Die Tulliosche Reaktion in Zusammenhang mit der Funktion des Mittelohres

Abstract

A method is described which enables us to get an objective insight into the degree in which the sound effects upon the internal ear. For this the reaction of Tullio is used; this reaction appears to be an important aid for the experimental physiology of the middle ear. Especially in pigeons the reaction can easily be provoked by making an opening in the bony semicircular canal. In response to sound a movement of the head starts now in the plane of the canal involved. Since, with this reaction, the sound reaches the middle ear via the normal way, the reaction can be used for a further study of the function of the conducting-apparatus. In the middle ear different modifications can be made after which the effect of these interventions is examined. Herefore it is necessary that the result of the reaction is also determined quantitatively which has not taken place up to now. In the first chapter a review is given of the literature on the function of the middle ear apparatus. The most prominent place is taken by the theory of Weber-Helmholtz which considers the tympanic membrane and the ossicular chain to be of great importance for the transmission of sound. This system transfers the acoustic vibrations via the oval window to the labyrinth. A second opening, the round window, serves for the escape of the movements of the labyrinthine fluid. This theory has been disputed by several investigators. Some conceptions are pointed out which believe another way for the transmission of sound to be present: a. o: a hypothesis which thinks the transfer of sound to be one of the most important functions of the round window. Other investigators, f. i. Hugh-son and Crowe, are of opinion that the round window must be considered as a safety-valve, especially in case of strong sounds; under normal circumstances even the loss of energy, developing through the movements of the membrane, would be noxious. An important function of the conducting-apparatus would be the transmission of the low frequencies. For the main part the, for the otolaryngologist so important differential diagnosis between internal ear- and middle ear-deafness, is based on this fact. In the last years many objections, also from clinical quarters, have been raised against this conception. An important contribution may be expected from the results of experimental conducting disturbances and of audiometric investigations. Summarizing the following functions can be ascribed to the middle ear apparatus: I. Transmission of sound. II. Sensitiveness of the ear for given frequencies. III. Protection of the internal ear. IV. Generation of subjective tones. An attempt is made to furnish a contribution about the importance of the middle ear apparatus in I and II by experiments in pigeons. The anatomy of the hearing organ of the pigeon is discussed as far as this is of importance for this investigation. The relations of the middle ear space are illustrated by half-schematic drawings. The middle ear of the pigeon is divided distinctly into two parts: a major part behind the tympanic membrane, a minor one embracing the two labyrinthine windows. Boths parts communicate by means of an opening, through which the stem of the ossicle, the columella, passes. The smaller part communicates with the air-containing space around the bony labyrinth by an opening, called by Ewald the foramen communicans. Through this opening interventions at both labyrinthine windows can be performed. Moreover an opening in the roof of the eminence is described which enables operation in the middle ear without impairing the tympanic membrane. The name foramen epitympanicum seems appropriate for it. The reaction of Tullio is discussed. This reaction is caused by an inadequate stimulation of the crista by sound. The opening must have the same value with regard to sound waves as the foramen rotundum has to the cochlea, to which the faculty is ascribed of enabling the labyrinthine fluid to allow the escape of sound waves which otherwise would have been extinguished through interference. The reaction and all its symptoms are extensively discussed. Tullio's explanation for this reaction is that the making of a fistula in the semicircular canal gives rise to a greater excitability of the crista. Huizinga, however, is of opinion that the reaction is due to the above mentioned dynamic development. The fact that the reaction disappears completely after sealing the opening with wax provides strong evidence in support of this supposition. After removal of the plug the reaction promptly reappears. This may be repeated several times in succession. We made use of the so-called minimum-reaction. Some operations in the middle ear have been performed, the importance of which has been ascertained by means of the quantitative alterations of the sound. The operations of the making of an aperture in the semicircular canal, the removal of the cochlea, the exclusion of the function of the round window and some procedures to prevent the function of the conducting-apparatus are described. Also in the auditory canal and the tympanic membrane some modifications may be made by which the hearing conduction is damaged. A plastic is described for a simple exposure of the tympanic membrane. The apparatus for the recording of the threshold values of the reaction in different sound frequencies is described. The sound is delivered to the pigeon by means of a loudspeaker; the intensity is measured by a sound-level-meter placed near the pigeon as near as possible. The minimum reaction is always read in the same way. It appears that when the values in decibels, obtained with frequencies of 100–3200 Hz are graphically laid aut, always a curve of a characteristic form is obtained. This is illustrated by different figures in the text. The minimum value of the reaction with 100 Hz is nearly always in the region of 100 db, decreases rather rapidly with the rise of the frequency, to reach at 600–800 Hz the lowest...