Walter Hughson

LXIV An Experimental Study of Bone Conduction

A very satisfactory material was finally found; it is a loosely strung fine-wire mesh, supported on small posts of soft rubber. This material proved to be an excellent screen against mechanically conducted tremors. Not only did it obliterate the threshold tremors to one’s hand held in contact with the wire surface, but it equally screened against tremor when the sound intensity emitted by the speaker was greatly increased. When the deaf cats were placed on this material and retrained, the responses occurred a t the previous thresholds. As we had thus satisfactorily excluded the occurrence of tactile stimulation by way of the feet, at all frequencies up to 1,000, we were forced to conclude that the stimuli were acting on receptors other than those in feet or legs. While the possibility of some extra-cochlear, cranial receptor cannot be entirely excluded, a more obvious source of tremor reception turned out to be the body surface of the animals, particularly the fur! The unexpected but conspicuous ability of a cat’s pelt (bearing its fur) to pick up and to hand on tremor at the threshold intensities was tested and definitely proved. If one may argue from the qualities of the dried pelt to the skin of the living animal, it seems reasonable to conclude that in cats the body surface may provide a good medium for amplificatory reception of loud sounds.

XXIV Estimation of Improvement in Hearing following Therapy of Deafness

For many years all therapeutic efforts directed towards the prevention and alleviation of deafness have represented a relatively remote approach to the problem. The chief concern has been the control of infection in the upper respiratory tract and in the ears, its prompt recognition when present, and the immediate adoption of appropriate therapeutic measures. Strangely enough, the hereditary factor was given great importance long before general constitutional disorders were considered as contributory to impaired hearing, regardless of the acute infectious episodes so frequently developed in the establishment of a well taken past history. The pendulum has swung far back in the past ten years or at least swung far the other way. We now know that true hereditary deafness or congenital deafness, in the sense that the parents contributed a mutual defect to the offspring, is probably a rare condition. In the natural course of prenatal development, certain biologic defects occasionally manifest themselves in the normal development of the organ of hearing. These biologic defects render this particular anatomic structure peculiarly susceptible to the trauma of infection or constitutional disease of any character. The breakdown may occur in utero, it may be a neonatal development, or may manifest itself at any time in the first three years of life. Its incidence thereafter is progressively and strikingly less.

XXV A Summary of round Window Graft Operations Performed for Deafness

A brief review of the history and experimental background of round window grafts in the surgical treatment of deafness might serve to place the procedure on a clearer and more rational basis. The actual function of the round window may still be a matter of some uncertainty but an observed and repeatedly confirmed experimental finding led to the belief that one function of the window and its membrane, at least, was to dampen the intensity of acoustically induced stimuli reaching the perceptive mechanism of the inner ear.

An experimental study of the neural mechanism hearing

The technical difficulties involved in an investigation of this kind invariably make the information obtained rather insignificant in relation to the amount of time and effort put forth. Experiments must be repeated many times before a dependable method can be developed, and even then an inevitably high mortality in the experimental animals persists Before consistent success can normally be achieved. The data upon which the following observations are based represents a series of chronic experiments carried out in the Laboratory of Otological Research at the Johns Hopkins in 1934, 14 in number, and a subsequent extensive investigation during the past year in the Otological Research Laboratory of the Abington Memorial Hospital. In the first group, partial and graded division of the auditory nerve was carried out under high binocular magnification. In all experiments partial or complete division of the nerve was considered successful only if the blood supply of the cochlea remained intact.

III. Discussion from the Point of View of Animal Experimentation. LXXVII

A striking feature of these results is the indication that the resonant area for each particular tone is located in the ear of the guinea pig in the same relative position as in the human ear when the human location is determined by graphical integration of the most recent data for differential sensitivity to pitch. The same close grouping of low tones near the helicotrema appears in both cases.

VI The Inner Ear from an Experimental and Clinical Standpoint

The present discussion will be confined entirely to that part of the inner ear concerned with auditory sensation and not with the vestibular apparatus. The extraordinary delicacy of this apparatus and its amazingly designed structure have made it a fascinating field of investigation both for physiologists and otologists since Cortis organ was first described. In the past few years, as new methods of experimentation have been developed, great impetus has been given to scientific effort in this particular field of research. Few problems present more interesting material to the investigator than does this part of the auditory apparatus. In the same way its importance, from the standpoint of the clinician, has been emphasized repeatedly in recent years with an increasing appreciation of the role remote factors and conditions may have upon the development of impaired hearing. It is no longer possible to deal with inner ear deafness solely by prophylaxis against possible infection or the elimination of infection already present; nor can specific procedures designed to increase the efficiency of an end organ already impaired be the rational therapeutic effort. Established physiologic principles together with carefully analysed clinical data must furnish the foundation upon which any diagnostic structure is to be built.