Supravital reduction reaction of Nitro-BT for demonstration of reduction potency in electron transfer system of mitochondria was performed by intracochlear perfusion in guinea pigs treated wtih kanamycin (KM, 400mg/kg, i. m.) and 2 hr. later with furosemide (100mg/kg, i. v.). Differential pinna reflex test in wide frequency range (20k-500 Hz) was performed on 20 young adult guinea pigs. Marked swelling, intracellular edema and decrease in the reaction product occurred extensively in the outer hair cells (OHC) in guinea pigs with complete loss of the pinna reflex 5 min. after the furosemide injection. These changes of OHC became decreased 2 hr. later, when the pinna reflex showed transient improvement. However, these changes became again increased 24 hr. after the injection, when the loss of the pinna reflex recurred. On 7 days after the injection, loss of OHC in the lower turn occurred.

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Changes in osmolality of perilymph, CSF and serum with time after peroral and intravenous administration of 2g/kg urea were investigated. After peroral administration, the osmolality of these three body fluids elevated slowly, reaching a peak in 2 hours. In case of intravenous administration, the serum osmolality peaked rapidly at 15 minites and then decreased gradually. The osmolality of perilymph and CSF, however, had a gradual increase, reaching a peak in 1 hour. The Lyper-osmolality induced by urea administration perorally or intravenously remained for full observation periods of 3 hours. This hyper-osmolality may have a possibility of the reduction of the endlymphatic pressure.

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Serum, CSF, scala tympani perilymph and scala vestibuli perilymph werecollected from normal guinea pigs both before and after peroral administration of 50% Glycerol (12ml/kg), and the sodium and potassium concentration were assessed using a microflamephotometer.
Substantial increases in sodium concetration were found in scala tympani perilymph, scala vestibuli perilymph, and CSF, while no significant change was observed in serum.
Increases in potassium concentration were found in the same fluids in which the sodium concentration increased.
These results are considered to have been caused by dehydration induced by the osmotic agent, Glycerol.

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The medical decompression of endolymphatic hydrops is the chief therapy of Meniere's disease. Especially, Isosorbide, one of the osmotic diuretics, is clinicaly confirmed to be effective for Meniere's disease. In order to establish the ground of the medical decompression of endolymphatic hydrops, Isosorbide was administered to the guinea pigs with experimental endolymphatic hydrops. Endolymphatic hydrops was readily produced experimentaly by cauterizing the endolymphatic sac with 10% silver nitrate solution.
The following results were obtained, 1) The cochlear structures were observed after administering Isosorbide and foldings in Reissner's membrane were commonly seen.
2) The hearing loss of guinea pigs with hydrops were not remarkably improved by intravenous injection of Isosorbide.
3) Administration of Isosorbide reduced endolymphatic pressure of guinea pigs with hydrops.
4) The osmotic pressure of serum and perilymphatic fluid of normal guinea pigs ascended after administering Isosorbide.

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The effectiveness of isosorbide, the dianhydrate of sorbitol, in lowering the perilymphatic pressure and elevating the perilymphatic oxygen tension was shown in ten fasting cats. The cochlear aqueduct of the cat was obliterated two to four weeks proir to the measurements. The perilymphatic pressure was measured using servo-controlled micropipet system. The oxygen tension was measured using polarographic technique. Both the effects of the intravenous and oral administration were tested. By the intravenous administration (2g/kg), the perilymphatic pressure has shown 158% drop in 24 minutes. Strong rebound phenomenon (135% rise to the initial value), However, was noted in 150 minutes. On the contrally, there noticed was no rebound phenomenon in oral administration where 60% drop was monitored in 50 minutes. Perilymphatic oxygen tension was elevated up to 246% of the initial value in 13 minutes by the intravenous administration of isosorbide.

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The modification of the endocochlear potential (EP) in double sound exposed guinea-pigs was studied. The sound used for 4 hours to expose was a pure tone of 2 KHz at 145 dB SPL. The second sound exposure was made 30 to 40 days after the first. The EP, in 1 to 10 days after the second sound exposure, was in low level, however, in 20 to 30 days, it returned to the normal level. The anoxic EP in double sound exposed guinea-pigs never gave value more negative than O mV. These results were similar to the modification of the EP in single sound exposed guinea-pigs which we had previously reported, except the longer recovery period.

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The influences of blast on auditory organs were studied experimentally with a scanning electron microscope. Guinea pigs were loaded with maximum pressure 1.0kg/cm2 for 0.2 sec. or 1.0 sec. via the external auditory canal. the changes of sensory hairs of inner and outer hair cells were observed with a scanning electron microscope, and the following results were obtained. 1) Sensory hairs were injuried more in basal and second turns than in third and subsequent turns. 2) Outer sensory hairs were injuried more than inner ones, the changes of inner hairs often slight, but where outer hairs were injuried severely, inner hairs were injuried too. 3) The injury of sensory hairs was not continuous, and the extent of injury was not constant. 4) When pressure loading was prolonged to 1.0 sec., the injury of sensory hairs became severer, the extent of injury wider, and the injury often continuous from the basal to the upper turns.

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Effects of the long-term electrode implantation in the scala tympani were investigated with normal guinea pigs. Teflon-coated Pt-Ir wire of about 0.12mm in outer diameter was implanted through the round window into the scala tympani without any damage to the ossicular chain. Hearing of the animal was evaluated sequentially with ABR. Recordings were made with the electrodes implanted in the bone at the top of the head.
In two of the five animals examined, hearing worsened more than 30 dB in half a year after electrode implantation. This was not due to the damage of the inner ear, but to the middle ear pathology such as adhesion of the tympanic membrane to the promontrium and the growth of the granulation tissue around the electrode. Other three animals showed less than 15 dB hearing loss. SEM examination showed that electrodes were coated with thin membrane of connective tissue at its entrance to the round window membrane and at the portion implanted in the scala tympani.

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Observations were made on the development of the round window and its membrane in human embryos. Materials subjected to this study were nine fetuses of 8-36 weeks with C. R. length of 20.7mm, 50.5mm, 60.0mm, 72.0mm, 84.0mm, 155.0mm, 184.0mm, 205.0mm, and 313.0mm respectively. After these materials were fixed with formalin and embedded in paraffin, serially sliced specimens of 5um were prepared. The following findings were obtained from this experiment:
1. Crista semilunaris located at the bottom line of the niche of the round window protruded from the praninentia utriculoampullaris inferior of the canalicular part, and was shaped by ossification of cartilage in about 22 weeks.
2. Niche of the round window was related to the hiatus tympanameningealis, which was the passageway from the cranial cavity to the middle ear.
3. The round window membrane was partly produced by the dura-like structure lining cell, which surrounded the cochlea aqueduct and glossopharyngeal nerve.

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A model study of round window membrane rupture was carried out on the human temporal bones and guinea pigs. Perilymphatic pressure was increased either via the cochlear aqueduct or through a needle which was introduced into the scala tympani of the basal turn. At the same time, we produced a negative pressure around the cochlear, like the middle ear negative pressure.
Half of the cochlear aqueducts were able to reflect the pressure. Among the perilymphatic fistulae, oval window ruptures were more commonly observed than round window ruptures. Ruptures of the round window membrane were slit-like perforations along the fibers of the membrane.

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Permeability of the round window membrane was investigated in normal ears and in ears with serous otitis media. Serous otitis media was produced experimentally by obstructing the eustachian tube of the guinea pig on one side. The other side served as a control. Neomycin was applied directly to the round window membrane on both sides, and the inner ear changes were observed under a light microscope. Most of the ears with serous otitis media showed no cochlear pathology or only slight changes, while moderate to severe changes were observed in all of the control ears. The results indicate that the round window membrane is permeable to neomycin, and that the transport of neomycin into the inner ear decreases in most instances of serous otitis media. The latter may be explained on the basis of fluid remaining and blocking the transport of neomycin mechanically on the surface of the round window membrane.

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Adult guinea pigs were studied after the obstruction of the round window membrane by various adhesive agents in order to investigate thechanges in the cochlear microphonics (CM) and succinate dehydrogenase (SDH) activity. After obstruction for three weeks, CM and SDH activityin the basal turn of the obstruction group obviously dropped compared with the normal group. After a histological examination of the cochlea and round window membrane, the direct poisonous influence by adhesiveagents was not found. We assumed that this result was caused by a disruption of oxygen transport from the middle ear cavity to the perilymphatic space.

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Round window embranes were incised in guinea pigs with experimentally induced serous otitis media, and the cochlear function was monitored before and after the treatment. The thresholds of tone burst-evoked ABR and Nl potentials were measured. Main findings are summarized as follows:
1. Incised membranes healed within 30 days.
2. Marked hearing loss was found in high frequency area (5-8 KHZ), and the nature of this hearing loss was sensorineural on Nl input-output curve.

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A rapid increase of CSF pressure was caused by infusion of 0.5 ml of saline solution into the lateral ventricle of the guinea pig. Electrocochleogram of 10 animals showed no change in 6, increase of AP latency in 2, and disappearance followed by recovery of AP and CM in 2 animals. Serial histological sections of the inner ear demonstrated localized small perforation of the Reissner's membrane, adhesion of the tip of the tectorial membrane to the Reissner's membrane and large space formation in the aleolar tissue of the perilymphatic space of the semicircular canal. These findings suggest that rapid increase of the CSF pressure may induce inner ear damage without association of rupture of the inner ear window.

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Simultaneous recordings of the perilymphatic (Pp) and the cerebrospinal fluid (Pcsf) pressures have been performed on anesthetized guinea pigs. There is no time lag between the changes of the Pp and the Pcsf in their respiration induced pressure variations and in their pressure changes caused by anoxia. Increasing Pcsf produced smooth increase of Pp, while increasing Pp was shown to cause very slow increase of Pcsf. After blocking of pressure increasing system on conditions of increased or decreased Pp, Pp could not maintain the increased or decreased pressure level and recovered to its original level rapidly. The results are interpreted that the cerebrospinal fluid space may serve as a pressure buffer mechanism for the perilymphatic pressure in case of an endolymphatic hypertention.

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We observed the cochlear aqueduct of the normal guinea pig by a scanning electron microscope, mainly fracture preparations.
Some groups of animals were also sacrificed at daily intervals during the period up to 7 days after the phisiological salt solution, the India ink or staphylococcus aureus was injected into the cisterna magna and we studied the changes in the cochlear aqueduct by the same method.
1) No barrier membrane was seen at the scala tympani in the internal orifice. The lumen was filled with periotic duct tissue with a mesh network structure.
2) The cochlear aqueduct has a pressure regulating function for the cerebrospinal fluid and perilymph.
3) It seems that there is a rather strong defense mechanism against foreign matter and inflammation in the cerebrospinal fluid and cochlea. However, in a few cases, meningitis developed into labyrinthitis via the cochlear aqueduct

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In patients with chronic otitis media the ossicles were examined using H-E stained preparation fixed by cyanuric chloride and microradiography by soft-X-ray.
In cholesteatomatous otitis media more severe injuries of ossicles were detected with higher incidences. However, (pathologic) decalcification of ossicles included that in the caries area and that through the vascular channel, which were seen commonly in both the ossicles of cholesteatomatous otitis media and chronic otitis media without cholesteatoma.
The deformity of vascular channel tended to be proportional to the degree of destruction of ossicles.

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Renal insufficiency is often accompanied by the disturbance of calcium metabolism, renal osteodystrophy, osteitis fibrosa and osteomalacia. Many clinical studies including auditory and equilibrium tests have been performed in renal insufficiency however, histopathological study of the auditory ossicles is rare. The techniques employed in the present histopathological study include light and polarization microscopy of the decalcified and non-decalcified ossicles, electron probe X'ray microanalysis and microradiography. Results of the observation on the ossicles in the patients with chronic renal insufficiency were compared to those of normal and chronic otitis media. Quantitative analysis showed that calcium contents of the ossicles in renal insufficiency was about half as much as that of normal ossicles as measured by electron probe X'ray microanalysis. Microradiography and histopathological observation revealed slight dilatation of the vascular channel and radiolucency of the surrounding structures in microradiography. It is known that such histological changes are not specific to uremic bones. The results of the present study seem to indicate that similar changes are occurring both in the auditory ossicles and illiac bone.

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This project was designed to localize colagenase in resorbing bone andadjacent tissue with immunocytochemical method. A granulation tissue was produced in various ways on the rat scalp, compared of which from an open wound, tissue in response to 1% suspension of carrageenan and tissue produced in response to 1% suspension of epithelial debris. The animals were killed two weeks after injection. Scalp bone with adjacent granulation tissue were removed and placed in 1% paraformaldehyde in 0.1M sodium phosphate buffer for fixation at 4°C for 4 hours and the tissue was decalcified in 7% to 1% EDTA at 4°C for 3 weeks. Decalcified bone were frozen and sectioned for immunocytochemistry, using anti-collagenase antisera and the antibody labeled with fluorescein isothiocyanate.
Inflamatory mononuclar cells were seen at the resorping margin while areas within the bone were undergoing destruction suggesting osteocvtic osteolvsis. The epithelium did not contain collagenase. The specific collagenase was concentrated around mononuclear cells and at the irregular bone resorption margins. Within the bone, collagenase staining was found at the periphery osteocyte lacunae. Collagenase staining of osteocytes was primarily limited to cells adjacent to resorbing margins. No collagenase staining was observed with the nonimmune serum. The finding of increased staining either in inflamatory conective tissue and in bone cells adjacent to the inflammation suggests that inflammatiory products may turn on a collagenase in mononuclear cells and in osteocytes.

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Eroded ossicles were obtained from patients with cholesteatoma otitis at the time of surgery. 80 μm thick sections were studied with microradiographic technique. The same specimens were stained by Cole's H-E and examined in a light microscope. After decalcification, these were also observed under an electromicroscope. The microradiographic studies show the faint fibrous radio-opaque structures on the irregular surface of the ossicles. The Light microscopic examination of the non-decalcified specimens revealed many violet precipitations on the same fibrous materials. According to electromicroscopic findings, eroded part shows amorphous substance without collagen and cells and then it appeared degenerating collagen and intact collagen tward bone.

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Collagenase activity was investigated in cholesteatoma epithelium, temporal bone and ear canal skin. The enzyme extracted from tissues was proven to be collage nase by disc electrophoresis. Cholesteatomas displayed different two types; where activity in cholesteatoma was higher than that in bone, conversely where activity in bone was higher than that in cholesteatoma. These findings suggest that collagenase is synthesized in cholesteatoma epithelium, resulting in collagen degradation and bone destruction, and that some variation of collagenase activity in cholesteatoma may be due to the type of cholesteatoma, active or inactive.

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This time, we have studied the ultrastructure of the stapedio-vestibular joint of the human fetus and adult, on a optical and a transmission electron microscopies. As a result, we have obtained the following results concerning the connective tissue which composes the stapedio-vestibular joint.
1) In the fetus at the 13 week stage, immature collagenous fibers and elastic fibers slightly confirmed.
2) In the fetus at the 16 week stage, cross striated structures were observed in the collagenous fibers.
3) In the fetus at the 18 week stage, mature elastic fibers were found.

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The distribution pattern of ciliated cells in the normal mucosa of the human adult middle ear was determined by means of scanning electron microscope. In general, the density of ciliated cells decreased from the anterior part of the tympanum to the antrum, furthermore to the mastoid cavity and from the floor to the roof of the middle ear cavity. Most ciliated cells possessed about 80-160 cilia (average 115 cilia) and the average length of cilia was approximately 8 u. The surface shape and size of nonciliated cells were variable. Goblet cells showed various processes of mucous production. Ciliated epithelial cells in the floor and the lower parts of the middle ear cavity undoubtedly play an important role in an active mucociliary mechanism as in other parts of the upper respiratory system.

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Adrenergic innervation of the guinea pig's middle ear mucosa was topographically studied by the fluorescence method with glyoxylic acid. There was an abundant innervation with a great number of axon terminals in the mucosa around the Eustachian tubal orifice.
Innervations of peptidergic nerves, such as vasoactive intestinal polypeptide and substance P, of the middle ear mucosa were also observed by the method of FITC and PAP. Both these nerve fibers of the mucosa were found especially along small vessels.

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The epithelial layer of the middle ear, a modified respiratory epithelium, has an important role in the defense system; under inflammatory or pathological conditions this mucosa may undergo some protective changes. Mucosal specimens of the middle ear from patients who had chronic otitis media were studied and compared with specimens of normal middle ear using SEM. The epithelia were usually thick and the surface structure varied depending upon the place the biopsy was taken. Moreover, the structure was not uniform even in the same biopsy; areas with great proliferation of secretory cells, other areas with high population of ciliated cells and areas with loss of superficial layer were observed. There were less ciliated cells than we expected. They were not homogeneously distributed, except for the Eustachian tube region. Most of these ciliated cells were morphologically normal, however a few isolated atrophic ones were also found. Cholesteatoma cases showed squamous epithelia with desquamating flat keratinized cells.

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Prostaglandins (PGs) were found in human middle ear effusion (MEE) at levels higher than corresponding serum or plasma. Mucoid effusions cotained higher concentrations of PGs than serous effusions. We have demonstrated the ability of human middle ear effusions to synthesize PGs from ³H-arachidonic acid. Furthermore, we suggested the active roles of inflammatory cells, especially polymorphonuclear leucocytes (PMNs), for PGs biosynthesis in secretory otitis media.

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The purpose of this work is to evaluate etiologic factors in otitis media. By using Boyden Chamber method, we investigated the functions of neutrophils in middle ear effusions (MEE) to clarify their role in the chronicity and progression of middle ear inflammation.
In addition, chemotactic activity of MEE was also investigated by measuring the chemotaxis of normal neutrophils incubated with MEE.
The results were as follows;
Chemotactic index (C. I) of middle ear neutrophils (MEN) was higher in 40% of cases with otitis media than that of peripheral blood neutrophils.
C. I in the group in which neutrophils were incubated with MEE was higher than that in the group studied without MEE.

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We reported previously that chronic inflammatory process in the middle ear inhibited pneumatization of the mastoid cells in young pigs and also the poor pneumatization might be caused by the disturbance of bone metabolism.
We performed further experiment to observe change in each structure of the ear. Paraffin was injected to the left middle eras of new born pigs and right ears were used as controls. Animals were decapitated on the 180th day after birth. The eustachian tubes, middle ears and mastoid cells were obtained from both sides and observed microscopically.
Inflammatory cell infiltration, edema and metaplasia were recognized in the mucosa and inflammatory cell infiltration in poorly pneumatized mastoid cells of the treated ears. Normal mucosa and well pneumatized mastoid cells were observed in the non-treated ears. We discuss microscopic findings for difference between treated and non-treated ears.

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In order to determine the role of the tensor tympani muscle in Eustachian tube function, pressure change of external and middle ear of 13 cats were measured under 4 experimental conditions. It was revealed that single contraction of the tensor tympani muscle during swallowing elicited no pressure change in the tympanum. Then, acoustic stimulation was used as a measure of consistent contraction of the tensor tympani muscle. Simultaneous contraction of the tensor tympani muscle by sound and that of the tensor veli palatini muscle by electrical stimulation failed to open the tube. As a result it may be concluded that the tensor tympani muscle does not play any role in tubal function.

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The spatial orientation of the stapedial nerve fibers in the facial nerve trunk was investigated by serial sectioning method using adult guinea pig. The cross serial sections, Araldite embedded and toluidin blue stained, showed that the stapedial nerve emerging from the posteromedian aspect of the vertical segment, gradually ramified into small bundles toward the horizontal segment.
The stapedial nerve bundles intermingled into the facial trunk as they further ramified without investment into smaller bundles in the horizontal segment, while in the vertical segment they were encircled by the perineurium. The stapedial nerve fibers mainly distributed on the posterior side of the facial trunk.
By their small outer diameter (1-3μm) and their thin myeline sheath (0.2-0.3μm) they could be identified in the trunk.

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The tinnitus due to stapedial contraction has been reported in a few literatures. The stapedial contraction, that brings the tinnitus, is induced by 1) nonacoustical stimulation 2) tight closure of the eyes 3) facial spasmus and 4) associated movement after facial palsy. The nature of the tinnitus is, whatever the cause is, almost same in every literature, a low-pitched blowing sound. But the controversial problems still remain 1) is every person complains the tinnitus during the stapedial muscle contraction? (OCCRENCE RATE) 2) is the tinnitus audible by other persons? (OBJECTIVITY). We have already demonstrated that the occurence rate of the tinnitus brough by the associated movement is low. At this time, we have studied the occurence rate of the tinnitus brought by the electrical stimulation. We studied 30 healthy subjects, 22 facial palsy patients and 19 sensorineural deaf patients with the true tinnitus. We concluded that the occurence rate of the tinnitus brought by the electrical stimulation is as low as the occurence rate of the tinnitus brought by the associated movement after facial palsy.

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It is generally accepted that so called reversed reflex in ipsilateral acoustic stimulation is not rarely observed in patient with severe sensori-neural hearing loss, facial nerve paralysis and ossicular chian discontinuity. Thus, the reversed reflex seemed to be different from physiological one. In order to reveal the origin of the reversed reflex, experiments were carried out in ear model and in cat with two. impedance meters (Amplaid 702). The following results were obtained: 1) In the ear model reversed reflex was consistently obtained. 2) The reversed reflex was not artifact due to some mechanical defect of built-in filter of the impedance meter. 3) Contraction of the tensor tympani muscle had no effect upon the reversed reflex. 4) An extremely mobile eardrum was essential for elicitation of the reversed reflex. Based on the results origin of the reversed reflex was discussed.

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An observatory study was performed on 40 temporal bones with perforated tympanic membrane.
In cases where the epidermis of external auditory canal invaded to the middle ear cavity, many central perforations were observed; as a result, it was considered that central perforation is not always benign. Encroachment of mucosa of middle ear upon the external ear canal, which has been thought to be exceptional, was also found in about 20%, prooving it was not rare.
Loose tubing should be avoided because it may induce epidermic invation of middle ear.

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The paravestibular canaliculus (PVC) was observed on serial sections of the temporal bones from otosclerotic patients operated with fenestration or stapes surgery. Materials consisted of 23 specimens (13 cases). In all specimens, endolymphatic duct and sac were observed to be normally developed with no pathological findings. The PVC was found in 14 of them (60.9%). The course of the PVC was traced from the proximal to the distal area corresponding to the portions of the vestibular aqueduct (VA) on 12 specimens. In seven of them, merging points of the PVC into the VA were the distal portion of the endolymphatic sac, containing veins within it. Remaining five appeared to merge into the same portions of the sac. The contents of the PVC was vein in eight, and three of them had several veins. No artery was found in all. The beginning of the PVC in the vestibular area could be seen in seven, and all of them were small vascular channels around the vestibule in otic capsule, lateral to and near the orifice of the VA containing small veins. The PVC must be kept in mind to have an important role to vascular drainage from the vestibule.

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Temporal bone findings in two infants demonstrating congenital aural atresia with microtia were presented mostly focusing to the external and middle ears. These two cases were proved to have chromosome aberration, that is, 13-15 trisomy and extra chromosome in group G individually. Temporal bones showed the multiple anomalies through the external, middle and internal ears. The external canals were filled with connective tissue in one case and with bony plate in the other to form aural atresia. There were no development of the tubotympanic recess in a case of 13-15 trisomy. The oval window area in both cases was poorly developed resulting in a connective tissue fissure in the lateral wall of the vestibule except for one ear, while the round windows were normally formed in all ears. The facial nerves were thin and showed an abnormal running course without forming the geniculate ganglion and the horizontal segment. In addition, congenital cholesteatomas were found in the middle ear of a case of trisomy G.

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Temporal bone findings in a case of Goldenhar syndrome were presented. This rare syndrome is characterized by a triad of anomalies comprising epibulbar dermoids, accessory auricular appendages and aural fistulae. Principal anomalous features of a 49-day-old female included the triad and complete situs inversus. It was noted that the left corner of her mouth drooped when she cried and her eyes did not move. The cause of death in this case was cardiac failure. The temporal bones were removed and fixed twelve hours after death.
The most striking pathological feature of the temporal bone was that the facial nerve ended in the horizontal segment in the temporal bone on the left. Fallopian canal peripheral to the site was occupied by vascular structures. The identical findings on the facial nerve in a case of MEibius syndrome were recently reported by us. These features gives direct evidence that the site of nerve lesion in some congenital facial paralysis is in the periphery in the horizontal segment of the nerve.

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The developing process of sensory cells in the equilibrium organs of golden hamster was observed by SEM with styrene resin cracking method. The newborn babies were decapitated under ether anesthesia everyday from the day of birth until 5 days-after-birth, and the same experiments were made on the 7th day, 10th day, 14th day and 21st day. The sensory hairs of otolithic organs, both saccule and utricle, had almost reached maturity on the day of birth. Stereocilia showed step-like formation, and we could recognize the kinocilium which was longer than stereocilia. But the length of the hairs was slightly shorter than those of adult. Although some of the sensory cells of crista ampullaris had step-like formed stereocilia and a kinocilium which was slightly longer and thicker on the day of birth, the hairs were so immature that the length was much shorter than those of adult. They had made a rapid growth until 5 days-after-birth and almost reached the adult level on the 10th day.

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The sensory epithelia of the vertical canals were saddle-shaped riding upon the septum transversum of the ampulla with the long axis right-angled to the canal. The sensory epithelium of the horizontal canal is just of the half cut in the middle of the vertical one in shape, and a little larger than that in size. In the middle part of the sensory epithelium, the sensory cells were larger in the surface of each cell, while in the lateral periphery which distended fan-wise the sensory cells were smaller in the cell surface. The average numbers and areas of sensory cells in three samples were 3427, 0.2506mm² in the lateral crista, 4293, 0.2835mm² in the anterior one, and 4403, 0.2939mm² in the posterior one. The horizontal crista was smaller in size and less in number than the vertical one in the frog.

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At the 16th day of fetal life, Cupula was often observed on the crista, and homogenous structure substances were found on the supporting cells of crista. At the 17th day of fetal life, the similar homogenous structure substances buldged on the supportings cells and connected with the marginal processus of the cupula. Therefore, it is strongly suggested that the cupula possibly originates from the supporting cells on the crista at the 16th day of fetal life in rats. At the 19th day of fetal life, the cupula was almost completely formed. Immediately after birth, morphological findings such as thickness, extension, surface structure of the cupula and subcupular space were almost complete. On the other hand, TEM examination revealed that restiform structure of the cupula first appeared at the 19th day of fetal life, while mesh or fibrous structure was observed in the cupula on as early as the 17th day of fetal life.

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Non-sensory ciliated cells were seen under a scanning electron microscope (SEM) in the vestibule of four 14 to 18 week human foetuses. These cells were observed scattered at the border area between the three semicircular canal ampullae and the utricle. As these ciliated cells were not observed in the postnatal inner ear, the presence of these cells seems to be transient during foetal life. Similar ciliated cells observed under a SEM in the utricle of a normal adult cat were also reported.

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Process of degradation & absorption of otoconia in the utricle of two groups of guinea pigs (one was no injection, the other was streptomycin [SM] 200mg/kg/day im for 10 days injections) was observed with SEM. In normal guinea pigs without injection, otoconia in the utricle showed the typical calcite crystal form as reported before. On the dark cell area near the utricle, variously shaped otoconia were observed; smaller size of original crystal, thinning around mid-portion of crystal, degradation into small two or three pieces and particles. Some otoconial crystals on otolithic membrane of SM injection group showed fibrous body surface and fracture lines. The otoconial crystals on the dark cell area showed remarkably fibrous and hollow surface on their bodies. This degradation process seemed to be further advanced in crystal body than bilateral end portions and in the crystals located just on the dark cell surface.

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The vascular corrosion casts of the Vestibule were studied under the scanning electron microscope to define the three dementional ultrastructure of Capillary areas of the membranous vestibular labyrinth. Twelve guinea pigs, two rabbits, and a man were irrigated through ascending aorta with a mixture of PH-A solution and clot disperser in physiological salt solution, and methacrylate resin of low viscosity (Mercox) was used to obtain vascular corrosion casts. Although the dense capillary networks were observed in every maculae and cristae, no new findings were added to the previous knowledge by the present SEM studies, as these networks show most of two dimentional construction. In the guinea pigs, however, SEM revealed characteristic coiling and twisting pattern just before vestilular arterioles enter the capillary networks beneath the sensory epithelium. These coiling structures were morphologically similar to those of the glomerulus, and the arterioles decreased in their diameters after several ramifications in this area. Although it is not obvious whether this coiling arteriole system is found in other animals vestibule, this system many play a specific role in the microcirculation of the inner ear.

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The utricle has a communication with three spmicircular system and utricular duct. The utricle is found to contact with saccular wall and to be suspended by the connective utricular ligament in the upper part of it. Utricular wall is free in the lower portion while the upper part has a firm wall. The volume change of the utricle is poorly documented even in Ménière's disease. Comparising with the cochlear duct, the utricalo-endolymphatic system has a big volume including 3 semicircular canal system. The utricular volume and utricular endolymphatic valvular function were discussed in this report.

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The ultrastructure of the human vestibular ganglion cells was studied. The majority of the ganglion cells are unmyelinated bipolar cells. Their cell size vmaries from 23 to 50 u. In addition to the bipolar cells, unmyelinated multipolar cells are observed. The smaller cells among the multipolar cells receive, on their cell bodies and processes, nerve endings that contain granular vesicles together with agranular vesicles. Two types of synaptic structures are classified in our study. Both of them show the specialized zones of plasma membrane associated with presynaptic vesicles. However, the first type of synapses on the process contain many spherical vesicles and elongated vesicles are dominant in the second type of synapses on the perikarya. The functional significance of these nerve terminals is yet to be determined.

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The origins of vestibular efferent fibers of cats were examined using a horseradish peroxidase (HRP) method. Crystals of HRP were placed into the ampulla of anterior, posterior or lateral semicircular canal, respectively. The remaining ampullae of untreated canals and cochlea were completely destroyed and filled with bone wax in order to prevent leakage of HRP. After keeping the animal survival for 2-3 days, the animal was sacrificed and the brain was treated using a benzidine method. When HRP was put into the ampulla of anterior canal, the HRP reactive cells were found in the bilateral parvocellular nucleus (PCRN), contralateral gigantocellular reticular nucleus (GCRN) and ipsilateral lateral reticular nucleus (LRN). With HRP into the posterior canal, the HRP reactive cells were observed in the ipsilateral PCRN as well as lateral and medial vestibular nuclei. Upon the HRP placement into the lateral canal, there were the HRP reactive cells in the ipsilateral PCRN and LRN as well as lateral vestibular nucleus. These results indicate different origins of the efferent fibers to the anterior, posterior and lateral semicircular canals.

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The study was performed to elucidate the effect of inferior olive (I0) stimulation on the lateral vestibular nucleus (LVN) neurons monosynaptically activated by vestibular nerve stimulation using decerebellated cats. Furthermore, possible neurotransmitters involved in the transmission from IO to LVN were studied. Forty-three out of 160 LVN neurons were monosynaptically activated by IO stimulation and the excitatory response was blocked by iontophoretic application of atropine. An inhibition by IO conditioning stimulation of orthodromic spikes with vestibular nerve stimulation was observed in 22 LVN neurons, and the inhibition was antagonized by iontophoretic application of bicuculline, a GABA antagonist. HRP study showed existence of fiber connection from the dorsal cap and β nucleus of IO to the LVN. These results suggest that the LVN neurons monosynaptically activated by vestibular nerve stimulation receive both excitatory and inhibitory inputs from the contralateral IO and neurotransmitters involved in the excitatory and inhibitory transmission are acetylcholine and GABA, respectively.

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Experimental direction-changing positional nystagmus was elicited in Rabbit by Intra-tympanic infusion of the drugs with different specific gravity such as Ethanol and Heavy water. Ethanol provoked horizontal positional nystagmus to the right when Rabbit was hold with right side down, to the left with left side down, to the non-infusion ear with nose up and to the infusion ear with nose down. The directions of horizontal positional nystagmus induced by Heavy water were opposite to those by Ethanol. These drugs probably made some effect to the inner ear reffered to the change of the specific gravity.

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The authors made a series of experiment, using 70 rabbits. The authors tried to inject Indian ink into perineurium and outside of the perineurium of the facial nerve at the entrance of the stylomastoid foramen. The authors found the Indian ink which had been injected inside of the perineurium penetrated to the chochlear nerve, superior vestibular nerve and inferior vestibular nerve in the internal auditory canal, however, the Indian ink which had been injected outside of the perineurium penetrated, as far as Bill's bar. Moreover, in some cases, the Indian ink which had been injected inside of the perineurium penetrated into the subarchnoid space and spread over the surface of the brain by way of the perineurium and the arachnoid membran of the facial nerve or cochlear aqueduct. In the latter case the dehiscence of the facial canal at its horizontal portion had been found. And the Indian ink seemed to reach the cochlear aqueduct by way of the round window.

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