. Text-book of normal histology: including an account of the development of the tissues and of the organs. cala media, including the crista, thesulcus, and the organ of Corti. The development of these structures includes the differentiationof two epithelial ridges ; from the inner and larger of these isderived the lining of the sulcus spiralis and the overhanging mem-brana tectoria, and from the outer and smaller ridge is producedthe elaborate and complicated organ of Corti. The crista appearsbetween the sulcal cells and the cochlear axis as a thickening of thespiral lamina. The cochlear outgr
. Text-book of normal histology: including an account of the development of the tissues and of the organs. cala media, including the crista, thesulcus, and the organ of Corti. The development of these structures includes the differentiationof two epithelial ridges ; from the inner and larger of these isderived the lining of the sulcus spiralis and the overhanging mem-brana tectoria, and from the outer and smaller ridge is producedthe elaborate and complicated organ of Corti. The crista appearsbetween the sulcal cells and the cochlear axis as a thickening of thespiral lamina. The cochlear outgrowth of the primary otic vesicle forms themembranous cochlea, or scala media, alone, the walls of theadjacent divisions, the scala vestibuli and scala media, resultingfrom the changes within the surrounding mesoderm. The latterdifferentiates into two zones, an outer, which becomes the car-tilaginous, and finally osseous, capsule, and an inner, lyingimmediately around the membranous canal, which for a time consti-tutes a stratum of delicate connecting tissue between the denser 400 NORMAL HISTOLOGY. Fio. capsule and the ectodermic canal. Within this layer clefts appear,which gradually extend until two large spaces bound the mem-branous cochlea above and below. These spaces, the scala vestibuli and the scala tympani, areseparated for a time from the scala media by a robust septumconsisting of a mesodermic layer of considerable thickness and thewall of the ectodermic tube. With the further increase in the dimensions of the lymph-spaces the par-titions separating them from the cochlearduct are correspondingly reduced, until,finally, the once broad layers are rep-resented by frail and attenuated struct-ures, the membrane of Reissner andthe basilar membrane, which con-sequently include an ectodermicstratum, the epithelial layer, strength-/ / ened by a mesodermic lamina, rep- ^- ^ v/If resented by the substantia propria and its endothelioid covering. The main sac of the otic vesi
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphiladelphiajblipp
