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- II.


THERE is at times a solemn gloom,
Ere yet the lovely Spring assume
Sole empire, with the lingering cold,
Content divided sway to hold;
A sort of interreign, which throws
On all around a dull repose,
Dull, not unpleasing; when the rest
Nor rain, nor snow, nor winds molest;
Nor aught by listening ear is heard
Save first-fruit notes of vernal bird,
Alone, or with responsive call,
Or sound of tinkling waterfall.
Yet is no radiant brightness seen
To pierce the clouds opposing skreen
Or hazy vapour; and illume

The thickness of that solemn gloom.

Such is the garb, his natal morn
Oft times by February worn:
And such the garment that arrays
Full often his succeeding days.—MANT'S Months.

Is the "dull, not unpleasing" weather, which frequently prevails at the commencement of the present month, so truly described in the preceding lines, the agriculturist is busily employed in that which he justly considers as the most important of all rural occupations, i.e., ploughing. On the way in which this is performed depends the ease and success of all succeeding operations on the same soil; therefore he is naturally anxious to have it performed in the best and most efficient manner. The plough being a fundamental implement of agriculture, is common to all ages and countries where the cultivation of the soil has formed part of the occupation of the people; hence we find that, in its simplest form, it is almost everywhere the same. The ploughs of the Greeks and Romans were nearly, if not exactly the same as those which afterwards came into use throughout Europe. These remained without alteration until about the sixteenth century, when they received some improvement in their form from the Dutch and Flemish. During the seventeenth and eighteenth centuries the plough underwent great improvement in England, and especially in Scotland; and at the present time there is a great variety of excellent forms of this implement; of which the best for general purposes is the Scotch plough, or, as it is called in Scotland, the improved Scotch plough. Ploughs are either with or without wheels. Wheel-ploughs work with greater steadiness, and less care on the part of the manager than swing-ploughs, but the latter are lighter of draught. It is considered that a district ploughed with wheel-ploughs shows the greatest neatness of work; but that in one where the improved form of swing-plough is generally adopted, the ploughmen are superior workmen, and the work is better done, and with less expense of labour. Ploughmen should, if possible, be yearly servants, residing on the farm, and attached by interest and duty to their master. The way in which labouring men are treated in Scotland appears to us so well worthy of attention, as conducing to the welfare of both master and servant, that we cannot forbear describing it.

In the best cultivated districts of that country, proper houses are built near every farmstead, for the residence of the farm-servants, which gives them an opportunity of settling in life, and greatly tends to promote their future welfare. The farmer has thus also his people within reach at all times. The married servants receive the greater part of their wages in the produce of the soil, which gives them an interest in the prosperity of the concern in which they are employed, and to a certain degree obliges them to eat and drink comfortably; while young men often deny themselves proper food that they may have the more to spend in drinking and in clothes; and thus they are deficient in strength and activity. The habits of sobriety and economy so conspicuous among the

farm-servants of Scotland, are found to prevail especially in districts subject to the above management. Another most important feature in this system is, that almost every married man has a cow kept for him all the year round by the farmer. The prospect of enjoying this advantage has an excellent effect upon the morals of young unmarried servants, who generally make it a point to lay up as much of their yearly wages as will be sufficient to buy a cow, and furniture for a house when they enter into the married state. They have also several other perquisites, such as a piece of ground for potatoes and flax, (about one-eighth of an acre,) liberty to keep a pig, half a dozen. hens, and bees; their fuel is carried home to them; they receive a small allowance in money per journey when sent from home with corn, or for coals or lime; and, during harvest, they are maintained by the farmer that they may always be at hand. There are nowhere to be met with more active, respectable, and conscientious servants than those who are kept according to this system, and there is hardly such a thing known as one of them requiring relief from the public.

But we return to the operations of the present month, of which ploughing, though the most important, is not the all prevailing one. The able and experienced ploughman is, nevertheless, a valuable person, and it is one of the pleasant sights of February to mark the progress of his work, and the preparations which are making for the approaching spring. We are often reminded of Bloomfield's description of the ploughman's task, during this month.

No wheels support the diving, pointed share;
No groaning ox is doomed to labour there;
No helpmates teach the docile steed his road;
(Alike unknown the ploughboy and the goad ;)
But unassisted through cach toilsome day
With smiling brows, the ploughman cleaves his way,
Draws his fresh parallels, and widening still,
Treads slow the heavy dale, or climbs the hill;
Strong on the wing his busy followers play,
Where writhing earth-worms meet the unwelcome day;
Till all is changed, and hill and level down
Assume a livery of sober brown.

This is also the usual time for sowing beans, an operation which is always performed as soon as possible after winter is over. In the southern parts of England bean-sowing is carried on during January, and in all districts it is completed before the end of March. The mode of sowing is almost always in rows. They are still sometimes sown broad-cast, and sometimes dibbled; but they are for the most part drilled, or deposited after the plough in every furrow, or in every second and third furrow. The quantity of seed allowed per acre is very different in the northern and southern parts of Britain; in the latter, even when the rows are narrow, only two bushels, or two bushels and a half per acre are usually allowed, while in the former four bushels to the acre are employed, with an additional bushel per acre if sown broadcast. The dibbling of beans, that is, planting them in holes made by the hand, is considered an excellent mode of sowing when well performed, but the grand objection seems to be the difficulty of getting it well done. The system of drilling, which was comparatively unknown in England a century ago, is now be come so general that it has in a great measure superseded the other methods of sowing. This general employment of the drill may be principally attributed to the introduction of turnip husbandry, and to the observations then made that this method possessed certain advantages which might be made available in the case of other crops. Yet there are some tenacious soils where the drill cannot be profitably employed, as for the proper operation of the machine it is necessary that the soil, at the period of sowing, should be in a pulverised state. Beans are tolerably hardy, and are not much affected by dry frosts, but in the changing weather so common in February they often suffer much, and this is the reason that many

cultivators delay sowing them till the latter end of the month, or the commencement of March. The sorts most esteemed for general field cultivation are the tick bean, the horse bean, and the small Dutch bean. There are varieties of these beans, differing but little from each other, and experience alone can enable the farmer to choose the seed which best suits his land.

The soil which produces good wheat is also that which is best adapted for beans. In rich land of this description extraordinary crops have been obtained, by sowing beans broad-cast, and very thick, the stems being drawn up to a great height and completely smothering the weeds. But this plan would only succeed in favourable seasons; so that the cultivation of beans in rows, with careful hoeing and manuring, is much more generally advantageous. This latter plan is sometimes adopted alternately with wheat crops for many years in succession, without any necessity for change or fallow; as in some parts of Kent. The most approved plan of managing these alternate crops is thus described by an experienced agriculturist.

The beans must be drilled or set in rows, with intervals of from twenty-four to thirty inches between the rows; and the intervals must be repeatedly stirred and hoed with proper instruments, so as to prevent the growth of weeds, and keep the soil in a perfectly clean and mellow state; the weeds which rise in the rows are removed by hand. Immediately after bean harvest the land is scarified, or skimmed over with a plough having a very broad share, whence the operation is sometimes called broad sharing. All roots of weeds and the remains of bean-halm are collected and burned, or put into a heap with quick-lime to be converted into manure. The ground is then ploughed once or several times according to circumstances, and wheat is sown about the month of October, either broad-cast or by means of a drilling machine in rows ten or twelve inches asunder, which gives greater facility for hoeing and weeding the crop when necessary. The wheat which follows beans is generally good and heavy, and seldom runs to straw. After wheat harvest the stubble is ploughed up and turned in with a very deep furrow: the land is harrowed flat, and a good coating of manure is put on in a moderately rotten state, and this is covered with a shallow ploughing: the land is well water-furrowed, and left so till spring, when the beans are drilled in the mellow surface produced by the winter's frost.

This method varies according to different soils, and different opinions among cultivators: and we may remark that the distance between the rows, as above-mentioned, is greater than is commonly allowed, eighteen or twenty inches being nearer the average in the case of beans, and from seven to ten inches in that of wheat. In some places pease are sown along with the beans; but as they are apt to twine round the stalks and interfere with the growth of the beans, as well as to impede the operations of hoeing and weeding, this practice is not recommended.

According to the best authorities there is scarcely another crop bearing seed, which gives so great a return with so small an expenditure of the nutritive juices of the soil, as the bean, and none that repays manure better, or leaves the land in a fitter condition for wheat or oats.

The particular period at which spring crops should be sown, is a matter on which there is much diversity of opinion. The present month is chosen by some agriculturists for the sowing of Spring wheat, and if the weather is favourable, barley sowing commences before its close. In our changing climate, it is impossible to fix any particular date, as the best time for getting the into the ground; for the advocates of early sowing crops are of course guided by the state of the weather, and their operations are frequently delayed by the continuance of frost and snow. The nature of the soil has also to be considered; for what would be prudent in one situation, would be quite the reverse in another. In favourable seasons, the early sower may gain a considerable advantage over the advocate for later sowing; but if the

weather be inauspicious he may not be so well off as if he had sown a month or two later.

Spring or Summer wheat is a weaker and more delicate plant than Winter or Lammas wheat. The ear is slender and drooping, and is provided with long beards or awns. It is cultivated with the best success in the midland and southern districts of this country; but at the best, the grain is smaller and the produce less abundant than in the commoner sort, so that the farmer probably would not be led to its cultivation, were his land always ready for extensive autumn sowings, and could he ensure success from the earlier sown seed. When through the unpropitious nature of the season, the winter-sown wheat has been so much injured as to destroy all prospects of a harvest, Spring wheat offers a valuable resource to the farmer, and being often sown as late as April or May, little farther danger is likely to accrue to it from the weather, and as it is a rapidly growing species, it may be confidently depended on for yielding its increase. By the analysis of Sir Humphrey Davy we learn that the nutritive quality of Spring wheat is not quite equal to that of Winter wheat, the proportions being 95 per cent. in the latter, and only 94 per cent. in the former, of the entire bulk of the grains. The gluten varies in a greater degree, that of Winter wheat being 24, while that of spring-sown corn is only 19, so that the Winter variety is most advantageous for the purpose of the


The celebrated Linnæus was of opinion that the best means of regulating the sowing season in any particular district was by the leafing of trees. He recommended the cultivator of the soil, to take notice in what order the different kinds of trees put forth their leaves, according to their species, the heat of the atmosphere, and the nature of the soil, and by comparing the observations of several years to form his judgment as to the time of sowing.

It will be necessary likewise (he remarks,) to observe what sowings made in the different parts of the Spring produce the best crops, that by comparing these with the leafing of trees, it may appear which is the most proper season for sowing; nor will it be amiss in like manner to note at what time certain plants, especially the most remarkable in every province, blow; that it may appear whether the year makes a quicker or slower progress.

The present month generally demands much careful assiduity on the part of the sheep-farmer, for without attention, a serious loss is suffered among the lambs during the cold nights that are usually prevalent. The shepherd cannot finish his task as usual at the close of day, but must be prepared to visit his fold at midnight, to suckle the youngest lambs, and to see that all are warm and sheltered. It is interesting to observe the sudden change in the habits and disposition of the ewe, as soon as she becomes a mother. From being a timid quiet animal, shunning and dreading all around her, she now becoines a fearless guardian of the little one at her side, and ready to meet any danger for its sake.

For ewes that stood aloof with fearful eye,
With stamping foot now men and dogs defy,
And obstinately faithful to their young,
Guard their first steps to join the bleating throng.
But casualties and death, from damps and cold,
Will still attend the well-conducted fold:
Her tender offspring dead, the dam aloud
Calls, and runs wild amidst the unconscious crowd:
And orphan'd sucklings raise the piteous cry;
No wool to warm them, no defenders nigh.


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THE mechanical and chemical functions of the animal body are sufficient for the maintenance of simply vital existence: they are sufficient to continue and support mere vegetative life; but when we regard them as a foundation for the endowment of those higher functions, sensation, perception, and voluntary motion,-the scheme of nature then becomes opened and displayed in all its grandeur.



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(From the Antique Statue in the Royal Gallery of Florence.)



To provide for these functions the Divine Architect has introduced into the animal structure a substance endowed with very remarkable properties: the medullary substance,

composes the greater part of the brain, the spinal marrow and the nerves, the assemblage of which organs is comprised in the general term, the nervous system. The sentient and intelligent principle within us is in some way connected with certain affections of this medullary substance, and constitutes the medium of communication between the world without and the mind within; but how physical effects merge into mental perceptions, science is totally inadequate to explain.

The brain is regarded as the primary and essential organ of sensation, or the organ of which the physical affections are immediately attended by that change in the percipient being which we term sensation. As external objects can in

The Arrotino, or the Grinder, commonly known in England under the name of the Listening Slave, has been supposed by some to have been raised in honour of a slave who detected the secret machinations of the

Catilinarian conspiracy. Nothing however is really known relative to the

original design of the artist, but its taste and execution are such as seem worthy of the best sculptors of Greece.


the first instance make impressions only on the organs situated at the surface of the body, a medium of communication is provided between the external organ and the brain by means of nerves. These are white cords, consisting of bundles of threads, or filaments of medullary matter, enveloped in sheaths of membrane, and extending continuously from the external organ to the brain, where they all terminate. The nerves, which subserve the purposes of sensation, transmit the impressions they receive at an extremity along their whole course to their termination in the brain, with a velocity that exceeds all powers of computation.

The brain is furnished with a large number of these nerves, which extend from all those parts of the body which are rendered sensible, and unite at their other extremities in that central organ. It is of especial importance that the surface of the body, in particular, should communicate all the impressions received from contact of external bodies; and that these impressions should produce the most distinct perceptions of touch. Hence, the skin is most abundantly supplied with nerves; each nerve, however, communicating a sensation mind to discriminate between them, and refer them to distinguishable from that of every other, so as to enable the their respective origins in different parts of the surface. It is also expedient that the internal organs of the body should have some sensibility; but it is better that this should be very limited in degree, since the occasions are few in which its exercise would be useful, and many in which it would be positively injurious: hence the nerves of sen

sation are distributed in less abundance to these organs.
The nerves of touch also inform the mind of the qualities

of bodies, such for example as warmth or coldness. They also give warning of any action which threatens to be injurious to the part impressed or to the system at large, and this is done by the sensation of pain which the nerves are commissioned to excite on all these occasions. "They act the part of sentinels," says Dr. Roget, "placed at the outposts to give signals of alarm on the approach of danger."

The system of nerves, comprising those which are designed to convey the impressions of touch, is universally present in all classes of animals; and among the lowest orders they appear to constitute the sole medium of communication with the external world. By ascending in the scale of organization, the faculties of perception are found to take a wider range; and many qualities depending on the chemical action of bodies are rendered sensible, more especially those which belong to the substances employed as food. Hence arises the sense of taste, which may be regarded as a new and more refined species of touch. This difference in the nature of the impressions to be conveyed, renders it necessary that the structure of the nerves, or, at least, of those parts of the nerves which are to receive the impression, should be modified and adapted to this particular mode of action.

As the sphere of perception is enlarged, it is made to comprehend, not merely those objects which are actually in contact with the body, but also those at a distance, the existence and properties of which it is highly important the individual should be apprised. It is also necessary that he acquire an accurate knowledge of the distances, situations, and motions of surrounding objects. He is, therefore, provided with suitable organs for vision, for hearing, and for the perception of odours; all of which senses establish extensive relations between him and the external world, and give him the command of various objects which are necessary to supply his wants, or procure him gratification; and which also apprise him of danger while it is yet remote and may be avoided. Endowed with the power of combining all these perceptions, he commences his career of sensitive and intellectual existence; and though he soon learns that he is dependent for most of his sensations on the changes which take place in the external world, he is also conscious of an internal power which gives him some kind of control over many of those changes, and that he moves his limbs by his own voluntary act. We are so much accustomed to the phenomena of sensation and perception, that, in order to understand them, they scarcely appear to require an elaborate investigation. To behold external objects nothing more seems necessary than to direct our eyes towards them; the sight of those objects seems a necessary consequence of the motion of the eyeballs; and there seems not to be anything marvellous in the function of the eye, or that any other organ is required in a simple act of vision. To ascertain the solidity of an object we have but to stretch forth the hand, and to feel in what degree it resists the pressure we give to it. Even this simple exertion is not required for hearing the voices of our companions, or being apprised by the increasing loudness of falling waters, that we are approaching nearer and nearer to the cataract. Yet, how much is really implied in all these apparently simple phenomena! Science teaches us that these perceptions, far from being direct or intuitive, are only the final results of a long series of operations, produced by agents of a most subtle nature, which act by curious and complicated laws upon a refined organization, disposed in particular situations in our bodies, and adjusted with admirable art to receive their impressions, to modify and combine them in a certain order, and to convey them in regular succession, and without confusion, to the immediate seat of sensation.

Yet this process, complicated as it may appear, constitutes but the first stage of the entire function of perception; for before the mind can acquire a distinct knowledge of the presence and peculiar qualities of an external object, a long series of mental changes must intervene, and many intelLectual operations must be performed. All these take place in such rapid succession that the whole appears to occupy but a single instant. There are, however, according to Dr. Roget, no less than twelve distinguishable kinds of changes, or rather processes, some of which imply many changes, which must always intervene in regular succession between the action of the external object on the organ of sense, and the voluntary movement of that part of the body

which it excites.

The external agents which affect the different parts of the nervous system so as to produce sensation, are of different kinds, and are governed by peculiar laws. The structure

of the organs must accordingly be adapted in each particular case to receive the impression made by these agents, and must be modified in exact conformity with the physical laws they obey. The eye must be constructed with strict reference to the laws of optics, and the ear to the reception of those minute impressions from the aerial vibrations which occasion sound. The extremities of the nerves in these and other organs of sense are spread out into a delicate expansion of surface, having a softer and more uniform texture than the rest of the nerve, whereby they are susceptible of being affected by their own appropriate agents and by no other.

In most cases the impression made on the sentient extremity of the nerve appropriated to sensation, is not the direct effect of the external body, but results from the agency of some intervening medium. There is always a portion of the organ of sense interposed between the object and the nerve on which the impression is to be made. The object is never allowed to come into direct contact with the nerves; not even in the case of touch, where the organ is defended by the cuticle, through which the impression is made, and by which that impression is modified so as to produce the proper effect on the subjacent nerves. So also with the organs of taste and of smell, the nerves are not only sheathed with cuticle, but defended from too violent an action by a secretion expressly provided for that purpose. In the senses of hearing and of vision, the changes which take place in the organs interposed between the external impressions and the nerves are still more remarkable and important. The objects of these senses, as well as those of smell, being situated at a distance, produce their first impressions by the aid of some medium, exterior to our bodies, through which their influence extends; thus the air is the usual medium through which both light and sound are conveyed to our organs. Hence, in order to understand the whole series of phenomena belonging to sensation, regard must be had to the physical laws which regulate the transmission of these agents. We propose, therefore, to consider these intermediate processes in the case of each of the senses, describing for each organ of sense, first, its structure and the way in which its functions are performed, and secondly, the laws which regulate the physical phenomena by which the organ is affected*.


THE eye, which, from the wonderful power of its exterior
expression and the extreme beauty of its internal arrange-
ments is called "Nature's master-piece," does not present to
our contemplation a more beautiful piece of apparatus than
the ear.
Indeed, it is difficult, and even invidious, to
speak of the excellence of one of Nature's works in parti-
cular, since all are excellent, and evince such skill as belongs
only to Omnipotence.

Hearing is only a refinement of the sense of touch: a solid while in the act of emitting a sound will convey to the finger placed upon it a sense of rapid motion; it will also communicate to the air a motion by which a series of undulations is excited; each undulation being formed by the advance and recoil of the aerial particles, and communicating with the external ear, imparts motion to its internal


It has been thought by physiologists that all animals hear,-that those which are not provided with a distinct organ receive impressions of sound through their nervous system generally, but we find that, according as the animal is low in the scale of creation, its organs are more simple, less is required of them, and accordingly the means furnished to them are adequate only to the performance of their simple parts in the scheme of creation. As an animal rises in the scale of intelligence, so also does its frame become more complex as its wants become multiplied: we have in it the parts of the lower animal together with something in addition; and so, as we advance, each lower grade has the germ of some additional provision which is developed in the one next above it, until the organ is met with in its most complex and perfect state in man.

The organ of hearing consists essentially of the expansion of a peculiarly sensitive nerve over a delicate membrane. In the perfect ear there is much additional mechanism, of the particular use of which we are ignorant, but there can be no doubt, since Nature effects her object by the most perfect means, and generally in the shortest way, that the design *For a more extended view of this important subject, we refer the reader to Dr. ROGET'S Bridgewater Treatise.

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of the unexplained portions of the ear is to increase the force and vividness of the impression, to indicate the direction, the difference in pitch, the continuance, and the minute variations of those pulses of sound, which are to be finally communicated to the mind through the medium of the auditory nerve. Other portions probably fit and adjust and retain in a state of fitness and adjustment, the more important parts of the organ, so as to render them, as it were, independent of the atmospheric changes which often so materially influence our sensations.

The parts of the human ear are usually considered under three divisions. 1st, The external ear, leading by means of a curved tube to-2nd, the middle ear, consisting of the tympanum or drum of the ear, a cavity containing air, a membrane, bones, and a muscular arrangement, all which increase the force or manner of vibration, and convey it to -3rd, the inner ear, which contains the labyrinth, a general name applied to the intricate canals which contain the portio mollis, or soft portion of the seventh pair of nerves; this then is the proper seat of hearing. In fig. 1 are exhibited in one view, the principal parts of this complicated organ, as they exist in man, in their relative situations, and of their natural size: thereby affording a scale by which the real dimensions of those portions which will afterwards be explained by magnified representations, may be properly appreciated. In all the figures similar parts are indicated by the same letters.

Fig. 1.


1. The form of the shell (concha) or external ear, c, is, of course familiar to every one. It projects a little forward, presenting five prominences and three cavities, the whole forming a sort of funnel, which by its concave shape and the sinuosities all leading into each other, is well adapted to the reception and collection of sound. The substance of which it is formed is admirably adapted to its office, being very sensitive, and composed of a firm though elastic cartilage, and provided with small muscles, which stretch or relax it as occasion may require. It is covered by a thin dry skin attached to the cartilage by a strong tissue. Many nerves and blood vessels run through it, whereby its sensibility is great, and it becomes red from a very small exciting cause. The lap of the ear, or that part usually pierced for ear-rings, is peculiar to the human ear. Its texture is very different to the other part of the external ear. Instead of being composed of firm cartilage it is soft and full of fat, a provision made probably to prevent the escape of the sound collected in the windings of the concha when it has reached the entrance of the passage. Analogy would lead as to suppose, from the free motions which other animals give to their ears, that man is also capable of moving his ear towards the direction of the sound without moving his head; and accordingly we find that savages and natives of the Oriental nations generally possess this power, but that the bandages and head-dresses applied to the heads of European infants, prevent, in limine, the action of the muscles destined to this motion, and they accordingly dwindle into an insignificant size, with loss of all motive


The aperture (M), or entrance into the ear from without, is called the meatus auditorius externus, or the external path of hearing. This is a tube about three-fourths of an inch in length, curved into the form of an Italic letter, probably to prevent the sound from being reflected into the air again before the sensation of sound be produced, which

would partially be the case if the tube were straight. The structure of this tube is partly bony and partly cartilaginous; it is formed in the petrous or rocky portion of the temporal bone; its surface is covered with a cuticle furnished with short stiff hairs, and also with a set of small glands under the cuticle, which secrete and pour into the meatus their cerumen, which is a wax-like substance of an orange yellow colour and bitter taste; its object is to guard the internal ear from insects, and also it is said to moisten the passage, in the same way that a flute, in order to produce sound, must have its interior surface moist.

Here we may offer a remark against the vulgar prejudice which condemns a harmless insect to the unmitigated horror of the ignorant and the timid, and gives it a name calculated to excite fear and disgust; we refer to the ear-wig. This insect is a nocturnal one, and having a great dread of exposure to the light, one of its kind may possibly by chance have taken shelter in the ear, not for the purpose of resting in and feeding upon the brain, as has been supposed, but simply as a refuge from the light. This, however, is a situation which no ear-wig in its senses would prefer. The ear-wig, in common with all insects, has an especial dislike to the taste and odour of the bitter wax which lines the path of hearing, and an insect would at all times rather avoid the ears of animals than seek them. Small insects have been known to get accidentally into the ear, and to produce uncomfortable sensations by crawling over the membrane of the tympanum, but they soon get out again; and no instance of real injury to the ear by insects is on record.

It has been remarked by Smellie that infants hear bluntly, because the bones of their ears are soft and cartilaginous; and therefore the vibrations excited in them comparatively weak. "Young children accordingly are extremely fond of noise: it rouses their attention, and conveys to them the agreeable sensation of sound; but feeble sounds are not perecived, which gives infants, like deaf persons, the appearance of inattention, or rather of stupidity."

Fig. 2.

2. The tympanum, r, is an irregular cavity containing air, and communicating with the external air through a tube called the Eustachian tube, E, (from the name of the anatomist who first pointed out its use,) which runs by the side of the labyrinth, gradually increasing in width, until it ends in a trumpetshaped opening behind the curtain which separates the nostrils from the mouth. This is the only means which the internal surface of the tympanum has of communicating with the external air, but by this tube a free access of air is admitted into the cavity to equipoise the atmospheric pressure on the external surface of the membrane of the tympanum, D, and to allow it free motion. This membrane is extended across the inner end of the meatus auditorius, where a circular sort of osseous groove is adapted to its reception. It consists externally of a continuation of the cuticle which lines the meatus; there is also an internal layer continuous with that of the cavity beyond it; and a middle layer composed of radiating muscular fibres proceeding from the circumference to the centre, where they are inserted into the extremity of a minute bony process, H, fig. 4. In fig. 1 the inner surface of the tympanum is shown, the cavity T being laid open. The opposite side of the cavity of the tympanum contains a rounded eminence, P, called the promontory; on each side of which is an opening in the bone, closed, however, by the membrane lining the internal surface of the cavity. At the upper edge of the promontory is an opening, o, called the fenestra ovalis, or oval window; and the other situated near the under edge R, fenestra rotunda, or round window. These are shown in fig. 2.

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Any sonorous impulse communicated to the air falling upon the membrane of the tympanum, sets it in motion in a manner somewhat similar to the parchment head of a drum. This is a favourite comparison with most writers, but here all further analogy ends, for although the membrane of the tympanum is tensely stretched, it is not a plane surface like a drum-head, but it is drawn into a funnel shape by the adhesion of the long process of a bone (called the malleus) to its centre. This is effected by means of a muscle called the tensor, which pulls the malleus inward, and so tightens the membrane as to prevent too energetic a sonorous impression; and there are two other muscles which act in an opposite direction and relax

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