Cochlea

“ These theories, dispensing with peripheral analysis, leave out of account the highly complex structure of the cochlea, or, in other words, they assign to that structure a comparatively simple function which could be performed by a simple membrane capable of vibrating. We find that the cochlea becomes more elaborate as we ascend the scale of animals, until in man, who possesses greater powers of analysis than any other being, the number of hair-cells, fibres of the basilar membrane and arches of Corti are all much increased in number (see Retzius’s table, supra) . ”

“ In this class the tympanum and Eustachian tube are first developed; the membrana tympani lies flush with the skin of the side of the head, and the sound-waves are transmitted from it to the internal ear by a single bony rod—the columella.
In the Reptilia the internal ear passes through a great range of development. In the Chelonia and Ophidia the cochlea is as rudimentary as in the Amphibia, but in the higher forms (Crocodilia) there is a lengthened and slightly twisted cochlea, at the end of which the lagena forms a minute terminal appendage. ”

“ The analysis of compound wave-forms is supposed (after Helmholtz) to be effected through the different rates of sympathetic resonance of the different parts of the membranous cochlea. The basilar membrane is some twelve times broader at the apex of the cochlea than at the base where it begins, and is largely composed of radiating fibres which may be likened to stretched strings. Now the physical principle of sympathetic resonance says that when stretched strings are near a source of vibration those whose own rate agrees with that of the source also vibrate, the others remaining at rest. ”

“ The auditory nerve terminates in eight sense organs, which contain hair cells. There is no cochlea as in the mammalian ear. The assumption commonly made is that vibrations in the water or air by direct contact cause the tympanic membrane to vibrate; this in turn causes a movement of the columella, which is transmitted to the perilymphatic fluid of the inner ear. The sensory hair cells are disturbed by the movements of the otoliths in the endolymph, and thus an impulse is originated in the auditory nerve which results in a sensation more or less resembling our auditory sensation. ”

“ Now it is evident that the cochlea must act either as a whole, all the nerve fibres being affected by any variations of pressure, or the nerve fibres may have a selective action, each fibre being excited by a wave of a definite period, or there may exist small vibratile bodies between the nerve filaments and the pressures sent into the organ. The last hypothesis gives the most rational explanation of the phenomena, and on it is founded a theory generally accepted and associated with the names of Thomas Young and Hermann Helmholtz. ”

“ As to the auditory apparatus itself, we see that the elaborate organ for hearing—the cochlea—has been evolved in the vertebrate phylum itself. In the lowest vertebrates the auditory apparatus tends more and more to resolve itself into a simple epithelial sac, the walls of which in places bear auditory hairs projecting into the sac, and in part form otoliths. Such a simple sac forms the early stage of the auditory vesicle in Ammocœtes, according to Shipley ”

“ The human cochlea contains about 3000 of the rods or fibres known as 'Corti's arches.' The human ear, in fact, is a highly sensitive musical instrument, furnished with 3000 strings, which are set in motion by the concurrent vibration of external sonorous bodies, exactly in the same way in which the 'resonator' responds to a musical sound, or in which the strings of a silent violoncello or pianoforte are set in vibration by the production, in a sufficient degree of strength, of notes of equivalent pitch on any other instrument placed near it. ”

“ The sacs of the internal ear, known as the utricle and saccule, receive the impulses of the base of the stapes. They are organs connected with the perception of sounds as sounds, without reference to pitch or quality. For the analysis of tone a cochlea is necessary. Even in mammals all the parts of the ear may be destroyed or affected by disease, except these sacs, without causing complete deafness. ”

“ Animals furnished with otoliths can thus analyze rhythms and disturbances which are synthetized in our cochlea into sounds of different tones. The otolithic bell can only reveal a trepidation, and continues unfit to provoke a continuous sensation other than that which results from the persistance of nervous, terminal, or central impressions, a limit beyond which it can not estimate the pitch without such an arrangement as that of the cochlear formations. ”

“ It is by means of the cochlea that we discriminate pitch, hear beats, and are affected by quality of tone.
Since the size of the membranous labyrinth is so small, measuring, in man, not more than 1/2 in. in length by 1/8 in. in diameter at its widest part, and since it is a chamber consisting partly of conduits of very irregular form, it is impossible to state accurately the course of vibrations transmitted to it by impulses communicated from the base of the stirrup. ”

“ This end-organ in the cochlea may be compared very fitly to the telephone which receives the message, and that portion of the brain where the auditory tract ends, to the telephone at the distant end of the path, the listener there representing consciousness. The auditory path within the brain is long and complicated, there being, in fact, many way-stations through which the message passes before it reaches the final one. ”

“ What we call the auditive organ is in the lower animals simply a sac containing auditive stones. As we ascend the scale, 1, 2, 3 semi-circular canals gradually develop from them, whilst the structure of the otolith organ itself becomes more complicated. Finally, in the higher vertebrates, and particularly in the mammals, a part of the latter organ (the lagena) becomes the cochlea, which Helmholtz explained as the organ for sensations of tone. ”

“ With respect to the Eustachian tube, its aperture into the throat seems indispensable to hearing; and whenever closed, from malconfirmation or disease, deafness is the certain consequence.
The third division of the organ is the internal ear, which is called the labyrinth; it is divided into the vestibule, three semicircular canals, and the cochlea: the whole are incased within the petrous portion of the temporal bone. The internal ear may be considered as the actual seat of the organ ”

“ These variations in structure, if they really exist, go far toward justifying the tendency of Cyon and Alexander and Kreidl, as well as many other investigators, to regard the dancer as abnormal or even pathological.
The functions of the ear as at present known to the comparative physiologist are grouped as the acoustic and the non-acoustic. The cochlea is supposed on very good grounds to have to do with the acoustic functions, and the organs of the semicircular canals on equally good evidence are thought to have to do with such of the non-acoustic functions as equilibration and orientation. ”

“ BETWEEN the external sensation and the internal perception stands the time-sense, adapted to the distinction and estimation of the succession; it is really a grosser hearing and sight, for the cochlea and retina do nothing more than distinguish the more or less rapid succession of impressions. ”

“ In the same way the organ of hearing in its essential structure is entirely mammalian, having not only the sacculi and semicircular canals common to all but the lowest vertebrates, but the cochlea, and tympanic cavity with its ossicles and membrane, all, however, buried deep in the solid substance of the head; while the parts specially belonging to terrestrial mammals, those which collect the vibrations of the sound traveling through air, the pinna and the tube which conveys it to the sentient structures within, are entirely or practically wanting. ”

“ For since each terminal nerve, of the thousands in the cochlea, responds to a given simple tone, the group of such tones forming a musical sound will excite a corresponding group of nerves, which will of course be related among themselves, as are the exciting tones among themselves ”

“ The inner wall shows a promontory caused by the cochlea and grooved by the tympanic plexus of nerves; above and behind it is the fenestra ovalis, while below and behind the fenestra rotunda is seen, closed by a membrane. Curving round, above and behind the promontory and fenestrae, is a ridge caused by the aqueductus Fallopii or canal for the facial nerve. The whole tympanum is about half an inch from before backward, and half an inch high, and is spanned from side to side by three small bones, of which the malleus (fig. 1, 1 ) is the most external. ”

“ His great work on Physiological Optics (1856–1866) is by far the most important book that has appeared on the physiology and physics of vision. Equally distinguished were his labours in physiological acoustics. He explained accurately the mechanism of the bones of the ear, and he discussed the physiological action of the cochlea on the principles of sympathetic vibration. Perhaps his greatest contribution, however, was his attempt to account for our perception of quality of tone. ”

“ On the other hand, we never meet with a Reptile, Bird, or Mammal which at any period of its existence breathes through gills, and the gill-arches and openings which do exist in the embryos, are, during the course of the ontogeny, changed into entirely different structures, viz., into parts of the jaw-apparatus and the organ of hearing. (Compare above, vol. i. p. 307.) All Amnionate animals have a so-called cochlea in the organ of hearing, and a “round window” corresponding with it. These parts are wanting in the Amnion-less animals ”

“ Sc., 1886) , who compared the action of the cochlea to that of a telephone plate. According to this theory, all the hairs of the auditory cells vibrate to every note, and the hair-cells transform sound vibrations into nerve vibrations or impulses, similar in frequency, amplitude and character to the sound vibrations. There is no analysis in the peripheral organ. A. D. Waller, in 1891 (Proc. Physiol. Soc., Jan. 20, 1891) suggested that the basilar membrane as a whole vibrates to every note, thus repeating the vibrations of the membrana tympani ”

“ This Hole being very large, is the Entrance of a Ductus that is hollow'd in the Os Petrosum, and which sinking obliquely from the fore-part backward, for the depth of about two Hairs breadth, forms as it were the bottom of a Sack, the lowermost part whereof is terminated partly by the Basis of the Cochlea, and partly by a Portion of the Mouth of the Vestibulum. At the bottom of this Ductus are many Holes, but the most considerable is that of the upper-part, thro' which passeth a Portion of the Auditory Nerve. ”

“ When young it makes a good dish, and when old can be used to advantage in soups.
231L. cochlea ́tus Fr.—cochlea, a snail. Pileus 2–3 in. broad, flesh-color, but becoming pale, somewhat tan, fleshy-pliant, thin, commonly excentric, imbricated, very unequal, somewhat lobed or contorted, sometimes plane, sometimes funnel-shaped-umbilicate, but not pervious, smooth. Stem solid, firm, sometimes central, most frequently excentric, sometimes wholly lateral, always sulcate, smooth, flesh-colored upward, reddish-brown downward. Gills decurrent, crowded, serrated, white-flesh-color. Fries. ”

“ This variety of imbricate aestivation has been termed cochlear. In flowers such as those of the pea (fig. 40) , one of the parts, the vexillum, is often large and folded over the others, giving rise to vexillary aestivation (fig. 48) , or the carina may perform a similar office, and then the aestivation is carinal, as in the Judas-tree (Cercis Siliquastrum) . The parts of the several verticils often differ in their mode of aestivation. Thus, in Malvaceae the corolla is contorted and the calyx valvate, or reduplicate; in St John’s-wort the calyx is imbricate, and the corolla contorted. ”

“ If the patient is a woman, who because of offensive breath is barred from society, she will become morbid and hypochondriacal in time. There is so much of the thick mucus hanging on the walls of the pharynx that the openings into the eustachian tubes are filled up and in a short time a certain degree of deafness appears—roaring in the head and other manifestations of ear trouble. As soon as the hearing is noticed to be abnormal the patient will be ready to consult some physician. ”

“ In some forms of deafness blisters behind the ears are useful. A clove of garlic wrapped in cotton or gauze, or a few drops of the juice introduced into the ear, is extremely efficacious in nervous deafness. When imperfect hearing depends upon obtundity of the auditory nerve, or an extensive obliteration or malformation of the internal ear, it scarcely admits of cure.
Deafness, Taylor’s Remedy for. Prep. From oil of almonds, 1 lb.; garlic, bruised, 2 oz.; alkanet root, 1⁄2 oz.; digest for a week, and strain. A little is poured into the ear in deafness. ”

“ The pain may generally be relieved by throwing warm water into the ear by means of a syringe, and fomenting the surrounding parts with decoction of poppy-heads and chamomile flowers. Should this treatment not succeed, a drop or two of laudanum, with one drop of oil of cloves and a little oil of almonds, may be dropped in the ear, and a piece of cotton wool introduced afterwards. Cases of acute inflammation of the internal ear are occasionally met with in adults, which assume a very serious character, and demand the most careful treatment. See Deafness. ”