title: Diseases of the ear, nose and throat; medical and surgical.
text: (8) (A £ H x «> < » 2 J ° -i Z £ * O =* m 5 2 Z a ■ * O u» 3 °- « Z k f 0) »- (ft < OS a z cc IB a o o 3 J H < h o (0 > £ 05 V) o (/> z o Id t- V z o K 4 <* a S l ° S I u. o O u I </) 6 > Fl -a be { fc N l -1 u. t- u J LT1 o Z 1. o hi \¥ 0) ^ ^D o 2 1 00 b. i ! o CD 05 -1 , •, M l VO ae c Ul I u h Ul S UI* Ul 05 X 5 1 Z o o < J til o Ul Mil z I 1 ; J u. 1-' tt •J 8 Z 5 — — — •* u 2 1.1 ° h O UJ 1 03 j 5 i 1 6 R 5: jl- 2 z 7 — — t- z < UJ — — z u 1 o 1 < CG 10 GENERAL CONSIDERATIONS. Ear. — This includes thorough inspection of the pinna (Fig. 61), noting its general formation, its color, its sensitiveness to touch, and the presence or absence of swelling or cutaneous affec- tions. In examining the external auditory canal and fundus of the ear, the relative positions of the patient and examiner are of impor- tance. If reflected light is used, the source of light should be at least six inches farther back than the patient's head and upon the same level as his ear. The patient's gaze should be directly at right angles to that of the operator, which brings his ear broadside to his view. The introduction of the speculum requires considerable prac- tice before the proper degree of skill is acquired. The upper portion Fig. 10. — Introducing the aural speculum. Showing method of grasp- ing the patient's ear, 'how to hold the speculum in situ and the angle of the patient's head. of the pinna should be grasped between the second and third fingers and the ear drawn backward and upward, a procedure which tends to straighten the canal and to permit a better view of the fundus, while the speculum is held between the index finger and thumb of the left hand (Fig. 10). The right hand thus remains free for adjusting the head mirror and for the instrumentation incident to the examination .and the treatment. The introduction of the speculum never evokes pain unless it is clumsily handled, or when there is some disease of the canal walls. Upon its introduction the canal should be searched for evidences of inflammation, swelling, cutaneous disease, impacted cerumen, exostoses or foreign bodies. The fundus is next observed. It is rarely possible to obtain a com- plete view of the entire drum at one time except by moving the THE EXAMINATION OF PATIENTS. 11 speculum in different directions in order to inspect all the segments, and it is essential that the view be obtained by directing the eye directly through the central opening in the head mirror. Note upon the history chart, and if possible make a rough drawing of the appearance of the drum and ossicles; record the relative position and color of the surrounding structures, whether or not there is secretion, the size, location and general appearance of perforations, and the size and location of polypi and granulations when observed. 11. — Sharp's modification of Boswortlrs nasal speculum. In acute purulent otitis media a smear or culture from the pus may be prepared for bacteriological examination. It is possible to observe the condition of the lining membrane of the tympanum, and also to use a probe for the purpose of detect- ing uncovered bone through large perforations. In purulent cases the mastoid process should be inspected for swelling, redness and tenderness to pressure. If the mastoid symp- Fig. 12. — Author's modification of Bosworth's speculum with solid flaring blades. toms are positive, the temperature and pulse rate must be ascer- tained. Nose, Throat and Larynx. — The first step in the inspection of the nose is anterior rhinoscopy, by which is meant the inspection of the anterior portion of the nasal chambers, by means of reflected light. For the purpose of distending the nasal orifices numerous specula have been devised. Habit has much to do with each indi- vidual surgeon as to his favorite type. The author varies the form of speculum to meet the requirements of the nose to be inspected or upon which he intends to operate. The steel-wire speculum of Bosworth (Fig. 3), made in differ- 12 GENERAL CONSIDERATIONS. ent sizes, is an admirable one for examining both adults and children. When the vestibule is hairy, it may be necessary to employ a speculum with solid blades. Sharp's modification of Bosworth's (Fig. 11) fulfills the requirement. For operations the author makes use of his large-size modification of Bosworth's nasal speculum (Fig. 12), which flares at the end of the blade, or the one devised by Myles (Fig. 13). Fig. 13. — Myles's nasal speculum. While making the examination a note should be made of the size of the nasal apertures and the character and location of the secretions. If pus is found, its origin should be sought. A deeper view will determine the size of the turbinals and the color of the membrane covering them, the presence of septal deflec- tions, spurs, ridges, lesions of the septum or perforations. The view may be interfered with by the presence of mucus or scabs, which may be blown or wiped away. Swellings, polypi or new growths should now be observed. At this point the fuller examina- Fig. 14. — Flat wide platinum applicator. tion is facilitated by holding aside any soft tissue with a flat platinum applicator (Fig. 14), or it may become advisable to make an application of a weak solution of adrenalin chloride in order that the behavior of the tissue under its action may be observed." It may be necessary to make an effort to pass a probe into the opening of the maxillary, sphenoid or frontal sinus, a procedure which cannot always be accomplished until after the removal of the major portion of the middle turbinate bone. Posterior Rhinoscopy. — By this is meant the inspection of the posterior portion of the nasal cavities and of the epi- or rhino- THE EXAMINATION OF PATIENTS. 13 pharynx. This is accomplished by reflecting the light on to a small mirror passed through the mouth, beyond the soft palate (Fig. 15). The tongue of the patient is depressed by a tongue depressor held in the surgeon's left hand, while the mirror is manipulated by his right hand, the patient being instructed to relax the soft palate by attempting to breathe through the nose. Considerable practice is often necessary before a patient is able to submit to posterior rhinoscopy without gagging. In examining nervous patients or those with unusually sensitive throats, it may become necessary to anesthetize the pharynx and soft palate with a 4 per cent, cocaine solution, or draw the soft palate forward by means of a palate Fig. 15. — Posterior rhinoscopy, retractor (Fig. 16). Small laryngeal mirrors or Michael's post- nasal mirror (Fig. 17) should be employed. The office armamentarium should contain tongue depressors of various shapes. The Chapin tongue depressor (Fig. 3) is light, convenient and answers many needs. Glass and wood depressors, the former boilable and the latter to be destroyed after use upon one patient, have their advocates. To properly depress the tongue the mouth should be fully opened, the tongue to lie in its natural position (not protruded) and the depressor when laid firmly upon the dorsum in the median line forces it downward between the rami of the inferior maxillary bone. A good rhinoscopic view of the nasopharynx and postnasal chambers reveals the size of the posterior ends of the turbinals, projecting polypi, or discharges when present and the presence of adenoids or new growths in the nasopharynx. 14 GENERAL CONSIDERATIONS. Fauces and Pharynx. — In examining the oropharynx (Fig. 18), the surgeon should take a bird's-eye view of the gross appear- ance of the entire area, then observe the condition of the various parts, meanwhile recording abnormalities and diseases when found. To fully inspect the tonsils it is often necessary to employ a ring curette to search the crypts, or a tenaculum to pull the tonsil well out between the pillars. Any visible tonsil is pathologic, but in some the hypertrophy is extensive and the crypts contain cheesy ephithelial detritus. The color and thickness of the pharyngeal membrane are Fig. 16. — White's palate retractor. matters of importance. Hypertrophied glands upon the postpharyn- geal wall (Fig. 462) commonly indicate general lymphatic enlarge- ment of tonsils and adenoids, while atrophic conditions indicate chronic inflammation of the nasopharyngeal mucosa. The Larynx. — In examining the larynx either direct or indirect laryngoscopy may be employed. By direct laryngoscopy is meant the observation of the larynx through a straight tube inserted beyond the epiglottis, obtaining the illumination either by means of a small electric light situated at the distal end of the spatula Fig. 17. — Michael's postnasal mirror after the manner of Jackson's invention (Fig. 526), or by the Killian method, the light being reflected through the tube by means of a Kirstein headlight. By both of these means a direct view not only of the larynx is obtainable, but also of a large portion of the trachea. The indirect method of examination of the larynx is accom- plished by inserting the laryngeal mirror under the soft palate and pressing the entire soft palate upward, the tongue meanwhile being drawn well out of the mouth with a napkin held between the thumb and index finger of the surgeon's left hand (Fig. 19). The THE EXAMINATION OF PATIENTS. 15 light is now thrown upon the face of the mirror and thus the interior of the larynx may be observed during respiration and phona- tion. It will be found that during inspiration the cords open widely, but when the patient phonates "A" as in "HA" or "E" as in "HE" the cords approximate in the median line (Fig. 20). The laryngeal image must be quickly observed, as most patients are intolerant of prolonged manipulation of the larynx. Before introducing a throat mirror it should be warmed over a flame or immersed in hot water. In making laryngeal examinations it is necessary to note the ap- pearance of the epiglottis with regard to its color, position, ulcera- tion or swelling; likewise the arytenoids, aryepiglottidean and glosso- epiglottic folds. Attention is then directed to the laryngeal ventricles Fig. 18. — Anatomical conformation of the mouth and pharynx. 1, Palate. 2, Tongue. 3, Posterior wall of pharynx. 4, Uvula. 5, Anterior pillars. 6, Posterior pillars. 7, Tonsils. and the true and false cords; meanwhile the motility, color and elasticity of the cords are noted, and the presence or absence of nodes, crusts, foreign bodies and new growths is observed. Looking beyond the cords, it is sometimes possible to observe several rings of the trachea and even its bifurcation. Throat mirrors which admit of boiling are now manufactured, hence they may be kept sterile. A variety of sizes are requisite and numerous angles and bends in the shaft or mirror attachment will be found applicable to the great variety of throats. About five variations in diameter of mirrors (Fig. 3) from half to one inch will suffice. Recently an instrument has been devised by Flays (Fig. 494), which permits of direct inspection of the entire rhinopharynx and also the larynx, with the patient's mouth closed. The instrument is a cystoscope modified for use in this region and is known as Hays's 16 GENERAL CONSIDERATIONS. pharyngoscope. The light is furnished by two small electric bulbs, and the surgeon's eye placed to the telescope views the inspected field. The invention is quite recent and as yet the instrument has only a value as a diagnostic aid, but is especially useful in examin- ing bedridden persons. Fig. 19. — The laryngeal picture — cords widely separated. Additional Information. — In addition to the information thus far obtained by means of inspection, there are other procedures necessary to the complete examination of the ear, nose and throat. Ear. — Among these may be mentioned inflation of the ears through the Eustachian tube. The chief methods employed for this purpose are Valsalva's, Politzer's and direct inflation by means of the Eustachian catheter. THE EXAMINATION OF PATIENTS. 17 In Valsalva's method the patient is instructed to firmly grasp the nose between the thumb and forefinger to prevent the escape of air; then with the mouth closed the air is forced from the lungs into the nasal chambers and pharynx. Its normal avenue of escape being shut off, and the Eustachian tubes offering the least resistance, they open and the air rushes into the tympanic cavity. This method may be conveniently used while the ear is under inspection, and the presence of a perforation can occasionally be detected when otherwise it would escape observation. In Politzer's method a cone-shaped nose-piece connected to a compressible rubber bag by rubber tubing is fitted snugly into one nostril and the other nostril is closed by the index finger of the physician. The patient is then instructed to freely puff air into his cheeks without allowing it to escape, or he is instructed to perform the act of swallowing either with or without water, or he is told to Fig. 20. — The laryngeal picture — cords in apposition. repeat rapidly the letter "K," and while so engaged the surgeon compresses the rubber bag and forces air through the Eustachian tube into the tympanic cavity. The most efficacious and exact method is Eustachian cathe- terization. The Eustachian catheter (Fig. 3) should be constructed from pure silver, and be about eight inches in length and the distal end curved sufficiently to rotate snugly into the Eustachian orifice. Opinions vary as to whether the curve should be long and gradual or sharp. The advantage of pure silver in its construction is found in the flexibility of the instrument to meet the variations made necessary by intranasal irregularities and digressions in faucial conformation. For purposes of diagnosis in the routine treatment of chronic and of some acute affections of the middle ear, catheterization secures the most favorable results (Fig. 21). It is applicable mostly to adults, but even young children often submit to catheterization with good grace. Under favorable circumstances, with wide-open nares, the introduction of the catheter is unpleasant. Furthermore it is a painful procedure in patients whose membranes are hyper- 2 18 GENERAL CONSIDERATIONS. sensitive, or in those with lesions which obstruct the nose. This should be remembered by the surgeon while manipulating the catheter. A reputation for gentle and painless catheterization When catheterizing for the first time the brings many loyal allies. Fig. 21. — Proper position of surgeon and patient during catheterization of the Eustachian tube. 1, Catheter in position. 2, Otoscope. (Diag- nostic tube.) 3, The Dench middle-ear vaporizer with air douche in sur- geon's right hand. patient's confidence may be gained by making a preliminary appli- cation of a mild solution of cocaine and adrenalin chloride along the inferior nasal meatus and the Eustachian orifice. By doing this the tissues are both shrunken and anesthetized, and thus cathe- terization is made easy. It is not advisable to cocanize all cases as THE EXAMINATION OF PATIENTS. 19 a routine method. In introducing the catheter the nostril may be dilated with a speculum under reflected illumination, or the tip of the nose elevated with the surgeon's ringer. The catheter tip is now slid along the floor of the inferior meatus (Figs. 21, 22, 24), and its shank held in a horizontal position until it passes through the choana and dips toward the nasopharynx. At exactly this point the author ignores the usual rules, rotates the tip outward and upward with slight and gentle manipulation until it engages in the Eustachian orifice ; or following the same method of intro- duction the catheter may be first carried well over into the epi- pharynx and then drawn forward until it is firmly in contact with Fig. 22. — Catheter properly introduced along the inferior meatal floor. The catheter is shown as it emerges into the epipharynx and is about to be rotated into the Eustachian orifice. the posterior aspect of the soft palate, from which point it is rotated outward to little more than a right angle and its point enters the Eustachian orifice. A favorite method of catheterization with many operators is to rotate the tip of the catheter toward the median line after its point falls into the nasopharynx, then draw it firmly against the posterior border of the septum itself, after which it is rotated out- ward slightly more than 180° ; this usually brings its point in apposi- tion with the pharyngeal orifice of the tube. The catheter having been properly inserted many operators insert the tip of a Politzer air-douche bag directly into the funnel of the catheter and drive a blast of air into the middle ear. The direct contact of the hard- rubber tip of the air-douche bag with the catheter, in spite of the greatest care, usually gives rise to more or less pain, owing to the movement which is imparted to the catheter while squeezing the air douche. In order to avoid this a length of soft-rubber tubing may be interposed between the air bag and the tip which fits into the 20 GENERAL CONSIDERATIONS. catheter, and thus no shock is occasioned when the air douche is squeezed. The Dench middle-ear vaporizer (Fig. 21) is an admirable apparatus for tubal and tympanic inflation. It consists of a hard- rubber reservoir fitted with a stopcock, the turning of which changes the current of air so that it passes directly to the catheter or is diverted and made to carry medicated vapor from the solution in the reservoir. In order to determine the patency of the Eustachian tube the diagnostic tube (otoscope) is employed. This is a section of small, soft-rubber tubing about 30 inches long, into each end of which is Fig. 23. — Faulty introduction of the Eustachian catheter. The catheter tip has been inserted through the middle meatus, consequently it fails to enter the orifice of the Eustachian tube when rotated. inserted a conical tip (Fig. 21), one of which is placed in the ear of the patient, the other in the ear of the operator during catheteriza- tion. The character of the sound imparted to the ear of the surgeon is of diagnostic value in determining the condition of the Eus- tachian tube. In a normal tube the current of air produces a low, soft-blowing sound. In stenosis of the tube the note is high-pitched and rough. No sound is conveyed by the otoscope when the stenosis is complete. A tube which contains mucus emits a bub- bling sound. When a perforation exists in the drum, the otoscopic bruit felt by the operator is like that of air coming into actual con- tact with his own tympanic membrane. Obstacles to Catheterization. — The chief difficulties which arise during catheterization are, first, inability to pass even the smallest catheter through the nasal meatus on account of septal deflections or spurs. When the deformity is small it is often possible to enlarge the space by contracting the soft tissues by applying adrenalin THE EXAMINATION OF PATIENTS. 21 chloric! ; otherwise the surgical removal of the obstruction is indicated. As a substitute for such emergencies a catheter with a longer curve may be passed through the opposite side of the nose, and turned behind the posterior border of the septum into the affected tube. An annoying difficulty commonly encountered is the variation in the form, position and prominence of the tubal orifice. These difficulties are overcome by adjusting the curve of the catheter together with skillful manipulation, and, in extreme cases, the rhinopharyngeal mirror allows a visual inspection of the field. Whenever the Eustachian tube is found to be obstructed, a Fig. 24. — Catheter tip in position within the Eustachian orifice. Eustachian bougie should be passed through the catheter and along the Eustachian tube into the tympanum. Eustachian bougies are made of celluloid, whalebone or gold, and should be of sufficient length to project at least one and one- half inches beyond the distal opening of the catheter (Fig. 25). Method of Passing the Bougie. — The catheter is first intro- duced in the usual manner described for inflation, and air is blown through the tube in order that the patient's statement may be con- firmed by the diagnostic tube bruit and its proper position verified. A small-sized bougie is then passed through the catheter until its end comes in contact with the walls of the Eustachian orifice, where it produces a slight sensation of discomfort to the patient. The utmost gentleness must be used in forcing the bougie through the Eustachian tube, in order to prevent the formation of false passages or lacerations of the tubal membrane. If an obstruction is encoun- tered, then gentle continuous pressure usually serves to overcome it. If not overcome after a few seconds of pressure, it is advisable to withdraw the bougie a short distance and make a second attempt. 22 GENERAL CONSIDERATIONS. It is rare to find an obstruction which cannot eventually be over- come. In obstinate cases it may become necessary to employ the electric bougie, perfected by Duel. As the bougie approaches the tympanic cavity the patient usually experiences a bubbling sound. Occasionally the operator is able to see the dark outlines of the bougie through the semitransparent drum membrane. Even in normal Eustachian tubes, slight resistance is usually found when the bougie passes from the membranous to the bony portion of the tube. If care is not exercised in properly adjusting the catheter Fig. 25. — Eustachian bougie passed through a catheter, and projecting about 1*4 inches (about the length of the Eustachian tube) from the distal end. before attempting to pass the bougie, the latter instead of engaging the Eustachian tube may pass down along the pharyngeal wall (Fig. 22). Whenever this occurs the catheter immediately rotates downward away from its position in the tubal opening. Dangers of the Eustachian Bougie. — As before stated, great care must be exercised in order to prevent the formation of false passages or abrasions in the tubal membrane. If inflation is prac- tised after such an accident there is danger of forcing air into the Fig. 26. — Siegel pneumatic speculum. submucous tissue, and this evokes alarming emphysema. Emphy- sema from this source is immediately relieved by puncture at any convenient point. The distance traversed by the bougie must be carefully gauged, either by markings or by previous knowledge gained by comparing the proportionate lengths of the bougie and catheter; otherwise the bougie might be forced across the tympanum and made to perforate the drum membrane. Bougies should be inspected at frequent intervals and discarded upon the slightest evidence of weakness at any point, in order to prevent accidental breaking of a small segment while within the lumen of the tube. THE EXAMINATION OF PATIENTS. 23 Siegel Pneumatic Speculum. — In order to ascertain the mobility of the drum membrane and ossicles a suction or pneumatic specu- lum is employed. Two well-known varieties are in general use, the Siegel and the Delstanche. The Siegel speculum is a modification of the usual aural speculum, so constructed that when snugly inserted (Fig. 26) into the aural meatus its interior is rendered air-tight by means of an oblique glass window covering the distal end, through which the movements of the drum may be observed. The speculum is fitted with a compressible rubber bulb attachment which enables the surgeon to exhaust or compress the column of air in the external auditory canal. A lens is sometimes provided which serves to magnify the drum and its landmarks, and gives a clearer view of its mobility. By compressing and relaxing the bulb, the long process of the malleus and the drum are forced fully inward and outward unless they are bound down by adhesions. The functional tests of hearing are fully described in Chapter IV. For a description of transamination and radiography of the nasal accessory sinuses the reader is referred to Chapters XXXVII and XXXVIII. CHAPTER III. THE PHYSIOLOGY OF HEARING. To better understand the physics of sound production, trans- mission and perception, we will briefly allude to some of the most authentic laws relating thereto. Sound is a physiological phe- nomenon or sensation, induced in the mechanism of hearing by the vibratory motion of matter. Any elastic medium is capable of con- ducting sound vibrations, and their intensity varies inversely as the square of the distance from the ear, not depending on the density of the air in which the sound is heard, but on that in which it is generated. The intensity is directly proportional to the square of the maximum velocity, and also to the square of the amplitude of vibration. The intensity of sound does not weaken according to the law of inverse squares provided the sound is confined in tubes, inasmuch as the walls of the tubes prevent loss by diffusion. The velocity of sound depends on the elasticity, density, and somewhat on the molecular structure of the medium through which it is transmitted, and it is directly proportionate to the square root of the elasticity of the air, and inversely proportionate to the square root of the density of the air; hence, velocity is not affected by changes in density if the temperature remains the same, as the elasticity and density vary in the same proportion but act differ- ently. The velocity of sound in water is four times its velocity in air, in iron nineteen times, and in pine wood ten times, because the elasticity of these media is vastly greater in relation to their density than is the elasticity of air in relation to its density. The disturb- ance of bodies by any form of impact or friction produces vibration in the molecules of such bodies ; this results in sound. Variations in the quality or pitch of sound depends upon the regularity and rapidity of the vibrations. If sonorous vibrations are rapid and occur at regular intervals, they are perceived by the normal ear as musical sounds. It has been proven by experiment that less than 16 double vibrations per second are received individually. The rapidity of the vibrations in order to procure musical sounds must be between 16 D.V. and 32,500 D.V. per second. When the vibra- tions are irregularly repeated, or are below 16 double vibrations per second, the resultant sound is perceived by the ear as a noise. Depending upon the rate of vibration, the note is of low or high pitch, until the vibrations follow each other too rapidly for the ear to perceive them. The limits of sound perception are called the tone limits of the ear, and range from about 16 double vibrations per second to about 35,500 double vibrations per second. These figures are only ap- proximate, as many ears can distinguish sounds below and above the figures given. (24) THE PHYSIOLOGY OF HEARING. 25 The sound conducting or transmitting apparatus is that portion of the hearing organ from the concha to the labyrinth. The perceptive or analytic portion of the organ of hearing consists of that part of the ear extending from the labyrinth to the brain, and includes the labyrinth, Corti's organ, auditory nerve, and the distribution of the auditory nerve fibres to their respective brain centres. It may be remarked in passing that the peri- and endolymph circulating in the labyrinth belong to both parts of the hearing apparatus, since these fluids act as agents which assist both in conducting and in receiving wave impulses. Individual sounds or musical notes, as ordinarily produced, are almost invariably accompanied by overtones of higher pitch which modify the timbre of the fundamental note. Harmonics (over- tones) are more noticeable in the lower portions of the musical scale, and this should be remembered as a fact of considerable import in connection with the functional examination of the ear. YVe record the various rates of vibration as follows: (C~ 2 , C" 1 , C, Ci, Co, Co, C 4 , etc.). This means that C" 2 , having 16 double vibrations (D.V.) per second, is one octave below C" 1 , having 32 D.V. per second, and this in turn is an octave below C, which has 32 D.V. per second. Whenever two notes are an octave apart they differ in their rates of vibration in the proportion of two to one. Any one or all portions of the conducting apparatus may become diseased, and it is the purpose of the hearing tests to differentiate, localize and diagnosticate the nature and degree of the lesion. To illustrate : A sound wave, striking the concha, collected and reflected by its folds, travels through the column of air in the external auditory canal and impinges upon the membrana tympani. This starts a molecular movement in the ossicles, which, in their turn, transmit this impulse to the endolymph, compressing and then rarifying it, sensations which are perceptible at various parts of Corti's organ and interpreted in the remainder of the perceptive apparatus. The impulse thus received is carried, as every impulse received by a specific nerve is carried, to its proper receptive and analytical centre in the brain, and is there recognized as a given sound. In order that this physiological function shall be properly carried out it is necessary that the ear in all its parts be normal. THE SOUND- CONDUCTING APPARATUS. The Auricle (Pinna). — The functional value of the auricle is that of a collecting appendage — to collect the sound waves — and while its value as such is not very great, it undoubtedly exercises considerable influence in directing the sound waves toward the meatus. This peculiarity is more marked in animals than in man. Of the different depressions in the pinna that of the concha has been proven to have the most important bearing upon the act of hearing. The acuteness of hearing is slightly influenced by the angle at which the auricle is attached to the head, but the direction from 26 GENERAL CONSIDERATIONS. whence a sound emanates cannot be accurately determined except by binaural hearing. The tragus acts as a reflector for the sound collected and reflected from the concha, and from it the sound caroms into the external auditory meatus. The muscles attached to the human pinna have practically no influence in aiding in the collection of sound waves. The External Auditory Canal. — The external auditory canal conveys the sound waves to the tympanic membrane. Owing to the exaggerated concavity of the posterior end of the cartilaginous meatus and that of the anterior-inferior portion of the osseous canal, a considerable portion of the sound waves are deflected from their course, and thus do not directly strike the surface of the drum membrane. Experiments show that the width of the auditory meatus has but slight effect on sound perception. The external auditory canal, like all tubes, has an intrinsic note of its own, but unless the canal is filled with fluid, or its membranes have become much thickened, this intrinsic note is difficult of demonstration, for it lies far above the range of the speaking voice. The Membrana Tympani. — The drum membrane has two func- tions. It not only protects the middle ear from atmospheric, mechanical influences and bacterial invasion ; but it also acts as a drumhead to receive and transmit sound waves to the ossicular chain. Being only slightly elastic, it is stiff enough to lessen the effect of after-vibrations. Its large size in proportion to that of the stapes footplate is a mechanical advantage for increased power transmission. Like the auditory canal, its intrinsic note exerts an unappre- ciable influence upon the sense of hearing, and the drum therefore can receive and transmit simultaneously tones varying in intensity, in pitch and in velocity. A similar principle is observed in the artificially constructed diaphragms such as are used in the Edison and Victor phonographs ; the most complicated combinations of sound are simultaneously transmitted. According to Helmholtz, the funnel shape of the drum increases its power of resonance and mechanically augments the force trans- mitted to the malleus. Mach and Kessel observed that the greatest excursion of the membrane is obtainable in its posterior segment. The Ossicles. — The vibrations of the membrana tympani induced by sound waves are now believed to be transmitted to the labyrinth, chiefly through the ossicular chain, although to some extent they reach the labyrinth through the medium of the air con- tained in the tympanic cavity and the fenestra rotunda. The experiments of Politzer give considerable weight to his contention that the ossicles vibrate as whole bodies with extensive amplitudes, by the action of the sound waves upon the drum mem- brane, and that proportionately the amount of vibrations of the ossicles depends largely upon the mechanism of their joints. By further experiments the same author demonstrated that when the air is condensed in the tympanic cavity a considerable out- THE PHYSIOLOGY OF HEARING. 27 ward excursion of the membrana tympani with the handle of the malleus takes place, and a distinct motion of the articular surfaces of the malleus and incus is visible, while the excursions of the long process of the incus are trifling. Helmholtz emphasizes the impor- tance of the peculiar mechanism of the malleo-incudal articulation, wherein with the inward excursion of the malleus its cog catches that on the body of the incus, forcing the latter to follow in turn. On the other hand, with the outward excursion of the malleus its cog unhooks itself from the incus, thus allowing the former to make a wide excursion outward ; meanwhile the incus and stapes move only slightly. This principle serves as a protection against the injurious influences of violent concussions upon the drum membrane, and in like manner shields the labyrinth from excessive intratympanic pressure induced by violent inflation through the Eustachian tube. The relative range of motion attributable to the ossicles is roughly estimated in the following proportions : Stapes 1, incus 2, malleus 4. Over-vibration of the ossicular chain is prevented, in large measure, by the articular ligaments and by the ligaments and the folds of mucous membrane which connect them with the walls of the tympanum. According to Rieman and Helmholtz, these liga- ments and folds and the ossicular muscles maintain the necessary tension between the drum and the ossicles for a uniform reception and conduction of the various sound waves. Tympanic Muscles. — The mobility of the ossicles is directly modified by two muscles which regulate the degree of tension between the ossicles, drum and labyrinth. The tensor tympani muscle, innervated through a branch of the fifth nerve, is attached to the manubrium, and on contraction draws the ossicles inward and upward, tensities the drum membrane, crowds together the ossicular articular surfaces, forces the stapes footplate into the oval window and increases the intralabyrinthine pressure. The stapedius muscle, innervated through the seventh nerve, antagonizes the mechanism described above, since by its 'traction the drum membrane is relaxed, the stapes footplate is rotated out of the oval window, the incus and malleus are pushed slightly outward against the drum membrane, and the tension in the labyrinth is diminished. Politzer maintains that the chief func- tion of these muscles is to relieve alterations in the position and tension of the ossicular chain, and to protect the labyrinth from sudden condensations or rarifications of the air in the middle ear or external auditor}- meatus ; hence, they regulate the degree of tension of the hearing apparatus. The Eustachian Tube. — The Eustachian tube is chiefly con- cerned in the two important functions of (1) ventilation and con- densation of atmospheric pressure, and (2) drainage of the middle- ear cavities. A consideration of the action of the muscles attached to the pharyngeal end of the Eustachian tube is important, for the normal pneumatic balance in the middle ear is dependent on their efficacy as openers of the Eustachian tube. Experiments have conclusively 28 GENERAL CONSIDERATIONS. proven that the walls of the Eustachian tube during quiescence are in the main in contact throughout, and that the act of swallow- ing is the chief agency by which the air balance of the middle ear is maintained. The tensor palati and the levator palati muscles, both of which are concerned in the act of swallowing, possess the further function of increasing the patency of the Eustachian tube during contraction as a result of their area of attachment to its fibrocarti- laginous orifice. When at rest the cartilaginous portion of the tube becomes permeable as a result of even a slight increase in air pressure. This is especially true if the intratympanic pressure is raised, for the tube permits of air transit toward its pharyngeal mouth with more facility than in the opposite direction (Fowler). It can be seen readily that the combined action of these muscles greatly increases the calibre of the inner end of the tube, and that the act of deglutition brings this combined action into play as often as it is repeated, so that under normal conditions the air balance in the middle ear is so frequently adjusted that the membrana tympani and middle-ear structures are not disturbed from their normal equilibrium. Considered pathologically, the permeability of the Eustachian tube is in close relation to the hearing function. Inflammatory swelling and thickening of the tubal mucosa, accumulations of mucus within its calibre, tend to induce rarification of the air con- tained in the tympanic cavity and consequent retraction of the drum membrane, tinnitus and hardness of hearing. A partial vacuum may also occur in the middle ear because of nasal obstruction, inasmuch as with this condition combined with deglutition the tube is opened and the air in the nasopharynx becomes rarified, and this rarification necessarily affects the middle ear. Rarification of the air in the middle ear, besides causing con- gestion and exudation, allows the atmospheric pressure in the external auditory meatus to carfy the drum and ossicles inward, and thus the stapes crowds against the oval window. Fowler has shown, by a series of interesting experiments, that the normal air tension in the middle ear is slightly above atmos- pheric pressure, especially after each act of swallowing, and he also claims that with each deglutition there is a tensification of the tensor tympani muscle to prevent disturbances in sound trans- mission and possible trauma to the conducting mechanism. Fowlers Experiment. — At first sight this may appear to be a modification of Valsalva's or Toynbee's experiment, but as its per- formance is different from either of these and its results opposite to the latter, it would appear that the experiment is quite distinct. While the nostrils are tightly closed by pinching them together with the thumb and forefinger as near their free borders as pos- sible, gently increase the air pressure in the nose and nasopharynx by attempting to expire through the nose, and without letting up on this pressure execute the act of swallowing. The result will be the inflation of both middle ears. This is brought about by the THE PHYSIOLOGY OF HEARING. 29 opening of the Eustachian tubes during the increased nasopharyn- geal air pressure due to the patient's efforts and to the ascent of the soft palate. During the second stage of deglutition a negative pressure is avoided because the primary increase in pressure and the bulging of the elastic lateral walls of the nose supply a sufficient amount of air to enable the descent of the soft palate to occur without creating a vacuum in the nasopharynx. This method is of value because it accomplishes the inflation of the middle ears in a more physiological manner than any method which does not necessitate the use of instruments. In selected cases it may be used by the patient for regular inflation. To remove all possibility of harm Fowler uses a small rubber balloon attached to a nose piece (Fig. 27). If the patient closes one nostril and inserts the nose piece tightly into the other, he can automati- cally inflate his ears by distending the bag by filling it with air Fig. 27. — Fowler's middle-car inflation apparatus. through his nose and then swallowing several times, or until the balloon has collapsed. The balloons are made of different tensile strengths so that any pressure desired may be brought to act on the Eustachian tubes during the act of swallowing. It is a peculiar property of these balloons that the pressure necessary for their inflation remains almost stationary no matter how fully they are inflated, and likewise during their deflation the pressure does not materially change until the balloon is on the point of collapse. SOUND-PERCEIVING APPARATUS. A study of the physiology of the sound-perceiving apparatus or internal ear necessitates a division of this portion of the hearing apparatus into that of: {a) the vestibule; (b) the semicircular canals; (cj the cochlea. The inward excursion of the footplate of the stapes induced by the sound waves carries a like impulse to the labyrinthine fluid, which becomes displaced in the direction of the round window, which is the point of least resistance, and according to Helmholtz the membrana basilaris of the cochlea is forced in the direction of the scala vestibuli, where it is made extremely tense on account of the resistance encountered at the cochlear apex. The exact function of the various structures of the labyrinth is not yet fully known, but it may be stated as the general opinion 30 GENERAL CONSIDERATIONS. of physicists that the vestibular apparatus is chiefly instrumental in controlling bodily equilibrium (Fig. 28). The otoliths are supported in the medium within the utricle and saccule, upon delicate hair-like projections, and, according to Breuer, with each forward movement or inclination of the head they tend to retain their normal position and thus bend the hairs which are their support, thereby inducing the specific sensations in the brain centres, the interpretation of which gives to the individual a conception of the relation of the head to the line of gravity. The Semicircular Canals. — Contrary to the belief of the earlier writers that the semicircular canals by their peculiar arrangement enable the ear to locate the direction of sound waves, it is now known that they have no influence relating to the perception of sound. On the other hand they constitute the organ of co-ordi- nation of the movements of the body. The tests of Barany and Fig. 28.— Showing thick membrana basilaris near the lower end of the basal coil. (From Shambaugh's collection. With permission.) others, hereinafter described (see Chapter XXIII), explain more fully the function of the semicircular canals. Cochlea. — Corti's cells (ciliated), about 2000 in number, are generally believed to" constitute the terminal apparatus of the acoustic nerve. The cochlea, therefore, constitutes the organ for the reception and differentiation of sound waves, which are in turn conveyed through the auditory nerve trunk to the cortical centre of hearing. Many investigators believe the latter to be situated in the posterior two-thirds of the first and second temporal convolu- tions. Upon reaching the acoustic centres the waves are inter- preted as sound. Helmholtz's theory of sound analysis assumes that the basilar membrane of the cochlea contains a considerable number of sound- ing boards or resonators which are attuned to certain tones. These resonators are set into action by the aqua cotunnii, and the^ vibra- tions thus produced are transmitted to the brain as impressions of sound by the nerve fibres corresponding to these sounding boards. Shambaugh, whose researches in the anatomy of the labyrinth of the ear have given him an intimate acquaintance with the details of the complicated structure to be found in the inner ear, has formu- THE PHYSIOLOGY OF HEARING. 31 lated the following conclusions regarding the physiology of the cochlea : — 1. The end organ in the cochlea, the so-called organ of Corti, is the mechanism whereby the physical impulses of sound waves are transformed into the nerve impulses which result in tone perception. 2. The particular structure of the organ of Corti in which this transformation from a physical to a nerve impulse is accomplished is the hair cell. 3. The stimulation of these hair cells is brought about by an interaction between the projecting hairs and the overhanging mem- brana tectoria. Fig. 29.— 3ft, Membrana tectoria about one-half turn from the lower end of the basal coil. (From Shambaugh's collection. With permission.) 4. While Helmholtz, and those who have followed him, advocate the hypothesis that the membrana basilaris (Fig. 28) is thrown into vibrations by the impulses of sound waves passing through the fluids in the labyrinth, in this way carrying the hair cells up against the under surface of the membrana tectoria (Fig. 29) and resulting in their stimulation, Shambaugh concludes that the membrana tectoria is the active agent which, by respond- ing to the impulses in the endolymph, vibrates and thus brings about the stimulation of the underlying hair cells. His reasons for placing the active agent in the membrana tectoria rather than the membrana basilaris are stated as follows : In the first place, the three end organs found in the labyrinth of the ear, the macula acustica in the vestibule, the crista acustica in the semicircular canals, and the organ of Corti in the cochlea, -all have a common origin in the primitive otic vesicle. They are all three constructed on exactlv the same fundamental plan, consisting of hair-bearing cells and a superimposed epithelial structure. This 32 GENERAL CONSIDERATIONS. overhanging epithelial structure in the macula acustica is the otolith membrane, in the crista acustica it is the cupula, while in the organ of Corti it is the membrana tectoria. Since the stimula- tion of the hair cells in the macula acustica, as well as in the crista acustica, is brought about by a movement of the super- imposed epithelial structure, the otolith membrane and the cupula respectively, it is rational to conclude that the stimulation of the hair cells in the organ of Corti is also brought about by the move- ments in its superimposed epithelial structure, namely, the mem- brana tectoria. In the second place, he has found that the mem- brana basilaris is incapable of performing the role of a vibrating structure, attributed to it by Helmholtz and those who have fol- lowed him, for the following anatomical reasons : The membrana ^s-*^7 Fig. 30.— Mt, membrana tectoria near the apex of the cochlea. S II, streifen of Henson. (From Shambaugh's collection. With permission.) basilaris disappears as a possible vibrating structure near the lower end of the basal coil at a point where the organ of Corti is still found. The radiating fibres off he membrana basilaris toward the lower end of the basa-1 coil, where they are becoming shorter instead of becoming thinner, as they should do in order to fulfill the physi- cal requirements of string resonators, in reality are found to become thicker as the end of the coil is approached. Again, a fundamental principle in the Helmholtz theory is that each radiating fibre of the basilar membrane must always respond to the same tone. This is rendered impossible because of a blood-vessel attached to its under surface, the dilation and contraction of which must cause the several radiating fibres to respond at different times to tones of different pitch. For these fundamental anatomical reasons Shambaugh concludes that the membrana tectoria is not only the logical struc- ture for responding to sound impulses in the endolymph, but that it is anatomically impossible for the membrana basilaris to fill this role. 