The questions of aural surgery

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Chapter I. General Observations

The chief peculiarities of aural disease are determined by simple facts of structure : as, that sound is conveyed to the nerve of hearing by means of a cavity containing air, supplied from the throat by a somewhat long and narrow channel ; that this cavity is deeply seated, is bounded both externally and internally by a thin vascular membrane, and is crossed by a delicately-jointed chain of bones. There are also some negative circumstances wdiich are important ; namely, that the nervous apparatus is inaccessible to direct observation, and is divided into structures of some of which the functions are at present a matter of doubt. Finally the nerve of hearing is, in its origin, intimately connected with the nuclei of the great nerves of the digestive and respiratory apparatus, and appears to have peculiarly close relations with the parts of the brain concerned in the emotions.

But it is to the part played by air contained within the

ft B tympanum, in the conduction of sound, that the most practically important characters of aural disease are due. Generally speaking, the main object of the surgeon will be to see that this air-containing cavity with the passages leading to it are subject to no obstruction, either occluding their calibre, or impairing the delicacy of oscillation of the structures pertaining to them. As the conducting portion of the eye is a camera with lenses, so that of the ear is a pneumatic apparatus, and the surgical methods appropriate are corresponding in their character. Our business here is with the air — that the channels it should permeate be free ; that the organs it bathes, and essentially supports by its pressure, encounter no hindrance in their reception and transmission of impulses.

Bearing these things in mind, aural surgery is simply surgical common sense, and needs comparatively little insistence on special points, beyond that which a trained surgical instinct would suggest. Owing to the structure of the ear, however — that the tympanum lies so deeply, and is itself so irregular a cavity with its only outlet placed not at its most dependent portion, while, when diseased, its lining membrane pours out viscid secretion in extreme abundance — one duty lies on the surgeon, in treating the ear, with somewhat peculiar exigence : that of ensuring a perfect cleansing. In every case connected with discharge his sheet anchor is cleanliness.

Another requisite is patience. In so far as the feeling,

STRUCTURE OF THE EAR. 3

so widely spread, that in disease of the ear the resources of medicine are of little avail is justified, its grounds are chiefly two ; first the ignorance which until lately invested the whole subject, and secondly, the fact that even the diseases which are remediable are, when they have advanced beyond a certain stage, apt to be tedious in their progress, and especially to be discouraging on account of their liability to temporary relapses. This liability is in great part to be accounted for by the connection between the tympanum and the throat, which is so especially subject to atmospheric influences. But even in cases that on this ground seem to baffle hope, if the affection do not involve the nerve-structure, perseverance will almost always effect a satisfactory result ; and such a result is the more often attained because, on the one hand, the hearing may be very considerably below the average with no appreciable inconvenience, and on the other an even extreme amount of permanent damage to the membrane, and to some of the parts contained within the tympanum, may co -exist with a very slightly diminished function. The membrane may be not only almost wholly wanting, but may be so altered as to form irregular fleshy or fibroid masses presenting no visible resemblance to its original structure, both malleus and incus may apparently have been lost, and yet the patient scarcely desire to hear better. Thus, indeed, there arises one of the most interesting problems that the study of diseases of the ear presents— the real relation of the membrana tympani to the function

b 2 of the organ, which is by no means so simple as would at first appear.

Among points of interest in respect to the structure of the ear may be mentioned its markedly spiral form. It is true that, on an observant scrutiny, clear traces of a spiral form are visible in almost every organ of the body,* but perhaps in none, except the heart, is this fundamental mode of structure so plainly marked as in the ear. It is visible not only in the cochlea, but throughout ; the meatus winds with a slight spiral turn — backwards, upwards, forwards, and downwards ; the tympanic bone in which the membrane is inserted is a distinct spiral ring, as can be well seen before osseous union occurs ; a line traversing the ossicula takes a spiral course ; and in the canals, perhaps, this relation is most intensely marked. For not only is each canal in itself a segment of a spiral curve, but the relations of the three canals. to each other, lying at right angles as they do, reveal the very secret of the spiral form, which represents indeed simply a continuous motion passing successively into these three directions. In this respect the ear is eminently typical of the whole body, displaying visibly a plan or law of structure which is none the less paramount elsewhere because it is more concealed.

It can, perhaps, hardly be doubted that this markedly

* For the illustration of this fact I may refer to a paper on " Physical Morphology," in the "Brit, and For. Med. Chir. Rev.," 1S58. The paper is reprinted in "Life in Nature. "

THE SPIRAL FORM. |

spiral structure is of a functional value : for all motions tend to propagate themselves (at least thro' media in any degree resisting) in a spiral direction. . The spiral lines formed on glass rods thrown into sonorous vibrations are well known, and Sir John Herschel remarks* that the waves of sound may be traced in expanding spirals in the air. In the meatus, this form becomes of practical importance, in respect to the removal of foreign bodies, the introduction of the cotton wool or other form of artificial membrane, syringing, &c. — The meatus acts as a resonator to certain tones of the fourth octave (c"' — e""), especially to g"".t

In respect to the functions of the different parts of the ear the most minute investigations have as yet failed to gain any finally satisfactory results. By means of threads of glass, starch granules, or the plumules of a feather, attached to the ossicles, it has been demonstrated % that vibrations impinging on the membrane are transmitted through the chain of bones, which moves as a whole, and imparts corresponding motions to the fluid of the labyrinth,

Dr. Buck gives the following as the results of his

* Treatise on Sound, reprinted from the "Encyclopaedia Britannica." f Helmholz : " Lehre vod den Tonempfindungen," p. 175. % By Politzer, Lucae, and others : see the various volumes of the "Archiv fur Ohrenheilkunde," 1864 and subsequently; and more recently by Dr. A. H.Buck (who used grains of starch); "Archives of Ophthalmology and Otology," 1870, No. 2. For the completest details on all these points see Helmholz, " On the Mechanism of the Ossicles of the Ear." (Sydenham Society.)

experiments: — On the dead subject, with a glass tube attached to an organ pipe inserted into the meatus, the malleus may be made to make an excursion inwards of 0*43 mm. without injury ; but this exceeds, probably very greatly, its motion during life. The axis of rotation of the malleus lies nearly midway between its two extremities, so that the head moves outwards as the end of the handle moves inwards. The rotation takes place upon a ligamentous structure passing from the malleus to the anterior and posterior walls of the membrane, and which is termed by Helmholz the axis -ligament. The upper part of the head of the malleus moves horizontally outwards, while the part below the articulation with the incus moves upwards as much as outwards ; and the incus is so articulated with the malleus as to share this motion ; so that it is carried upwards and outwards when the membrane is carried inwards by a wave of sound. But in addition to this motion the body of the incus is thrown slightly backwards, and the end of its long process slightly forwards. The stapes moves correspondingly ; namely upwards, slightly inwards, and forwards. As a result of this, the upper and anterior border of the base of the stapes is driven farther into the vestibule than the lower and posterior border. Hence a displacement of the entire mass of the labyrinth-fluid ensues. An impulse given to the centre of the membrane is communicated from ossicle to ossicle, with a loss in the following ratio : —

FUNCTIONS OF THE OSSICLES. 7

Malleus = 4 Incus = 2 Stapes = 1

But this refers to the utmost excursions ; when they are feeble, scarcely any loss occurs in the transmission, so that probably during life the proportion between the motions of the various bones is much more equal than that given above. Section of the tendons of the tensor tympani and stapedius had no effect on the motions. Helmholz* found that the greatest natural motion of the stapes was T1j mm. If the ossicula lie firmly together, each excursion of the long process of the incus will equal only § of that of the malleus handle ; but the force it transmits to the stapes will be one and a half times as great as that which acts on the extremity of the malleus.

By an arrangement of the heads of the malleus and incus, after the fashion of a cog, both malleus and incus move together on pressure inwards ; but the malleus may move very considerably outivards without carrying the incus with it, thus guarding in part against the effects of too powerful inflation of the drum.

According to Biidinger, the malleus and incus and the incus and stapes are articulated b}^ means of a true joint, containing a freely movable meniscus of cartilage, like that of the clavicle. The articulation of the stapes with the fenestra ovalis belongs to the group of the * "Mechanism of the Ossicles of the Ear."

symphyses, and is similar to that of the bodies of the vertebrae.

Dr. Burnett, of Philadelphia,* has also examined the motions of the membrane of the fenestra rotunda by means of starch granules, observed with a microscope, and found that t\\ey corresponded accurately with those of the stapes. A great increase of fluid pressure in the canals stopped the vibrations of the membrana rotunda, and rendered the membrana tympani and ossicula also immobile ; this repressive effect of increased pressure in the labyrinth was greater with the higher than with the lower notes. Mach and Kessel t also found, by the use of a sirene, that the basilar membrane of the cochlea moves from the scala vestibuli towards the scala tympani when the stapes presses inwards.

The same observers \ experimented on the effect of traction on the tensor tympani and stapedius muscles, with a view to ascertain whether an accommodation of the ear to sounds of different pitch was effected by them. Traction on the stapedius gave no effect ; but traction on the tensor tympani reduced the motions of the membrane under both grave and acute sounds, but more in proportion for the grave ones. The membrane was observed under a microscope, and its vibrations measured by a micrometer; one millimetre equalling 50 lines. A pipe

* "Monthly Jl. of Aural Surg.," July, 1871. f " Versarn. D. jSatur forsch." 1871. % "Arch. f. Ohr.," 1873, p. 121.

MOTIONS OF THE OSSICLES. 9

of 256 vibrations gave a motion of the membrane equal to five lines of the micrometer ; a weight of 3 grammes was then attached to the tensor tjmpani and the motion was reduced to three lines. On using a pipe of 1024 vibrations, the excursion of the membrane was only 1|- lines of the micrometer, but the same traction on the tensor reduced it less : only in the proportion of 5 to 4.

Carrying their experiments farther, Drs. Mach and Kessel obtained vibration-figures from the head of the malleus, alike for lower and higher tones ; and on uniting the two they found that the two figures were presented together ; traction on the tensor tympani altered the form of the low, but not of the high note.

1 2 3 4

Description of Figure : — Fig. 1 shows the vibrationline given by a pipe of 256 vibrations in the second ; this was changed by traction on the tensor tympani into Fig. 2. A pipe of 1,024 vibrations gave the line shown in Fig. 3 ; and on combining them Fig. 4 was formed. Traction on the tensor did not affect the form given by the higher note, and scarcely affected even that of the lower when both were sounded together. The higher note produced more vivid and ample motions when the lower was also sounded.

On the. living subject parallel experiments were carried

out to test the action of the tensor tympani, but no change

could be traced as arising from the act of listening to the io THE QUESTIONS OF AURAL SURGERY.

higher tones, either in the extent of the movements of the membrane, or in the figures produced. This, however, does not contradict the assertion of Schapringer (who can at will contract the tensor tympani with visible indrawing of the membrane), that such contraction diminishes the intensity of all sounds, since these experiments go to show that the vibrations are in all cases diminished, only for the higher tones less than for the lower. All other attempts to discover an alteration of tension in the membrane during life have also failed. But Dr. 0. Wolf holds that the occurrence of such increased tension as a protection against very loud sounds, is proved by the fact that the sounds of an organ-pipe are heard as much as half a tone higher when close than at a distance.* Helmholz has pointed out that contraction of the tensor tympani puts on the stretch at once all the ligaments of the ossicula, except the superior ligament of the malleus.

In respect to the function of the stapedius muscle there is little ground for affirmation. It has been suggested t that it is specially employed in listening, or adapting the ear to rapid changes in sound, an idea to which its supply by the portio dura perhaps lends countenance. "Sir. Toynbee endeavoured to use this function as an aid in the diagnosis of deafness arising from loss of the due

* "Sprache undOhr." Braunschweig, 1871. I have not been able to find confirmation of this statement.

t As e.g., by the late Mr. Toynbee, " Diseases of the Ear," p. 281 ; and more recently again by Dr. Allen.

MUSCLES OF THE OSSICLES, . 1 1

mobility [anchylosis] of the stapes. Professor Helmliolz, however, whose opinion must carry the utmost weight, has been good enough to inform me that his researches have led him to consider it simply as a damper of sound. Kesse'l* assigns to it a strictly counteracting effect to that of the tensor tympani. He observes that the membrane consists of three distinct portions, an anterior, posterior, and superior portion. The superior is the thin part known as Pdvini's segment, and most easily yields to impulses, being supposed to be adapted to slight and irregular sounds (answering to the supposed function of the vestibule) : of the lower segments the posterior is the most yielding, and on air pressure in the meatus the malleus rotates inwards and backwards, the hort sprocess moves also slightly downwards, the anterior segment is rendered more tense than the posterior ; and the superior segment is rendered convex while the inferior becomes concave. The effect of traction on the stapedius is, in all respects, the opposite to these movements.

On producing vibrations (in a preparation) with an organ-pipe, the membrane vibrates with a direction inwards and backwards, the anterior portion much less than the posterior. Hy section of the tendon of the tensor tympani, the excursions of the head of the malleus are increased a fourth, and its rotation also much increased.

By traction on the tensor, on the other hand, the * Loc. cit., p. 80.

J 2 THE QUESTIONS OF AURAL SURGERY.

movement of all the parts is diminished, and that of the anterior portion may be entirely stopped, while the sound continues undiminished. If now the tendon of the stapedius be drawn upon the suspended movements of the anterior segment may be renewed, even while the traction on the tensor is continued. When a note is sounded with its octave, and the vibrations of the membrane observed, traction on the tensor is seen to diminish, first, those of the octave in all the lower segments ; but they continue undiminished in the thin upper portion of the membrane, and to this is due the preponderance given by traction on the tensor to the higher notes, and not to its effect on the membrane as a whole.*

Dr. AVolf f has investigated the reception of the various elements of speech by the ear. Among the consonants sch is heard loudest, and h least loud ; the force of any letter depending very much upon the harmonics which accompany its ground-tone. The vowels range as follows : — a, o, el, e, i, eu, an, n, pronounced as in German. In cases of partial destruction of the membrane the vowels were heard disproportionately better than the consonants, which were worse heard in proportion to the size of the defect, and the better in

* These investigations are carried out by means of the Stroboscopic method, which consists in observing a motion at interrupted points, on a principle analogous to that of the familiar "Wheel of Life." An account of it is given in the Appendix.

f Loc. cit.

HEARING OF SPEECH. 13

proportion to the pitch of their ground-tone, and the number of their harmonics; a rhythmical utterance diminished the difficulty. On experimenting with an artificial meatus and membrane it was found that the resonance was much greater for the voice than for a violoncello, and that partial destruction weakened, and raised the pitch of, the resonance. This was more diminished by hindrances to the propagation of the vibration than by losses of substance. Politzer also found that weights attached to the ossicula impeded the transmission of vibrations much more than when attached to the membrane. It must be held, Wolf thinks, that sounds are conveyed both by movement of the stapes in the fenestra and by the molecular movements of the ossicula also. In cases of defect of the membrane, the last syllable of a word was often heard as if prolonged, especially with an I added. This he ascribes to an unchecked motion of the stapes in the fenestra, and therefore infers that the ossicula lhnit as well as convey vibrations ; a function in which the Eustachian tube participates by permitting their escape.

But it still remains inconceivable how all the innumerable varieties of sound can be conveyed simultaneously to the labyrinth. Whatever our supposition, every attempt to imagine the passage, together, of such complexities and delicate shades and varieties of sound as we are capable of appreciating, thro' such an apparatus as the chain of ossicula, serves but to make the wonder greater.

Our knowledge of the structure of the membrana tympani has been chiefly advanced of late years by Professor Josef Gruber, of Vienna. He has pointed out (and it is confirmed by Professor Helmholz) that the malleus is attached to the membrane by a small layer of cartilage which is thickest around the short process, and that at that part, though no true joint exists, it is slightly movable upon the membrane. He describes also a layer of " strengthening fibres/' situated mostly at the loAver and posterior part of the membrane, immediately beneath the epithelium, and running in irregular directions, to which he assigns the function of restoring the membrane to its normal position after tension has been exerted on it. Kessel found that this structure furnished a series of channels, lined with epithelium, thro' which the vessels, nerves and lymphatics, and the membrane pass on their way to the more external layers.

Dr. Yon Troeltsch's two "pockets" of the membrane are well known ; they consist of two small folds of the mucous membrane of the tympanum, one behind, the other in front of, the short process of the malleus. The chorda tympani nerve runs along the inferior edge of the posterior fold, which also contains some of the proper fibres of the membrane. These "pockets" are of importance, because they seem often to retain secretion. The same may perhaps be said of the folds of membrane which exist above the neck of the malleus and form there

THE MEMBRANA TYMPANA. ,15

a series of minute cavities ;* in these, morbid secretion probably is entangled during catarrhs and so gives rise to the discharges which sometimes take place thro' small ulcerations of the thinner membrane, above the short process of the malleus, and which are often extremely tedious in their recovery.!

Helmholz J has pointed out an advantage, in respect to the reception of vibrations, arising from the form given to the membrane by the arching of the radial fibres. A very small air-pressure upon them is thus rendered equivalent to a great force acting on the malleus, the extent of its movements being proportionately less : they also guard against excessive pressure on the stapes, because, beyond the point at which they are made straight, force applied to them would bend them inwards, and so draw the malleus outwards. The membrane thus, by its curvature, acts first the part of a lever on the malleus, and secondly that of a regulator of the force conveyed. [The corresponding function of the cogs of the malleoincudal joint in guarding against outward pressure has been mentioned before.] The fibres of the membrane are inextensile, like tendon. § Politzer, by means of an appa-

* Described at large by Politzer: "Wiener Med. "Wochenschrift," 1870'.

f See "Atlas of Diseases of the Membrana Tympani," plate xxiii.,

% 1.

+ Loc. cit.

§ Mr. E. Moon ("Philos. Mag.," 1869-70) has argued from the inelastic structure of the membrane that only the waves of rarefaction in the air are transmitted to the labyrinth, and not those of condensation ; and ratus representing a greatly magnified tympanum, foimd that a membrane which, while flat, scarcely responded at all to either high or low timing forks, was thrown into strong vibrations as soon as it was drawn inwards at the centre, and this equally, whether the sound fell on the concave or the convex side ; * and he considers the different tension of the individual parts of the membrane between the malleus and the periphery produced by its curvature to be an important factor for the simultaneous reception of different notes. Lucae t has shown that vibrations that fall perpendicularly on the membrane produce much the most strong vibrations ; and hence a tuning-fork placed on the side of the head, each meatus being closed, is heard chiefly on the opposite ear.

Dr. Blake J examined the limit of hearing for high notes, and the effect upon it of perforation of the membrane. He found that in health it diminished with age from 40,960 (single) vibrations in a second, at twelve years, to 32,768 at fifty ; the sound used being the vibrations of a suspended steel rod, and the distance thirty-four feet ; any thickening of the membrane lowered the limit ; perforations, as a rule, raised it, especially when situated in the

he ascribes to the muscles of the ossicula the function of restoring the membraue to the former plane after the rarefied waves have drawn it outwards. The perception of sound would thus be caused by the flow of the liquid in the cochlea from the fenestra rotunda to the fenestra ovalis, and vice versd.

t "Berlin. Kl. Woch.," 1871. No. 10.

% "Trans. Amer. Otol. Soc.," July, 1872.

HIGHEST LIMIT OF HEARING. 1 7

posterior superior segment. Size did not make so much difference as situation and the degree of retraction of the tensor t3rmpani. An experiment was happily afforded by a case of disease of the membrane, in which an incision, followed by the introduction of a ring to maintain theopening, as suggested by Politzer, greatly improved the hearing, and especially raised the limit of sound from 35,000 to 80,000 vibrations in the second.

Of the labyrinth I abstain from speaking. Veiy many minute investigations have lately added to the knowledge of its structure ; but the details of its functions may be said to remain as undecided as ever ; especially since the report of a case by Dr. Cassels of Glasgow, in which "the whole cochlea was removed," by caries, " without loss of hearing or impairing the perception of the transmitted tones of the diapason."* This case, for the accuracy of which Dr. Cassels' statement is ample authority, would seem to set aside for the present all the suggestions which have been made, with so exquisite an appearance of reason, by Helmholz, respecting the special functions of various fibres of the laminae of the cochlea in responding to particular musical tones, upon which doubt has also been thrown from other quarters. Perhaps the other portions of the organ are capable of partially compensating for the functions usually performed by the cochlea, tlio' it is hardly possible to understand how the functions of any of the other portions of the labyrinth

* The case is given at length in Chap. xiv.

iS THE QUESTIONS OF AURAL SURGERY.

can have been preserved during exfoliation of that organ.

But clinical experience decidedly indicates that different parts of the labyrinthine structures are appropriated to the reception of different pitches of sound, since the power of hearing certain notes only may be lost, while the rest are unaffected. Such a case is reported by Magnus, and the power was restored during the use of resonators corresponding to the notes involved. In a patient of my own also, a lady aged 40, with whom conversation could be carried on quite easily, the notes of the upper octaves were entirely inaudible. She had never heard a railway whistle. The pitches of certain notes also may be altered, as if by mistiming of particular strings within the ear. Sometimes there is a difference, as of half a tone, between the two ears. But the true significance of these symptoms is doubtless yet to be found, and it were a pity to preoccupy the ground with, conjectures. Variations of fluid pressure of course can hardly account for affections limited to one part of a continuous cavity.

In reference to the effect of section of the semi-circular canals upon the equilibrium of the body, the last experiments appear to show that the effects differ in different animals. Bottcher* found that no movements of turning ensued on careful section of the canals in frogs, and Mr. E. Hart obtained similar results, but Lowenberg* found * Report in " Journ. Anat. and Pliys.," Nov., 1873.

SECTION OF SEMI-CIRCULAR CANALS. 19

the case different with pigeons. By a modification in the method of operating, he sought to determine whether the movements were caused hy pain, as supposed by Flourens, or whether the presence of consciousness was necessary for these disturbed movements, and whether the cause consists in an irritation or paralysis of nerves. The results of his experiments are, (1) the disturbance of movement occurring after section of the semi-circular canals of the ear depends only upon this injury, and not upon any injury to the brain. (2) The vomiting observed by Czermak in his experiments depends upon injury of the cerebellum. (3) The disturbance of movement is the consequence of irritation of the membranous canals and not of paralysis of the same. (4) The irritation of the canals produces the spasmodic movements in a reflex manner without the co-operation of consciousness. (5) The transference of this reflex irritation of the nerves of the membranous canals to the motor nerves takes place in the thalamus opticus. With regard to the statement of Brown- Sequard, that section of the N. acusticus produces these movements, Lowenberg, operating upon rabbits, found that section of this nerve from the tympanum yields the same results, but in this case the semicircular canals are at the same time partly pinched and partly pierced.

It may be hoped that before long Professor Ferrier's experiments will give us a key to the real significance of these facts. The slightest affections of the tympanum,

c 2 among others syringing with cold water, or with water much above blood-heat, or the pressure of a column of cold water upon the membrane, will produce giddiness, often extreme ; the cerebral centres not only of emotion but of motion being thus eminently liable to be affected thro' impressions on the ear. It seems, therefore, the more remarkable that — in strong contrast to the eye — Dr. Hughlings Jackson should have found no lesion of the brain or cerebellum that has deafness for its result, result except thro' mechanically involving the auditory nerve.*

I may add that in one case, that of an elderly lady, long deaf with symptoms of nerve-affection, I have known an attack of hemiplegia distinctly improve the hearing ; and quite recently I examined the ears of a woman aged 45, extremely deaf, and found collapse and thickening of the membrane, with great impairment of the nervous power, forbidding all hope of benefit from treatment ; her death took place from disease of the heart shortly afterwards, and for more than a week previously her hearing was greatly sharpened.