. Natural philosophy. including statics, hydrostatics, pneumatics, dynamics, hydrodynamics, the general theory of undulations, the science of sound, the mechanical theory of music, etc. : designed for the use of normal and grammar schools, and the higher classes in common schools . mporal bone, extendingfrom the drum to the vestibule, and is filled with air. Theparts of the middle ear are:— I. The Memhrana Tympani, or drum of the ear. II. The Eustachian Tube. in. The four small bones of the ear. The membrana tympani is placed obliquely across theinner end of the auditory canal. It is thin and
. Natural philosophy. including statics, hydrostatics, pneumatics, dynamics, hydrodynamics, the general theory of undulations, the science of sound, the mechanical theory of music, etc. : designed for the use of normal and grammar schools, and the higher classes in common schools . mporal bone, extendingfrom the drum to the vestibule, and is filled with air. Theparts of the middle ear are:— I. The Memhrana Tympani, or drum of the ear. II. The Eustachian Tube. in. The four small bones of the ear. The membrana tympani is placed obliquely across theinner end of the auditory canal. It is thin and oval, andis placed at an angle of 45^, its outward plane lookingforwards and downwards. The Eustachian tube is a membraneous canal leadingfrom the middle ear downwards and forwards into thepharynx, with which it communicates by means of avalvular opening that is generally closed. It gives exitto the mucus which forms in the middle ear, and also per-mits the entrance of air into the tympanic cavity, whenclosed by a cold it causes partial deafness. The ossicles of the tympa- ^° num are four small bones whichconnect the membrana tympaniwith the fenestra ovalis. Theyare shown magnified in the Fig,,and are named from theirshapes; the malleus or ham-mer, m, the incus or anvil,. AET. THE ORGANS OF HEARING. 183 the OS orbiculare or round bone o, (the smallest bone inthe body), and the stapes or stirrup, s. The handle h ofthe malleus is fastened to the membrana tympani, and thebase of the stapes to the membrane covering the fenestraoxalis. The bones are joined to one another in the positionrepresented in the figure, and are capable of slight move-ment by means of attached muscles. 440. The labyrinth or internal ear has its channelsexcavated in the petreous bone, the hardest of any in thebody. It consists of the following parts :—- I. The Vestibule. II. The Semi-circular Canals. III. The Cochlea. The vestibule (I) is a chamber formed in the petreousbone. Various branches of th
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectphysics, bookyear1861
