It is a state of passive congestion, and often exists in the mucous membrane of the stomach, after attacks of inflammation or acute irritation, and embarrasses its digestive operations. In all the extensive. irritations of the alimentary canal, especially when attended with fever, having a paroxysmal character, the great portal system of the abdomen becomes loaded with blood, and congestion of its radical vessels ensues. The functions of the viscera are then disordered, the secretions are defective, and indigestion, costiveness, and their attendant nervous affections, are the necessary consequences of this condition.

constituting gastrelgia. At other times, the secreted fluids of the stomach are morbidly acid.

The stomach appears, in other cases, to be partially paralysed, and the peristaltic movements necessary for the admixture of the food, and the gastric fluids, and the continuous passage of the chyme into the duodenum, are suspended. At the same time, considerable quantities of flatus collect in and distend the stomach, preventing its action on the food. Mechanical manipulation of the abdomen, and particularly of the epigastrium, after a meal, becomes a substitute for the natural motion of the stomach, expels the wind, and facilitates digestion, that would otherwise be laborious and painful.

Dyspepsia, or indigestion, from this analysis of its modes of production, is seen not to be a disease of uniform character, and depending on an identical state of the digestive organs. It is attached, as a symptom, rather, to a variety of conditions, each of

A third state of the stomach, a cause of dyspeptic symptoms, is precisely the reverse of the preceding. Asthenia, or diminution of vitality and actions below he healthy degree, occasionally takes possession of the stomach. Its circulation is then deficient, its secreted fluids are defective in quantity or quality, its sensibility is impaired, and digestion is imper-which requires to be managed in its appropriate mode. fect. It is not probable that gastric asthenia is ever primitive. It succeeds to previous irritation, and is often occasioned by irritation in other organs. -The preceding form a first class of dyspeptic diseases, which, depending entirely on the stomach, may be termed gastric dyspepsia. They present characters totally different, and require a very opposite treatment. This class embraces three species.

A second class of dyspeptic diseases is connected with the duodenum and its functions. This viscus, similarly constituted to the stomach, is subject to the same morbid alterations. Its mucous membrane is the seat of irritation, in its various grades, and productive of its usual consequences-augmented irritability, sensibility, perversion of secretions, vitiation of structure, and disorder of function. Duodenic irritation most commonly accompanies gastric irritation, and the symptoms of the two are blended together. It exists, however, in many instances, independently, and then manifests particular symptoms, which are often termed dyspepsia. It is, more especially, the chronic irritation of the duodenum, that passes for dyspepsia.

It is not probable that congestion, or asthenia, ever affect the duodenum exclusively to the detriment of its function. When these states prevail, it is in conjunction with similar conditions of the whole digestive apparatus. At least, we have no knowledge of these states limited to the duodenum.

It is not possible that it can be remedied by any one general mode of treatment, or by any set of specific remedies. The most common causes of dyspepsia are excesses of various kinds, especially in the quantity of food eaten. Most individuals, in this country, err in this respect. Meat at three meals, daily, can be borne only by the most robust frames, and by hard labourers. Persons of a sedentary life require less nutriment; the economy makes less demand on the stomach for supplies; and if it be compelled then to labour, it is at its own loss. Exercise, or the expenditure of the nutritive elements by the economy, and the quantity of food to be digested, must be proportioned to each other, for the preservation of health and the due vigour of digestion.

Good cookery, by rendering food more digestible, is one preservative against dyspepsia. The food, by being rendered tender and pulpy, is reduced to chyme in a shorter period, with a smaller expenditure of the secreted fluids, and less excitement of the stomach, than when it is not properly concocted. The art of long and healthful living will depend on a perfect system of cooking, and a rational mode of eating.

The powers of the stomach differ, in individuals, as much as the force of their muscles; and each one must adopt a mode of nutrition, both as to quantity and quality of food, suitable to the wants of his economy and the digestive capacity of his stomach. The quality of food is a frequent cause of dyspepsia. A third class of dyspeptic diseases depend on the Tough and badly dressed meats, and crude vegetables, Arvous organs, which furnish nerves to the digestive are among the prominent causes of this affliction, as viscera. The ganglionic system of nerves, distributed are also hot bread and cakes, heavy and fresh bread, on each side of the spine, from the head to the pelvis, and the immoderate use of hot fluids for breakfast. transmits nerves to all the organs connected with the In enumerating the more common causes of dyspeptic auritive function. The stomach, especially, is largely symptoms, we ought not to omit the frequent exasupplied from the solar plexus, and it receives, like- cerbations of the malevolent passions, as anger, wise, numerous nervous filaments from the pneumo-hatred, envy, jealousy, and, what is not often susgastric, placing it in connection with the functions of pected, excessive indulgence and abuses of the venerelation. real propensity Another fruitful source of the diThe offices of the ganglionic system are not ascer-gestive disorders is found in the employment of emetained with precision. It is, however, well determined, that diseases of the ganglions disorder the functions of the viscera to which they transmit nerves. Hence arises an order of dyspeptic symptoms, independent of any immediate affection of the stomach, but occasioned by disease in the great solar, or other neighbouring plexus. The disorders of the digestive functions, from this cause, are various. The sensibility of the stomach is sometimes greatly increased,

DYSPEPSY. See preceding article.
DYSPHONIA; & difficulty of speaking.
DYSPNOEA; a difficulty of breathing, usually called
asthma, which see.

ceeding, or middle portion of the organ. Beyond, or on the opposite side of this membrane, we meet with a small cavity, hollowed out in bone, which has been termed the barrel of the tympanum. Of the several

EAGLE, in astronomy; a constellation of the nor-openings into it, there is one more particularly dethern hemisphere, having its right wing contiguous to the equinoctial.

EAGLE, in architecture, is a figure of that bird anciently used as an attribute of Jupiter in the capitals and friezes of the columns of temples consecrated to that god.

membrane, which, in conjunction with it, shuts up the entrance to a still more deepened cavity, called the labyrinth of the ear. This last hollow, excavated as it were in the solid bone, consists of a middle portion of irregular figure, and of different channels, which proceed from it in various directions, and, finally, return, with the exception of one only, to the same chamber. All these passages are lined by a membrane, on which the sentient extremity of the auditory nerve is expanded in different shapes; from these it is collected into one trunk, and goes on to join a particular part of the brain, and thus completes the communication between the external agent and the sensorium.

manding our attention here. It is the internal aperture of a tube, the other extremity of which opens at the posterior part of the nose, behind and above the palate. By means of this communication, the external air is admitted into the chamber, and equipoises the weight of the atmosphere on the other side of the EAR. The mechanism of hearing is simple in its membrane. Across the cavity there is extended, arrangement, and beautifully adapted to the pur- though by no means in a straight line, a series of poses of life. Fitted in an eminent degree to the little bones, the exterior one of which is attached to purposes it is designed to execute, the ear offers an the membrane we have just mentioned, the most ininviting subject to such as are disposed to inves-ternal of the set being firmly connected with another tigate the minute mechanism of an organ, which contributes remarkably to some of our most exquisite and refined enjoyments. Whoever has witnessed and attentively observed the distressing effects arising from a loss, or diminution of its sensibility, will readily acknowledge that such deprivation throws us at a distance from our fellow-creatures, and, in the present state of society, renders us more solitary beings than the loss of sight itself. Though the rapid glance of the eye, the immense distance to which it enables us to carry our perceptions, and the extended circle it embraces, have given rise to some of our most pleasurable and refined sensations; though it has brought us acquainted with objects which seemed ever placed far beyond our reach; still, the more humble sense which we are now considering, the more confined dominion of the ear, has contributed most effi- The meatus externus is seen detached from the ciently to the every-day happiness of life. It en- bone at b. The oblique direction of its internal end ables us to hold communication with our fellow-is shown at de, the membrana tympani stretched on creatures; to improve and exalt our understandings by the mutual interchange of ideas; and thus to increase the circle, not only of our physical, but of our moral relations. The charms of eloquence, the pleasure resulting from the concord of sweet sounds, inexplicable perhaps as it remains, are other sources of intellectual enjoyment, which contribute to place this sense among the most delightful as well as the VH A, the curved labyrinth n p, the cochlea; n, most important we possess. Whatever, therefore, its beginning, its termination at p; this is followed by explaining its structure, or examining its func-by the vestibule; V, the bony case of the anterior, or tions, can lead us to improve its natural, or restore smaller of the semicircular canals; H, the posterior, its disordered sensibility, cannot be a subject of or largest semicircular canal; A, the outer, or smalltrivial moment. Our more immediate object is to est canal. consider the human ear, observing only, that the The external part of the ear is differently formed structure of the organ, being suited to one great in different animals; and admirably suited to their end, is in all cases fundamentally the same; its various situations and habits. In man, it is close to different forms and varieties depending on the pe- the head, but so formed as to collect the various culiar economy and abode of each individual crea-pulses with great accuracy; in other animals it is

ture.

The anatomy of the external ear may, however, be best understood by referring to the illustrative engraving, figure 1, plate of the Ear and Eye.

its bony ring, and bulging inwards.

f g h, the malleus: f, the handle or process attached to the membrana tympani; g, the long process; h, the head.

ik, the incus: i, the short leg or process; k, the long process.

m, the stapes.

more simple, where less accuracy is required, but it is in general much larger, having the appearance of an oblong funnel; and this gives them a greater delicacy of hearing, which was necessary for them.

The organ of hearing, in its simplest form, consists of the expansion of a nerve, gifted with peculiar sensitive qualities, over the surface of a delicate membrane. In man and the more perfect animals, Dr. Savart considers the external ear as an imthere is an additional apparatus connected with this, portant auxiliary to the tympanum, capable also of the design of which is supposed to be that of col-entering into vibration by communication, and having lecting and modifying those pulses of sound which are finally to be impressed on the nervous pulp. In man this apparatus consists of a piece of cartilage, scated externally to the head, which contracts into a funnel leading to the internal parts. The bottom of this tube is truncated obliquely, and its aperture closed by a firm membrane stretched across it, which separates this external part of the ear from the suc

for its principal function to present always to the air (by the various directions and inclinations of its surfaces to one another) a certain number of parts, upon which the undulations of the air shall fall perpendicularly. The little muscles which are inserted in it, he thinks, contribute by their action to increas its tension, and render it more elastic.

Within the cavity of the tympanum are placed for

small bones, which facilitate the hearing: the first is the malleus, or hammer, so called from its shape: the upper part of its round head rests upon the concavity of the tympanum, from whence the handle is extended down, along the membrane of the tympanum. This bone has several muscles, which move it in different directions, and cause it to stretch, or brace the membrana tympani, when we wish to hear with accuracy.

Connected with the malleus is another small bone called the incus, or anvil, which is connected with another called the stapes, or stirrup, from its shape. These two bones are connected by a small ovalshaped bone called os orbiculare, placed between them the whole forming a little chain of bones.

The stapes, or stirrup, has its end of an oval form, which fits a small hole called fenestra ovalis, in that part of the ear called the labyrinth, or innermost chamber of the ear.

The labyrinth consists of three parts: first, the vestibule, which is a round cavity in a hard part of the os petrosum; secondly, the semicircular canals, so called from their shape, which, however, is not exactly semicircular; thirdly, the cochlea, which is a beautifully convoluted canal, like the shell of a snail. This part has a round cavity called fenestra rotunda, which is a vered with a thin elastic membrane, and looks into the tympanum.

ment, the opposite end being grasped between the teeth.

We have now to notice the labours of M. Savart, who has paid considerable attention to the anatomy and uses of the tympanum.

By a series of experiments, which, fortunately for the cause of humanity, have not been verified in this country, he ascertained that the membrane of the tympanum exactly resembled in its effects the vibrations of a drum, or plate. (See ACOUSTICS.)

That the membrane of the tympanum may justly be compared with an ordinary membrane acted upon by communicated vibrations. This was proved, by submitting the real ear to the following experiment: -after having removed the temporal bone, he made with the saw a section parallel to the external surface of the membrane, so as to lay it open, and to be enabled to cover it with sand: the sand was observed to be slightly put in motion, when a vibrating plate was brought parallel with the membrane, and very near its surface; but it was impossible, from its limited extent, and particularly on account of its form, to prove the existence of any distinct nodal line. The existence of the motions was rendered much more evident, by substituting for the human tympanum the drum of a calf's ear.

He observed, also, that when the internal muscle of the malleous acted, and, consequently, that when the The vestible, semicircular canals, and cochlea, the membrane was tightened, it was more difficult to prowhole of which is called the labyrinth, form one duce evident motions in the grains of sand; so that cavity, which is filled with a very limpid fluid re- the uses of this little muscle appear, like those of the sembling water, and the whole lined with a fine deli-iris, to consist in preserving the organ from imprescate membrane, upon which the auditory nerve is expanded, like the retina upon the vitreous humour of the eye. This beautiful apparatus was lately discovered by an Italian physician, Scarpa. The auditory nerve is a portion of the seventh pair, which is called the portio mollis, or soft portion.

There is one part of the ear still to be described; namely, the Eustachian tube, so called from Eustachius, the anatomist, who first described it.

This tube opens by a wide elliptical aperture into the tympanum behind the membrane; the other end, which gradually grows wider, opens into the cavity of the mouth. By this canal the inspired air enters the tympanum to be changed and renewed; it likewise serves some important purpose in hearing, with the nature of which we are yet unacquainted. It is certain that we can hear through this passage, for if a watch be put into the mouth, and the ears stopped, its ticking may be distinctly heard; and in several instances of deafness this tube has been found completely blocked up. Though the use of the Eustachian tube has been doubted, as conveying sound by the mouth, yet a simple experiment will convince us, that it has some influence in this respect; thus, if a deaf person is to converse with another, and a wire or other medium of communication is made to pass to the mouth of each, by placing its extremity between the teeth, the deaf person will hear the conversation better than without this assistance, which certainly proves, that part of the vibrations of sound is carried along the wire into the mouth, and applied to the ear through the Eustachian tube in the throat; while a part also reaches the ear externally, and is collected in the auricle in the usual manner. have scen people quite deaf to outward sounds, enjoy a concert on the piano-forte, by means of a long narrow b2: of wood placed on the instru

sions too intense, which, under certain circumstances, it might otherwise receive.

The membrane of the tympanum may be considered as a body put in motion by the air, and performing always a number of vibrations equal to that of the body which has produced the oscillations in the air; but, besides, as the direction of the molecular motions of the membranes, and generally of all bodies, continually vary with the direction of the vibrations of the body directly put in motion, it may be presumed that it is by this means that we are able to judge of the direction of the sound, when it arrives without having been reflected.

The following experiment shows, that if the auditory passage, the concha, and the bell of the ear, serve to render the aerial oscillations more intense, they also are of use to reciprocate the vibrations of the air, and to transmit them to the membrane of the tympanum, with the same degree of force, whatever may be their direction. A very wide conical tube was formed of thin pasteboard, and to its smaller end a thin and tended membrane was firmly fastened: on bringing in a parallel direction to the upper and external surface of this membrane, when covered with sand, a vibrating plate, the grains of sand were but slightly put in motion; but on placing the plate near the large orifice of the tube, they became strongly agitated. Another conical tube was opposed by its summit to the preceding, but without touching the membrane, and afterwards the plate was put in vibration at the larger orifice of each of the tubes : it was observed that the communicated motions were incomparably more energetic when the aerial unduWelations arrived through the tube which was in immediate contact with the membrane, than when they arrived through that which did not touch it.

Another experiment shows the important influence