5«v* tV.:\rOiA ivr. •C* »:,; ' '*'<-'': '"■ " /.'•''. '.: „ •'''••' ", '_ r ' $:$;£'::• /".' ^x's^i;-.,:..; .^'^feb :. ■ i ; ..''',v; :. ■'*'.!••; Fig. /. Pll Fig. 3. Fiff. 4 .v V *s l Tig 1. PI 'L Fo9. 2 PI 3. Fi9.2. Fig 3 PI 4r Fi9. / Fuf 4. v Fig J -_^J^ POPULAR AMTOMY AND PHYSIOLOGY, ADAPTED TO THE USE OF STUDENTS AND GENERAL READERS. T. S. LAMBERT, M. D., Prof of Anatomy and Physiology in Pittsfield (Young Ladies') Institute, Brooklyn (Greenlcaf's Young Ladies') Institute ; Author of Notes to Erasmus Wilson on the Skin, Popular Treatise on Bathing, etc. oitfi'L. WITH ONE HUNDRED AND FIFFY WOOD-CUT AND BEAUTIFUL LITHOGRAPHIC DESCRIPTIVE ILLUSTRATIONS. NEW-YORK : LEAVITT AND COMPANY 191 BROADWAY. 1850. 'ANNFX 1850 h'l*i hier .lay.; The 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 its 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 fjuv jjjj 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. 1. 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, 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). 6, The superior, e, The external, and c, the inferior recti (straight) muscles, a, The inferior oblique. Fig. 64.—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 comea, 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. Fig. 66. 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 Iachry- 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 thing 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 conscienceless 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, [CHAP. II, 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. fc. 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 portion cut out that other parts may be shown. 13, The inferior rectus. 14, The edge of the sclerotic, 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. 163 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. H. 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 finger 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-work, 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 in 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 i«» 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 either side. Fig. 68. Fig, 68.—The artery and its coarser branches found at the back part of the eye 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. le"? 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 Buch 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 part 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 nerves, 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, PI. 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. pjcr. 69.—A front view of the iris, showing the circular fibres about Ihe pupil. Fi". 70.—A back view of the iris, showing the radiated fibres. The use of the iris is to admit a greater or less 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, PI. 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 light 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 b>ht 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 lens must depend, of course, upon the 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, which 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; this 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 Fig. 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 1 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 persona 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 nerve ; 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, the foewa would be formed too far from the lens; and they SEC. 3.] ORGANS OF SENSE. 173 Fig. 72. Fis. 72.—B, C, concavo-concave lens. Light in passing through it is observed to be 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 a, is bent to a, while if the object producing light be moved to d, the light coming from a more distant point is bsnt 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. t 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 that the light from a distant object passing through the centre of the lens produces a focus at the same nerve ; for in this case objects in the same direction from the eye would have their foci upon the same nerve at the same time, and could not be distinguished. No theory yet suggested is valid. 480. There is, however, no doubt of the fact, that the eye possesses the power of adaptation, for people have it and lose it, as in case of those who become near-sighted, or long-sighted. This last is many times produced from not exerting the power. The sailor who is in the habit of using his eyes to look at distant objects, loses to a degree the power of examining near objects; while the student who occupies the most of his SEC. 3.] ORGANS OF SENSE. 175 time in reading, loses the power of seeing distinctly distant objects. This loss is to be prevented by seasonable and frequent attempts to look at distant objects ; a persevering course of the same kind will enable a person to recover the power in many instances, though it has been lost for years. Except by sailors, it seldom happens that the power of seeing objects near at hand is lost until advanced age. The cause for its loss then, is not satisfactorily determined. It has been by many sup- posed to be owing to a flattening of the cornea, but there is a strong ob- jection to this. True, the cornea is flattened in old people, but it is much fuller, as a usual thing, in children than in middle age ; yet more middle-aged people than children are near-sighted; the power possessed at birth, being lost for want of exercise. How in extreme old age the power of seeing with the acuteness of youth is sometimes regained, can- not, with present knowledge, be explained. 481. The eye serves another very important purpose. By means of the eye we know the direction of an object from us. To explain how this is done many theories have been advanced. I shall adopt that advanced by Volkman, for I cannot perceive any objec- tion to it, though I have looked upon it with much caution, as Muller thinks it cannot be sustained. If the reader will turn to Fig. 59, he will see, that the central lines drawn from A to d, and from B to a, pass through the same point at o. If there were a hundred objects with their light falling upon different points of the retina, a line drawn from the objects to the point acted upon, would pass through this point o. This may be called, therefore, the stationary point, for though the object and the point of the retina acted on may change, that point (o) remains the same. The precise position of this point de- pends upon the form of the lens. In case of the eye, it has been found by very accurate measurements, to be just back of the crystalline lens. 482. There is therefore always a point at which all the straight lines, drawn from objects to their foci, will cross. 483. If, therefore, a line be drawn from the focus through this point and extended, it will reach the object from which the light causing the focus has come. 484. Volkman therefore believes, and I think he is right, that we are so made or constituted, as to believe that an ob- 176 ORGANS OF SENSATION OR FEELING. [CHAP. II. ject which causes light to act on a part of the retina, is in a straight line extended from that point through the stationary point. In the same manner, when we feel a sensation which has been pro- duced through any nerve, we believe the object producing the sensation acts on the part where that nerve commences. 485. Another question is, How do we know the distances from us of different objects, and the distance of these from each other ? These questions have been answered in various ways. 486. In the first place, we learn by experience the dis- tance of objects. For instance, we leam that an object is twenty steps distant, by the fact that it requires the contraction and relaxation of certain muscles twenty times. This we know by sensation, as heretofore shown. If it require forty contractions, &c, of the muscles, to reach an object, we consider that it is twice as far distant as the first. Now when we look at the first object, a certain adaptation of the eye is necessary, that it may be seen distinctly; producing this adaptation produces a certain sensation. When we look at the second object, another adaptation of the eye is necessary, and this produces another sensation. Remembering these sensations, we shall think, when these are produced again, that the objects are at the same proportionate distance as before. Much experience, and often produced sensations, make us remember them, and we are therefore able to form good judgments of the distance of objects. A near object acts on a greater number of nerves than the same object at a distance. Thus we judge of the size of objects, first, by judging of their distance, and then of the number of nerves upon which they act. Such is my belief. 487. Thus, if all the nerves throughout the body were alike, the eye would be necessary, that we may know the direction of objects from us, and the distance and size of objects, when not in contact with us. Nei- ther can the color of objects, by which they are distinguished from each other while at a distance, be known, without the eye. To see, therefore, the eye is necessary. It has been made a source of exceedingly pleasurable sensations. These are usually produced by the combined action of certain colors. Hence it is very important, in selecting the colors of a dress, that the colors be such, that if they act at the same time upon the same nerve, and produce compound sensations, these may be agreeable. SEC. 3.] ORGANS OF SENSE. 177 488. There are in this connection two things worthy of particular notice. Certain objects transmit only certain kinds of light, and when these are reflected to the eye, mingled with other light, they produce a very unpleasant effect, while other objects transmit those kinds of light that, reflected from various objects, produce pleasant sensations, and render the objects attractive. I shall be understood by an illustration. Green paper curtains transmit mostly green light, or more properly speaking, yellow and blue. If this green light be reflected from a lady's cheek, it produces a very unpleasant effect. The person will look ghastly and unwell. 489. In the next place, the light reflected from objects a lady wears as dress, will be more or less mingled with the light from the com- plexion, and thus compound sensations will be produced, which will be pleasant or not, according to the dress. An example will illustrate. If a lady wear pea-green trimming, it reflects green light of course, and some of it being reflected to the cheek, will be reflected from the cheek with other light to the eye of another person, and an unpleasant effect will many times be produced. 490. These principles are also to be kept in mind, viz., that colors are judged by comparison ; and still more important, that when sensa- tions of any strong kind are produced for any length of time, an unpleas- ant sensation is the result, however pleasing at first. Thus we become tired of " decided colors." It is in better taste, therefore, to dress in subdued colors. In regard to the point first mentioned, however, it is to be kept in mind that it is not the comparative color of an object, but the positive sensation it produces, which gives the pleasure. Thus a lady may wear a bit of court-plaster, that her complexion may appear white by contrast, but the positive sensation her complexion produces does not depend at all, or at most but very little, on the court-plaster. That affects merely what is said of her, not the sensation she can pro- duce. Nature has never intended man or woman should pass for any thing other than what he or she is. 491. If it be asked how these principles can be made use of, the answer is, that a person must learn what compound sensations are agreeable, and surround herself with such articles of dress and furniture as will be pleasing by the effects they will produce ; for we always love those in whose society we find agreeable sensations produced, of sight or sound, or any other sense. 492. It will be proper in conclusion, to speak briefly of images, opti- cal instruments—such as telescopes, microscopes, &c. All mention of 178 ORGANS OF SENSATION OR FEELING. [CHAP. II. them has been purposely avoided, because much confusion is produced in the mind by the introduction of the indefinite term images, in lan- guage generally used where these subjects are treated upon, and so far as I can judge, the mind of the learner finds it difficult to conceive cf an image of a dart in the eye when one is represented there in a draw- ing. There is nothing like the dart in the eye. The dart is that which acts upon the light, while the image is the light itself. To illustrate. If light be coming from a thousand different points of an object, it will arrive in the eye at a thousand different points or foci. These bear the same relative distance from each other as the points of the object from which the light has come, as seen in Lith. PI. 5, Fig. 2. That is, if it be as great a distance from the first point of an object to the second, as it is from the second to the third, it will be as far from the focus of the first point to the focus of the second, as it is from the focus of the second point to the focus of the third point. The distance between the points of the object may be twelve inches, and the distance between the foci but half of an inch; it matters not, if the ratio of the distance between the foci be similar to the ratio of the distance between the points from whence come the foci causing light. These foci are called images of the points of an object from which the light has come, and the foci formed by light from all the points of an object are called the image of the object. Again, when light passes from an object to a mirror, it will be reflected entire. That is to say, whatever kind of light passed to the mirror, will be reflected from it, for the mirror does not change the nature of the light, but only the direction. If the mirror have a " true " surface, the light, as in Fig. 74, will be in the same relations after being reflected as before. It will, of course, make no difference how many times a single particle of red light, for instance, is bent in its course to the eye; acting by itself, it can produce but one effect on the eye, under any circumstances, and that will be the sensation of red. Its being bent only affects our belief of the direction whence it comes, which is, that it has come in a straight line, drawn from the point of the nerve, where the impression was produced through the " stationary " point; so, also, if the light of many different kinds, from many different points, produce many different foci, it will make no difference if all the light be bent, provided the light from all the objects be bent at the same time and in the same manner, by which the same relative distances will exist between the foci as existed between the objects from which the light came. An image is said to be produced at the mirror, but there is no more an image there than at any other point between the object and mirror, or SEC. 3.] ORGANS OF SENSE. 179 between the mirror and eye. For at any such point, the light exists in the same relations as when it left the object. And wherever the light from an object exists in the same relations as when it left the object, there is an image in an optical sense. It is not known to be there, till the eye be placed there, or an object which shall reflect the light to the eye without altering its relations, any more than the place of the focus of the light from a candle, passing through a sun-glass, is known till the eye be placed where it is, or an object be so placed as to bend the light to the eye ; for the eye must either go to the focus or the focus must be brought to the eye that it may produce a sensation, without which its existence is unknown. But it will be said, perhaps, that the image appears to exist behind the mirror. Very well. It is readily seen that the light reflected from the mirror should appear to be produced in that direction, for it is so with all reflecting objects in nature. They reflect the light of the sun, for instance, yet the mind thinks nothing about the sun, and till taught, knows nothing where the light was produced, but believes it came from, and was produced, by the object that last reflected it. It may have been reflected a thousand times before, or not once ; the mind is not influenced thereby. Fig. 74. Fig. 74.—Represents light passing from the points A, B, to the mirror m, from which it is reflected or turned backward more or less, according as it strikes perpendicularly upon the mirror or in a slanting direction. 493. In the next place I have endeavored to show, that from experi- ence the mind learns, or is constituted so as to believe, that when one adaptation of the eye produces a sensation, the object seen is distant; 180 ORGANS OF SENSATION OR FEELING. [CHAP. II. and when another adaptation of the eye produces another sensation, the object is near. I have endeavored to show, that the reason why an adaptation of the eye was necessary, was, because the light from a dis- tant object falls less obliquely, or slanting, upon the cornea, as seen in Fig. 73, than the light from a near object; hence, though in fact bent less than the light from a near object, it is not necessary it should be, and yet it will be brought to a focus, nearer to the lens than the light from a near object. Hence the adaptation of the eye will be required, not abso- lutely according to the distance of the object, but according to whether the light fall perpendicularly, or obliquely, on the surface of the cornea. If the object be near, and the fight by glasses can be made to fall quite perpendicularly upon the cornea, the same adaptation of the eye will be required to cause the light to bend to a focus at the nerve, as if the light came perpendicularly upon the cornea from a distant object. It is seen by Fig. 74, that light coming from any point of an object after being re- flected, passes in the same manner as before, viz., in a diverging man- ner ; and of course, when it falls upon the eye, has the same obliquity to the surface of the eye, as if it had passed through the same distance without being reflected ; and of course, the same adaptation of the eye is required, that the focus may be at the nerve. Consequently, the light seems to come, as it does, from the direction of the mirror ; but from a much greater distance, and hence seems to be behind the mirror. An image then—in an optical sense—is not a picture, not a representation, not an outline, but is an arrangement of light which has come from an object; not the object, nor the shadow of an object, nor the painting of an object: all these things will cause light to produce the same effects as an image would; indeed, will cause light to become an image— optically speaking. 494. It is desirable many times to obtain more light from any given object than will fall upon the cornea, and enter the pupil. In a dark room, there may be light enough coming from the objects to produce on the nerves slight sensations, but so slight, the objects cannot be seen distinctly. Two ways may now be taken, to make the object more dis- tinct ; either admit light to the room, or gather more of the light coming from an object, and cause it to enter the pupil. This last can be done by means of a large lens, as seen in Fig. 57. Without this, the light is so feeble that only six rays of light, for example, can enter an opening the size of the pupil; but one hundred rays fall upon a large lens, which will bo bend them that all the hundred can enter the pupil, and act on the end of the same nerve, as seen in Fig. 57, that six only acted upoq SEC. 3.] ORGANS OF SENSE. 181 before—the sensation becomes much more intense of course. This is the grand principle upon which a telescope or microscope is constructed. It will be seen, however, that another glass or lens is required ; as the light which has passed through the large lens, called an object-glass, is so bent that if it fall on the cornea before it reach the focus, it will be too perpendicular to the surface of the cornea, as seen in Fig. 57, sup- posing the cornea should be placed at 2. If the light, after it has passed the focus, fall on the cornea, it will be too oblique to be bent by the eye in such a manner that its focus may be at the retina. Such evils are corrected by a convex-glass, placed beyond the focus; the light in passing through this is bent to a degree, and the eye can accomplish the rest (Fig. 75). Other glasses are added, to obtain minor benefits, the nature of which may be better learned elsewhere. In case of a microscope and magnifying-glass, much the same principles operate. It is desirable to have a great deal of light from a small object enter the pupil. If an object be held very near a lens, a great deal of light from a few points will fall upon it, and fall very obliquely—hence it will be very much bent; but if the distance of the object be right, not so much as to pass to a focus, but to go to the eye in parallel lines—as in Fig. 57. Suppose m to be the object, and the light to pass from it through the lens. If the object be too far from the lens, the light will be bent so as to cross; if the object be too near the lens, the fight will not ■ be bent enough to form parallel rays—and in either case the eye could not cause the light passing from the lens into it, to form a focus at the retina. The distance of the object from the lens, will of course depend upon the convexity of the lens. In this case, represented by Fig. 58, some of the light falling upon the lens, does not enter the eye. But if the lens be very convex and the object brought very near the lens, a great deal of the light passing from any point of an object, must fall upon the lens, in the first place ; and by the convexity of the lens, it will be so bent as to produce a focus. In this case, however, there must be another glass between the object-lens and the eye, for the same reason there must be in case of the telescope, viz., to bend the light in such a way, that in passing through the eye, the bending powers of the eye may bring the focus upon the retina. By the application of principles, previously laid down, it is easily seen why an object viewed through a telescope, should appear so near; and why an object seen through a microscope, should appear so large. Reflecting telescopes, camera obscuras, and the like, are made with only a variation of the application of the principles mentioned. The grand principle being, to cause the light from an object to bend in 182 ORGANS OF SENSATION OR FEELING. [CHAP. II. such a manner that a large amount of light may so fall upon the cornea, that the refracting apparatus of the eye may cause it to act on a single nerve and produce a distinct impression, which will cause a distinct sen- sation. Fig. 75. F. The Sense of Hearing. 495. The ear is the organ of this sense. By means of the ear, distant objects cause sensations. For if the ear be perfectly closed, sound is not caused by surrounding objects. By experiment it has been found, that if a bell be shaken in a glass from which the air has been removed, sound is not caused by the bell, but the instant the air is admitted the usual ringing is heard. It follows therefore, that, 496. Surrounding objects act upon the air, and cause the air to produce effects upon the ear. These effects are called impressions, and acting through the nerve of hearing and the brain, they cause sensations. 497. Four things are necessary that sound may be pro- duced. 1. An object to act upon the air. 2. The air to be acted on by the object, and then to act on the ear. 3. The ear, including all its connectives of nerve, brain, &c. 4. The mind. 498. The sensation produced or the quality of sound will depend, therefore, on the nature of the object, the character of the air, the nature and condition of the ear and its connectives, and the mind. 499. So far as we can learn, the nature of objects is always the same under similar circumstances. It is exceedingly different in case of dif- ferent objects, or the same objects under dissimilar circumstances. Al- SEC. 3.] ORGANS OF SENSE. 183 most every object in nature has a voice, distinguishing it from every other object, even of its own kind, in every other respect. There are millions of the human family, more numerous still are the beasts of the field and of the forest, besides almost innumerable birds and a tenfold number of insects ; but the blind man distinguishes the voice he has ever heard ; each sheep knows the bleating of her own lamb, and every bird the call of its own mate. It would be as difficult to find two objects producing precisely similar sounds, as for the child to find two similar blades of ribbon-grass, which every one has probably tried in vain. If the hand be placed upon a ringing bell, a jarring feeling will be pro- duced. This is owing to the motions of the particles of the bell, for though it seems so solid and thick, its substance is thrown into very rapid but not very extensive motions. If a tuning-fork be struck and brought near the eye, its rapid motions will be perceived. If the eye be directed to the strings of the piano or violin when played, or if the hand be laid upon them, their rapid motions will be at once perceived. If a tumbler be struck, a similar effect will be produced. 500. Vibrations is the name given to the motions of ob- jects when they are acting to produce sound. 501. If a tumbler containing water be struck, the water will be thrown into waves by the action of the vibrations of the tumbler upon it. If air instead of water were in the tumbler, the vibrations of the tumbler would throw the air into waves similar to the waves of the water. In the same manner the strings of the violin, the guitar, the piano, the head of a drum, &c, produce waves in the air in contact with them. When a cannon is fired, a heavy bell rung, or the deep tones of an organ played, the waves are so powerful as to jar the body in a very perceptible man- ner, to rattle the windows, or in case of the cannon, to break the glass. If the fingers be brought near the lips of a person while speaking, the waves produced by the voice will be noticed; hence, 502. All sound-producing objects, by vibrating, act upon the air and throw it into waves. 503. The peculiar character of the waves will depend upon the vibrations producing them, and the state of the air in which they are produced. 504. If a stone be dropped into water, waves will be noticed to flow out in a circular direction from the point acted upon. It will also be ob- served, that the waves grow smaller the greater the distance from where 184 ORGANS OF SENSATION OR FEELING. [CHAP. II. they commenced, until at a certain distance the water is undisturbed. If the water be calm the waves will flow in a circular manner, but if the water be running in any direction, the waves will extend to a greater distance in that direction, and the waves instead of being circular, will be more or less oblong. It is the same with the air, except that the waves of air are spherical; they pass off in all directions, growing less and less, and extending farthest in any direction with a current of air than against it; thus, 505. The air-waves produced by the vibrations of sound- producing objects, act through the ear upon nerves and cause impressions. The nearer the object producing the sound, all other things being simi- lar, the more powerful the impression. If the wind be blowing towards the ear from the sound-producing object, a more powerful impression is produced than if the wind be blowing from the ear towards the object; hence, 506. The more powerful the wave of air, all other things being equal, the more powerful the impression. 507. We learn also, that, other things being similar, the more powerful the impression, the nearer is the object pro- ducing it. 508. If a stone be dropped in the water near the perpendicular face of a rock or aught else in the water, the waves will be seen to strike against the rock, and then be apparently sent back, or reflected, as the expression is ; and as they go backward they grow smaller and smaller, to the same degree precisely as if the rock had not been there, and the waves had gone on in a straight line; that is to say, if the stone were dropped into the water three feet from the rock, and caused waves to strike against the rock and flow back, when they had gone back one foot from the rock, they would 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 long dis- 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 others, it is thought of much importance. 513. F^rom 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*s commencement, and by what is called ear-wax. This is found in follicles or cryptae, 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 bf cotton, chewed paper, or the like, when the oil and any collections 18G 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 of the cells is not known. They are supposed in some way to facilitate th* power of hearing. At the lower part, the drum of the ear terminates in a small tube, called the Eustachian tube, which leads down into 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. 187 Fig. 76. 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 crypts, 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, b, 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. /, is a muscle, the use of which is not well determined. C. may be taken to repre- sent the labyrinth filled 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 surface of the sac, as seen at the extremities of the lines with which t 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 the-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 (coiVit) bones are seen with a portion removed. The line A, m, extends to the opening of the Eustachian 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 membrane. By this means, air of course would be admitted to the drum of the ear, 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 bones 190 ORGANS OF SENSATION OR FEELING. [CHAP. II. Fig. 78. 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 (stirrup). Fig. 79. Fig. 79.—Represents a section of the bone containing the drum of the ear in which the bones arc seen. stretching across to membrane 2. Each movement of the first membrane will, therefore, act upon membrane 2. 524. It is, however, certain that persons 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 surface 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. [CHAP. II. Fig. 80. Fig. 80.— The labyrinth; V, ventricle ; O, foramen ovale; R, foramen rotundum; A, a, ampullae ; x, 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 y, 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. In 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.] ORGANS OF SENSE. Fig. 81. 193 Fi<, 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; d, the anvil; e, the round bone connecting the anvil with the stirrup ; g, the semicircular canals ; n, the cochlea; 2, 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 proper 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. Kit be either removed or 9 194 ORGANS OF SENSATION OR FEELING. [CHAP. II. 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 had, 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 unpardonably 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 his 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 soli- tude." * Not quite correct, for the sense of hearing is at times " hushed Jrj 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 is 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 196 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 act 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. lit 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 threugh the pit of the stomach, their fingers' ends, the tap 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. by 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 ol the class is able to produce any sensation that any other nerve of 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 distase, 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 produced, 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 SEiNSATION OR KEELING. [CHAP. II. 549. Various kinds of food, and indeed, the whole manner of living, will either exalt or depress the 6tate 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 through 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 pass across 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 effects 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. 1 2 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 the nerves, are easily recognized. 9* 202 ORGANS OF SENSATION OR FEELING. [CHAP. II. 553, 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 BRAIN 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., inabil- * 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 state 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 right 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' 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 samev comparative judgment formed, if the disease be such that no sensations are caused by certain parts of the body; the cause of the paralysis mu6t be looked for at such part where it will include all the nerves from the paralyzed part. 565. There are two exceptions to the proposition of paragraph 5S1: 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, such 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 fight; 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 singular that " flower makers" should combine flowers and colors as nature never does, taking pains to avoid a perfect model, and always with a bad effect. 214 ORGANS 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 caases 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 1 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 6tates 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, and 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 FEELING. [CHAP. II. sensations; and also as the 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. 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 senses 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 morphine 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 Bymptoms 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 tlie 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 eqnal 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. Aid 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 bv 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 tins 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 tune. ' SEC. 7.] CONCLUDING REMARKS. 221 to the requirements made upon them, as it is a umversal 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 III. ORGANS 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 speak, 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 Bpeaking). 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 1 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 there 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 good 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 or 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 it3 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. These 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 which 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; 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. b. 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. b. 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 the 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 the changes in the brain assist in perfecting the muscles. 228 ORGANS WITH WHICH TO THINK. [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-perlect 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, so 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 m 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 SEC. 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. 6. 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 be 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. 230 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, warming 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 and 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. those means which will draw the blood from the brain into other parts ot 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 haa 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 eave 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 vvas 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 with 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 sight, 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 c/ 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." 646. 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 BRAIN. 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 stale of the brain be produced by disease, or the action of medi- cine, the same feelings might be experienced. Hence we see that some diseases produce sensations as if emotions of the happiest character ex- isted. 651. b. 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 alone 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 Btate 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 despondmg 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. 111. 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 in 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 denied 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 operations 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. GENEEAL 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 the 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 the water is kept too warm for their health. But the whale, 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 is 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, which 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; 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, an 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 is * 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 less 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 air 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 moist 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 hi 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 sprinkle the animal pretty effectually. It cools him. 11* 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 certain, 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 is 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 united 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 necessary 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 are now evident. CHAPTER I. 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 l.—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 with 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. [CHAP. I. Fig. 86. 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. In 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. 1.] 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, 9 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 mouth 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 gums. 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 tQ 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 uf 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 forming 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 parts. 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, &c, and the vigor of the nervous system, at least in respect to these parts. 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 cryptse, and thus an immense extent of surface ob- tained. Sometimes the tubes have no cryptse, 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 ^pbout 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 crypta? laid open. The black 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 crypta? of 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 subdivide, and about the twigs, cryptae 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 /nay be owing to some difference which has not been perceived in their structure; it may be owing to the differences excited by the 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 cryptse 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-jaw, 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-jaw) 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 is 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, and if confined to bed, change and air the clothing and bed itself very frequently ; keep themselves cool and calm as possible, avoid all causes SEC. 1.] THE MOUTH.* 267 of chills, such as draughts of air,