body, each nerve in its particu- lar part. Not excluding those parts in which commence the nerves already mentioned, and called for distinction sake special nerves of sense ; they being nerves for the especial purposes already signified. In some parts of the body, however, the nerves, if they exist, cannot be seen ; and the only proof of their existence is, that they are the causes of sensation which, from what is known, is supposed to be always produced through the Agency of nerves. SEC. 4.] THE NERVES OF SENSATION, 203 558. Immediately after the nerves commence, they begin to unite with each other in such way that they are found by the side of each other, but yet distinct from each other ; and in the same manner, they unite with any nerves of motion in their vicinity till at last large trunks are formed, which may be traced into the back-bone, or through the skull into the head, as the case may be. 559. Within the back-bone, the nerves divide into two parts called the anterior (front), and posterior (back) roots, (Fig. 84). Here, but a few years ago, Sir Charles Bell and Magendie, by experiment, discovered the double nature and duties of the nerves. If the front root of the nerves of a frog's leg be cut, he cannot move the leg, because he has no means of communicating a contraction-causing-influence to the muscles of the leg ; but the frog appears to suffer pain, if the leg be pricked. Fig. 84. Fig. 84. Represents the double roots of a spinal nerve, with a ganglion D on the back or posterior root. 560. If the back root of the nerve be cut, while the front root is entire, the animal can move the leg, but feels no pain when the foot is even burned. These things show that the front roots are the agents through which motions are pro- duced, and the back roots the agents through which the sen- sations are produced. 204 ORGANS OF SENSATION OR FEELING. [CHAP. II. 561. The posterior roots unite with the spinal cord, at a line produced by the gray substance coming to the surface of the cord, as in Fig. 43. The anterior roots unite with the sides of the front parts of the cord in the neck ; but as they unite with the cord lower down, they unite with it more in front. 562. After the nerves of sensation have united with the spinal cord, it is impossible to trace them to the brain ; and the only proof that they extend to the brain, is found in the proof that the brain is the seat of the mind, which distin- guishes every part of the body in which an effect is pro- duced on a sensitive nerve. 563. Some have supposed that they could distinguish two parts in each half of the spinal cord. Sir Charles Bell thought he had proof, that in the neck at least, there are three columns, as he termed them, in each half of the cord, viz., the front column, the back or posterior column, and a middle column, called the respiratory tract. Those of this opinion think the front column is composed of the nerves forming the front roots of the nerves, the agents in producing motion ; and that the back column is composed of nervous filaments from the posterior roots of the nerves, the agents in producing sensation. But there seems to be such an inter- lacing and blending of nervous filaments in the spinal cord, that it is not possible for any anatomist, however skilful, with present means, to separate the different nerves composing the cord. 564. On the posterior root of each of the nerves entering the back-bone, is found a collection of reddish gray substance called a ganglion. The use of this part is not known. By some it has been considered as a nervous centre in which some effects are produced on the nerves passing through it, or in which terminates or commences some effect. There is no substantial proof of any of the hypotheses so liberally ad- SEC. 5.] THE BRAIN AS AN ORGAN OF SENSATION. 205 vanced, and though a mortification to one's pride, truth compels the ac- knowledgment that their use is unknown. They are found on nearly, if not all the nerves of general sensation. 565. Thus it might be expected, as is the case, that injury to the spinal cord at any point would prevent any sensations from being pro- duced by the parts below, and this might be of such a character as to affect either one class of nerves, or the other, or both. The injury might affect one side only of the spinal cord, or both sides, or it might one class of nerves on one side and the other class on the other side. If the in- jury affected only a few fibres of the cord, a corresponding effect would be produced. If the cord were injured in the neck, it would not be ex- pected that the nerves entering the head would be included in the injury. 566. If again, any such cause as disease or injury affected the nerves of sensations in their course through the cord, so as to produce certain states of the nerve, sensations would result necessarily.* SECTION 5. The Brain as an Organ of Sensation. 567. The first duty of the brain as an organ of sensa- tion, is to produce effects which may be perceived by the mind, and which are called sensations. Whether the brain can produce any effects on the mind, which are not felt, is not, and of course cannot be known. We know that persons * From the remarks in this section it might be inferred, that com- pression of a nerve would prevent any thing acting on the nerve below the compressed point from producing any effect. This is certainly cor- rect. The sensations caused when a nerve is compressed, are owing, not to any effect produced on the organs of sense of the nerve, but to the state produced in the nerve by compression. It might also be inferred, that compression of the proper nerves would prevent pain in case of surgical operations. I am not aware that any experiments have been tried which would show whether any benefits could be obtained from such a course, nor has any opportunity occurred for experiment, since the idea suggested itself, except on animals, in which case no pain seemed to be produced by pricking, cutting, or even burning the foot, the nerves of that part being compressed. Compression of the nerve in case of neuralgia, has been suggested and tried, in case of neuralgia and it would seem that in some cases amputation, &c., might be done with less pain, the nerves being compressed. 206 ORGANS OF SENSATION OR FEELING. [CHAP. II. speak to us without our knowing it. The vibrations of the voice of the speaker must reach the ear, and through the ear effects must be produced on the nerve of hearing, and it would seem that through the nerve effects must be produced on the brain, but whether any effect is produced on the mind and not noticed, or whether the effect stops with the nerve or the brain in such cases, is not known. 568. The first duty of the brain is proved by the impor- tant fact, that sensations depend upon the state of the brain. If a person be stunned, the state of the brain is such that sensations cannot be produced. Some diseases, such as apoplexy and many other " fits," some medicines such as opium, intoxicating draughts of alcohol, &c., produce such a stupor of the brain, that sensations cannot be pro- duced. On the other hand, inflammation of the brain, and various medi- cines, in small or large quantities, produce such a state of the brain, that the slightest causes will produce powerful effects. 569. The manner in which this duty is performed is not known. Some suppose that the nerves through which various parts of the body cause sensations to be produced, do themselves act on the mind ; that in other words, those parts of the brain through which sensations are produced, are composed of the nerves through which sensations are caused. Others suppose that these nerves do not act on the mind, but on distinct parts of the brain, which hold communion with the mind, and transmit effects to it which vary as the effects of the nerves vary. Others again suppose, that the nerves terminate at one part of the brain, it may be large, or it may be small, which part is acted on differently by every different state of the nerves producing effects thereon, and that this part transmits effects to the mind. These last suppositions involve unneces- sary considerations, it seems to me ; besides, I cannot conceive how the various parts of the body can produce such distinct sensations as they do, without nerves extend from every point capable of producing sensa- tions to the mind itself. I therefore suppose that, 570. Those parts of the brain concerned in producing sensations caused by any part of the body, are the cerebral (brain) extremities of the nerves of sensation, which produce effects on the mind according to their nature and state. The same remarks which applied to the nerves, in Sec. 4, will apply SEC. 5.] THE BEAIN AS AN ORGAN OF SENSATION. 207 to the brain in the fulfilment of its present duty ; for so much of the brain as is under present consideration, is but the continuation of the same nerves there spoken of. Indeed it will make no difference in relation to the application of those remarks, what philosophy is chosen, though it will perhaps do no harm to repeat, with slight variation, the principles there laid down ; for all will agree that, 471. If the brain be acted on, the effect produced by it on the mind will depend on its nature and condition. 472. Whether its nature, as it regards sensation, differs in different persons, cannot be ascertained ;* but it has been gifted with certain pow- ers by the Creator, which it cannot transcend. 573. The condition of the brain is partly natural and partly artificial. One person is so constituted that slight causes produce intense sensa- tions, and no cultivation will entirely change this inclination of his sys- tem. Another person is so constituted that the most powerful causes may act on the brain, and yet cause but slight sensations. 574. An artificial state or condition may be either transient or per" manent. Many medicines produce a transient effect on the brain such that causes act very easily, or on the other hand, with difficulty, or even such a state of the brain that sensations will be produced merely by the state of the brain. The effects caused by the use of alcoholics till deli- rium tremens are produced, is a terrible proof of this. The brain is in such a condition, that it will cause sensations of sight and sound never caused by aught in this beautiful world ; and the pitiful object of such visitations believes himself surrounded by demons, from which he in vain attempts to escape, for the cause of his sensations is in his poor abused brain, which the Creator has intended shall be the agent in the produc- tion of unspeakable delight to those who observe his laws, which is not to obey, but to seek our highest good. 575. It matters not to the mind, whether the sensation be produced by the brain, or through the brain, the channel through which the mind is acted on being the same, every sensation seems a reality ; and when, as hereafter seen, the brain is in such a condition, the mind cannot use it to reason with, and the mind is left unprotected to the torment of brain-produced sensations. 576. If the brain be inflamed, so slight a cause as the pulsation of the blood will produce sensations, perhaps of sight, of sound, of smell, taste, &c. ; while the use of opiates can produce such stupor, viz., inabii- * The brain is now spoken of merely in reference to sensations. 208 ORGANS OF SENSATION OR FEELING. [CHAP. II. ity to produce sensations, that the most powerful causes cannot produce sensations. 577. A permanently artificial state of the brain is caused by the use of medicines, by continued diseases, and by continued habits of living. An overloaded stomach for a single time, produces an obtuse <=tate of the brain for a short while only ; but constant overfeeding dulls the senses permanently ; while wholesome food, air, drink, clothing, and regular, reasonable, common-sense habits of every kind, will tend to perfect* the state of the brain, and render it an active agent in the production of agreeable sensations. 578. It is therefore evident, that whoever is unhealthy, or uses articles as food or drink, or in any way so acts upon the brain, as to produce an unhealthy or unnatural state of the brain, cannot form a good judgment, as the sensations which will be produced are not healthy and natural, and his mind will be acted upon by agreeable or disagreeable sensations, but not such as would be produced by objects acting through a perfect brain. And upon any trial, it will be found that a man's judgment will be influ- enced very much by the sensations produced, not only by the thing under consideration, but by any thing. 579. It will, therefore, be exceedingly difficult to find persons who will think alike on the same subjects, or any person who will be uniform in his feelings or opinions ; for his mind has such a changeable brain and nerves through which to receive sensations, that if itself be always the same, it must form very different opinions at different times, the testimony is so different at different times.* 580. It is especially worthy of notice, that a person is under obliga- tion not to unfit his brain for producing natural sensations, by the * use of such articles as poisonous alcohol, tobacco, etc., or by any such course of life as unfits him for judging correctly of himself or others, and of the world. To illustrate ; a person by the use of tobacco produces such an effect upon his brain and nerves, that he cannot form a correct * It will be found that people form favorable opinions of almost any thing which is presented to them, when they are acted upon by causes of agreeable sensations. Hence the custom of " feeding" our legis- lators when a request is to be made of them. And as first impressions are so strong and lasting with most people, it is always preferable to present a new topic before the mind, in connection with something which with certainty will produce agreeable sensations. And if a dis- agreeable thing must necessarily be brought before the mind, let it be combined with something which will produce agreeable sensations. SEC. 5.] THE BRAIN AS AN ORGAN OF SENSATION. 209 judgment of how offensive his breath is to others, who certainly have a nght to receive the common air, pure and uncontaminated. A person who has used alcoholic beverages, has unfitted, for the time, his brain for producing disgusting sensations, such as his deportment and con- versation produce through a brain unclouded by the effects of poisons. He will often so much mistake, as to think himself exceedingly agree- able ; indeed, be so much deceived as to think the exhilaration which he has produced, gives brilliancy to what he supposes accomplishments, but which an undeceived mind would look upon as awkward at best, but exceedingly clownish when exaggerated by dissipation. 581. The second duty of the brain is to cause the sensa- tions to appear to be at the commencement of the nerve through which they are produced. If a nerve be pricked in the finger, the sensation appears to be in the finger, and we say, it seems to us that the finger is pained. 582. The object of this is to call attention to the part exposed to danger.' If the finger be injured, it is necessary to call attention to the part injured, that the cause of the injury may be removed. 583. If the disease or cause producing injury be not found at the commencement of the nerve, it must be in the course of the nerve, between its commencement and the brain. . If the elbow be struck, two sensations are produced, one of acute pain, which appears to be at the elbow where the cause is acting, and the other of a prickling character, appears to be in the little finger ; but the cause of the sensation is not there, but at the elbow in the course of the nerve. If certain diseases affect the spinal cord, some of the nerves composing it will be so acted upon as to cause sensations like the creep- ing of animals ; these sensations will appear to be at the commencement of the nerves through which they were produced. A person frequently has " chills run over " certain parts of the body, owing to effects pro- duced on certain nerves in some part of their course. In fever and ague the nerves in some part of their course, perhaps the spinal cord, are so acted on as to be in the same state as if their commencing points were affected by cold ; the person feels as if his skin were cold, and goes to the fire to warm the nerves, but his hopes are vain. It is disease, not 210 ORGANS OF SENSATION OR FEELING. [CHAP. II. any want of heat, that causes the state of the nerves producing the sen- sations he feels. 584. The seat of disease is determined in these cases, by examining, in the first place, the parts in which disease ap- pears to exist : if they are healthy, it must exist in such a part as to affect all the nerves extending from the parts ap- parently affected, to the brain ; and as the part where the nerves from these parts come into each others 5 vicinity, is known, the disease is at once located. Hence in neuralgia, when the pain seems to be produced, now here, now there " darting about " it would be natural to conclude, that the disease existed at some point where it affected all the nerves, extending from the parts where the pain seemed to be produced and the brain. If the pain be confined to any particular part of the body as the face the seat of the disease must be comparatively small ; while if the pain seems to range over the entire body, the seat of the disease must be more ex- tensive. The same comparative course would be pursued, and the same comparative judgment formed, if the disease be such that no sensations are caused by certain parts of the body ; the cause of the paralysis must be looked for at such part where it will include all the nerves from the paralyzed part. 585. There are two exceptions to the proposition of paragraph 581 : 1st, some sensations appear to be produced at the commencement of nerves which have been in no way agents in producing the sensa- tions. Thus disease of the liver is apt to cause sensations to appear to be produced under the shoulder. In " hip complaint," the first sensa- tions of pain seem to be in the knee, while the nerves extending from the knee to the brain, as far as we know, are not affected in any way. Why this is so, is not known. 586. The second exception is in case of many sensations, such as hunger and thirst. These and the like, do not appear to be produced any where in particular ; nor is it known by what part of the body they are caused. Some have supposed they were produced by the stomach ; and a variety of other suppositions, equally groundless, have been made. They are for the purpose of causing us to eat, drink, &c., and of that general character having reference to the good of the entire body, that there is no necessity for their being produced, or seeming to be produced, by any particular part. SEC. 6.] THE MIND IN RESPECT TO SENSATION. 211 587. There is another class of sensations produced by the action of the brain upon the mind when we think, but a proper place for dis- cussing these briefly, is in another chapter. SEC. 6. The Mind in respect to Sensation. 588. What office the mind performs in the production of sensations, is uncertain. Some suppose that the mind itself, in itself, is capable of producing sensations similar to those of sight, &c., produced ordi- narily by the action of the nervous system. Some suppose that the mind is capable of acting upon the nervous system, so as to produce those states which cause sensations ; but that by itself, it cannot cause sensa- tions. Some have supposed that the mind was of different qualities in different persons, so that if the same state of the brain should be brought to act on the different minds, similar effects would not be produced on account of the different constitution of the minds. Some have thought that different states of the mind were produced by the different states of the brain ; and that also, these different states of the mind could be pro- duced without the agency of the brain ; consequently that all the sensa- tions of sight, &c. ? could be produced in the mind of the person, blind not only, but wanting the nerves of sight. All these, and a hundred like questions, I readily confess my inability to solve ; but from all the proofs afforded by physiology, I am inclined to think that, 589. Sensations are never produced, except by action of the brain upon the mind ; and that the character of the sensation depends entirely on the state of the brain, because, 590. 1st, I cannot find any good proof that sensations are ever pro- duced except when there is an opportunity for the action of the brain upon the mind. When a person dreams, there is not only an opportu- nity for the brain to act, but late suppers, and other such causes as tend to produce certain states of the brain, are the most frequent causes of dreams. 591. 2d, When certain states of the brain are produced, sch that it cannot act on the mind, the mind does not realize sensations. The brain has frequently by accident been exposed, so that it could be pressed ; the instant pressure was made, sensation was suspended, and when the pres- eure was removed, sensation was again produced ; so perfect would be 212 ORGANS OF SENSATION OR FEELING. [CHAP. II. the suspension, that if every thing remained in the same place, during the pressure, without the person's anticipating it, he would neither know it had been made, nor suppose any time had elapsed, but as if nothing had happened continue the sentence in the midst of which he was inter- rupted. 592. 3d. The sensation produced, is always, so far as we can learn, in accordance with the state of the brain and nervous system. If the nerve of a tooth be touched, we can anticipate what sensation will be produced. If the eye be inflamed in certain parts, we can anticipate that a little light will produce a sensation of dazzling, and the skilful physi- cian, by taking into consideration the condition of his patient's nervous system, can usually judge what kind and degree of sensation he feels, If the eye, nerve, and brain, be perfectly healthy, we know what colors will produce agreeable sensations. The world over, a combination of blue and orange colors are pleasing, so are red and green, or any colors a mixture of which will produce white light ; blue and red, red and yel- low, are disagreeable (Fig. 85).* Fig. 85. * Those colors which mingled produce white, are called harmoni- ous, or complimentary when spoken of in reference to each other. The combinations not producing white, are called disharmonious. In Fig. 85, the simple colors are placed at the angles of a triangle, in a circle. They are of course harmonious and complimentary of each other. At intermediate points of the circle and at extremities of diameters are placed colors formed of those at the nearest corners of the triangle, and it will be seen that colors at the extremities of diameters are harmonious or complimentary' ; so will be all shades of the same colors which would be formed at the extremities of any diameters. In consideration of this Muller remarks, " Women of good taste, when they have a single pre- dominant color in their dress, select a dull one ; or if they wear pure colors, combine those which harmonize from being complimentary of each SEC. 6.] THE MIND IN RESPECT TO SENSATION. 213 593. 4th. The character of the sensation changes too easily for us to suppose that it depends on the mind. Various articles of food pro- duce a high relish for other articles ; a " taste" is soon acquired for food at first " very disagreeable." A glass of wine will often make a person pleased with the effect of objects otherwise disliked; a thousand other instances could be suggested. 594. It would seem, therefore, as the tendency of objects to produce effects is uniform and invariable, and on the other side, so to speak, of the nervous system, the character cr nature of the mind uniform and invariable, that all variation in sensations is to be attributed to the variable character or other ; for instance, they wear a red shawl over a green dress, combine lilac with yellow, or blue with orange. How beautiful and pleasing to the eye, is the combination of a golden orange color with blue ; for in- stance, of an orange fringe with a blue drapery, while the dress of a fe- male in which pure yellow were combined with red, or yellow with blue, or blue with red, would by every person be regarded as hideous and out of taste. Such striking combinations of disharmonic colors are chosen only for national signs and the dress of soldiers. The disharmony be- tween two colors may however be removed by the interposition of a third color which is the harmonic of one of them, and is indifferent in relation to the other, as in red, green and yellow ; blue, orange and red, &c. Painters, either intentionally or without being aware of it, make constant application of these physiological principles ; and the pleasing effect of colors in a picture, depends on the skilful combination of harmonic colors. By employing principally the dull gray colors the danger of disharmonies is avoided, but the whole charm arising from the harmonic combination of colors is renounced." Thus persons may dress or furnish their houses in a pleasing manner by applying physiological principles ; but in dress, what has been said upon the reflection of light, must be remembered ; viz., that light from the dress passes to the complexion and is reflected, mingled with any other light reflected from the face. Some articles of dress would improve the complexion, therefore, and if at the same time harmonious in colors, very pleasing sensations will be produced. But the greatest care will be requisite in arranging bright or pure colors either by natural taste, or by rule ; hence it is safest for most persons to be sure and never offend good taste, but to wear unobtrusive colors and small figures and furnish their apartments in a similar manner. Yet by study a person can improve upon this plan and secure much admiration.* * It is worthy of admiration that in all the natural objects, among millions of flow- ers of every hue and tint of color, in the " ever changing glories of the sky," colors in near relation to each other are always harmonious. Hence why flowers and imitations of natural flowers are ever so attractive and adorning and it is a little eineular that " flower makers" should combine flowers and colors as nature never does, taking paina to avaid a perfect model, and always with a bad effect. 214 OEGANS OF SENSATION OR FEELING. [CHAP. II. state of the organs of sense, nerves and brain ; to wit, as these parts are, so are the sensations. 595. The duty of the mind seems therefore, in respect to sensations, to be : to perceive them, to judge where they have been produced, and to be pleased with them if their causes are productive of no harm to the body, and to be repugnant towards all which are produced by causes acting harmfully, to remember them, to compare those remembered with each other and with new ones, and thus acquire knowledge of the objects which surround us and of the states of the internal parts of the body. 596. Perceiving sensations. Nothing is known of the manner in which sensations are perceived, in other words, how the brain acts upon the mind. It may be curious to ask if the mind occupy much space in the brain, or if all the nerves of sensation terminate almost at the same point? No reply can be given. The only light that is shed upon the subject, is obtained from this ; that nerves from different organs of sense, do not seem to pass towards the same identical point of the brain.* The nerve of sight does not follow the course of the olfactory nerve, though they are very near each other at one point. The nerve of sight takes a very cir- cuitous route to where it appears to terminate, as if there were a necessity in the fulfilment of its duties that it should visit certain parts of the brain. But where it appears to terminate may not be its stopping place. Much might be written therefore, and yet be but little, as it would be so unsat- isfactory. 597. The mind has control over its powers of perceiving sensations. As the expression is, " it can give attention " to sensations, or divert its attention. How this is done is not known. Whether it removes itself from the part of the brain through which sensations are produced, * If metaphysicians find any fault (which they reasonably may) with language used in a physiological discussion of mental operations, they are desired to remember, that it is the wish not to be considered as entering on their department of learning at all. What is said is merely in connection with physiology, and to convey clear ideas on that subject ; metaphysical interpretation is not, therefore, ever to be given to terms used, but a physiological sense merely. Any point in metaphysics will be instantly yielded, as belonging to a subject upon which men more learned in that department, are better qualified to express an opinion. SEC. 6.] THE MIND IN RESPECT TO SENSATION. 215 or whether it stills the action of the brain, is all unknown. The ex- ercise of this power of attention affects the intensity of sensations in a remarkable degree. If attention be given to the sensations produced by food, they will be very much heightened thereby, as hereafter seen ; facilitating the process of digestion, if the food be wholesome. But if the attention of the mind be absorbed with business etc., food will be swallowed without relish, and very soon such a course will be followed by dyspepsy. A person may ride through the pleasantest section of country and appreciate none of its charms, because his mind gives no attention to causes of sight and sound. To one person there are " ser- mons in stones, books in brooks ;" another person looks upon the beau- tiful flower and no admiration is awakened, for his mind heeds not the sensations it was made to produce. 598. The attention of the mind being engrossed with the importance of staying the ravages of fire, or with the strife of battle, a person feels not a wound, or the most exhausting fatigue. On the other hand, the attention of the mind will cause the slightest sensations to appear in- supportable. He who gives attention to every ache and ail, will soon appear to himself to be the most afflicted of the human family, and indeed, he will suffer more than those who are acted upon by the most powerful causes of painful sensations. To nurse every pain of a child, caused by cut or bruise, etc., is to make it suffer on the slightest occa- sion ; while to call off its attention and make it " forget " the hurt, is to teach it to be manly, and use the true means of relieving unavoidable misfortunes of their intensity. 599. Judgment of where the sensations have been produced. How this is arrived at by the mind is not, of course, known. Some sensations are general, but most seem to be produced at the commencement of the nerve through which they have been produced. The mind is liable, therefore, to many errors in respect to the state of the body. Sometimes diseases seem to be at the commencement of nerves, not, as far as can be judged, being at all concerned in the production of the sensation. Some suppose the state of nerve necessary to produce a sensation, is caused in the nerve of the unaffected part by the nerve of the affected part, which passes near to it, but this is uncertain. Disease, and various causes, by acting on the nerve in some part of its course, as has been shown, would lead the mind astray in the formation of its opinion. The most tormenting itchings, and terrible pains, are thus very frequently thought to be produced by the state of a part which, in fact, is quite healthy, and many applications will be made without avail. The power 216 ORGANS OF SENSATION OR FEELING. [CHAP. II. of causes producing sensation, is judged by the intensity of sensation ; but this depends not only on a cause, but on the state of the nervous system through which the cause acts. A slight cause, therefore, in one person produces acute pain, and from similar pain in another, it might be argued that the cause was slight, when, in fact, it was not so. In the first case nothing being done, the person would recover perhaps ; in the last he would die. Thus is evidently seen the importance of edu- cated, experienced skill. 600. In a similar manner is the mind liable to misjudge of causes surrounding us. There being so many causes beside surrounding objects which modify the sensations upon which the mind bases its judgment ; for instance, a rush of blood through or across inflamed nerves causes sensations which make the mind believe that a carriage is rumbling, a bell ringing, etc. So an "excited" state of the nervous system will cause sensations of sight entirely unworthy of confidence. 601. Production of pleasing and disagreeable sensations. The mind is so made as to be usually pleased with the sensations caused by harmless objects or a healthy state of the system, and disagreeably af- fected by those of harmful objects or states of the system. But there are exceptions: the exhilarating effects of alcoholics, and the "reconciling" effects of tobacco, are seductive to man, but refused by animals. Why this is so is evident, if the destiny of man be considered. He has not been designed to occupy so narrow a portion of the world as any other species of animal. The whole earth is his inheritance ; his hand com- bines the weapons of every other animal ; his reason more than compensates for the instinct of the geometrical bee or the architectural beaver, and the range of his tastes includes every variety of pleasure that air, earth, and water are capable of producing through nerves and brain. To think, however, is the chief duty of man, as well as the source of his highest pleasure. To preserve himself from danger, in many cases, nature there- fore has made it necessary for him to acquire knowledge and apply it, of which necessity she has deprived animals, supplanting it by unmerit- ing instinct, which always compels the animal to act for its good ; but man can use his powers or not, and for his good or harm, as he chooses. His instincts warn him, therefore, only of dangers of which the applica- tion of his cultivated mind could not warn him, and this they do most perfectly. 602. Memory of sensations. This is an exceedingly important duty of the mind. It would seem that the mind performs this act unassisted by the brain, since, as will hereafter be shown, the brain is continually SEC. 6.] THE MIND IN RESPECT TO SENSATION. 217 undergoing changes in all its parts, so that no portion of it remains much length of time in one position. Some suppose, that when the mind would remember a sensation, it so acts on the brain as to produce a similar state as that which previously existed when the desirable sensation was per- ceived, and that when the state of the brain cannot thus be reproduced by the mind, the sensation cannot be recalled. Others suppose that an effect once made upon the mind by the brain, can be recalled by the mind without the assistance of the brain. It matters not sensations are re- membered, and by that means, 603. Sensations can be compared. By this important process the mind stores itself with useful ideas, and knows the cause of sensations. For instance, if a pound weight be taken in the hand, and the sensation be remembered, the next time a weight be taken in the hand that upon comparison produces a similar sensation, it is considered to weigh a pound. If sugar has caused its sensation, which is remembered, sugar will be thought the cause of any similar sensation, and so of other things, and also of the internal states of the system ; for instance, if a person have suffered any kind of pain in any part of the body, and feels the like again, the cause having been learned or told him in the first instance, he will think it exists again. Thus from the kind of pain and location of it, the physician judges very much in respect to disease. 604. But the mind is very liable to fall into errors. Causes produc- ing sensations are so numerous, that it requires a very long time to expe- rience in regard to them all. Many produce similar sensations, fcnd mistakes may be made, like that of the negroes of the West Indies em- ployed to unload the first cargo of ice ever carried to those places. They threw down the first lumps, declaring they were burned. Such sensa- tions they had never felt, except produced by heat. They knew not that intense cold produces similar sensations. Again, objects with which we are acquainted produce sensations so similar, that much skill and experi- ence is required that an accurate comparison may be made. Again, the sensations produced by a cause, and the comparisons made, depend much upon what causes have preceded. The taste is altered by various arti- cles, as already shown. If the eye have been fixed on a bright red object, and then turned to a white one, it will appear green ; for the effect of the red has so fatigued the nerves, if the expression may be used, that the red light from the white object produces no effect, and the blue and yellow acting without the red, produce the effect of green. If heavy weights have been held, a pound weight will seem very light. So also different states of the same or different parts of the body produce similar 10 218 ORGANS OF SENSATION OR PEELING. [CHAP. II. sensations ; and also as tne sensations produced by surrounding objects and the states of the body depend on the condition of the nervous system, it is evident that great experience is necessary, as well as a very retentive memory of sensations, and an accurate judgment to compare, that the mind may arrive at correct conclusions in respect to the causes producing the sensations it perceives. The mind obtains assistance also in deter- mining the character of objects, by causing any object about which there is doubt, to produce more than one kind of sensation ; for if different ob- jects produce similar sensations of one kind, they will produce different sensations of some kind. It is of much importance, therefore, to know what similar and what dissimilar sensations different objects, especially different diseases, produce. For if similar sensations of two or three different kinds are produced, we are apt too hastily to think that the causes are similar. A dropsy, for instance, may exist, and one in- experienced would, perhaps, think there is one cause and one cure ; but greater skill would teach that dropsy is an effect produced by many different causes, and other signs would be looked for, till by them the common cause of them and the dropsy would be found.* SECTION 7. Concluding Remarks on the Organs of Sensation. 9 605. So little is known of the precise manner in which any organ of sensation performs its duty, that it is impossible to make any very par- ticular inferences in respect to the particular mode of managing the va- rious parts of them. From the powerful sensations produced by the minute particles of odoriferous substances, too subtle to be appreciated by other se.ises than that of smell ; from the ready action of the feeblest causes of sound, which can only be produced by a change in the state of the nerve ; from the powerful action of only a single grain of morphin^ or a drop of prussic acid, which will lock the nervous system in the soundest slumbers many times the sleep of death it would be expected that, 606. What would usually be called insignificant causes will be sufficient to produce disease of the nervous system, * Here the folly is seen of " doctoring" signs or symptoms, or ad- ministering remedies without great knowledge, the result of study and experience, and especially without a knowledge of the cause of the ymptoms exhibited. SEC. 7.] CONCLUDING REMARKS. 219 causing dreadful suffering and most tedious in its duration ; that the suffering might commence suddenly and terminate as quickly ; that as the slightest causes may bring it on, so the slightest causes may remove it ; that, if the state of the nervous system be changed by any cause, there will be a change in the sensations produced by the disease, perhaps for the better, perhaps for the worse ; and from what has heretofore been said, it would be expected that sometimes one thing, sometimes another, would change the state of the nerve, by which painful sensations are caused. It is also in accordance with common sense, that while an endeavor is made to change the state of the nerve causing pain, ALL CAUSES TENDING TO PRODUCE SUCH A STATE MUST BE SEDULOUSLY AVOIDED. For instance, it is useless to call on the doctor to cure neuralgia, while a person is continually exposed to take cold, etc. 607. It is also found that pain, by the effect produced on the good nature of a person, and by the bad effect produced upon the nervous system, is one of the most powerful causes for deranging the action of all parts of the body, and wearing out life. 608. If any state of the nerves producing pain can be changed without doing decided injury, it should be done ; not more for the purpose of preventing pain, than for pre- venting the farther progress of disease. The usefulness of this principle is shown by the great reputation which some physicians have acquired almost solely by the use of opium and its compounds, and of other narcotics (inducing sleep) . These articles are indeed great blessings, if used judiciously, but productive of eqnaj harm if improperly used. 609. If the skin be exposed to the cold, and the blood thus driven from the nerves in the skin, the sensations produced through the skin are correspondingly blunted. Thus, if the skin may be taken as a crite- rion, and also, from the fact that the wants of all parts of the body are supplied from the blood; it may be inferred, 610. A free supply of pure blood is requisite that the organs of sensation may fulfil their duties. 220 ORGANS OF SENSATION OR FEELING. [CHAP. II. This is obtained by the use of proper food, drink, air, and all the means hereafter shown to produce pure blood ; and by muscular exercise, and rubbing the system, which sends the blood more rapidly through every part of the body, by proper clothes, etc. And if the exercise of the eye may be taken as a criterion, 611. Exercise of the organs of sensation causes a brisker flow of blood through them. The eyes of the student frequently afford evidence that exercise increases the quantity of blood passing through an organ of sensation. Some suppose that exercise is useful only by causing the mind to give stricter attention to the sensations produced ; but while it may be allowed that attention is all that is necessary in many instances, yet it is also certain that the sailor, by the exercise of his eye, not only concentrates his attention, but perfects his power of adapting the eye for long sights ; while by exercise, the watchmaker gains the power of adapting the eye to near objects.* 612. Proper exercise of the organs of sensation improves their physical condition and powers. In what way is not certain, as it is not known which part is improved when vivid sensations are produced. Without doubt the power of giving attention is increased, and considering things hereafter to be shown, it is probable that the constituents of the organs of sensation undergo changes in the fulfilment of their duty, which changes are made more rapid by exercise, causing the increased flow of blood necessary to effect the change,t and as the parts undergo their changes, they become adapted * When the eye turns in (is cross-eyed) from want of power of adaptation, which is a frequent case, it can be trained to adapt itself by having the other eye covered for a short time together, but very fre- quently, and then using the ill adapted eye in looking at distant or near objects, as the case may require. In some cases the eyes alternately turn in, because one can adapt itself to near, while the other can only adapt itself to distant objects. In this case the eyes must be alternately covered and exercised in those ways in which they ordinarily fail. Nothing of tin's kind must be expected to succeed except with months of practice, resolutely persevered in every day. t When an eye is found to be weak, on which account it turns, it may many times be strengthened by a proper course of exercise, the other eye being covered, but great care must be taken not to use the feeble eye too long at one time. SEC. 7.] CONCLUDING REMARKS. 221 to the requirements made upon them, as it is a universal rule of nature to adapt a part as far as possible to fulfil the duty required of it. 613. Whatever may be the particular cause, there is no doubt that exercise renders the sense of touch more delicate, the sense of taste more refined, the sense of smell more acute, the sense of hearing more exquisite, the sense of sight more perfect, and the muscular sense more accurate. 614. Over exercise enfeebles the organs of sensation. There is, however, little danger of over-exercise of any organs except those of sight. Inhalation of intensely acting odors, such as smelling-salts, etc., have in some cases much injured the sense of smell, while strong spices, etc., act as injuriously upon the sense of taste. 615. The remedy for over-exercise is rest, entire, and prolonged.* 616. Thus is concluded the chapter on sensations, the contents of which, may not "have been easy to understand without some study and thought ; but the principles herein developed it is hoped will induce the reader to cultivate to the full, his powers of rationally enjoying this world, and he will exclaim with Campbell the poet in a letter to a friend, " What adorable beauties of God's and nature's bounties we live in without knowing." * If an eye be weak, and turn because it requires rest, this should be allowed by covering it for a long while, after which it is to be grad- ually strengthened by exercise. CHAPTER IIL OKGANS WITH WHICH TO THINK. General Observations. 617. 1st. Facts already advanced prove that from the brain influences are exerted upon all parts of the body, and that from all parts of the body influences are exerted through the brain upon the mind, producing sensations. These things prove that the mind is enthroned in the brain as a political capital, from which centre, through the nerves as avenues of communication, it can issue its mandates to every part of its corporeal kingdom, and from every part of it receive by nerves, continual reports of its condition, welfare, and wants. Hence it would be necessary that the same centre, the brain, should furnish the mind with the apparatus necessary for thinking, if any be required. 618. 2d. When engaged in thinking a person experiences a sensation distinct and perfect as any produced through the ear or eye ; the location at which it is produced, appears as decided as in case of sensations of sound, and more so than in case of the general sensations of thirst, hun- ger, &c. Intense thought will call attention to the front part of the head, as if the acting cause of thought were there. If the hand be ap- plied to the forehead it will feel hot, and the application of a cold cloth will give immediate relief; the thoughts, from being confused and vexing will become clear and pleasure-giving. When a new idea has been gained not only is there a feeling that knowledge has been acquired, and pleasure thereat, but also a sensation of a more physical character, so to epeak, in a certain sense like the sensations produced through the ear, eye, &c. So when memory is exercised or judgment formed, a sensa- tion is felt, feeble or intense, of a pleasurable or unpleasant character, in the same manner as sensations treated upon in the previous chapter". A sensation of this character is called consciousness (physiologically speaking) . Another reason why consciousness may be considered as a GENERAL OBSERVATIONS. 223 sensation produced by the action of the brain upon the mind is, that con- sciousness ceases the instant the action of the brain ceases, as found in cases where the brain is or can be pressed, by which unconsciousness even of passing time is produced. Fits of apoplexy, " fainting away," and even profound sleep, produce a similar unconsciousness even of ex- istence, for the brain cannot then produce sensations. 619. 3d. If the brain be slightly inflamed, not only are sensations of sound, sight, &c., readily produced, but the thoughts spring up to the mind with facility and succeed each other in a very rapid manner, while if the state of the brain be such that sensations of feeling, &c., are pro- duced with difficulty, the intensity of a person's thoughts, as well as their activity, is slight ; thus showing that the character of a person's thinking powers can be determined, in a general manner at least, by the condi- tion of the brain. 620. 4th. It has been often noticed by the student, that the head be- comes hot and the feet cold when engaged in intense study. Nothing is more common than to hear professional and indoor business men com- plain of" cold feet," no matter how warm the apartment is kept. Why is this, except that the activity of the brain necessary when thinking is done, requires an increased supply of blood 1 621. 5th. Two persons may hear at the same time, of the death of some dear friend of one of them ; the voice of him who tells the tidings falls on the ear of each alike, the same effect is produced on the nerves of hearing in each case, and they produce the same effect on the brain, and the physical brain produces the same effect on the mind. But the eyes of one remain dry, while tears gush from those of the other. Why the difference, except that the emotions of one mind act upon the brain with which it is connected and through nerves upon the tear apparatus ? The cheeks redden and the limbs quiver with anger, rage will even gnash the teeth, while smiles are indicative of gentle feelings, the down- cast eyes of reserve, nor can the beautiful blush of modesty be ever seen on the face where haughtiness rules the mind. But when by disease or accident the nerves connecting between the brain and body are unfitted for use, an unmeaning stolidity stares from the expressionless face. 622. 6th. In the morning, the heated brain of the evening previous has become cool, and after a bath of cold water upon the head, feels ready for action, and in a corresponding manner the composed thoughts of the evening become regular, and thinking becomes a pleasure ; the bu- siness man gives his attention to his business, the farmer to his labors, the student to his studies, and all with delight. So during the day, if 224 ORGANS WITH WHICH TO THINK. [CHAP. III. the mind become confused, muscular exercise, a walk, a ride, or aught else which gives repose to the tasked brain, will produce in a short time regular action of the mind. 623. 7th. There is a large amount of nervous substance forming a great part of the brain for which thef'e seems to be no use, except the mind make use of it in its thinking operations. Other arguments might be advanced, but these are sufficient to prove, it would seem, that 624. There are two requirements for thinking : 1st, a mind, the efficient cause of thinking ; 2d, a brain, with which to think. SECTION 1. The Brain. 625. How the mind acts upon the brain, or the brain upon the mind, in the production of thought, is not known, and most of the curious questions which might be asked in reference to the matters under con- sideration can only be answered by supposition, supported sometimes by very gcod arguments, but usually only by probabilities. We may first, therefore, notice facts, and secondly, follow them with inferences. 626. a. The brain is composed of many parts, differing in color, structure, composition, form, position, relation, and mode of connection with other parts, and in respect to the quantity of blood received. The difference in any of these respects is not, however, very great. b. The mind, through the brain, has different duties to perform. It must receive sensations, it must exert influences, it must have thoughts, emotions, &c. c. When one kind of intellectual pursuit has caused fa- tigue, attention can be given to another with nearly o^ quite the same efficiency as if no fatigue had been felt. 627. From these facts it is inferred, that different parts of the brain are used by" the mind in fulfilling its various duties. To this it may be objected, that disease of any part does not always produce like results. Sometimes no appreciable results are produced by extensive disease. Sir Charles Bell states that he has seen every part of the brain except SEC. 1.] THE BRAIN. 225 the gray part extensively diseased, and yet the duties of the mind well performed ; while others have seen the gray part as much affected, with- out producing any apparent influence on the accomplishment of the men- tal duties.* Large portions of certain parts of the brain may be lost, by accident, without producing any apparent effect on the mental operations. Such facts are against almost any inference that may be made in respect to the action of the mind and brain upon each other.t * By some, it has not only been inferred that the brain consists of parts, but that the situation of these parts has been determined ; for in- stance, that the front parts of the brain are the organs used in the intel- lectual operations of the mind. Thesq grand divisions have again been divided, by some, into a small number, by others, into a multitude of parts. One step further has been taken, and it has been inferred by some, that the larger these parts or organs, used by the mind, the more efficiently, other things being equal, can its duties be performed. Still another step being made, it has been inferred that the size of these parts or organs could be determined by examining the head externally, and thereby the capacities of a person determined, other things being equal. Whether this be so, any person, it would seem, could satisfy himself by making a few experimental examinations, and especially by examining and comparing the skulls of different skeletons, and noticing if there be such uniformity in their thickness in corresponding parts as to warrant the inference that the size of the different parts of the brain could be determin- ed by an examination of the head externally, even if it were allowed that the brain was composed of a congeries of organs, all coming to the surface of the brain, and that the larger any part of the brain, other things being equal, the more effectual the operations of the mind through it. He might then examine and compare brains of different heads, to learn if the apparent enlargement of any part of the brain might not be produced by the enlargement of some other part crowding upon it, so to speak, and causing- it to be prominent ; for there will be found many parts in the brain \\hich do not come to the surface, but are buried deeply below the parts forming the surface. He may notice, likewise, that many parts of the brain having the same appearance as those directly within the skull, are found at the surface of the brain, where the falx (Fig. 47) separates one half the brain from the other. He might ask if these parts do not perform important duties for the mind, and if there be any way of de- termining what, or how much effect, the action or size of those parts of the brain would have upon the character and capacities of a person. Many similar questions he might ask, and settle in his own mind, it would seem, by a slight examination. Assertions, no matter by whom, either upon one side or the other, would of course be of no avail ; the matter is therefore left with these hints of some of the points to which a person might give his attention, before making a decision. t One case is at present in mind, where a boy from the front part of the brain lost more than half a teacupful of substance. In a few months he was well and attended school, making as rapid intellectual progress as ever, and he was always remarkable for proficiency in his studies. 10* 226 ORGANS WITH WHICH TO THINK. [CHAP. III. 628. a. There is a very large quantity of blood passing to the head ; in proportion to its size, from five to ten times as much as passes to any other part of the body, except the kidneys. b. The quantity, as already stated, increases with the activity of thought ; and vice versa, the activity of thought is increased by an increase of the rapidity of the circulation. c. The blood which passes to the head is of one quality, and goes through one set of vessels j the blood which passes from the head, is the same in quantity but differs in quality, and comes through another set of vessels : that is, the blood undergoes a change as it is passing through the brain. It would seem to be correctly inferred, therefore, that the brain had undergone changes corresponding to the changes in the blood ; and that as the circulation of the blood corresponds with the activity of thought, so the activity of thought must correspond with the changes which take place in the brain. 629. a. If the blood be ever so large in quantity in the brain, the thoughts are not active, if the blood be stagnant as in case of apoplexy in which many times or always, the bloodvessels of the head are crowded with blood, but the mind is inactive. J. If the blood have not been properly acted upon in the lungs, it is found that though it flows through the brain in sufficient quantities, a person becomes insensible. The inference is, therefore, that it is not the quantity of blood which the brain receives, merely ; but the quantity and quality of the blood which prevents or facilitates the changes in the brain necessary to the production of thought. 630. a. For the fulfilment of their duties in a perfect manner, all parts of the body depend upon the blood. &. As in case of the muscles, all parts are found to require more blood when active, than when in a state of repose. SEC. 1.] THE BRAIN. -.& 227 c. There is only a given amount of blood in the body at any one time ; and if this be in one part, it cannot be in an- other at the same time. It is, therefore, inferred that when the blood is elsewhere than in the brain, the thoughts cannot be active in the highest degree ; and vice versa, when the thoughts are active and producing rapid changes in the brain, blood in large quantity is then required, and it cannot at the same time be allowed to circulate rapidly in other parts : hence the feet become cold, the food in the stomach is not digested, and muscular exercise can- not be taken with profit. Hence severe study should never be allowed just before or after a repast of food, or during the active performance of duty by any part of the body beside the brain. While, on the other hand, a person should not direct the blood to any other part of the body when the brain requires it during the production of thought. 631. Only a small portion of the blood is adapted to take part in the changes produced in the brain during mental operations. It would be inferred from this, that the production of thought would be limited, not only by the quantity of blood the brain received, but by the quality of it ; and that whatever would contribute to improve the quality of the blood, would equally contribute to facilitate the production of thought: hence, that pure air and a healthy condition of the lungs would be necessary for the perfect accomplishment of mental duties ; and not less necessary will be a supply and healthy digestion of wholesome food. 632. a. Proper exercise of the muscles, has been found to have a favorable effect upon the thinking powers. b. It has been already seen that exercise of the muscles furnishes to the blood a supply of substance no longer of use to the muscle, but indeed a detriment if allowed to remain in the muscle. It might be inferred, that among other ways in which exercise of th muscles and other parts benefited the brain, one was that of supplying the blood with substances, which though no longer useful to the muscle, might serve a purpose in effecting the important changes which thinking produces in the brain ; and so on the other hand, may the results of th changes in the brain assist in perfecting the muscles. 228 ORGANS. WITS WHICH TO THIPCK. [CHAP. III. 633. a. Time is necessarily required in producing the changes which take place in the brain during thinking. b. After intense thinking for a time, the thoughts become confused ; but after a repose, they are again rapidly pro- duced in a regular manner. The inference is, that the power of producing thought is limited not only by the quantity and quality of the blood, but by the length of time required to re-periect the brain ; and that the best time for thought and study will be in the early part of the day, after the repose of the night and after a little exercise has been taken to circulate the blood through the entire system, in some parts of which it may have become stagnant, BO to speak, during the night. 634. a. The powers of different persons are very dif- ferent in respect to the offices of the lungs, the digestive organs, the circulation, the blood, &c. b. In the same person the health affects the lungs, the stomach, &c., in the performance of their duties, and intense thinking soon exhausts the powers of the brain. c. If the body be rapidly growing, it is necessary that the blood should circulate very freely through the. growing parts especially, as some of the ingredients required by the growing parts exist in the blood in only very small quantities; the blood must not, therefore, be monopolized by the brain, and thinking will soon exhaust it. It is to be inferred, therefore, that one person will require more fre- quent and longer repose than another ; that in ill health longer and more frequent repose will be required than in health, and that in childhood, very frequent intervals of repose will be required, and it is also to be inferred, that compelling active thought and intense thinking for a long while, in case of a child, will sacrifice the welfare of the various parts of the hody, and undermine those organs, the vigorous action of which is necessary to sustain the efforts of the mind in mature years.* * It unfortunately happens that those children with a .brain altogether too active for their age, are urged many times to study instead of being encouraged in those exercises which would turn the flow of blood from SUC. 1.] THE BRAIN. 229 635. a. Intense thought for a long time is attended with a fulness and heat of the head, from which the application of cold gives relief. b. In such cases the slightest exposures sometimes bring on the most alarming diseases. From this it is to be inferred, that a very active circulation of blood through the brain, at last produces a measure of stagnation of the blood, or a distended state of the bloodvessels of the head, which prevents the proper changes of the brain, and of course, the production of regular thought, and brings the brain to the brink of- disease ; and that to pre- vent this, it is very important not only that intervals of repose be given to the brain, in which to recover its perfection ; but also, that the inju- rious effects of too active circulation of blood through the brain le pre- vented by vigorous exercise of other parts of the body, especially the MUSCLES ; for, as during their exercise they require the blood in large quantities, it will be drawn off from the brain. Thus on the one hand, the heat of the head will be lowered, and that of the other parts of the body raised ; and as the student is so constantly on the verge of too active circulation through the head, he must avoid every other cause besides study which tends to increase the flow of blood through the head, whether it be in the form of a glass of wine, an overloaded stomach, or a " common cold." Indeed, over the desk of every student, and every business man, it should be inscribed in golden letters, " KEEP THE FEET WARM BY EXERCISE AND THE HEAD COOL BY TEMPERANCE." It IS also to be inferred, that the child should have frequent moments of relaxation devoted to exercise of its lungs, its muscles, etc. 636. As the muscles when first used, or unfrequently used, do not receive the blood in proper quantity, but as by exercise, increased from time to time, the vessels become larger, and the flow of blood through them greater, and the muscles capable of perfecting themselves, in accordance with what is required of them : so, also, does the brain become capable of accomplishing more and more, by grad- the over active brain to the undeveloped parts of the body, which being strengthened, will labor in the service of the brain with great effect at the period of maturity. 1&30 ORGANS WITH WHICH TO THINK. [cHAP. III. ually increased exercise, while every attempt to overdo, ex- hausts and diminishes the powers of the brain. Hence children should not be overtasked with studies, for as the growth of other parts of the body is stunted by too severe labor, so is the brain prevented from developing its powers by too assiduous mental application in early life ; and those who enter upon a course of study, must accustom the brain to its duties by slow degrees. 637. Mental exercise is attended by increased circula- tion of the blood, which does not at once subside, as is seen in the continued excitement once produced by any cause. It is, however, reduced by exercise of the muscles, &c., by cold applications to the head, and warm applications to the feet. It is hence to be inferred, that study should not be engaged in for a time previous to the hour of retiring to sleep, as quiet of the brain is desirable in order to secure quiet of the mind. Also, that gentle muscu- lar exercise, wanning the feet, rubbing the skin briskly, and a cool application to the head, will subdue the circulation of blood through the brain. To do some or all these things just before retiring, is desirable on the part of all, but especially should they be done by any person subject to apoplexy, or fits of any kind, dreams, disturbed sleep, or any of the causes of wakefulness. 638. a. When a man becomes insensible from intoxication, he is brought to his senses by cold applications to his head, and heat applied to his feet and hands. b. When a person has taken opium and becomes stupid, or sleepy, he is roused by rubbing, by heat applied to his hands ani feet, and by cold applied to his head. c. When the physician is called to a man in a fit of apoplexy, he rubs him, applies heat to his feet and hands, and perhaps draws blood. From these things it is safe to infer, that when a person is stupid or insensible from any cause of disease or accident, it is proper to use. thos means which will draw the blood from the brain into other parts of the body, viz., keep the head cool, rub the skin, and make warm applica- tions to the extremities, and if the case be severe, let blood flow out of SEC. 1.] THE BRAIN. 231 the system altogether. Especially it is important when a person has met with any accident to the head, such as a severe blow, though the skull has not been fractured, that the head be kept cool, and the brain kept from exercise that shall tend to draw the blood to the head, and the skin generally, but the feet in particular, from exposure to the cold.* 639. We may now consider the sensations produced by those parts of the brain employed in thinking. They are of three kinds, a. When the mind is exercised according to the laws already inferred, the most satisfactory and delightful sensations are experienced. To think; and acquire knowledge is the sphere, the duty of man, to think and acquire know- ledge is also his highest pleasure. We are therefore to infer, that when changes of the brain take place in accordance with its best welfare, such a state is produced in the brain as acting on the mind causes agreeable sensations, and a desire to do that which shall be productive of such pleasurable results. 640. b. When the mind is over-tasked, mental fatigue is produced, and an intense desire for repose, until at last, all effort to continue the process of thinking is overcome, and " tired nature's sweet restorer, balmy sleep," comes to the relief of body and mind. Hence it may be inferred, that when the changes of the brain have been carried to that degree which is injurious, they produce a state which, acting on the mind, causes disagreeable sensations, which at last over- come the exercise of the most determined will, thus acting as their own regulator. 641. c. When the mind is not engaged in thinking, it soon feels an uneasiness, an unsatisfied want, a desire to perceive sensations, which must be gratified, for it is the nature of * A case occurred last summer, in illustration. A young man was kicked on the head by a horse. He was doing well ; the physician ordered his head kept cool by cold cloths, and advised him not to leave his room ; but feeling well one pleasant afternoon, he laid off the cloths, went into a back kitchen with earthen floor, and sat with his bare feet upon the ground and his head near a heated cooking-stove, for some time. It was the cause of his death. 232 ORGANS WITH WHICH TO THINK. [CHAP. III. man to desire to perceive new sensations. As the old proverb is, " Those who have nothing to do, will do mischief." The plaything received by the child is turned on every side and torn in pieces that it may produce new sensations, and when it knows all it can in regard to the thing, it is cast aside and a new article demanded. This desire is usually called a nat- ural curiosity ; but It may be inferred that the brain is so constituted as to produce sen- sations of uneasiness when those changes have not taken place in the brain which are for the good of man, by the cultivation of his mind at- tendant upon a certain action and changes of the brain. 642. The man therefore who gains the idea that ac- quiring knowledge is not ' for him, does not understand his nature, the constitution of his mind and brain ; he talks of the weather, he goes in and comes out, rises up and sits down, yokes himself reluctantly to labor, and wonders why he was made a slave, to work, to drudge, like the horse that toils by his side. He is mistaken. He was not made so to be. His horse is thoughtless, and while he is thoughtless, how can he claim more than his fellow animal ? But let him awake to the importance of his estate, enter the walks of useful knowledge, exercise his mind and brain gradually till both mutually assisting to develop each other, reach ma- turity, and he will find there are no " common men" but those who satisfy themselves with the mere physical enjoy- ments of animals, which perhaps even the oyster may share vith them but that whoever makes study his diversion and the pursuit of wisdom his satisfaction, according to the intentions of the Creator, will have the noblest spirits of the past and present ages for his intimate friends, and raise him- self to a point of eminence from which he can " look up" to no being but God. 643. Whoever likewise, pictured the temple of science on a steep and stony hill, up which a long life the student SEC. 1.] THE BRAIN. 233 must drag his weary steps to reach the summit, and then be satisfied with what? a wreath bestowed upon his ambition! knew not the nature of man nor how to open before him the gates to the smooth and sunny paths of science, where flow- ers and fruits abound on every hand, not as delicious near the entrance, as farther on, for every step proves more se- ductive, but such as are well adapted to the relish of the mind commencing its progress. Commend me to the teacher whose scholars will cry if kept at home, and save my chil- dren from one who thinks he must drag the unwilling votary to bend in worship before the shrine he has wrongly learned to hate. Disgust of thinking will be produced when the mind is compelled to apply itself against every law of nature, when the body, the brain of which the mind is to think with, is so placed that it must constantly warn by aches and wea- riness, of the harm it is suffering, when the buoyancy and playfulness of youth are denied their action, and after all, not that the mind may be caused to think, but made to con something, to " learn by heart" what is not understood, in short, to encounter all the drudgery, but not arrive at the pleasure of thinking. 644. Every thing about the student should, on the other hand, be pleasant, and every agreeable sensation of sigh 4 , sound, &c., should in its place, for it has a place, be made to add to the delight of fulfilling this important duty of man cultivating a desire to obtain knowledge, cultivating a pleasure in the exercise of the mind and brain. School houses should be in pleasant situations, should be comfortably and attractively furnished, and abundant opportunity allowed for physical recreation, and the grand principle, acted upon, that The human mind can better be led than driven to the acquirement of knowledge, or another still more excellent but embracing the same idea : " To please is the first step to- wards instructing." 234 ORGANS WITH WHICH TO THINK. [CHAP. III. 645. In the attempts to reform society, it is too frequently forgotten that the cause of vice, many times, is want of oc- cupation. The mind will have sensations produced, and cannot bear the ennui of "nothing to do." Cultivate, in younger or older, the desire to acquire knowledge, the power and pleasure of thinking, and the mind will always find something wherewith to occupy itself. The world around upon the murkiest day, or the wonders of his own body, will afford subjects to the thinking man, such that he will never be ready for the setting sun. But if the mind be not in the habit of thinking, the instant the young man is free from his business or his labors, he is solicited to the haunts of dissipa- tion, where the delirium of strong drinks and the accompa- nying revelry may make the mind forget its self- weariness for the worst of burdens is an unoccupied mind. Hence it is better for the public to educate the ignorant, than to sup- port them as paupers or criminals for the ignorant are al- most sure to become either paupers through dissipation, or criminals, by putting their hand to mischief rather than want something to " drive dull care away." G46.. We may now consider the emotions : a. The language of the emotions is uniform the tearful eye is the language of pity, &c. b. The emotions exhibit themselves by increasing or di- minishing the health of the system. Dr. Beaumont testifies, that " anger would check the digestive process sometimes for an hour ;" and melancholy feelings are universally known to depress the action of all parts of the body, while lively emo- tions invigorate. Says some old philosopher " Every hearty laugh draws a nail from a person's coffin, while every sigh drives two in." Indeed it will be found, that all those emo- tions which tend to render a person a good member of soci- ety, tend to improve health and beauty, and to lengthen life ; SEC. 1.] THE BHAIN. 235 while all those which tend to promote selfishness, such as anger, revenge, &c., depress health and shorten life. It may be inferred that the brain is active when the emotions are active, and in a degree corresponding with them, and that man is intend- ed to live in society, and that the true refinements of civilized, educated society, are most conducive to health and longevity. 647. Uneducated persons exhibit emotions of every kind in the highest degree. It is to be inferred, that that condition of mind and brain most pro- per for developing thought, is not necessary for the exhibition of emo- tions. 648. a. When the exhilarating or exciting passions are ex- hibited, there is evidence of a very rapid circulation of blood through the head, but when the depressing emotions are ex- hibited it is quite the reverse. b. After the exciting passions have continued for a time, they produce exhaustion of the most decided character. From these things it is inferred, that as in case of thinking, so in the exercise of the emotions, there are changes produced in the brain, if the emotions are of an exciting character ; while if they are depressing, not only are changes of one kind, but of various kinds, checked or altogether prevented. It would also be inferred, that in different persons, and in the same person at different times, the emotions would differ very much in intensity. Especially when the brain is inflamed or the nervous sys- tem easily excited, it would be expected that the emotions would be easily excited and rendered intense ; that in females the emotions would be more easily excited, more acute, and less enduring, than in man. Some would infer that the emotions are almost, if not entirely, physical a weakness of the body that strength of mind is wanted to control ; but it will be seen by the following paragraph, that the mind is the cause of emotions, and the brain merely the instrument. 649. The signs of the emotions can only be perfectly produced by exciting emotions in the mind. A person can- not cause the tears of pity to flow, without the feelings of pity are first produced ; while if a person think of objects which will move his pity, the tears flow as a natural effect. 236 ORGANS WITH WHICH TO THINK. [CHAP. III. Persons who try to counterfeit the signs of pity do not suc- ceed. Actors, instead of laboring to counterfeit the signs of the emotions, strive to counterfeit the emotions, or more pro- perly speaking, cultivate the power of producing real emo- tions, whenever it is desirable, and the emotion once pro- duced, the signs of it are exhibited as a matter of course, and without, effort. From this it is to be inferred that the mind is active in the produc- tion of emotions, and that the facility of producing emotions can be easily cultivated ; also, that as certain emotions are healthful, they should be cultivated in the child by the parent, and in every one by himself; that the mode of cultivating the emotions is to present before the mind objects calculated to- excite the desirable emotion ; and that a speaker who wishes to be impressive, must not study so much how to make the ges- tures of emotion, as to feel the emotions he wishes to have act upon his hearers, when the gestures will be properly made as a necessary con- sequence ; and the hypocrite may infer that, though he may " smile and smile," such language not being produced by real emotions, has a " brogue " which shows decidedly his true character. 650. Those parts of the brain employed by the mind in the production of emotions, cause in the mind four kinds of sensations. a. A pleasurable sensation when the indulgence of the emotion is for the good of the individual and of society. From this it is to be inferred, that the constitution of the brain is such that the changes taking place in it, under the action of the proper emo- tions, produce such a state as is agreeable to the mind. If, therefore, a similar state of the brain be produced by disease, or the action of medi- cine, th same feelings might be experienced. Hence we see that some diseases produce sensations as if emotions of the happiest character ex- isted. C51. I. The exercise of the emotions to a certain degree produces feelings of exhaustion. From this it would be inferred, that too long continued exercise of the emotions produces harmful changes of the brain, which time alono can re-perfect. When, therefore, wine or the like is used to produce such SEC. 1.] THE BRAIN. 237 a state of the brain that the exhaustion is no longer felt, and an excited state of the emotions may be continued, as when the same is done that a person may study after fatigue is produced, the most harmful conse- quences will result ; sometimes such exhaustion of the mind and brain, that it can never be restored. It would also be inferred, that cool appli- cations to the head and warm applications to the feet, rubbing the skin, and gentle muscular exercise, would be advisable under such circum- stances, and especially before retiring for sleep, if the emotions have been active. 652. c. Certain degrees and certain kinds of emotions are disagreeable. It is to be inferred that certain states of the brain, viz., such as exist in case of the emotions referred to, are intended to produce disagreeable sensations. If, therefore, the same state of the brain be produced by disease, the same sensation will be caused, and the sensations being sim- ilar, the cause will many times be thought to be the same. But melan- choly feelings may be produced by disease of the stomach, or other parts of the body, and also by the sorrows of the mind. To remove these feelings, it is, therefore, sometimes necessary to remove physical disease, and sometimes to direct the attention of the mind from the cause of its affliction, by causing sensations which are of a different char- acter to overpower those resulting from its sorrowful state. Hence why, for desponding states of the mind, the physician advises riding, jour- neying, new scenes, new faces, and whatever shall cause a variety of agreeable sensations, while in other cases a dose of medicine effects a cure. Hence is seen why changes in weather, by conducing to a certain state of the brain, will cause desponding feelings, from which a person only recovers with the return of fair weather. 653. d. When under proper circumstances the brain is not exercised by certain emotions, it causes sensations of uneasiness a want that cannot be satisfied till the desirable exercise of the brain is allowed. Thus the mind must love at a certain period of life, and must have something to love. The most ardent attachment is sometimes seen for a dog- a horse, and those who are very dissimilar, to each other, as husband and wife, will love each other most devotedly. There is inexpressible delight in the exercise of this emotion, 238 ORGANS WITH WHICH TO THINK. [CHAP. III. and want of its exercise is insufferable by most of the hu- man species. From this it is to be inferred, that nature has constituted the brain in such a manner, that if the changes which take place in it when the emotions are active, are not produced, it will cause uneasy sensations, such as will at last compel a person to exercise those emotions, which are for his own good and that of his race. 654. We may now take notice of both the emotions and the thoughts. a. It will be observed, that deep thought and intense emotion cannot take place together. b. It will also be noticed that excitement of the emotions, from time to time, relieves from the fatigue of profound thought. From these things it would be inferred, that the same parts of the brain are not engaged in the production of thoughts and emotions. 655. If an idea which may either awaken thought or emotion, be presented before a multitude even of educated persons emotions rather than thoughts will be exerted in a large majority. Emotion is also exhibited earlier than deep thought ; and by the most uneducated, in an intense degree. It is to be inferred from this, that the parts of the brain employed in the exercise of the emotions, are more easily brought into action than the parts employed in thinking. That the emotions are the nearest avenues to the human mind, and the means by which many times thoughts can be awakened ; for, if by exciting the emotions, an active flow of blood through the brain be produced, an increased flow must be received by the organs of thought, and, as we have seen, the circulation of blood through them prompts to thought. Hence, when a speaker's emotions are warm, they assist his thoughts. 656. We may now refer to the fact, that the attention of the mind may be given either to the sensations produced by thinking, by exercising the emotions, or by the action of the physical senses ; and it will be found, that as the plea- sure resulting from these last is the lowest, so it is the SEC. 1.] THE BRAIN. 239 most universal. It will also be found, that as the attention of the mind of the majority will be arrested sooner by a cause which excites emotion, than by one which excites thought ; so it will be arrested more quickly by any thing acting upon the physical senses, than by any cause exciting the emotions. This indeed is the order in which attention should be arrested. Our physical senses warn us of imme- diate danger to ourselves. Our emotions excite us to protect society ; while thought must take place without haste, and with time for deliberation. 657. The attention of the young child is chiefly to be occupied with physical sensations, as those are very early produced, and may be indulged without danger of overwork- ing the brain ; and it should be kept in mind, that while the mind is occupied with one sensation it cannot be with an- other. If, therefore, the mind be occupied with sensations produced by causes of a harmless character, the child will not cry for articles to eat, &c. As the child grows older, its emotions may be cultivated and the mind satisfied therewith ; and as time advances, it may be gently led to think and to increase its desire for obtaining knowledge, and applying it for its own and others' good. 658. As in case of the muscles by exercise, gently and gradually increased in early years, the muscular man is produced, who not only uses his muscles with efficiency but delights in their exercise : so should the brain be fitted m early years, by gentle and gradually increased exercise in the fulfilment of all its duties of thinking, feeling emotions, and giving attention to physical sensations, to enjoy as it in- creases in years, all the pleasure which the world and its own powers are capable of producing. For though we know not on what peculiar property of the nervous substance its powers of acting depend, or what particular requirements are necessary in the fulfilment of its duties ; though it is 240 ORGANS WITH WHICH TO THINK. [CHAP. III. generally dented to increase in size by exercise and it would seem correctly yet it would also seem, and I believe it will be universally allowed, to be improved in its powers, by exercise ; and by gentle exercise in youth while it is growing, it is natural to suppose that its powers would re- ceive a favorable direction, and be developed in a higher degree, than if its cultivation be neglected till advanced years. 659. In the fulfilment of all the duties of the mind, the blood being required by the brain in large quantity and of a pure quality ; not only must attention be given to develop the mind by its own exercise, but to develop the powers of its organ, the brain, by muscular action, healthy, pure air and in large quantities taking wholesome food with a health, fully produced appetite, by the use of nature's beverage as a drink, great attention to cleanliness and activity of the skin, and an undeviating observance of the best habits in every respect. SECTION 2. The Mind. 660. The duty of the mind in the production of thoughts, emotions, and sensations, or the mode of fulfilling the duty, cannot be specified. Whether the nature of the mind is different in different individuals, or whether its apparent difference is owing entirely to the constitution and state of the brain, is disputed. That mental operntions depend a great deal upon the state of the brain, is conclusive ; but some suppose that certain duties of the mind are accomplished by the mind itself, without the employment of the brain. 661. Some think that the mind is a unit, others think that it may be considered as possessing faculties, one of which may be more efficient than the same faculty belonging to other minds. Some think also that exercise strengthens these faculties of the mind. Some think that the different faculties make use of different parts of the brain, and that of course there are as many divisions of the brain as there are faculties of SEC. 2.] THE MIND. 241 the mind. Some suppose that the faculties can be exercised separately, and thus are invigorated, while others may be enfeebled by want of ex- ercise. 662. But in practical treatment of the body, all these persons very fortunately perfectly agree ; and the rules laid down for the exercise of the mind, perfectly correspond with those by which exercise of the brain should be regulated. It is very happy for the physiologist, therefore, that it is not his duty to discuss the subjects of mental or moral philosophy, but that it is his privilege to leave those profound departments of know- ledge in the hands of those learned men who have shown their ability to handle them with the most flattering success.* . * There is one thing, however, in respect to which the physiologist and physician must be humored. They must be allowed to maintain that insanity is the result of disease, that though it may be caused by the mind, yet it never exists till disease has been produced ; and the indi- vidual exhibiting insanity should be considered as afflicted with disease, and looked upon with pity, not frowned upon by friends and neighbors as if he were laboring under some curse, nor should any unwillingness be felt by friends, or a person himself, to allow that insanity exists, if it really do not more, that is to say, than in allowing the existence of any disease. Those noble institutions erected by many of our States, usually afford the best aid in the restoration of the sick who exhibit insanity ; and it is well to take advantage of them before the disease has been long fixed, as the cure is at first easily effected in many cases, which, neglected in the outset from the wrong views of insanity that many en- tertain in not considering it a disease, never recover. 11 BOOK II. SECOND CLASS OF ORGANS. GENERAL OBSERVATIONS. 1. The organs described in the first book, require that four duties should be performed in respect to them. 2. 1st. They must be preserved of a proper temperature. For when the skin becomes cold, the sensations are evidently blunted, a person rendered irritable, &c. If the head be hot it aches, and thought is confused. 3. 2d. The various parts of the body, as they become unfit for use, must be cast out of .the system. This process is called excretion. For it has been shown that action of the brain, the muscles, and it is supposed of any part, is attended with a wearing out, so to speak, of portions of the part used. 4. 3d. The parts which have become unfit for use and are removed, must be replaced by new material fit for use. Doing this is called the process of nutrition. The substance with which it is done is called nutritive substance, nutri ? ment, &c. 5. 4th. During the early periods of life the various parts of tho body must increase in size ; accomplishing this, is also called the process of nutrition, and the substance with which it is done is called nutriment. 244 GENERAL OBSERVATIONS. 6. How the temperature of the body is preserved, will be understood by observing the habits of man and animals in different parts of the world. The first thing that strikes a person is, that nature has given man reason and ingenuity, by exercise of which he clothes himself, and protects himself and his domestic animals from the weather. 7. In respect to animals, it is observed that nature has given them instincts to seek refuge from the weather in burrows, in hollow trees, in nests or tenements which they build, or in the natural caves. 8. She has also given them a clothing, to some, of feathers ; to some of wool ; to some of hair ; to some of fur ; and her operations are so wonderful, that these coverings become thicker in the fall and remain so during the winter, but in the spring, the summer coat is regained and re- mains till fall. 9. To the swine, however, she has only given a thin coat of bristles, as an external coat. But directly within the skin is found a layer of fat, which is readily formed, and becomes very thick in the fall of the year. This, then, must be the protective coat of the swine. There are, there- fore, two kinds of protection furnished to animals, viz., an internal coat, and an external coat. 10. To most animals she has furnished both, in a greater or less de- gree ; to some but one. The hog can hardly be said to have any ex- ternal coat. Man, frequently compared to the swine, is similar in this respect, nature furnishing him with the internal coat only, which in case of infants is usually very abundant, and if not too abundant, is exceed- ingly favorable to their welfare, by preserving in their little bodies, with comparatively large surfaces, the small amount of heat produced therein. Here it may also be observed, that nature has given the young of ani- mals, which are lean, an instinct to come to the body of the parent for heat ; see the chicken " brooding " under the wings of the hen. 11. The whale has also a thick internal covering. The water in which the animal lives renders it impossible for him to be supplied with an external coat. Some other kinds of fishes have no such internal coat. Some have it. The reason for the difference will be found in this. It is necessary for the whale to be kept warmer than the fishes without the internal coat. They are warm enough if they are a little warmer than the water in which they live. Some are not any warmer than the surrounding water, and if the water be warmed, they will re- main cooler than the water. It is frequently observed, that placing a fish globe too near the fire kills the fish ; the reason being, that tha water is kept too warm for their health. But th whal, and all fish GENERAL OBSERVATIONS. 245 with the internal covering of fat, must be kept much warmer than the water in which they live. 12. It seems, therefore, that the covering of an animal is thick, corres- ponding with the importance that it should be kept warm. Therefore, animals clothed with feathers should be very warm. It will be found that the lark is the warmest blooded animal of any known. Its natural temperature is about 117 degrees. Therefore, the thick deposit of fat, in case of the child, shows that it is very important it be kept warm, and comparatively with after years, the importance of taking care that it be kept warm, is very great. In the first place, the organs of the infant are so little developed, it is doubtful whether it can perfectly perceive sensations; and indeed, it is doubtful if sensations are very perfectly produced. In the next place, if it perceive unpleasant sen- sations of chilliness or heat, it has not the power of telling its wants; it can only cry, which too frequently is misunderstood to signify a want of food. 13. Most animals have not only the external coat thickened in the fall ; but it is a thing of common note, that all animals fatten easily in the fall of the year. Man notices this in respect to himself. It may also be observed, that animals, including man, "grow thin" in the spring of the year, and remain so during the summer ; the reason of which is perfectly obvious; yet many would desire to preserve their " plump appearance " in summer as well as in winter, and think health must be failing, when they perceive their weight to lessen, and consider this one reason why they should have recourse to " spring medicines ;" all which ideas are evidently wrong. 14. In cold regions we should expect to find the internal and ex- ternal clothing of animals very thick and protective. The long shaggy fur, and thick coat of fat possessed by the polar bear, justifies our ex- pectations. 15. In warm regions, on the other hand, we would expect to find animals lean, and without external clothing. At first, the long furry coat of the tiger might disappoint our expectations, but one other con- sideration would satisfy our minds that the rule is of universal applica- tion, viz., the colder the weather, other things being equal, the more protective will be the external or internal clothing of any animal natu- rally exposed. 16. The clothing of man and animals is usually called protective against cold ; so, also, is the shelter provided for animals. In common conversation this is well enough ; but such language is not strictly correct, 246 GENERAL OBSERVATIONS. and it ia injurious, as it draws off the mind from seeing one important practical idea, viz., clothing and shelter protect the body by preventing heat from going out of it. There is no danger of cold coming in. Cold merely means, absence of heat, so when heat goes out of the body, the body, for want of the heat, is called cold. 17. If a person, when cold, retire to sleep in a cold chamber, he will wake in the morning not only warm himself, but he will find the clothing warm. He must, therefore, have produced heat within himself, tvhich the clothing, to a great degree, has prevented from passing off. If he load the bed with sufficient clothing, he will wake and find himself too warm for comfort ; he may be perspiring freely. This shows that heat is produced in his body, even after it is warm enough for comfort. It will now be seen that the quantity of clothing upon the bed, and which man or animals should wear, will not depend merely on the coldness of the weather, but also on the amount of heat produced. For it is evi- dent if a certain temperature is to be preserved, and there is only little heat produced in the body, that little must be husbanded very scrupu- lously. When, therefore, we see the thick coat of the tiger, an inhabi- tant of a warm climate, we can infer that in his body very little heat, indeed, is produced, which,must be very carefully preserved. 18. When we next inquire, by what means the heat is produced in the body, the attention will be directed to the fact, that man and all ani- mals eat more in the winter than in the summer ; much more in cold climates than in warm. Every one has noticed that the appetite dimin- ishes in the spring of the year ; and though many may think this owing to ill health, there is evidently a good reason why it should be so. It will also be noticed that the appetite is not as good in the warm days of winter, as in the cold. It will be noticed that the colder the weather is, the more do animals eat. It will be noticed that the more exposed to the cold a person is, the more does he eat j and that if he take a ride of a cold winter's day, it gives a keen appetite. It is evident, therefore, that the food we eat is the means of warming us, or has something to do with it. 19. It is also evident, that the better animals are protected by nature or by art, either in respect to shelter or clothing, external or internal, the less food will they require. The better stabled, the less will it cost to keep animals : a blanket upon a cow, will be as profitable as upon a horse. A fat animal, will eat less food than a lean one. An animal with a thick coat of hair, wool, or fur, will "winter" at less expense GENERAL OBSERVATIONS. 247 than otherwise. A swarm of bees will not eat so much of their honey if their hive be kept in a proper place, as they will if it be exposed. 20. But when we take another view of the tiger, it is found that though he eats plenty of food, his furry coat exhibits that only a little heat is produced in his system. It will then be inferred that the kind of food that an animal eats, has something to do with the warming of his body. If we notice, we shall see that the tiger lives upon lean meat ; and if the experiment be tried of throwing a piece of lean and fat meat into the cage of a tiger, he will be seen to carefully gnaw off the lean, and leave the fat. The polar bear, on the other hand, lives upon fat with delight ; for, though he be warmly clothed within and without, his native region is the birthplace of the iceberg, and he re- quires much food of a kind that will make him warm. 21. It will also be noticed, that man is inclined to live upon one kind of food in summer and another kind in winter. Buckwheat cakes, with an accompaniment of syrup and butter, are highly relished in win- ter, but set aside in warm weather. In cold climates man finds the animals which he uses for food, fat ; while in warm climates, they are lean : there also, fruits are more abundant, while in cold climates almost his only food consists of meat. The Esquimaux drinks the oil of the whale by the gallon.* 22. The squirrels also are plump and fat in the fall of the year, when they enter their holes ; so also are the bears, when they go into their winter dens but in the spring they are lean. That the fat is used on account of the cold weather, is evident from this ; that the colder the winter, the more lean are all such animals when spring comes. Indeed, if the winter be very cold and long, bears frequently come out from their dens in the mountains of Russia and Switzerland, and driven by neces- sity for food to keep themselves warm, they will attack even man whom they otherwise shun. Bees also keep themselves warm during winter, by the use of honey. Cows and other such animals when driven by hunger in cold weather, " browse " as the expression is that is, feed upon the tender buds of trees. These contain gum in abundance. We are told also, that travellers in Arabia supply their wants while passing from one village or city to another, by a small quantity of gum. Gum ia * This, when fresh, is much like lard. In the summers of the tem- perate zone, vegetables are abundant ; if the weather be hot, they will also be more watery ; while, if the weather be cold, vegetation is lest luxuriant and more solid. 248 GENERAL OBSERVATIONS. also frequently given to the sick, as a kind of food very easily digested and very wholesome. 23. The kind of food which many, indeed most animals are fattened upon, indicates that starch is well adapted as food to warm the system ; for the chief ingredient which renders grains, potatoes, &c., good to fat- ten animals, is the starch they contain. An experiment of throwing starch, fat, gum, sugar (for sugar may be taken to represent that class of food to which honey belongs), into the fire, will convince any one, that under certain circumstances they can produce much heat 24. But upon further inquiry it is ascertained, that though an animal be well-fed, he will not be kept warm if he be placed in a cold situation and compelled to breathe bad air ; or if a band be tied about his- chest, so that he does not receive a sufficient supply of air, even if it be good. This would signify that pure air, and a good supply of it, are essential to warmth of the body and thorough examination proves this ; for those who labor in close apartments, are very liable to complain of cold and be " pinched " with it, when they go out. In cold weather, also, fires will burn more briskly than in warm. The air is adapted, in cold weather, to the production of more heat than in summer. 25. It is also found, that there is great complaint of suffering among those who restrain the action of the chest by tight dresses, or whose lungs, on account of disease, cannot receive as much air as is necessary for warming the body. Those animals, also, which are most warm- blooded, receive the most air in proportion to their size. Birds receive a great deal of air ; for it not only passes into their lungs, but into their bones, and into various apartments of their bodies. The cold-blooded fishes are satisfied with what little air they obtain from the water ; but the warm-blooded whale is furnished with immense lungs, which he comes to the surface of the ocean to fill with the pure air. 26. The extremities of the body are of a lower natural temperature than the central parts -> the temperature rising as we pass from the sur- face of the body towards the heart, where it is found that all the blood in the body is continually flowing out to the lungs, from which it quickly returns a little warmer than it was. Again, when a person begins to take exercise, he begins to grow warmer, and at the same time he no- tices that the blood moves and he breathes more rapidly ; from which it follows that when he exercises, more air acts on the blood in a given length of time, than when he is quiet. When the ah- is blown against coals, or when a draught acts upon the fire, it burns more rapidly GENERAL OBSERVATIONS. 249 and causes more heat. It might be inferred that the greater the quantity of air acting on the blood in the lungs, the warmer would a person be. 27. Thus it may be considered as certain, that the heat of the body is produced by the food on the one hand, and by the air on the other. But in the next place, how shall it be distributed through the body? This could easily be accomplished by having a fluid continually moving through every part of the body, for if any part were warm the fluid would be- come warm, and if any part were cold the fluid would warm it. 28. But it is evident, that if the heat of the body should >e contin- ually produced, the body would grow too warm, and much harm would follow, as in case of fever. In this case it might be observed that the skin was dry, harsh, and hot, the brain delirious, &c. But as soon as a gentle perspiration breaks out, the skin becomes cool and flexible, the delirium subsides, and the doctor expresses hopes of his patient. In warm weather a person perspires freely, while in cold weather, perspi- ration ceases. An animal that sweats freely suffers but little from heat. The horse, intended by nature for active exercise and to produce much heat, sweats, and bears hard driving in summer weather while he sweats, but if the skin become dry, he will be injured except cooled by artificial means.* The ox is easily killed, " melted" as it is termed, by over-exercise on a hot day. That animal does not sweat except by its tongue, which is kept moisf and thrust from the mouth, as it will be by the horse if the case be extreme. 29. The dog is easily killed by over-exercise in hot weather, espe- cially if fed upon food that tends to produce heat and fat, while if he be fed upon the tiger's food and kept lean, there is no danger. The dog is remarkable for " lolling," as the term is, and also for panting, which is merely a fanning operation. The air which he draws into his mouth, does not pass deeply into his lungs so as to produce much heat, but is merely drawn in and thrown out, to assist in cooling him by carrying away the moisture more rapidly from the tongue. 30. The effect of the perspiration in cooling the body is evidently the same as the effect of the water thrown upon the floor in summer : the * If a horse driven upon the road on a hot day, be observed to be- come dry, which intense heat will frequently cause (it seeming to produce such a feverish state of the skin that it cannot sweat), it will greatly re- lieve the animal to dip some twigs with leaves upon them in water, and prinkle the animal pretty effectually. It cools him. n* 250 GENERAL OBSERVATIONS. water and the perspiration evaporate and produce coolness. In the Indies, before the introduction of ice, the people were in the habit of wrapping wet cloths around jugs filled with drink, and putting them in the sun, that the water might evaporate easily from the cloths and produce coolness of the drink. It is evident, then, that the perspiration is for the purpose of keeping the body properly cool. 31. But how shall the perspiration continue to ooze out of the body without drink be taken to supply it ? It will also be observed, that a person drinks more in warm weather than in cold ; those who work in warm exposures, for instance glass-blowers, perspire very much, and drink very freely. One office, therefore, of the drink, must be to cool the body, not merely by the coolness when swallowed, but by passing through the skin in the form of perspiration and evaporating from the body. 32. It might be asked, how shall the water drank through the mouth reach the skin ? But by passing into a set of vessels or tubes, which lead into every part of the body, it could be distributed to the skin and thrown out, as the system might require. 33. To preserve the temperature of the body, these several things then will be required : 1st. Food of a proper quality and in proper quan- tity. 2d. An apparatus to prepare the food to fulfil its purpose in respect to producing heat. 3d. Air of proper quality and in proper quantity. 4th. An apparatus in which it may be received and caused to fulfil its duties. 5th. Drink and an apparatus for its reception. 6th. An organ through which it may be perspired. 7th. A grand apparatus of circulation to serve the various purposes of carrying the food and air, if need be, to where they are needed to produce heat, to distribute the heat, and to dis- tribute the drink to the perspiring apparatus. The Nourishing of the Body. 34. This is necessary on account of the continual wear of the system, and in early life on account of the daily increase from infancy to man- hood in the size of the organs. The amount of nourishing to be done will therefore depend on the exercise of the various organs of the body, (for on their exercise depend the amount of their wear and decomposition) and on the rapidity with which the body is growing. 35. It will be noticed, that the more a person exercises, the more will he eat The laboring man has a heartier appetite than the professional GENERAL OBSERVATIONS. 251 man.* The animal that works hard has a keener appetite than the idle animal. When a child is growing rapidly it requires much food and has a hearty appetite. 36. It is therefore evident that the food affords nourishment, and if we examine the tiger again, we shall see that he is very strong, carrying off an ox with ease, it is said. If lean meat be little adapted to keep him warm, it is adapted to make him strong. The farmer finds, also, that buttermilk is adapted to his use, in the midst of the summer heats. 37. If we examine how this is, we shall immediately conclude that the food which is to nourish the body must contain the ingredients of which the body is composed. That milk -contains these ingredients is certai.i, for we see all parts of an animal to be formed of milk. A calf, for instance, eating nothing but milk, grows large and strong. The milk must contain all the substances necessary to form the bones, the nerves, the brain, and every part of the animal. So a chicken comes out of the shell, its bones, its flesh, and all its parts being formed from the contents of the shell. Whence eggs must be very nourishing.t 38. It may be proper in this place to mention, in further explanation of this matter, that the whole world is composed of some fifty-six differ- ent substances', some of which exist in very small quantities. Water is composed of two of these substances, called oxygen and hydrogen. One other substance called carbon, added to oxygen and hydrogen, forms fat. The proportions of the three substances being varied a little, sugar ia formed ; being varied again, starch or gum will be formed. Thus all the various things with which we are acquainted, are made up of some few things imited in certain proportions. In the human body, thirteen differ- ent substances are always found. So many are necessary. Some of them * This tends to show that fatigue after the use of the muscles is owing to the state of the muscles, and not merely to the state of the nervous system. For without doubt the professional man uses the nervous system more in thinking, than the laboring man in the same length of time ; but the laboring man requires more food to replace the large amount of his muscles which has become unfit for use during his labors. t It seems a fortunate thing that eggs are plenty in the commence ment of summer, that very time when food is required which shall be nourishing and not warming ; and that the egg does not contain much substance adapted to the latter purpose is evident, from its being necessa- ry for the hen to keep the eggs warm with the heat of her own body. The chick in the egg is not able to keep itself warm, and after it is hatched, it is necessary for some time that it obtain a great part of its heat from an external source. 252 GENERAL OBSERVATIONS. are in very small quantities, but they are always present, and the body cannot exist without every one of the thirteen, composing it. There are usually nineteen different substances, but of the last six sometimes one and sometimes another is wanting. If, therefore, a person growing should receive but twelve out of the thirteen necessary substances, he could not live long. Hence nourishment must contain the necessary constituents of the body not that every portion of nourishment must contain each of the thirteen, for as only -a small quantity of some of the thirteen is required, if they are used occasionally it is sufficient. More upon this point hereafter. 39. The food for nourishing the body appears so unlike, in many in- stances, the various parts it is to nourish", it is evident it must undergo some process of preparation. But in the next place it is evident it must be carried to every part of the body where it will be required. To ac- complish this, nothing seems more desirable than to have it become part of the fluid which is moving through every portion of the body. Nothing therefore is required for distributing it, in addition to the apparatus neces- sary for preserving the temperature of the body. The Process of Excretion. 40. This is rendered necessary by the constant action which is taking place in the various organs, on account of which parts of them become unfit for use, or are decomposed, as the expression is. It is easy to see that three things may be true of the substance decomposed in the organs : 1st. The whole or part of it may be of use in nourishing, that is, supply- ing the wants of some other part of the body. 2d. It may be of use in the production of heat ; and the increased heat attendant upon taking exercise of any part, points very strongly that way. 3d. A part or all of it must be cast out of the body as unfit to fulfil any duty therein, hav- ing performed the office for which it was designed. And sooner or later this is what must take place, in order that we may account for the large amount of food which persons every day use. 41. The first thing necessary, however, in regard to this substance thus become unfit for use, is, that it be removed from the organs in which it is unfitted any longer to serve a useful purpose ; for if it remain, it will only clog their action and produce unpleasant sensations. This can be accomplished in the easiest manner, by having the substance pass into the vessels before shown to be required, and become a part of the fluid that they contain. GENERAL OBSERVATIONS. 253 42. The second thing neceasary is, to have this substance subjected to such an action, that if it contain any substance profitable in any part of the body, or adapted to produce heat, it may be retained, and the re- mainder cast out of the system. 43. In the duty of excretion, therefore, one or more organs will be required, through which the fluid containing the decomposed substance may pass, and be acted upon as the case may require. The Nervous System of Organic Life. 44. But when there is much exercise, much substance will be decom- posed ; there will then be required increased action of the excreting ap- paratus, the nourishing process must take place more rapidly, a greater appetite will be necessary, and the circulation of the fluid containing the decomposed substance and the nutriment must be hurried. So also if a person be exposed to great heat or cold, the action of the respective organs having duties to perform in reference thereto, must be increased or diminished. 45. To accomplish what will be necessary in these respects, a ner- vous system will be required, which shall bind, so to speak, all parts into one. This nervous system must consist of one or more centres, upon which the states of any and all the organs of the body shall act, and from which effects shall be produced on any or all parts of the body, as the necessity of the case shall require. 46. From these various organs of the second class there must also be communication with the mind, upon which at times they can produce effects, that its assistance may be given in the fulfilment of duties which could not otherwise be accomplished. But that every act of these organs should be brought before the mind would not be at all proper, for as the processes referred to in the previous paragraphs of this book are constantly taking place, the attention of the mind would be so occupied that it could not attend to its legitimate business. It is like the arrangements in a grand manufacturing establishment ; the mind has a general oversight, and constantly exerts an unseen influence, but is only called on to give particular attention here or there on especial occasions ; but is left to do the " out-door business of the concern " the thinking, the " buying and selling," &c. The divisions which will be made in the second book we now evident. CHAPTER L THE DIGESTIVE OEGANS. 47. These receive the food and drink, and through these the drink without preparation, and the food after being subjected to certain pro- cesses, pass into the bloodvessels. The action of the digestive organs upon the drink is, therefore, very simple ; but the food is submitted to three different operations before passing into the bloodvessels. The first takes place in the mouth, the second in the stomach, the third in the second stomach. SECTION 1. The Mouth. 48. This may be divided into the front mouth and the back mouth or upper part of the throat, the part commenc- ing at the back part of the tongue and leading above into the nose, and below into the gullet, meat-pipe, swallow or oesophagus, and into the windpipe ; it is technically called the pharynx;. 49. The front mouth' every person understands, it being so readily presented to view. In this the food is subjected merely to a mechanical process. It is ground, masticated or chewed, and mixed with the saliva or spittle. The same process might be accomplished in a mortar if a proper portion of food and saliva were ground therein. It is a very important process ; for it is found that if the food be swallowed in haste, being but half masticated, dyspepsia soon follows ; it is also found very difficult to fatten animals which have lost their teeth, without very soft food be given to them. That it is important SEC. 1.] THE MOUTH. 255 saliva should be mixed Math food, is evident from the provisions of nature. The young of all animals which yield milk, obtain their food by drawing or sucking it into their mouth, by which means a large quantity of saliva is mingled with the food. Chewing the food has been so arranged by nature as to cause saliva to flow into the mouth in large quantities. It has also been found in certain diseases, where the saliva has not been formed, or if formed, lost by flowing through an opening in the cheek, that digestion of the food in the stomach did not take place well. Dr. Beaumont found also, that if food, unmixed with saliva, were placed in the stomach, it did not digest well. Persons who drink milk, often notice that it does not " set well upon the stomach." All nations, so far as I can learn, with milk eat bread or some like substance, which, by requiring to be chewed, may supply the proper quantity of saliva ; they having learned by experience that this is better. It is therefore to be inferred, and held as a golden rule, that a child should never be fed with a spoon, but caused to draw the food into its mouth by sucking, according to the intentions of nature. 50. The mouth may, therefore, be considered under four divisions : the teeth, the skin lining the mouth, the salivary apparatus, the muscles which move the jaws and bring the food under the teeth, and which, after the food is prepared, pass it into the back mouth. A. The Teeth. 51. These are firmly placed in the jaw by the parts called the roots or fangs. Another portion of the tooth is covered by the fleshy gum, the remaining portion projecting into the mouth, is called the crown of the tooth. 52. The outside of the crown is a hard, thin shell, called the enamel, covering the part within, as the thimble covers the end of the finger. The inner part of the tooth and the fangs, except a central canal, (Fig. 86), is composed, in fact, of two kinds of substance, one called the cortical and the other the ivory of the tooth; but usually the distinction is not noticed, and the whole is called the ivory. It is not as hard as the enamel. 256 THE DIGESTIVE ORGANS. Fig. 86. [CHAP, x. Fig. 86. A, Perpendicular section of a molar, magnified four diameters. 1, Ivory with wavy tubes, the openings of which are seen at 2, the canal for pulp, central nerve, &c. 3, Is called the cortical portion, and forms the outside of the fang. 4, Enamel worn away at the summit of the tooth. B, A greatly magnified view of a section across the tubes. 53. The enamel is destitute of nerves, and of course never causes any sensations. Jn the ivory of the tooth, there must be a great multitude of nerves ; it is so very sensitive at times. Whether these are branches of the nerves found in the central canal of the tooth, and called by way of distinction, the nerve of the tooth, or are branches of nerves entering the tooth from the outside, is uncertain. 54. There is a delicate skin covering the fang and neck SEC. l.J THE MOUTH. 257 of the tooth. This, when diseased, causes very acute pain if touched ever so gently. 55. The use of the enamel is to preserve the internal part of the tooth from exposure, for as soon as the air, the fluids of the mouth, or the food or drink, act on the inner portion of the tooth, they cause it to decay. The enamel has, therefore, been made hard that it may not be easily worn away, but on this account it is easily cracked by hot or cold articles of food or drink ; for as a cold tumbler will crack if put in hot water, because the heat swells the outside of the tumbler before it has time to act on the inside, and as a warm - tumbler cracks when put in cold water, so will high and low temperatures act on the outside of the tooth before they do on the inside. If the teeth be examined, in many persons the enamel will be found full of cracks, looking like a "glaze- cracked plate," or other articles. 56. Through these cracks substances find their way to the part within, and before a person is aware that decay is begun, the tooth is a " mere shell," viz , nothing but the enamel is left. Very hot or cold drinks, iced waters, especially when preceded by a cup of hot tea or coffee, iced food, iced creams, iced desserts, are not only unnatural, but must be very injurious to the teeth. Eating snow, sucking icicles, &c., should be avoided. 57. The hardness of the enamel is not only observed to differ in different persons, but in the different teeth of the same person. The color of the enamel is different; it crumbles very easily in case of some of the teeth, slivers off in case of others, while in other teeth of the same person, the enamel is solid, good colored, and enduring. It will also be noticed, that teeth grow in pairs, and that the appear- ance of the teeth in the same pairs is similar. If one tooth of the pair decay, the other will soon follow, showing that the same causes which operate on one injuriously, act in the same manner upon the other ; that, therefore, as the teeth were made at the same time, so they were made alike. 58. There are evidently two things which would affect injuriously the formation of teeth ; disease of the apparatus forming the teeth, and a want of proper material from which to form them. 258 THE DIGESTIVE ORGANS. [CHAP. I. Disease of the apparatus forming the tooth is found to exhibit itself most usually in the form of the tooth, which will have a "ridgy" or " wavy" that is, an uneven surface, while a want of proper material would be naturally exhibited in the too great softness of the tooth, or its tendency to crumble, &c. That such a state would frequently be produced is only what, would be expected by the educated person, who sees the mother setting aside the perfect milk, containing all the ingre- dients to form the teeth and every other part in a proper manner, and feeding her child upon " pap" and like substance, in the composition of which, some of the most important ingredients of the teeth are entirely wanting. 59. But though the enamel was intended by nature to be hard, it yet was intended in man to be used on food much softer than itself, for it is to last an entire life-time. The teeth of the squirrel are continually growing at the roots, he may therefore gnaw the hard shell of the nut without danger. But the boy should be warned against cracking nuts between his teeth, or biting pins, or breaking hard substances with the teeth, or prying upon the teeth with any thing hard, like a knife. The girl and lady who care either for the beauty or health, arising from preserved teeth, should be careful not to bite hooks or eyes, or bite off threads with the teeth, as there is danger, especially if a tooth happen to be of a crumbly character, as is frequently the case with the teeth of ladies. 60. As the enamel of the teeth is so liable to become cracked, it is exceedingly important that the teeth be kept clean : for bits of food, &c., being allowed to remain about the tooth and decay, will produce acids, which " soaking," through the cracks of the enamel, will exert an injurious influence upon the ivory of the teeth. Many recommend to wash the teeth after each repast, but they should be thoroughly cleansed twice per day, on rising in the morning and retiring at night, the mouth being not only rinsed out, but the teeth brushed above and below as well within as without, and the brush should be carried up and down as well as across the teeth. 61. If the teeth are not frequently brushed, not only do substances from the food remain about the teeth, but a substance from the fluids of the rnouth is apt to deposit and harden on the teeth. It is called tartar, and seems almost as hard as bone in some cases. It is of a brown or black color, and besides giving a very bad appearance to the teeth, tends to work down beneath the gum and loosen the teeth in their sockets. SEC. 1.] THE MOUTH. 259 producing also a very undesirable red, swollen and spongy appearance of the gums. 62. If the tartar have formed unawares to a person, he should have it immediately removed. If it have caused the gums to be diseased, they should be freely washed with cold water and gently brushed with a soft brush.* If a tooth have begun to decay, it should be attended to at once. The decayed portion must be entirely removed and the place filled with gold, if possible ; but if the tooth be " too far gone," the author can testify from ten years' experience with one tooth, to the wisdom of having the cavity filled with a composition made by the dentists. If the tooth can neither be filled nor pulled, a little pulverized charcoal held in the mouth several times per day, will somewhat correct the bad breath arising from decayed teeth. 63. If the gums remain spongy for several weeks after all the tartar has been removed from them, and they have been repeatedly washed with water, the attention of the physician had better- be invited, as dis- ease of the stomach and its connections is very frequently indicated by the appearance of the gums. 64. Tobacco is sometimes said to prevent the teeth from aching and decaying. It cannot do the last, but on the other hand, dentists testify that men using tobacco are more troubled with decayed teeth than those who do not use it. It can do the first, by producing such a state of the nerves that they have not the power to produce sensations, but the tooth continues to decay if the nerve do not give warning of it. Therefore the tobacco is doubly injurious, it increases the decay of the teeth, while at the same time it does not allow its ravages to be made known to the mind. 65. The teeth are thirty-two in the adult ; in front, four above and four below are called incisors, or cutting teeth. Back of these, one above and below on each side are called cuspid, (spear or one-pointed,) canine or dog teeth. Back of these upon either side, two above and below, are called bicus- pid, from having two points. Three on each side, above and below, are called the grinders, from their use ; and one of these * Indeed a softish rather than a hard brush is preferable for any 260 THE DIGESTIVE ORGANS. [CHAP. i. upon each side above and below, farthest back, from not ap- pearing till between the years of 15 and 25, is called the wisdom tooth (Fig. 87). Fig. 87. Fig. 87. 1, 2, Incisors.-3, Cuspid.-4, 5, Bicuspid.-6, 7, Molars.-8, Wisdom. 66. These take the -place of the first set, though larger and more numerous, the jaw having " grown." The first set usually disappears be- fore the appearance of the second. But sometimes a tooth of the first set is allowed to retain its place, and the tooth of the second set is obliged to appear on one side or the other of its true place, disfiguring a person or injuring his speech. A first tooth should always be " pulled" in sea- son. The position which the first teeth occupy is not of consequence, nor is the^ position of the second teeth, provided they be upon the ground which they ought to occupy. That is, if they be turned to one side or the other, it is not of much moment, for very frequently the jaw has not en- larged sufficiently to allow all the second teeth to make their appearance in due season and in an even manner ; but as the jaw enlarges, they will become even and properly adjusted, or if they do not, and there be room for the adjustment, the dentist can easily by springs, &c., move the teeth till they are right. If the jaw do not become large enough for the teeth, one tooth can be drawn, and this will give room for the rest. SEC. 1.] THE MOUTH. 261 It is now seen why the wisdom teeth appear so late ; there is not room for them in the mouth till maturer years. 67. The second set of teeth begins to form a long time before the first ones " become loose ;" in the earliest infancy their formation is progressing. Hence the material for the second set of teeth must be furnished to the babe even, that their foundation may be good B. The Lining of the Mouth. 68. This is very much like the external covering of the body, and by some is considered a continuation of it. It is composed of two layers ; the external is called epithelium, and corresponds to the external layer of the skin (the cuticle); but is much thinner and more delicate. In the lining of the mouth there is no coloring matter. Hence the blood of the skin gives it a red appearance, and the bright- ness or paleness of the red, indicates the health of the system in many cases, particularly the health of the lining of the stomach and bowels, as the same lining of the mouth continues on through the throat, to line the stomach, second stomach, &c. 69. The second layer of the lining of the mouth is called the chorion. It is the essential part, the external layer being merely a protection. In the second layer the bloodvessels and nerves are found. Near to its surface the bloodvessels form a network of superlative delicacy and beauty. Some parts of its surface are formed, as may be seen on the tongue, into prominences called papillae. In these some, perhaps all, the nerves of the lining commence. These nerves must be threefold, as heretofore seen ; by one kind a person tastes ; by another he feels : and there must be another kind to connect this part with the nervous system spoken of in the general obser- vations, and called the organic system, its nerves being called organic nerves. 70. In this lining there is found a multitude of little 262 THE DIGESTIVE ORGANS. [CHAP. I. pouches or sacs, called cryptse. They are like those of the external skin in their appearance, but in them is formed a kind of glutinous substance called mucus ; it can be seen by scraping the tongue with a spoon or knife. It is formed from the blood. Its character of course will depend upon the quality and quantity of the blood and the character of the apparatus fonning it, which is itself dependent also upon the quality and quantity of the blood, and the or- ganic nervous system before mentioned. This system, as heretofore proved, influences the circulation of the blood through each and all paits. Thus, looking in the mouth to learn the state of other parts of the body, is not useless ; for the color of the mouth will indicate the activity of the circulation of the blood, especially in the lining of the stomach, dtc., and the vigor of the nervous system, at least in respect to these |arts. The character of the mucus will be another indication of the character of the blood and the nervous system, especially as it respects the stomach, second stomach, &c. And it has been found by various means, that when the lining of the mouth is " sloughed," the stomach is in a simi- lar condition ; when the throat has a certain red appearance, the second stomach is in a similar state, &c. 71. The use of this mucus seems to be to preserve the lining of the mouth in a good condition, and perhaps it is of use by being mingled with the food ; remaining in the mouth, however, during the night, it fre- quently produces a " bad taste." To remove it by rinsing the mouth with cold water upon first rising, is a good habit. This habit also tends to prevent the deposit of tartar upon the teeth, and awaken an active circulation of the blood in the lining of the mouth, thus giving a good color to the gums. If at the same time the throat be well gargled, it will tend to prevent swellings of the throat and soreness of the back mouth and throat, and the "hanging down" of the palate so frequently complained of. C. Salivary Apparatus. 72. This consists of six glands, three upon either side of the mouth, and tubes leading from the mouth to them. But firstly, it will be best to describe the general principle upon which all glands are formed, since though the various glands of the body differ in particular arrangement, the same general plan is observed in all. SEC. 1.] THE MOUTH. 263 73. Glands are for the purpose of presenting a great extent of surface in a small space. The simplest form of a gland is that of a crypta, seen in Fig. 76. A more compound, but yet very simple gland, is seen in Fig. 88 ; while a compound gland with all its essentials is presented in Fig. 89. By this it is seen, that a gland is nothing more than a tube with a great many branches, about which there is an infinite num- ber of cryptae, and thus an immense extent of surface ob- tained. Sometimes the tubes have no cryptae, but are very long and coiled around so as to be packed in small com- pass ; sometimes other ways of gaining the same end are used. Fig. 88. Fig. 88.-a, One of the simplest glands of an animal. 6, Tube opening into the mouth. 74. The next essential thing is a great multitude of blood- vessels about the sides of these tubes in the glands, and a circulation of a great quantity of blood from which the fluid of the gland may be formed. In the next place, there must be nerves connecting between the gland and the mind, for when the salivary glands are affected with the mumps, they ache, and also when the mind thinks of any delicious food, the saliva is rapidly formed. There must also be a connec- 264 THE DIGESTIVE ORGANS. [CHAP. I. Fig. 89. Fig. 89. Part of a compound gland, with tubes and cryptae laid open. The bteck lines represent the larger bloodvessels of the part. The causes and appearance of the lobules are also seen. tion between the glands and the organic nervous system, be- cause the saliva being formed from blood and formed very freely, when we are eating, and at other times, in accordance with the wants of the body, there must be some cause for the increased circulation of blood required under such circum- stances. 75. 'The tube and cryptse or a gland, whatever form they may have, are in fact nothing more than the lining or skin of the part into which the tube opens, slightly and but slightly changed in its texture, and ex- isting in that form for the purpose of presenting much surface in a small space ; for instance, the skin lining the mouth is formed into a tube commencing at the centre of the cheek, at a slightly roughish place easily felt with the tongue. It leads to the back part of the jaw, being readily felt like a cord beneath the skin upon the outside of the cheek. At the back and side of the jaw, just before the ear, it forms branches. These ubdivide, and about the twigs, cryptse are formed. Between these is SEC. 1.] THE MOUTH. 265 found a kind of soft cellular flesh, called the parenchymatous substance of the gland. Enclosing the whole a delicate skin grows, and the appa- ratus is formed, and upon receiving the blood and nervous influence be- gins to act. 76. Why, when the glands are so similar in their structure, the dif- ferent kinds form such dissimilar fluids, is at present inexplicable. It may be owing to some difference which has not been perceived in their structure ; it may be owing to the differences excited by ?he nervous sys- tem upon the different glands, or both causes may combine to produce the effects seen. It would seem to depend much upon the nervous sys- tem, since when disease prevents one part from fulfilling its duty, it will sometimes in a measurably good degree, be performed by one which in health performs an office somewhat similar, perhaps, but yet different. 77. The small tubes and cryptae belonging to any one branch of the grand tube form what is called a lobe, and smaller branches of the larger form lobules, &c. The uneven appearance of the surface of many glands, is owing to the lobules, as in case of the salivary glands. 78. The salivary gland just "described, and its fellow upon the other side, are called the parotid glands. They are about the size of a dove's egg, or a little larger. Underneath the under-javv, about two-thirds of the way from the centre of the chin to the lower back corner or angle of the jaw, and, as it were, between the jaw and tongue, a gland about the size of a robin's egg is found ; it is called the submaxillary (under-javv) gland. Tubes from these open in the sides of the bottom of the front part of the mouth, near by the " string " which ties down the tongue. 79. A short distance in front of these, and rather more under the tongue, is found a gland, not as large as a sparrow's egg, with several short tubes opening directly above and in front of the gland. This, with its fellow, is called a sub- lingual (under-tongue) gland. .80 These different glands seem to differ somewhat in their structure and in the influences acting on them. The under-tongue gland is seldom diseased, or its disease attracts little attention. The under-jaw gland it 12 266 THE DIGESTIVE ORGANS. [CHAP. 1. liable to several diseases ; to the " mumps," more frequently than the sublingual, but less frequently than the parotid, and to enlargement and hardening very frequently. This seems to be, sometimes at least, the consequence of using hard water, or is aggravated thereby. The pro- gress of disease is usually so slow, that attention is not called to the im- portance of the complaint, till it is too late for the surgeon to give advice with the best effect. When this gland begins to enlarge, it may be safely judged that something serious is affecting the system and that very judicious advice should be taken and followed for a long while. The most common disease of the parotid is the " mumps," a disease some- times affecting one parotid, sometimes the other, sometimess both ; sometimes one parotid and one submaxillary on the same side, or on the other, or all the glands at once, or several, or all of them in succcession. Sometimes one at one time, and another at another. But seldom if ever does the disease exist twice in the same gland. This is a matter of great surprise, for the structure, duty and mode of accomplishing it, are the same to all appearance, before as after the disease, and yet the gland is so altered in regard to its structure or the nervous influences it receives, that it cannot be affected by the same causes that produced the " mumps." The same is true of other diseases, viz. whooping cough, small-pox, measles, &c. ; though sometimes the system is not so changed by these diseases that it cannot be affected to a degree, a second, or even a third time, though always lightly. An important question in regard to these diseases and the changes they produce is, are they natural, and do the changes they produce in the system fit it to contend with other causes of disease to better advantage ? It would seem from what evidence can be gained, that those who have all those diseases, as they are called, that affect the system but once, in their childhood, and are well taken care of, so that they entirely recover, are longer lived and hardier than others. All such diseases seem to be more fatal when taken in advanced life. The mortality formerly attendant upon small-pox, can well be accounted for by the treatment pursued, as at the present day few if any die. In olden times a great-grandfather of the writer being taken with the small- pox in the course of his practice, according to the approved method of that day, without a reason to sustain it, immediately shut himself in a close room, kindled a fire to keep the apartment very warm, and of course in a few days died. People now ventilate their rooms very perfectly, eat but little food, keep the bowels gently open, remain quiet, end if confined to bed, change and air the clothing and bed itself very frequently ; keep themselves cool and calm as possible, nvoid ail causes SEC. 1.] x,- THE MOUTH. 287 of chills, such as draughts of air, &c. ; drink no stimulants, but as much cool (not ice) water as the thirst craves ; gargling the throat with the same frequently if desirable. This course, with slight variation, and the administration of some medicines as the physician may think a peculiar case requires being carefully followed, a person recovers in a short time, not of small-pox merely, but of scarlet fever,* measles, mumps, &c. To return to these last, many, indeed most persons when affected by the mumps, immediately cover the face with a handkerchief,