A treatise on the anatomy, physiology and diseases of the human ear

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f LIBRARY OF CONGRESS. I

Preface

Having been in the habit for a number of years past, of delivering a course of lectures each year, to my private classes, on the subject of aural surgery : and having delivered a like course in the autumn of 1850, before the class attending the Philadelphia College of Medicine, the author resolved to embody the matter of those lectures in the following pages.

The universally admitted dearth of American literature on this subject, was another pretty strong incentive to the rash act of printing and publishing a book on a new subject.

In doing it, however, he will at least feel the satisfaction of ploughing in a comparative new field. The operative and theoretical surgery of our country will compare favorably, during the last half century, with that of Europe ; and it is hoped that, however imperfect the following little work may be in other respects, that it will exhibit all that is really valuable in American aural surgery, up to the present time.

6 PREFACE.

It will be seen, that personal observation, (which has now extended over twenty years,) in his profession, has been relied on for many of the facts and principles in the treatment of aural diseases, — while the best authorities have been freely, though carefully quoted.

The character of our people, like that of the Anglo- Saxons generally, is decidedly practical; the author has, therefore, avoided long dissertations, or theoretical speculations, on subjects purely speculative. Diseases whose existence has not been proved by post-obit or well attested clinical observations, are excluded. He has attempted to present as nearly as possible what is really known, and valuable, and avoided stating several operations which have not as yet received the sanction of the profession.

The itch for publishing novelties has not to his knowledge swayed the course of his pen or thoughts ; and he has preferred being a safe guide, to being more brilliant and striking, but less safe.

If his endeavors meet with the approbation of the wise and good of his profession, and at the same time assist the junior practitioner to lessen the number of diseases arranged under the general head of the opprobria medicorum y as well as relieve more satisfactorily those who suffer under these very common and difficult diseases, his object will be accomplished. He may add, in conclusion, to the profession,

Hor.

Introduction

The limits of this work will not admit any thing like a proper historical sketch of aural surgery. We will, therefore, merely say in passing that very little has been added in modern times to the anatomy of the Ear.

After the revival of literature, the discoveries of Eustachius, Scarpa and others leave us almost nothing to desire in reference to the Anatomy of this organ.

This is not the case, however, with the pathology of the Ear. Of this the older surgeons knew comparatively nothing, as may be easily seen from the speculations promulgated on this subject, with the varied and irregular treatment designed to cure diseases which existed only in the imaginations of the authors.

To Kramer, of Berlin, is doubtless due the credit of directing attention to a more philosophic mode of investigating these hitherto obscure diseases.

To Pilcher, that of a somewhat verbose exposition of what is considered by him, as known on the subject, and to Toynbee, Todd and other English and American

8 INTRODUCTION.

writers is due what we really know of the changes which the delicate structure of this organ is subject to. Deleau's work is chiefly practical, but is encumbered by a number of contrivances and speculations, which make it rather unsafe for a practitioner to rely upon the dicta of this author.

A TREATISE ON

THE HUMAN EAR.

BOOK L ANATOMY, PHYSIOLOGY, AND COPHOSIS.

CHAPTEE I.

ANATOMY OF THE HUMAN EAR.

The usual anatomical division of this organ, is that which separates it into External, Middle, and Internal.

The external embraces the auricle, which is divided into the lobus and pinna, together with the meatus auditorius externus, which extends from the auricle to the membrana tympani : the latter being sometimes arranged with the middle Ear. We will follow the latter arrangement.

The whole organ is situated on and in the temporal bones on each side of the head —

External Ear. — The soft portion which is pendulous from the pinna is termed the lobe of the Ear ; and is composed almost entirely of adipose tissue covered with the ordinary integument. It is not very sensitive, and after moderate pressure for a moment between the fingers, may be readily perforated with a knitting needle or perforator for the purpose of introducing a thread preparatory to wearing ornaments, or to keep up an irritation for the relief of sore eyes.

Kg J.

1. Pinna. — 2. Lobus. — 3. Helix. — 4. Anti-helix. — 5. Concha.

All above the lobe is called the pinna, from its resemblance to a certain shell of that name. The outer scroll, commencing on the anterior margin and terminating posteriorly, and at the lobe, is called the helix. The next ridge on the outer surface of the ear, which commences forwards by two elevated lines and terminates below and posteriorly in the anti-tragus, is termed the anti-helix. The little space between the anterior double elevated lines of this ridge, is the scapha : while the general cavity which is surrounded by the anti-helix, and in whose centre we find the external orifice of the outer meatus, is the concha.

Anterior and out from the concha and meatus, we see a little cartilaginous projection which, from its having sometimes short rough hairs projecting from it, like those of a goat, is termed the tragus — and a similar projection posteriorly is the anti-tragus. The orifice of the external meatus is not unfrequently garnished with hairs, which may be long and bristling. The dorsal projections and depressions of the auricle, correspond to the depressions and elevations of the ventral portion, and the whole auricle is attached to the margin of the hony meatus by ligamentous union — the cartilaginous portion extending into the canal from a quarter to half an inch.

Three ligaments bind the auricle to the temporal bone — the anterior, superior, and posterior.

Three muscles are also found connecting the auricle to the skull, which in some individuals are under the control of the will, and will move the ear in three several directions, viz : — upwards — the attollens auris — backwards — the retrahens auris — and forwards, the attrahens auris.

The meatus auditorius externus is from an inch to an inch and a half long in the adult, and much shorter in the child and foetus. About midway it is moderately curved, (according to some at an angle of forty-five degrees,) forwards, inwards, and downwards, so that to straighten the passage, and thus bring the membrana tympani in the line of vision, it is necessary to draw the auricle upwards and backwards. This canal contains the following structures. — 1. Numerous short hairs at its entrance. — 2. Ceruminous follicles, which secrete a waxy matter soluble (according to Buchanan) in water. — 3. The ordinary integument of the ear modified. — 4. Areolar tissue which may be denominated subcuticular. — 5. Periosteum. — 6. Bone and cartilage. The cartilaginous portion forms about half of the meatus, but does not make a complete tube, on account of its division into several distinct portions : these possess some motion on themselves. The upper and outer part is deficient in cartilage : its place being supplied by a dense fibrous structure. The bony part of the canal, to which the cartilaginous is attached, by condensed areolar tissue, is termed the processus auditivus 01 the temporal bone. This, in the foetus, is a mere bony ring, and becomes more developed in after life. It is consequently deeper in old age than at any other period.

In addition to the hairy development, which is found chiefly in the outer third of this tube, we have in the same locality, the above named ceruminous follicles — which secrete a thick, yellowish, viscid, inflammable, bitter substance : it contains oily fat, albumen, coloring matter and a peculiar animal matter. It is found to be offensive to insects, and probably preven 3 the passage from becoming too dry, a certain degree of moisture being necessary, not only to the healthy condition of the epidermoid tissue lining the canal, but to that of the membrana tympani itself.

It is supposed by Eicherand, that the act of opening the mouth in listening attentively, has the effect to enlarge the meatus, and thus allow the entrance of an increased number ot sonorous vibrations.

Middle Ear. The tympanum is a cavity found in the outer and posterior part of the petrous portion of the temporal bone, somewhat irregular in shape — rather the widest in its anteroposterior diameter, which is about half an inch in extent. The smallest width being transverse. It is bounded externally by the membrana tympani, internally by a thin osseous plate, which is perforated by two foramina, the fenestra ovalis, and the fenestra rotunda. An anterior canal, termed the Eustachian tube, communicates with the pharynx — and a posterior foramen with the mastoid cells. It is lined by a continuation of the mucous membrane of the pharynx, which also extends to the mastoid cells.

Fig. 2.

EXTERNAL, MIDDLE, AND INTERNAL EAR.

1. Auricle. — 2. Meatus Auditorius Extenms. — 3 Menibrana Tympani. — 4. Malleus. — 5. Incus. — 6. Tympanum. — 7. Stapes. — 8. Semi-circular Canals. — 9. Portio Mollis (auditory nerve.) — 10. Cochlea. — 11. Eustachian tube.

Membrana Tympani. A bony ring in the pars petrosa of the temporal bone, which forms the boundary between the auditory canal and the tympanum, gives attachment to the margin of this membrane. The latter is ovoid, the broader portion being above and backwards, while the narrower part is below, forward and downward. The outer surface forms with the floor of the auditory canal, an angle of about forty-five degrees — being inclined inwards and downwards. The outer surface is also convave a little below the centre, caused by the handle of the malleus drawing it inwards. Its color is a silvery brightness more or less, in a healthy state. Its structure according to Dr. Toynbee is as follows,

1. The external epidermoid layer.

2. The internal or mucous layer.

3. The middle layer — which he says is composed of two classes of fibres. — 1. Cellular. — 2. Radiating. — He describes the lamina of radiating fibres, the outer surface of which is covered by the epidermis, as continuous with the periosteum of the external meatus, with the exception of the uppermost layers, which being somewhat flaccid, have been termed membrana flaccida. The radiating layer is composed of fibres which extend from the circular cartilaginous ring to the malleus, interlacing with each other. These fibres are from 4 to 5,000 parts of an inch in diameter. The circular fibres are firm and strong towards the circumference, but very much attenuated towards the centre. The circular fibres are also smaller than the radiating, being from 6 to 10,900 parts of an inch in diameter. The great density of these fibres, with the absence of distinct nuclei, he thinks are adverse to the idea of their being muscular.

Circulation of the Membrana Tympani. — This consists in the stylo-mastoid branch of the auricular artery, and the ramus tympanicus of the internal maxillary, which forms an arterial circle around the osseous margin, analagous to that around the iris, from which small branches run to the centre.

Nerves. — The tympanic plexus is supplied probably chiefly from the chorda tympani.

The membrana tympani receives the vibrations of the air and transmits them to the bony chain, and to the air in the tympanum.

The tympanum is made irregular on the inner and posterior surface, by the promonitory, which is a projection of bone indicative of the situation of the commencement of the scala tympani. It is found between the fenestra rotunda and the fenestra ovalis, the latter being posterior and the former anterior to it. Its surface is grooved for the passage of nervous filaments, termed the tympanic plexus. Both these fenestra are subtended by membranes — the oval foramen, by the membrane of the sacculus

ANATOMY OE THE HUMAN EAR. 15

elipticus which lines the vestibule, and the round foramen, by a membrane connected with the cochlea. The oval orifice is covered in life by the base of the stapes, one of the small bones.

The eminentia pyramidalis is an irregular little cone of bone, on the posterior wall of the tympanum, which is perforated for the passage of a small muscle, called the stapedius.

u Around the superior and posterior margins of the cavity, a slight elevation forms the wall of the aquseductus fallopii, and marks its course ; a small opening, the apertura chordae, leads from it, behind and below the pyramid, giving passage to the chorda tympani."

The Mastoid Cells. — One large orifice or several small ones communicate between these cells and the tympanum. The enlargement of the ordinary deploic structure results in the formation of these cells, which are lined by the same membrane which lines the cavity of the tympanum

The Eustachian Tube. — A small aperture in the lower and fore part of the tympanum is the commencement of this tube, which proceeds downwards, inwards and forwards, and opens into the upper posterior and lateral parts of the pharynx a little above the level of the floor of the nostril, and about an inch back of the posterior opening. This tube is from an inch to an inch and a half long. The opening into the pharynx is enlarged, forms an oblique slit, and is guarded by a cartilaginous ring which tends to retain any solid body introduced. The tympanic portion is osseous and composed of the irregular extremity of the pars petrosa of the temporal bone, with a portion of the ala and root of the pteregoid process of the sphenoid bone. ct Along the superior edge of the osseous portion of the Eustachian tube is a canal, separated from the tube, partly by bone and partly by a fibrous membrane, transmitting the tensor tympani ) the extremity of the canal forms a pulley, around which the tendon of the muscle plays, and is thus directed towards the malleus."

(Pilcher.) The whole tube is lined by a continuation of the mucous membrane of the pharynx and the tympanum. The ordinary mucous follicles are abundant in it. The uses of this tube appear to be : first, to admit air to the tympanum ; second, to afford ready exit to the secretions of the latter cavity into the throat.

The bones of the ear are four in number, in the young subject, and three in the adult ; termed malleus or hammer, incus or anvil, orbiculare or round bone, and stapes or stirrup. They are named from their resemblance to these objects.

The malleus is divided into a caput, cervex, processus gracilis, processus brevis, and manubrium.

The manubrium or handle is inserted between the layers of the membrana tympani. It tapers towards the point, which latter, however, is a little enlarged and turned outwards.

The short process is thick and strong and projects outwards, forming a right angle with the manubrium, bearing a deep depression between itself and the neck.

The long or thin process is rarely separated from the skull in a perfect state. It proceeds forwards and downwards, the point being attached to the inner margin of the tympanic ring, close to the fissura glasseri.

The neck by which these processes are attached to the head, is short and marked by the attachment of muscles and ligaments.

The head forms the superior part, rises above the membrana tympani, and projects into what has been termed the tympanic sinus. It is, on the upper and outer part, convex and smooth, concave on its inner and posterior portion, which is divided into two parts by a transverse ridge, and articulated to the upper surface of the incus.

The anvil has a body and two limbs. The body is nearly square and flat, concave superiorly, and elevated to correspond to the depressions on the head of the malleus, forming in this way a double pulley joint. The smaller crus projects nearly directly backwards, and is united to the edge of the mastoid cells by a well marked ligament. The long crus hangs downwards, diverging from the manubrium of the malleus. Its extremity is moderately enlarged for the articulation with the round bone.

The os orbiculare or lenticulare is found distinct, in infancy, but becomes united to the long crus of the incus or the head of the stapes, in adult life. It is a mere particle of bone, about the size of a large pin-head.

Fig 3.

BONES OF THE EAR.

Malleus. — 2. Incus. — 3. Orbiculare. — L Stapes.

The stapes is so called from its marked resemblance to the ordinary saddle stirrup. Its is divided into a head, neck, two crura and a base. This division is perhaps a sufficient description, except to add that the posterior crus is the longer of the two — that the base or foot is placed in contact with the membrane inside the fenestra ovalis — nearly in a horizontal direction, being a little smaller than this foramen, and that the space between the crura is subtended by a ligament denominated the triangular.

Another ligament which unites the short crus of the incus to the edge of the mastoid cells, with certain duplicatures of the mucous membrane form what are termed the ligaments of the tympanum. The three following muscles, are perhaps all that can be clearly demonstrated as connected with this chain of bones.

1. Tensor Tympani or Interims Mallei. — This arises from the superior portion of the Eustachian tube and from the edge . of the petrous bone. It runs backwards into the tympanum, winding round by means of its tendon over the edge of the tube, to be attached to the inner surface of the manubrium of the malleus, near the long process. It in this way forms a very complete pulley. Use, to draw the bone inwards, and thus increase the internal convexity of the membrana tympani.

2. Laxator Tympani. — This muscle originates in the spinous process of the sphenoid bone, runs inwards and backwards through the fissure of the glenoid cavity, and is inserted by means of a long tendon into the long process of the malleus. Use, to draw the malleus outwards and a little forwards, relaxing the membrana tympani.

3. The Stapedius. — Arises from one of the mastoid cells and the interior of the eminentia pyramidalis, passing through the canal of the pyramid. Inserted tendonous into the posterior portion of the neck of the stapes. Use — to move the stapes backwards, turning its posterior edge towards the fenestra ovalis, thus increasing its tension.

" The exact influence the muscles of the tympanum exert, in regulating the vibrations of the membrane and the bones, is not ascertained. The general opinion is that they are voluntary, being supplied with nerves from the portio dura; and that the membrana tympani is tightened or relaxed at will, as the sound may be pleasing or discordant. More correct observations however show, that they all, and particularly the tensor tympani, receive especial branches from the ottic ganglion, besides twigs from the tympanic plexus, and thus they may be supposed to be involuntary, and to be acted upon sympathetically, through the medium of nervous connection with the portio mollis :

resembling the influence of the retina upon the muscular fibres of the iris. This forms an interesting problem for solution. Probably both opinions are correct; as the muscles are supplied from the two sources, — from the voluntary system by the portio dura, and from the ganglionic by the chorda tympani, and the ottic ganglion. Is it not probable that they may be of the mixed character, acting involuntarily when the acoustic nerve is over-excited, or when the mind is otherwise engaged, and attention not directed to the protection of the membrane and of the ear in general ; and being influenced by volition, when the individual is desirous to increase or to diminish his mental perception Y* (Pilcher, p. 60.)

Internal Ear, or the Labyrinth. — The internal ear may also be divided into three portions — viz, the cochlea, vestibule and serai-circular canals. Another division, is into the osseous and membranous labyrinths — the first includes the vestibule, semi-circular canals and cochlea — or the bones of the two first, and the whole structure of the latter.

The Cochlea. — Its resemblance to a snail's shell has induced this name. Their being two cavities however instead of one, the analogy is only in external form. It is twice and a half turned upon itself, having a base and point. This arrangement varies somewhat in the ears of the higher classes of animals : — for instance, in the porcupine, it has three and a half spiral turns; in the dog and fox three turns; in man, the cow, hog and cat, two and a half turns ; in the horse and dolphin, two and a quarter ; and in the rabbit two turns. Birds occupy the last place in the series. — (Dr. Ch. L. Esser, ffastner's Archives, fur aieges. JSfaturlehre, torn, xii., 1 er. Cah; 1827, p. 52.) An axis termed the modiolus, from its resemblance to the nave of a wheel — infundibulum, cupola, lamina spiralis, hamulus cochleae, canalis scalarum communis, and the zona cochleae, compose the cochlea.

The modiolus is the central pillar, which is hollow for the transmission of the branch of the portio mollis which supplies the cochlea — lateral perforations allow the nervous ramuscules to pass over the surfaces of the zonae and scalae cochleae. The infundibulum is an inverted conical cavity at the upper end of the cochlea, while the cupola is the dome which surmounts this cavity. The lamina spiralis doubles twice and a half upon itself, and passes round the modiolus. The hamulus cochleae is a small hook, forming the terminal point of the lamina spiralis above. The two canals meet at the upper end of the cochlea under the cupola, and unite, thus forming but one canal, which begins in the vestibule there termed scala vestibuli, and terminates in the tympanum at the foramen rotundum, and there termed scala tympani. The zona is the cartilaginous or membranous portion, which forms the outer border of the bony portion or lamina spiralis. On the surfaces of both this and the lamina, are distributed the nervous loops, which approach them through the cribriform orifices in the modiolus.

Three small orifices connect the interior of the coch.ea, vestibule and the bony structure of the pars petrosa, with the exterior surface. These are termed, from an erroneous opinion as to their functions, aquaeducts. They are designed to be the media of conducting nerves, bloodvessels, and perhaps some other tissues through the bone.

Aquceductus Cbchlece. — This duct proceeds from the scala tympani, near the fenestra rotunda, backwards, under the labyrinth, and perforating the bone, terminates by an irregular opening on the lower margin of the posterior surface of the petrous portion. Several smaller canals communicate with it from the cancelli, in its course.

Aquceductus Vestibidi. — Originates near the common orifice of the superior and posterior semi-circular canals, perforates the bone, and descends to the posterior surface of the pars petrosa near the jugular fossa. By some it has been traced to the scala vestibuli.

Aquccductus Fallopii. — This canal whose function is merely the transmission of the portio dura nerve, commences at the upper and inner part of the meatus auditorius internus, and passes outwards, at first a little upwards and forwards, then backwards and downwards, and finally almost directly downwards to the foramen stylo-mastoideum where it terminates. At the beginning of it, or near its course, it receives the hiatus Fallopii, a narrow canal on the dorsum of the petrous portion of the temporal bone, which conducts the vidian nerve to the portio dura. Several other small orifices open into it, which transmit the chorda tympani and other branches to the tympanum.

Meatus Auditorius Interims. — This is found on the posterior surface of the petrous portion of the temporal bone, and is a large canal for the transmission of the portio mollis, portio dura, portio intermedia and internal auditory artery to the interior of the bone. It is about half an inch in length — passing outwards and forwards; and at its outer extremity or bottom, terminates, in a cribriform plate which is divided by a well marked transverse ridge. In the upper and smaller portions we have the commencement as above described, of the aqueeductus Fallopii. Posteriorly, foramina transmit fibres of the portio mollis to the superior semi-circular canal. The lower or larger portion is divided into two parts, the anterior of which forms the base of the modiolus, and has a distinctly cribriform arrangement, the orifices being in circles one within another, with a large central orifice. The nerves which pass through this bone pass through the modiolus, and are distributed to the cochlea. They are branches also of the portio mollis. Through the posterior division of the bone, other branches, from the game, pass to the vestibule and to the ampulla of the posterior canal. The whole meatus is lined by dura mater. An internal periosteum lines the whole of the labyrinth, and has the portio mollis finely distributed over it. It also secretes the perilymph, or that fluid which is outside of the membranous sacks which are found in the vestibule and semi-circular canals.

The semi-circular canals, are three in number, superior, external and inferior. They are solid bone, and communicate with the vestibule.

The membranous labyrinth consists in sacks which do not entirely fill these canals and the vestibule, and contain a clear fluid, like water, called liquor Cotunnii. The vestibular portion is said by some to contain two sacks ; the larger and posterior is termed the sacculus vestibuli. The semi-circular canals all open into this, some by their expanded extremities, termed ampullae. The anterior sack is smaller and called alveus utriculosus. Brachet and Eoget describe, in each of these sacks, a white, calcareous body, which seems to be suspended by means of filaments of the acoustic nerve.

The nerves of the ear are,

1. The Auditory, as above described, in its distribution to both the solid and fluid portions of the ear;

2. Portio Dura or Facial Nerve. — It passes from the internal meatus, along the canal of Fallopius, until it reaches the stylo-mastoid foramen, where it emerges to the parotid gland, and thence to the face forming the pes anserinus.

" The facial in its course through the bone gives a good sized twig to the tensor tympani, part of which reaches the Eustachian tube, then a filament or two to the tympanic plexus; then a branch to the stapedius ; and, lastly, near the termination of the aqugeduct, the vidian nerve leaves it under the name of chorda tympani/ ;

3. The vidian nerve enters the cranium through the pterygoid foramen, then the hiatus Fallopii passing off from the portio dura as above described, it passes across the tympanum between the Ion or crus of the incus and the handle of the malleus : then enters and emerges from the fissura glasseri, unites with the true gustatory and passes to communicate with the submaxillary ganglion. In its course it communicates with — 1. The sympathetic in the carotid canal. — 2. With the portio dura. — 3. The tympanic plexus receives twigs from it. — 4. The laxator tympani. — 5. The ottic ganglion. — 6. The gustatory, and 7. The submaxillary ganglion.

The ottic ganglion, as described by Arnold, " is a small, soft, reddish body, larger in proportion in the foetus, situated immediately below the foramen ovale : it rests on the inner surface of the third branch of the fifth, between it and the Eustachian tube, and immediately in front of the great meningeal artery/'

The Tympanic Plexus. — According to Jacobson it is situated near the promontory of the tympanum, and is formed by the union of twigs from the sympathetic nerve, ottic ganglion, chorda tympani, portio dura, and glosso-pharyngeus. The mucous membrane of the tympanum, Eustachian tube and the muscles, &c. of this cavity are supplied by it.

The ear is supplied with blood, by branches from the carotid and basilar arteries.

The posterior aural, arises from the external carotid, and is distributed to the external ear. It gives off the stylo-mastoid branch, which passes through the foramen of the same name. This branch afterwards divides into numerous ramuscules which are distributed to the mastoid cells, labyrinth, and with a branch from the internal carotid termed the ramus tympanicus, forms a coronet around the membrana tympani, which sends branches towards the centre, like that around the iris.

The anterior aural arteries, are supplied by the temporal. The tympanic passes through the fissura glasseri, and is distributed to the coronet as above stated. The internal auditory arises from the basilar, and runs along the under margin of the portio mollis outwards, supplying this nerve in its course, and passing with its ramifications to the various portions of the labyrinth.

The veins and lymphatics correspond to, and are distributed with the arteries.

CHAPTER II.

PHYSIOLOGY OF THE EAR.

It is clearly demonstrable, that there enter into the structure and functions of the ear, at least three distinct forms of matter — viz : gases, fluids and solids : and that it is by an union of the acoustic proportions of these, that complete, or normal hearing is accomplished. The auricle and meatus auditorious externus, are beautifully adapted, to concentrate the sonorous vibrations of the atmosphere, and direct them in the most forcible manner to the membrana tympani. This membrane, receiving probably the vibrations both from the meatus and tympanum, vibrates and communicates the vibrations through the manubrium of the malleus, to the four bones which form a solid connection between the membrana tympani and the vestibule. The base of the stapes transmits through the foramen ovale, and its subtending membrane, those vibrations, which are thence conducted through the vestibule and semi-circular canals, by means of the liquor cotunnii. The atmospheric air, the bones and membranes, and the liquor cotunnii, are the three media, gaseous, solid and fluid, which conduct sonorous vibrations to the acoustic nerve, distributed to the semi-circular canals and vestibule.